Episode Transcript
Sarah Beck: You're listening to Garden Futurist. I'm Sarah Beck here with Adriana Lopez Villalobos. Hi Adriana.
Adriana López-Villalobos: Hi Sarah.
Sarah Beck: So, Adriana, I have to say that. After the last couple of conversations on fruit trees, I literally was ready to walk out and do some grafting. I may not actually have all the skills that I need yet, but I think I have the required enthusiasm.
Dr. Rachel has this way of both sharing really complex and interesting aspects of plant conservation and science, but at the same time, absolutely breaking through our barriers of fear around trying something and I just love that.
Here's this person with just a vast library of knowledge and she's really fun to talk to, but there's also this really interesting do-it-yourself element that is contagious and enjoy absorbing it.
Adriana López-Villalobos: Yeah, it was very interesting to hear about all the possibilities and the considerations when thinking about not only grafting, but in general growing fruit trees.
Because often we encounter problems because we act first and then we think later. When planting an orchard, it's more important to take a step back and visualize how it's going to look, not the next summer or this summer, but in 10 years down the road.
It's a very different approach than what we usually do when planting vegetable gardens.
Sarah Beck: Dr. Rachel Spaeth is interim curator of the Prunus collection for the USDA Agricultural Research Service in Davis, California.
Sarah Beck: We recently had an episode where we talked about the Lost Apple Project. That organization is focused on rediscovering heritage apple varieties.
I'm just wondering if you can give us a little bit of orientation to what that set of fruit trees that would have been in North America during anything that's before the 1920s, what I'm assuming is before modern breeding, right?
Rachel Spaeth: Humans have been breeding and selecting fruit and carrying it with them for thousands of years, as long as humans have been migrating around.
So there's this interesting thing where we have plants that actually evolved on North America that make edible and delicious fruits versus ones that evolved elsewhere and came with people across land bridges or across on boats. So we do see different waves of things that come to the United States or North America in general in various waves.
So some things that are native to North America in general that evolved here on our continent include things like blueberries (Vaccinium spp.)—fantastic, wonderful, right? Pawpaws (Asimina), which are a weird, not really tropical, but it tastes like it'd be tropical. There's persimmons (Diospyros virginiana). There's various types of plums (Prunus spp.). The saskatoon berries (Amelanchier alnifolia), they’re serviceberries I think is the other common name. Lots of different Rubus—so things like salmonberries, blackberries.
A lot of those things were already here, but then we have these waves of things that come with people just because if you're going to, if you're going to go for a long walk, you're going to have to bring some food with you. And if you're bringing food with you, one, it could be a food like a berry that you are ingesting and then depositing somewhere as compost later, right? So you could be carrying that in your digestive tract, or it could be something that you're actually saving the seed for with the intention to plant later.
Things like that would include, like, the Indian Free Blood peach (Prunus persica 'Indian Free'). It's an old, old peach that came to North America very, very long time ago. Very, very fuzzy on the outside, and on the inside, we call it blood peach because it’s very, very red on the inside.
Sarah Beck: Where did that come from?
Rachel Spaeth: So that probably came from Asia in general, and then just came across with people. Peaches are self-fertile, which means that the seed, whenever you plant it, it pretty much comes true to seed. You're not going to change the genetics too much that way. So it's one that if you had a bag of peaches with you and you saved the seeds, you could plant those and all the trees are going to pretty much be close to what you remembered eating when you had it with you.
Humans aren't the only ones that do that, right? So, animals also, as a means of vector dispersal, are going to move things around a little bit. So that we end up with various fruits here as we brought our animals along with us, too.
Sarah Beck: You just mentioned also a plum. So there is a North American native plum?
Rachel Spaeth: There are several actually. So there's American plum (Prunus americana, which is a very tinycherry plum. There's the Chickasaw plum (Prunus angustifolia), Catalina cherries (Prunus ilicifolia ssp. lyonii). So a lot of these things are smaller. They're not going to be big like the huge bred Asian plums that come from China or Japan, but they are still delicious and would have been part of food staples for people that were collecting and gathering.
Sarah Beck: And these can be found still?
Rachel Spaeth: Oh, sure. Yeah, there's wild stands of these all over the place. Arkansas, Texas, Catalina Islands.
Sarah Beck: Have any of those been bred into any contemporary varieties?
Rachel Spaeth: Absolutely. So there are some that Burbank was working with that he was using as interspecifics to breed everything together.
He was looking for things like disease resistance, especially for things in North America because we have some pretty gnarly soil pathogens to contend with for our Prunus. You'll still see bits of those flavor profiles or even just uses rootstocks here in the United States still.
Sarah Beck: Can you help me bridge this term, heirloom and landrace, to this conversation a bit? I think this is really important to understand what you're saying about the fact that there is a continuity to human interactions with especially fruit because we love it so much.
Can you give me a little bit of a bridge to this? Because clearly when we're talking about heirlooms, we start having this association with perhaps some historical periods.
Rachel Spaeth: So heirloom is interesting in the fruit realm, because if you're talking about an heirloom seed, typically it's something that breeds true to seed.
So if you're thinking like an heirloom tomato, you can save the seed from that tomato and you're going to get a tomato that's pretty much identical to the one that you bred, versus an F1 hybrid that's going to be something where you get a big mixed bag from that.
But trees are a little bit more variable so it's harder to identify what we would call an heirloom in a fruit tree, because any apple that you cut open is going to have five seeds in it, and if you plant those five seeds you're going to get five very different types of apples.
So instead of referring to heirloom with a fruit tree like that, as something that comes true to seed, instead they're going to put an age on that. So it's going to be something that was bred 100 years ago or more.
If you get a scion from the original Red Delicious apple, which we have some people that circulate those out here in California, it's a much different apple than the one that got grafted all over Washington state and that you taste that's like the yucky potato of the apple world. Just very starchy, but it has long shelf-life capacity.
What had probably happened with that is there was a bud sport mutation along some way, and then it got grafted over as that cultivar and it just became not great over time, by accident. But if you get scions from the original Red Delicious, the one that Stark Brothers originally circulated in the late 1800s, early 1900s, it's actually a quite delicious apple.
Sarah Beck: Have you tasted it?
Rachel Spaeth: I have, and I do have a scion to stick on one of my trees, probably later today since the sun's shining.
Sarah Beck: How interesting. This is really good context, and I think you did explain a little bit about the fact that the seeds themselves are going to give you a very interesting mixed bag of results. Do you want to just quickly explain what the more typical propagation method is and, and why we aren't just going around—
Rachel Spaeth: Johnny Appleseeding?
Sarah Beck: Yeah. I was just going to mention the Johnny Appleseed thing.
Rachel Spaeth: We’ll talk a little bit about that as far as what the goals were historically versus now for what we look for in a fruit in general, too.
Yeah, I would say that commercially and just in general for if you want to get the exact same fruit from a tree fruit, what you want to do is you want to graft that. You want to take a scion, a dormant stick from the tree that you thought was delicious, and you can either stick it onto a mature tree that you have in your yard if you want to create like a fruit salad type tree, or you can get something that's a rootstock which was bred for disease resistance and things like that. And then you graft that scion onto the rootstock, and now you have a tree that retains the genetics of the original plant, for the most part.
Sometimes there is a bud sport mutation. So on the nodes on the side of a branch there can be a mutation that just occurs in that meristem. So only that branch has a new genetic quality to it.
That’s how we got the seedless mandarin orange. It was a random bud sport that occurred on a different type of orange. Somebody was like, “Hey, this doesn't have any seeds in it and it's really good.” So just that one stick has been propagated the bejesus out of. And so now we have all these seedless mandarin oranges.
Especially anything that's seedless needs to be clonally propagated like that.
Sarah Beck: There's so much opportunity for discovery, clearly, at each of these steps.
Rachel Spaeth: There's two things that drive that source of mutation, because sometimes people get a little confused about that.
If you're a perennial plant that's stationary, you can't move and you're going to be in that space year after year, there's a couple of things that happen to you. One is you can be exposed to viruses and bacteria that can cause that somatic mutation, just from transmitted in pollen, grafting cuts, pruning cuts, whatever, something like that, or just being exposed to ultraviolet light persistently for a long period of time can cause that mutation that occurs in that bud.
Sarah Beck: I want to ask you about another term, which you had mentioned, which is noncommercial varieties or noncommercial cultivars.
Rachel Spaeth: So noncommercial just means that you're not really going to see it in the grocery store. Maybe it'll show up at the farmer's market. But when you go to the grocery store, you're going to see a couple of standards that are like always there, but there are thousands of kinds of apples and they just vary in their degree of what makes them useful to go to market.
So sometimes it's that they bruise too easily or they're hard to harvest because they don't ripen all at the same time. Sometimes they've got a very short shelf life. So these are things that would make it okay for a home grower to have in their own yard, but it's not going to be a commercially viable enterprise for a farmer to have lots of acreage of these types of varieties.
Sarah Beck: Thinking about this as a gardener, who's really interested in flavors that are not easily accessible, maybe you can help us get oriented towards what the options are.
I think what you're saying is that there are people who are continuing to develop some of these noncommercial varieties as well, and that's sort of all in the mix of the options. Is that right?
Rachel Spaeth: Oh yeah, absolutely. I mean, there's still hobbyist breeders out there that are selecting things or people who just get very excited about something that they ate somewhere and so they try to start the seed themselves.
Definitely with the apples, some people, if their goals are to have a lot of things to make hard cider, which would have been an older version of like, “Hey, let's just plant all of these apple seeds, like Johnny Appleseed,” maybe they can come up with a random sport mutation that will show up that actually is a delicious, fresh eating apple as well. But for the most part, those are going to end up being good for cider. So they still have a useful purpose.
Sarah Beck: When you start cooking fruit, you're looking for some very different qualities, right? Sometimes that fresh eating is a little overwhelming, or it's especially tart, once it gets in a cooked form, becomes just incredible.
Rachel Spaeth: Oh, sure. So there's differences in the acid levels, there's differences in the sugars, there's differences in the pectins and how they break down.
So something that might be a good fresh eating apple might be terrible for sauce or pie. Something that's good for sauce might be terrible for eating fresh and terrible for pie. And something that's good for pie might not work for sauce and most of the time they're okay for eating fresh, but you still add sugar to it when you're making pie.
Sarah Beck: Can you help us quantify just the fruit tree variety diversity? I know the USDA holds a lot within seed banks and germplasm repositories. There's a lot.
Rachel Spaeth: So the USDA has 22 research stations that they set up across the United States and each one holds the world's biodiversity for important perennial food staple crops.
I like to refer to it as the doomsday collection. They found that sometimes there'll be a disaster that comes through, like a disease or something, and decreases our ability to be resilient and robust if we are putting all of our eggs in these monoculture baskets and we have all of our things just in that genetic pool. It's nice to have a backup genetic pool to be able to pull things from.
There was a blight that came and decimated Russian wheat a long time ago, and they went to one of these collections, the one that theirs was the Vavilov Seed Bank in Russia, and out of the thousands of cultivars of wild wheat strains and bred wheat strains that they had, there were only five that were genetically resistant to this blight that caused major famine.
So, having these resources that you can pull from is very useful to make sure that we still have good food sustainability for a long time.
So the crops that we have over at the Davis Collection include all the Prunus, which is what I'm in charge of. So cherries, peaches, apricots, nectarines, plums, pluots, prunes, and almonds. Those are all things in the Prunus.
We have, I think it's like over 1,600 accessions. There are more Prunus than just that. There's the ones that I talked about, like the P. americana and the Catalina cherries and things like that. So some other land race things that evolved in a specific space that we also have there.
Some of them taste very, very bad.
Sarah Beck: But we still value holding the genetics from those, right? Absolutely. They could be important somewhere along the line.
Rachel Spaeth: Absolutely. They could be very important somewhere along the way. And maybe they make great jelly, you just have to add a lot of sugar and cook them to make them edible, right?
Or it could be that it's a good disease-resistant rootstock or it has other attributes, flavor profiles and things that we would like to have to breed into other stuff.
But they also hold the world's biological diversity for grapes, figs, mulberries, chestnuts, pistachios, pomegranates, oh, and persimmons.
It's a huge collection and they maintain that specifically for people that are in research institutions and for breeding purposes, and that's what that collection is intended for to be a pool that they can draw from whenever they're doing their research.
Sarah Beck: So as a civilian, you can't just call them up and say, “Hey, I want some of those seeds or I want a scion.”
Rachel Spaeth: There is a website that you can go to, it's the GRIN-Global database, that you can search and look for things, but there's a disclaimer on there that says, of you are a home grower in general, you probably will not have access to those collections.
However, they do have some public days sometimes where we have tastings and things. So you can come over and try some things and then maybe they're available commercially and we can link you with some sources on how to connect and find those fruits.
Sarah Beck: I think it's easy to say we love biodiversity. We say this all the time, but biodiversity is critical to our survival. This diversity is precious. It's a bank.
Rachel Spaeth: Oh, absolutely. Especially when we're facing such a huge crisis like climate. One of the main issues that we're seeing right now is the areas are not getting enough chill hours for their fruit trees to produce fruit reliably.
So we're seeing this all through the Central Valley in California, where we're not getting enough chill for our walnuts to produce walnuts. So we're losing an important staple crop and all of those walnuts are moving northward and people are having to come up with different crops that they can utilize.
So if we can take something that evolved closer to the equator that might have less chill hours in general, those would be the genetic pool resources that we're looking for to breed into plants that taste good so that we can reduce the number of chill hours required for them to reliably fruit.
Sarah Beck: It's interesting because at Pacific Horticulture, we've been having this conversation about the newly released USDA zones.
I think for a lot of us in the Pacific region, we're pretty much uninterested in the first freeze or the last frost. The freezing temperature piece is not anywhere near as concerning as what you're mentioning, which is this chill hour concept.
Let me get back to this idea about considerations for a gardener, and this could also be the case for professionals, because I'm noticing also that more and more professional landscape architects and designers are needing to include some selections for food-producing plants within landscapes because people love that.
How do you go about even making a decision about what you might want to look for?
Rachel Spaeth: So your space considerations are probably first. What is the orientation of your space? What kind of space do you have? How big can something get in your particular space? What is your hardiness zone, because you are going to have to know about chill hours if it's something that is dependent on that for fruiting?
It's important to note if the plant is going to be deciduous or evergreen. So how much maintenance is it going to be down the road? It is going to provide an ecosystem service, which is going to be food for you. But if it's food for you, it's food for wildlife in general, too.
We do have to make sure that sometimes people just really want a cherry, but if you're not going to get any cherries off of it, maybe you want something else instead.
Sarah Beck: Would that be like the case of you have a certain population of birds that are just really at the ready?
Rachel Spaeth: Yes, they're very hungry. Squirrels are huge. Rats are a big thing, especially in urban population centers. Deer, definitely, not just for them eating the fruits, but also whenever they're rutting their young antlers, for girdling trees and things like that. Gophers can be a major killer of a fruit tree because they love those delicious, tasty roots. Bears, if there are bears, that can be an issue, especially if you have peaches or apples. Raccoons, possums. It's the gamut. When you put food out there, the food is there, and yes, it's for you, but it's also going to be for anything else that finds that food available to them.
Sarah Beck: I don't know if you want to venture into this realm, but it is a fascinating question because we talk a lot about wanting to support food webs as we're gardening.
This is like the million-dollar question: is there a way to reconcile your desire to be supportive of your local ecosystem? We do love birds. We love all of the wildlife. Is there a way to make fruit tree selections and sort of reconcile or is there a compromise perhaps in terms of how we're selecting things?
Rachel Spaeth: With all of my fruit trees, I just automatically assume that at least 20 percent is going to be for wildlife. They're just going to get that much. So maybe I let a tree get extra tall, taller than I would really want it to be, because up there that's where birds and squirrels can go and where I can reach is where I'm going to get the fruit that I want.
I do silly things like save those plastic clamshells that your strawberries come in and then I clamshell in a couple of fruits on my branch. It just clips right on your branch then, so those are my fruits.
Sarah Beck: And then you can shop for them like you're at the store.
Rachel Spaeth: Maybe you're planting some things that aren't as delicious or attractive to wildlife. I know that the serviceberries are one that’s a native plant, and it's not as much on the radar for a lot of birds. Like you'll have to net your blueberries, so they won't eat the blueberries. I don't know if they just don't see it or it's not in their realm, but I seem to get a lot more serviceberries than I get blueberries.
The bush is very disease resistant. It's deciduous. So that's a thing that you have to deal with in your landscape. But I get a lot of fruit off of those, instead of blueberries. It doesn't have the soil requirements of blueberries. And so I found that it's a good replacement where I'm getting a lot of the fruit and it's providing the services that I wanted it to.
Sarah Beck: Can you share a little bit about some of the interesting flavors and some of the varieties that you have gotten excited about? Your brain is probably like such a vast library of these.
Rachel Spaeth: What got me into the rabbit hole of Prunus in general were the Burbank creations because I was the garden curator at the Luther Burbank Home and Gardens for 15 years. And he revolutionized the human perception for what a plum could be by doing all of these interspecific breedings and things like that.
So he introduced about 250 cultivars of plums and I just started collecting all of those and then I would just taste my way through all of those. Some of them are popular varieties that people still know and can get at stores.
So things like Beauty (Prunus salicina x 'Beauty'), that's a very early plum that you can find sometimes. Santa Rosa (P. salicina x ‘Santa Rosa’) is probably the most popular one that he invented. Shiro (P. salicina x ‘Shiro’) is one that people can find sometimes. It's a pointy-bottomed, round golden plum that's very good.
The really fancy one, actually, is Improved French (P. domestica ‘French Improved’), which is a prune and comprises the vast majority of the prune industry still today, a hundred years after he bred it. It's the prune that's the go-to prune.
Prunes are a hard market to be in because there's a strong market preference for a prune that on the outside is dark skinned, green on the inside, and has a particular flavor profile that people have come to associate with prune. And so it's very challenging for breeders.
There's another reason, too. They're hexaploid, which means it's really hard to breed. They've got six copies of DNA instead of like the two that you and I have. So that makes it a little bit tricky, too. But just even when you do breed something new and novel, getting the market to accept that new and novel thing can be very challenging.
Sarah Beck: I'm just trying to wrap my mind around the fact that, that a prune is more genetically complex than I am.
Rachel Spaeth: Oh, so much more complex. Plants are weird. Plants are fantastic.
So what I'm looking for in a plum, particularly, is I want something that has a nice sharp tart skin for my initial bite, and then I want it to have melting flesh. I want it to have a little firmness to it, I don't want it to just be mush when I eat it.
A little bit of an acid level in there. I like interesting flavors in mine.
There's one plum in particular that I'm thinking about that Burbank bred, that you can't really find most places. It's called Sultan (Prunus x ‘Sultan’) On the inside, it is red, red, red, bright, bright red on the inside. And when you taste this plum, it has hints of like cinnamon and cardamom to it.
It's a very, very interesting tasting plum, but there's like a five-to-eight-day, maybe, ripening period for this, and once the birds figure out that it's ready, they're all there.
Sarah Beck: It's all at once.
Rachel Spaeth: All at once. It bruises very easily and so it's one that it's great to have in your yard or even just a branch on a tree. But commercially you're probably not going to see it in the store. You might not even see it in a farmer's market.
Sarah Beck: You brought up something fascinating because I think for someone who is a home grower, the rate at which the ripening is happening is going to have a big impact on you.
As you're looking to make a purchase, is that something that is readily knowable?
Rachel Spaeth: It depends on the marketing that the tree company is putting out. Dave Wilson Nursery is a huge nursery, and they come forth with a lot of information about their particular plants. The ripening period is going to be dependent on not necessarily just your hardiness zone, but also your microclimate and even your nanoclimate.
By nanoclimate, I mean the specific spot in your yard. Is it right next to the front of your house? Is it really close to your driveway? Is it on a slope? Does it get early morning sun? Does it get late afternoon sun? Those are all parts of nanoclimate that are just specific to your yard and your space.
Sarah Beck: I don't think that gardeners find this surprising. I think everyone who has experienced a period of seasons, and certainly people who have been gardening in the same plot for many years.
Rachel Spaeth: I don't have a lot of space in my home yard, but I want to have a long season of things. And so that's why grafting is so important for me, because I can take one apple tree that I have that's a single straight stalk, get a semi-dwarfing root stalk, so something that's not going to be a full-size, 25-foot tree, I'm going to keep it at about 15 feet.
Every single branch that I have, I'm going to graft a new cultivar onto. So that I get from early-, mid-, late- and extremely late-ripening, a long, long season, I'm going to get a little overlap in bloom period with that. So that means I'm going to get adequate pollination from things. And I'm going to be able to enjoy a little bit of fresh fruit for a very long period of time.
I can get apples from just this one tree from like the middle of July all the way through November. It’s not a lot of any of those particular things. I’m not going to be canning bushels of applesauce because that's not my particular goal, but I am going to be able to enjoy fruit for a long period of time.
Sarah Beck: Our guest Dave Benscoter actually was saying you could go on YouTube and see some pretty good demonstrations of how to do this grafting. Are you encouraging folks?
Rachel Spaeth: Oh, absolutely. It requires a lot of practice. It requires some patience, and it requires some persistence.
One of the things that I tell people is if they've been practicing a lot, and it still doesn't seem like it's working for them, maybe they need to pick a different tool. There's a lot of different shapes and styles of grafting knives. I know some people who their favorite tool to use is a utility knife, like a box cutter. I know some people who work in the medical profession and so a scalpel is what they are most comfortable with in their hand and so that's what they use for grafting, and it works just fine.
There's so many different ways to do it that it's really important to just keep trying. And if people want one that's an easy success to start off with, I always recommend that they start with apple. Apple is very, very forgiving. You can have as many cultivars of apples as you can collect all on one tree. so you're saving space and you're just putting them all on there.
The tree that I have with the most grafts on it right now, I have a seven-foot apple tree that has 52 different cultivars of apples on it.
Sarah Beck: No way! So how are you keeping track of what you've got there?
Do you have like little dangling labels from every section?
Rachel Spaeth: If I had gone into it with a lot more forethought, I probably would have grafted green apples on this side and russeted apples on this side and yellow and red and had waves of things, but I was a lot more haphazard than that with mine.
And I did use metal tags for mine. You can get the little aluminum tags that you buy, or I have people that just cut aluminum cans with tin snips and make their own, or they'll go to the dump and they'll get aluminum blinds and they just cut strips into those and they use a little etcher and etch them.
So I hung all these wonderful metal tags on this tree, and then promptly the squirrels started to take them to woo their concubines. Squirrels and crows. They're like, “Hey, look, I got this shiny thing. Check this out.”
I have actually lost a lot of the tags on my 52-in-1 apple tree.
Sarah Beck: So only the squirrels know what varieties you actually have.
This is a really fun, like do-it-yourself angle. How do you begin looking at making a simple start of this process?
Rachel Spaeth: The two things that I think about most whenever I'm looking for a rootstock to start from, first, is how big do you want this plant to get with and how much maintenance do you want to have to put into it?
If you have a big space and you don't mind it turning into a big tree, standard rootstocks, that’s what they just call one that's going to grow to a regular height, are great. Most of them that they have commercially available are good for pathogen- and disease-resistance and it's going to get to be a big tree and you're going to share with the wildlife and everybody's going to be happy.
If you don't have a lot of space, then there are two other options. There's semidwarf and dwarfing. Semidwarf is going to be about half to three quarters of the size of a standard tree. And dwarfing are going to be considerably smaller than that.
With dwarfing rootstocks, it's great because they'll stay small, but you do also have to be very careful with your weight load that you're balancing on the top of your tree. If you have too big of a fruit set, you might exacerbate the amount of capacity that those roots can hold.
So then the second thing that I would think about is your soil type. if you don't know what your soil type is, you can go to the Web Soil Survey. Figuring out how much clay you have, how deep that clay is, what your soil type is, if it's sandy, what your drainage is like, those can be factors for whether or not a plant will tolerate your particular conditions.
Yeah, the next thing is probably use. What are you going to use? What are you going to enjoy? Are you going to enjoy 500 lemons? Maybe your neighbors will also enjoy 500 lemons. That's totally a possibility.
If you are like a commercial landscaper and you want to, let's say, put in a school garden. You're very excited about the school has a new garden. They got a new gardener project. It's going to be awesome. Make sure that the fruit is going to ripen when there are kids there.
Kiwi is another one. People don't think about kiwi as an incredibly long season. Our kiwi ripens December, January. If you are gone December, January, it's just food for rats and squirrels and birds and whatever else wants to enjoy your kiwi.
Sarah Beck: Fruit is a responsibility. It is not just a pleasure.
Rachel Spaeth: It's a long-term commitment.
Sarah Beck: We recently had a great episode where we talked about plant pests and pathogens and Tyler Hale told us a lot of the work that you can do here is up front in making good climate-appropriate selections of your plants, making sure your plants are where they belong. Very healthy, happy plants are much more resistant to pests and pathogens, to diseases.
Are there things that people in the Pacific region should be thinking about or specifically avoiding in that instance?
Rachel Spaeth: So sometimes our home gardens end up being pockets for diseases that we hold on to that can spread to commercial entities. And we do a lot of sharing of those sorts of things just by being gardeners and moving things around.
A couple that are really important to note. One is black knot fungus (Dibotryon morbosum), which affects cherries in particular. So people can get black knot fungus, it's native to the United States. It evolved with our native hardwood cherries on the East Coast. And so it's pretty ubiquitous in the soil.
I would say that cherry is very challenging to cultivate as a home grower, although up in the Pacific Northwest, there's tons of cherries up there, right, further north than we are here in California. But that's something to be aware of, is if that soil pathogen is in your area, then making sure that your rootstock is resistant to that is going to be very, very important.
If you have spots that are water logging. In the wintertime, when you get rain, it sits in pools. There are resistant rootstocks to those sorts of things for peaches, almonds, nectarines, all of that stuff. But you want to make sure that you're looking for that particular rootstock.
For apples, the big one is fire blight (Erwinia amylovora), and for pears, especially, as well. A lot of that is environmentally dependent. That's not a rootstock-resistant thing. It's a cultivar-resistant thing because it does get moved around by bees through pollen. We're not going to spray for bees. Nobody wants to spray for bees. That's not a thing that we do. So just being aware of maybe having a cultivar that blooms a little bit later in the season when the bees are more active and we've got warmer temperatures and maybe the pathogen’s not going to be as active is going to be important.
So the black knot fungus is one for cherry and then the other one is, oh, it's Pseudomonas syringae bacterial canker is the common name on it.
That's the other big one that is the killer of cherries and a lot of other stone fruits in our area. So protecting your plants when they're young can be very important too. So from sunburn or from damage. So painting your trunks when the trees are little or using that spiral tree wrap stuff so that things aren't damaging the bark, just setting yourself up for success.
Sarah Beck: It's like putting on sunscreen on your baby trees, like you do your baby children.
Rachel Spaeth: On your baby trees, exactly.
Sarah Beck: Especially when we’re limited on space, this idea of adding in a fruit tree is kind of a big decision and yet it's a really interesting one. I'm curious what your thoughts are on just how this idea of the fruit tree, especially the noncommercial variety relationship, and getting to know this plant diversity that is available to us through adopting a fruit tree into your life.
It's a way of expanding our relationship as gardeners and it's got a lot of depth. I think that's the part that really resonates with me—just the idea of our getting to know a plant story.
Adriana López-Villalobos: Yeah, just understanding like, is what I'm planting something that evolved in our continent, in our region, or is it a product of migration and movement, which is often the case, right? And what was the history of that plant? Why did it make it here? Growing fruit trees is like a very close-to-home thing.
And we're saying like fruit trees, but it could be like shrubs and could be berries could be. Right, right, right. Like some solanas have delicious, sweet fruits and yet we don't think about that as a fruit, even though it is a fruit, right? And it had that like component of connection to culture, to human history,
The berries here in Canada, they are so important for Indigenous peoples. They are fruits. These are foods that were carried for long journeys. They would just snack on them or harvest them for specific purposes.
Sarah Beck: It's super cool to think about. Our relationship to fruit is fascinating. Just even thinking about diets before people had really modern diets, like, the sweetness of fruit must have just really stood out on the palate, right? This idea of something sweet would have been just really intense.
Adriana, is there not a fruit festival, an apple festival that happens right at the UBC Botanic Garden every year?
Adriana López-Villalobos: Yeah, it's a very popular festival called the Apple Fest and it occurs in October and the garden, it's run by volunteers and they organize this annual event. And buy all the apples from growers from the entire province and sell them at this festival.
Sarah Beck: Most of us in the Pacific region are probably relatively near to a rare fruit group or society, and so it's possible any one of us could go to our local farmer's market or do a little research and see who in the area is propagating some of these rare varieties, noncommercial fruit varieties.
Something that I think is really worth noting, because it relates to a lot of conversations we've had recently about the different climatic zones and thinking about growing conditions changing looking at chill hours is going to kind of become more and more important.
Adriana López-Villalobos: She mentioned chilling hours and the chilling process. It's huge already and it's going to be really important as the climate warms more because not a lot of plants are going to have enough chilling hours.
Sarah Beck: That's really something that is very particular to the Pacific region, too. Certainly, there are other places that that is a concern, but I would say that the Pacific region should be acutely aware of chilling versus freezing in terms of some of these new statistical findings and really looking at what those requirements are. Because if we're making decisions about a long-term relationship with a fruit tree, making sure that we have the kinds of conditions that that tree is going to thrive in and really looking towards these future changes.
I think it's fascinating to look at those who are bringing plants north in some cases. We're going to over the next few years be really interested to watch as Baja California, Southern California, other places as well, the Southwest, become sources for a lot of the plant stock that we may be cultivating.
Adriana López-Villalobos: Yeah, but those subtle changes might have a huge effect in plants. We might not experience that very strongly, but native plants having less time in that period, it's going to impact a lot the phenology of different species.
Sarah Beck: Something to note is that we really like sharing resources and if you're excited about this story, and you want to follow up and find some sources, either for doing your own grafting or tree purchasing or if you just want to learn a little bit more about the work of the USDA, we have plenty of resources and links on our transcript page, which can be found at pacifichorticulture.org under Garden Futurist.
Resources
North American Fruit Explorers (NAFEX)
California Rare Fruit Growers
USDA Web Soil Survey
Germplasm Resource Information Network (GRIN)
UBC Apple Festival
For sourcing, Dr. Rachel Spaeth recommended Raintree Nursery, Trees of Antiquity, Dave Wilson Nursery, and Stark Bro’s Nurseries & Orchards in Missouri, with a caveat.
“Try to stick to companies that are in our states because they are going to be the ones that are distributing things that are good for your hardiness zone.” Dr. Spaeth explained. “If you're ordering things from Minnesota or somewhere in Florida, the East Coast, they might have some of the plants that you really want, but some of them might not have the same chill hours requirement.”
