The Ruminant: Audio Candy for Farmers, Gardeners and Food Lovers - e.09: Grafting Tomatoes with Carol Miles

Episode Date: October 29, 2015

This episode I have a really helpful conversation with WSU Veggie Extension Specialist Carol Miles about grafting tomatoes, eggplants, and other veggies. We cover definitions, the reasons for doing it, and a few techniques. Thanks to Carol for making the time, and for providing links to her very useful publications on the subject, which you'll find if you scroll down on the page the link sends you to.

Hey everyone, I am doing some traveling this week so I am putting up this rerun of an episode that hadn't yet made it onto the new podcast feed. And just before we get to that, I just want to quickly remind everyone that I'm still very interested in hearing from you if you want to talk about some of the challenges of raising kids while farming. I'm also working on an episode that's coming out soon about winter work and what farmers do to make ends meet if they're not farming during the winter. So if you want to email me about either of those two things so that I can call you back and do a quick

interview, editor at theruminant.ca. You can also send me a text if you like, 250-767-6636. Okay, talk to you soon soon everybody. Enjoy the episode. This is the Ruminant Podcast. I'm Jordan Marr. TheRuminant.ca is a website dedicated to sharing good ideas for farmers and gardeners. Most of the content on the site involves me posting other people's photos of their innovative farming tools, techniques, and ideas. I'd love to have a contribution from you, so please take some photos of what you're doing and send them to me at editor at theruminant.ca. Okay, let's do a podcast.

This episode, I speak with Carol Miles of Washington State University about grafting. Carol is a researcher and extension agent down there, and she graciously offered to talk to me about grafting vegetables like tomato plants and eggplants. I won't say much more. We may as well just get straight into the episode. I learned a lot, and I hope you do too. So I will talk to you again at the other end. Carol Miles, thanks very much for coming on the Ruminant Podcast. Oh, my pleasure. Thanks for calling.

Carol, before we get started talking about our topic today, grafting of tomatoes and eggplants, perhaps you could just tell us a little bit about what you do at Washington State University and what you're currently working on. I'm a research scientist at Washington State University. I'm a faculty member in the Department of Horticulture, and I'm the state vegetable specialist. I'm located in northwest Washington, so most of the crops and the issues I work on

are issues that are really relevant to the northwest section of Washington, but I also work statewide. What have you been focusing on most recently, Carol? One of the projects I've been focusing on for the last three years is grafting of vegetables for disease management purposes. I work with many small scale growers, growers that have maybe an acre or maybe five acres. A lot of growers are organic or certified organic. A lot of them have limited space and so really are trying to grow many different crops in a very small area. The rotation can be a challenge. And so we've been looking for disease management strategies that fit for those small scale growers

that grow many crops, 30 crops or more, and how can they grow crops that otherwise can be challenging in this environment? Okay, well, that's actually perfect, Carol, because I kind of fit all of those different descriptors. Vanessa and I are organic. We're very limited in space. We grow on 1.5 acres, so it's a fairly small area, and we have a lot of crops that we grow, so each individual crop doesn't get all that much space in the garden.

Now, so I've been interested in grafting for a while now, but always kind of intimidated about it in terms of how to get started. Is that a common problem? Do you meet other growers who are a little bit scared of going about using grafting? Yes, I think most people who are not familiar with grafting think it's a very difficult, complicated process, whereas in fact it's actually very simple and very easy to do. And I just wanted to set the stage a little bit more for why we started investigating grafting.

We're working with growers to manage a disease that tends to be a little bit ubiquitous. It's verticillium wilt. It tends to have a crop host range of maybe 60 crops. It lasts in the soil for up to 10 years. And so managing verticillium wilt in the cropping systems that I work in, again, those small, very diverse cropping systems where growers tend to be organic, they don't have chemical control options, has been a huge challenge. And so grafting was the one method that we came across that appeared to be very effective and was suitable for organic growers. So when we started grafting three years ago, it really only took us 10, 12 plants, years ago, really only took us 10, 12 plants, grafting 10 or 12 plants to really learn how to do it and how to do it well.

So it's a very simple process. And I think for growers that feel intimidated by it, I think you just have to try it and you'll soon see how easy it is. Okay. Well, that's really encouraging to hear. So before we get too far into the nitty gritty, maybe you could just define grafting for those who may not have even really heard of it and also explain why it's used. You already mentioned one reason to control this wilt, but more in general terms I guess.

So what is grafting and why should a grower consider using grafting? So grafting, the simple definition of grafting is cutting and attaching one plant material to another. In vegetable grafting, for the purposes that we use it, so the primary reason that growers would graft vegetable crops is usually for disease control. So usually you have a disease in your soil, so it's going to be a soil-borne disease, not a foliar disease. But you have a soil-borne disease and you find a resistant rootstock and then you graft the top material, also called the scion, that you would grow and harvest. You graft that to that resistant rootstock. So soil-borne diseases are a primary reason why growers graft. Another reason would be high salt concentrations.

So looking at the Mediterranean region, Africa, other parts of the world where they have very high salt concentrations because of their soil and irrigation practices, fertilizer practices, you can graft onto rootstocks that are salt-tolerant. fertilizer practices, you can graft onto rootstocks that are salt tolerant. That's a very common practice in Israel, for example, where they have very high salt levels in their soils. So some of the key points are you need a rootstock that will be resistant to the problem that you're trying to manage. So that's one key point. And then another key point is that you don't allow the top material or the scion material to come into contact with the soil because otherwise, you know, the whole point of grafting would be invalidated.

So those are some key points in using grafting to manage a problem. And, again, when looking at diseases, grafting is used to manage soil-borne diseases, not foliar diseases, because a foliar disease will just kind of, you know, blow into your field and it's going to attack the leafy material that it comes into contact with. So grafting doesn't help prevent those types of problems. So Carol, I've heard that in some cases you can graft an heirloom variety onto a hardier rootstock of, you know, a variety that is known to perform a lot better, and then have better results with your yields or your quality with your heirloom variety. Is that true?

Well, I've certainly heard those reports. It's not something that we've, again, I always am a little cautious. It's not something that we have done here in my program. I always am a little cautious. It's not something that we have done here in my program, but I've certainly heard the reports that grafting heirloom varieties onto vigorous rootstocks can improve yield. But more importantly, what it does is it improves marketable yield. So some heirloom varieties, and we work with Cherokee Purple and Brandywine. Those are the two we work with in our program.

And they're kind of notorious for having misshapen fruit, cracked fruit, and if you were marketing those fruit, you know, it can be a little bit marginal as to whether or not, you know, people would actually want to purchase them. If you're growing them for home consumption, then you're probably not overly worried about the shape and the cracking and that, but I've certainly heard from others working on grafting heirloom varieties. Most of that work in the United States is done in Southeast United States, and they have found there that they have been able to increase their marketable yield by grafting because the fruit tend to be not quite so misshapen, and they don't have as much cracking in the fruit. So they get a higher marketable yield and they also get a

higher total yield. So that appears to be the case, but again, it's not work that we've done in my program. Okay, but certainly something that I'm interested in experimenting with myself to see if it proves to be true. And I think that's a very good reason for trying grafting and again, setting up a little experiment where you have grafted plants of a variety. You know, maybe it's Cherokee purple or whatever your favorite variety is. And side by side, you have the non-grafted plants of exactly the same variety. It's really important to treat them the same so you're not, you know, giving one more fertilizer or the other more water. You've got to treat them exactly the same so that you can really see,

is there an advantage to grafting? And I think it's a great thing to do for yourself, and I think it's a good reason to experiment with grafting and see if you get a benefit like that. I guess what I can say is that we did some work this year with the Master Gardener Program here in Washington State where we provided grafted and non-grafted plants to groups around the state, so eastern Washington, which is more similar to you there in the Okanagan, for example, as well

as here in western Washington. And they planted out the grafted tomatoes and the non-grafted tomatoes, and all of them reported that they felt that they saw greater yields, greater plant health, greater vigor with their grafted plants as compared to the non-grafted plants. So that's some observational information that appears to indicate that grafting can help you, even if you don't think or know that you have a specific problem that you're trying to manage. Okay. Well, that was sufficiently cautionary that I don't think you'll get people storming your office with pitchforks or anything if they don't see really good results. So okay, so first I guess before we get into just a few comments about how to graft, how do you, where do you get the good rootstock or how do you know, like where do you, how

do you select good rootstock? Well, the rootstock question is a little bit simplistic in the sense that you might have to just grow what you can get. So getting rootstock in North America is still a little bit difficult. We do have a list on our website. So on my Washington State University vegetable website, we have a list of rootstocks for the various crops we've worked with. We've worked with tomatoes, eggplant, and watermelon. So we try to keep that. We just update that list once a year, and so we'll be updating it again in January for 2013.

So basically you're going to have to do a search. I'm going to say an Internet search for a root stock for the crop that you're interested in. And probably you're going to grow something that you can get and you're going to find that it's affordable. Many root stocks can be quite expensive because they're just not available in large numbers as of this time in North America. This is still a relatively new process, a new cropping technique. And so it's just, it can be difficult to find rootstocks and they can still be a little bit expensive at this time. Okay. Well, Carol, what about this? I hope I'm not displaying too much ignorance here. If in my garden, I've witnessed over a few years that a certain tomato variety always does really well and has really robust, healthy plants.

And another variety whose fruit I really want to have tends not to do as well. Would it be worth it to try grafting the scion of the fruit that I'm trying to get onto some rootstock of this other variety that always performs well in the garden and has healthy, robust plants? Would that be possibly worth trying out? Yeah, absolutely. I always encourage people to try, you know, their own experiments exactly as you've described. So, for example, this year, in 2012, we had a grower near Seattle, just outside of Seattle, a very large tomato grower, an organic grower. And he told me that, you know, he was really interested in Matt's wild cherry. Matt's wild cherry tends to be cold tolerant. So it always grows later in the season than other varieties. And it also tends to have late blight resistance. And late blight is

the primary disease we have here in the western part of Washington state. And so he asked us if we could graft, use the Matz Wild Cherry as a rootstock and graft some other varieties onto it, some heirloom varieties that tend to be a little bit more problematic. And so we did that this year, and what we learned was a couple of things. So certainly, you know, anybody is free and welcome to try to graft any top variety to any rootstock variety. The key to grafting is you're going to have to match the stem diameters. When you go to graft the two plants together, the stem diameters need to be approximately the same size. And so that's really the trick in grafting for successful grafting. So what we found with Matt's wild cherry, for example,

Matt's wild cherry is a cherry tomato, and the stems, it grows very slowly, and the stem diameter is quite small. So we actually had to grow that plant out for almost eight weeks, two months before we could graft onto it, whereas normally we graft at three weeks. So that's the only caution I would say is that you can graft any material any tomato onto any other

tomato you're just going to have to match the stem size at the time of grafting so you may have to adjust your planting dates to to get that to work okay all right so so let's assume then that I'm going to take one variety that I typically grow that always has really healthy, robust plants and take that rootstock and onto it put a scion of another variety that I've been struggling to have robust, healthy plants. And I'm going to just see if that works. I've played around with some timing. I'm going to just see if that works. I've played around

with some timing. I've planted at different times and now I've got a couple of seedlings of each type that are of similar diameter. Can you take it from there what I have to do next? Yeah, so once you're ready to cut and place the two plants together, so if you're working with tomato, that's just tomato as the grafting sample here, you would cut the rootstock below the cotyledons. And the reason you would do that is because if you cut the rootstock above the cotyledons, the rootstock will grow shoots, and those shoots will overpower your scion or your top variety. So with tomatoes, and I should start off by saying

tomatoes are probably the easiest crop to graft. They tend to be very, very forgiving. The grafting tends to take very easily. So it's really an ideal plant to start with. So starting with the rootstock, you cut the stem at a 45-degree angle below the cotyledon, and then you take your scion and you, matching stem diameter, so again the stem diameter of your scion and the stem diameter of your rootstock need to be essentially the same, and you would cut the scion rootstock below the cotyledons at the 45 degree angle and then you you put the two together and you use a grafting clip to clip them and hold them in place so if i got that right you you you cut you cut both below the cotyledons then

no oh sorry okay i apologize yes correct you cut both below the cotyledons, yes. Sorry. Okay. And what's a cotyledon for those who don't know what we're talking about? Cotyledons are the storage leaves that emerge when your seed germinates. It's the first leafy type structures that you see that emerge from the seedling. And then from that, then you get your first true leaves. And the cotyledons tend to be relatively thick, not serrated. And tomatoes, your true leaves are going to be serrated and relatively thin.

Okay. So you've taken, I think, I'm actually remembering from the document you've published, which we'll talk about at the end, you're perhaps using a razor blade that's been sterilized and you do matching 45 degree cuts below the cotyledons so that you can pair them together? That's correct. And in terms of the razor blade, we use a Wilson double-edged blade. We snap it in half. And so we use one half of a blade at a time. And the reason we use that blade, and I should say that probably most people in the world that graft use that blade, and I should say that probably most people in the world that graft use that blade,

is because it's very thin, and so it makes a very clean cut, and we can graft 70, 100 plants with one half of a blade before we throw that blade away and we start new. When we start with a fresh blade, it's generally sterilized, so the sterilization process is not that critical. Just to be aware that it's not necessary to be in a highly sanitized, clean, sterile environment when you graft. We graft in the greenhouse on a bench. Okay. Putting that in perspective.

Okay. And then so you've made your cuts, and then it's just a matter of taking the scion and placing it on the rootstock, and then I assume you have to bind the two with something. That's right. We use a grafting clip, and so grafting clips are, again, what most people use to join the two plants together, to hold them together. Grafting clips are, again, available from many sources, nurseries. We did just update our web page on sources of grafting clips for the United States, and I'm assuming that in Canada you can also access them from those sources as well as perhaps some others. And a grafting clip is sold in terms of diameter,

and so a tomato tends to be the smallest diameter plant that's grafted so you'd just be looking for a grafting clip of a relatively small size usually the the company that sells grafting clips tells you you know use for tomatoes okay all right so so we've gotten that far and and probably anyone who follows up and tries this is going to be using the document that uh that you've that you've published which which i'll have um i'll provide a link for on on And probably anyone who follows up and tries this is going to be using the document that you've published, which I'll provide a link for on our website. So then from there, you're ready to allow this new plant to recover and that's going

to happen in what's called a hybrid, sorry, what's the chamber called? We call it a healing chamber. Thank you. A healing chamber. Is that right? Is that the next step? Yeah. So what we do is we mist the plant at that point. So we just have a spray bottle, just a very average type of spray bottle that you'd use in the house. And we mist the plant with water, just tap water. And then we put it into what's called a healing chamber. The healing chamber is just a closed environment.

You can just as easily use a plastic tub. So working with people who are grafting just a handful of plants, up to 20 plants, it's really easy just to use a plastic tub with a lid. And the idea is to keep the humidity as close to 100% as possible and to keep the plants relatively cool, warm on the cool, warm side. So Fahrenheit, that would be about 75 degrees Fahrenheit. Celsius, that'd be about 20, 25 degrees Celsius. And we keep them in that closed environment for three days. And then at that point, and we put the lid on that box, but we don't seal it because it's important to allow oxygen in, but just place the lid loosely on the top of the box and the plants

are inside. When you finish grafting, you mist the plant. Before you put the plant inside the box, you just take a hose or your mist bottle and you mist all the sides of the box so that there's plenty of moisture in the box. Perhaps a thin coating of water on the bottom. Place your plants in the box. Place the lid over the box. Don't close it tightly, but just place it on top. And place it in a warm, coolish warm area. Again, target temperature is about 75 degrees.

And keep it there for about three days. And at that point, take the top off and check your plants. They hopefully should look fine. They should look healthy and vibrant. Miss them again at that point in time. Maybe leave the box open for about 30 minutes. Put the top back on and then check them the next day. So it's a process of bringing them back to the greenhouse. It takes about one

week from the day of grafting to being able to put the plants, bring the plants completely out of the box and leave them on the greenhouse bench. Okay and you've got again, you've got a document, you've got a document that you've published with step-by-step instructions now, now, which I'll, I'll provide the link for. Now, the whole purpose is that if I understand it, the scion, the top half of the, of the plant, uh, is not, is not getting moisture, um, through the vascular system, uh, during this early process, right? So you're keeping the box really humid so that, that you can maintain as much moisture in the scion as possible. Is, right? So you're keeping the box really humid so that you can

maintain as much moisture in the scion as possible. Is that right? Yeah, that's correct. So when you you've cut the two plants, you've severed the tops and the bottoms off of each one and you place them together. And at that point, they are not joined. And so any water that the rootstock would be bringing up into the stem will not be passed into the scion material. It stops at the cut. It doesn't go upwards. So all the moisture that the scion material is getting, it's getting from the air. So that's what that 100% humidity does is it keeps that scion material moist and keeps it from wilting.

And the reason that we close the box, that we block off the sunlight, is to reduce or eliminate photosynthesis because photosynthesis utilizes water. So we want to minimize the water usage in the scion material for that healing process. So again, it takes about five days for the vascular tissue to be joined and for water to move up and down the stem again. So it's about a five-day process. And then it takes about seven days for the plant to really be healthy and be able to withstand the daily fluctuations of being in a regular environment. Okay. And if you can successfully get the plant to that point,

can you then just transplant it out into the garden or there are other considerations once you transplant well generally what we do is so again five to seven days after grafting we the plant is on the greenhouse bench we like to keep it in the greenhouse for three to five days just so it will stabilize and then we harden our plants off so I like to move them outside in a process that takes maybe three to five days depending on on how either cold or dry your environment is, so how much of a difference it would be for the plant. The greater the difference, the slower the hardening off process. So here in northwest Washington, where we have a relatively cool, humid growing environment,

three days of hardening off is sufficient to adjust the plant to the outside climate. And at that point on, then we transplant out. All right. And then once you transplant out, I would think you need to keep the scion at a certain height above the soil so that it doesn't root into the soil. Is that right? That's right. We try to keep the scion at a certain height above the soil so that it doesn't root into the soil, is that right? That's right. We try to keep the graft union, we try to keep that at least one inch, if not two inches,

above the soil level. Okay, because otherwise the scion could put out roots and then you've just got rootstock off that upper portion that you were trying to avoid in the first place, correct? That's correct. And tomatoes will send out adventitious roots. So tomatoes will send out roots at every node. They have the potential to send out roots. So if those nodes come into contact with the soil, they will simply root.

Right. And is there much, have you noticed, have you noticed like our plants usually at the joiner part of the two pieces, are they pretty strong in the field? Do they tend to want to break from wind or anything like that, or is it okay? So the grass union can be fragile for the first several weeks, so generally we recommend that you don't plant into a windy environment. So if you know you have high winds coming into your area, then we delay planting until those winds are done. If you live in an area that's always windy, then we just add a straw or a small stake,

a bamboo stake, as an added support to the plant at transplanting just to keep it attached. About two weeks after transplanting, the plant is as strong as it would have been without grafting. Right, okay. Well this, I mean, having read your documents and having just listened to you talk about this, it really doesn't seem, it seems like something that most gardeners and farmers can try and be successful with, with very very little uh... efforts in the end grafting tomatoes as i mentioned earlier is is actually very very simple they're incredibly forgiving they tend to heal together

very fast and very well so success rates are are really high with tomatoes we we had seven workshops here over twenty and in two thousand and twelve seven workshops of people coming through, gardeners for the most part, but also some growers and some nursery people who had never grafted before. And for the most part, every one of them had 75% success in their first attempt. So they grafted their plants.

We held them for them. We monitored them. And easily they had 75% success for each one of them. So the key to tomato grafting and grafting in general, especially for those people who are, I'm going to say, east of the mountains, so west of the mountains it tends to be pretty humid here, and so we have that relative humidity that really the plants need for survival. East of the mountains you tend to be a little bit drier, and so the have that relative humidity that that really the plants need for for survival east of the mountains you tend to be a little bit drier and so the key to success there is to make sure you

provide that humidity and those first couple of weeks after grafting okay and then i i suppose a good idea for anyone trying this for the first time is to sort of grow some sort of control like grow grow some of the plants that you're taking the science from just without grafting those science off growing and then growing them next to the grafted ones just to see the difference in performance just to confirm whether it was worth the effort exactly that's it that's exactly what i suggest people do so if you're going to graft an heirloom variety let let's just say Cherokee Purple, for example, you graft six plants and you don't graft six plants. And then you put those six grafted

plants and the six non-grafted plants together in the same area and you treat them the same. So they're getting the same fertilizer, same irrigation, everything is the same. And just take a look at them and see if you see a benefit to grafting. Okay. Well, Carol, this has been- And I just want to mention one more thing. I forgot to mention about the grafting clip in terms of removal. Okay.

So what do we need to know about the grafting clip? Yeah. So for tomatoes, the grafting clip that is used for tomatoes is a round silicon sheath that when you cut the rootstock, you slip the grafting clip over the rootstock, and then you slide the scion into the clip. So it's a sheath or a tube, a plastic tube. If you purchase those and they're sold to you as grafting clips, as the plant grows, the stem will expand and the clip will fall off.

So that's the thing you need to know is you don't have to remove those clips. They will actually just fall off naturally. However, if you make your own grafting clips, I've seen many people take tubing, you know, cut tubing, use straws and other various materials, which all can be used, but you're probably going to have to take those clips off. They probably won't fall off naturally. So just something to be aware of. The clip will fall off when the stem is large enough. You can remove the clip either before transplanting or after transplanting. It's really, really up to you. But probably you want to get that clip off about two weeks after transplanting because at that point, that plant is probably growing pretty well and those stems will be

expanding and you don't want the clip to constrict the stem growth. Okay, great. And then if you're using, if you're using the purchase clips and they fall off, can you reuse them? Yes, absolutely. We just sterilize them in a 10% bleach solution. So we just put them in a 10% bleach, swirl them around for one minute, take them out, rinse them off really well in tap water, let them air dry, and they're ready to go for the next round. Oh, perfect. Well, Carol, thanks very much for coming on the room and sharing your knowledge today. You're welcome. Thanks so much for having me. Okay, so that's it. It's over. I hope you enjoyed it.

I hope you have fun grafting all kinds of vegetables, tomatoes, eggplants, that sort of thing. Anyway, Carol made reference to some documents on grafting tomatoes and eggplant on the WSC website. I've read those documents. They're really helpful, really clear and succinct. So I recommend you check them out and I will put links up on the page for this episode on my website at theruminant.ca. Thanks everyone. Talk to you next time. you Today I learned I don't need anything to live on except for a little old you. I've met a whole army of weasels, a legion of leeches trying to give me the screw. But if we bury ourselves in the woods in the country, we're no closer, we never have have laundry we'll owe nothing to this world of thieves live life like it was meant to be i don't fret honey i've got a plan to make our final

escape all we'll need is each other a hundred dollars And maybe a roll of duct tape And we'll run right outside of the city's reaches We'll live off chestnuts, spring water and peaches We'll owe nothing to this world of thieves And live life like it was meant to be Because why would we live in a place that don't want us? A place that is trying to bleed us dry. We could be happy with life in the country.

With salt on our skin and the dirt on our hands. and the dirt on our hands I've been doing a lot of thinking some real soul searching and here's my final resolve I don't need a big old house or some fancy car to keep my love going strong so we'll run right out into the wilds and graces

We'll keep close quarters with gentle faces And live next door to the birds and the bees And live life like it was meant to be Bye.