Under threat of impending snowstorm yesterday, I drove out to the middle of nowhere to attend the K-State Extension seminar on tomato grafting. And, boy, am I glad that I did. I had read about grafting heirloom tomatoes onto more disease-resist hybrid rootstocks last year (and
posted about it and some great resources on graftng here).
What I'm really excited about is how easy grafting is. After watching a demonstration, it took me about 2 minutes to graft 6 plants. I'm so excited about this - I came home with 6 Cherokee Purple heirlooms grafted onto Maxifort rootstock that I get to baby for the next 10 days. What does that mean? Read on, my friend....
Tomato Diseases
Tomatoes in general are susceptible to a variety of diseases: fusarium wilt, verticillium wilt, blight to name a few. In sandy soil, you can also add in soil nematodes that attack the roots. Here in Missouri and Kansas, fusarium and verticillium are the most common and we don't need to worry about bacterial wilt. Verticillium is a cool weather fungal pathogen and the bad news is that, once you have it, it can live in the soil for anywhere from 5 to years!
**By the way, a good way to tell if you have verticillium wilt is a V-shaped lesion (or lesions) on the tomato leaves.
The best way to fight these diseases and pests but still have your yummy, non-GMO tomatoes is to graft an heirloom onto a hybrid,disease resistant rootstock.
Now here's something I learned in the class and haven't found anywhere else. When you buy hybrid tomatoes or rootstock, they normally indicate their resistance levels with a combination of the following codes:
Notice that there are multiple races (or variants) or fusarium wilt listed. There are also now 2 races of verticillium wilt. If you see "V listed as a disease resistane, it is Race 1 only.
Currently, there are NO known tomato varieties that are resistant to Race 2! So, if you get that in your garden, you are screwed with a capital S.
Here's a great chart from
sare.org that shows the resistance of the rootstocks that are available.
Benefits of Grafting for Heirloom Growers
K-State has been performing research on various rootstocks, growing environments and grafting techniques in an effort to identify the best combinations for optimal growing here in the Midwest. So far, they are seeing a 43 to 52% increase in tomato yields when using grafting (versus standard planting methods). It may not seem so at first, though, as grafted tomatoes usually produce less on the first harvest but then produce more than a non-standard plant on successive harvests. They also tend to produce longer during the season.
In addition to a much bigger yield, you also get the following benefits with grafting:
- Disease an soil-bourne pathogen resistance
- Drought resistance (some rootstocks)
- Salt tolerance
- Higher fruit quality
- Bigger high tunnel production (bigger yield in smaller spaces)
That last one is perhaps the most important for someone like me as a backyard grower!
Buying RootStock or Grafted Vegetables
Determinate varieties are experts at turning grafts into fruit production - they're great at soaking up nutrients and pumping them up the stalk. Cherokee Purple heirlooms are a perfect partner, as they are able to take the increased nutrient and water flow and, since they're also less vegatative, they are able to produce higher yields of tomatoes. Here's a
There are lots of rootstock varieties out there but K-State is focusing on the most popular varieties - Maxifort, Beaufort, Arnold and BHN-589. According to their research so far, Maxifort has proven to provide the best yield so far. You can buy Maxifort and other rootstock varieties at
Johnny's Seeds, as well as already-grafted tomato plants and other veggies at
Territorial Seeds. You might check your local nurseries also, as many of them are starting to sell grafted plants.
Rootstocks are expensive! You'll probably pay somewhere from 40 cents to $1.70 per seed, depending on the variety. (50 Maxifort seeds are $27.00 at Johnny's.) That's because they are a very specialized hybrid tomato variety and they are often very hard to produce and don't germinate well. If you're considering growing your own rootstock, that's something to consider.
Tips for the Grafting Process
The process for grafting is fairly simple:
1. The rootstock and scion (the plant to be grafted onto the rootstock) must be the same size. Ideally, they will have 2to 4 leaves and the stems will be between 1.5 to 2.0 mm in diameter. You have to keep an eye on the plants, as tomatoes grow extremely fast. There may be only a 24 hour window when they are this size! If you need to slow a plant down to get the sizes right before grafting, put it in a cool place.
2. Always graft inside where you can control the environment - especially the temperature. The best time to graft is early in the morning or oafter dark, when there is little water stress on the plants. Placing the plants in a shaded area or 2 to 4 hours before grafting will also reduce stress.
3. Make sure you disinfect your tools,grafting clips, and hands (or wear gloves - it will keep potting soil out of your fingernails). Rubbing alcohol works fine for this. Also, as your grafting, clean your knife or razor blade every 20 plants.
4. Cut the rootstock right below the cotyledons (first set of 2 leaves) at a 45 degree angle.
5. Slide the grafting lip onto the tip of the rootstock. The clips that we used in class are made of plastic and are designed so that you can pinch them open (see below). As the plant grows, the clips fall off. There are also spring-loaded clips but, if you use those, make sure you pull them off after the graft has healed.
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| Flexible grafting clips. These fall off as the tomato heals and grows! |
6. Cut the scion below the cotyledons, but leave enough stem so that the leaves aren't stuck in the clip. You'll need to pay attention to the size of the stem here - if you have to go higher or lower to match up with the size of the rootstock, that's fine. You can also cut off the cotyledon leaves if needed.
7. Slide the scion into the top of the clip and push gently until the two stems are seated against each other.
8. The plants will appear to wilt fairly soon after you graft them. Place the plants in a healing chamber for 7 to 10 days (or until they no longer show signs of stress). For the first 2 days, it should have no light and a constant temperature of 72to 75 degrees. I covered mine with a plastic dome to maintain the humidity and placed them in closet. You could also cover them with a shade cloth or even use a walk-in cooler (if you have one!) Ideally, humidity should be around a steady 85 to 90%. Keep a close eye on their environment. If they appear to be perking up on Day 3, open a hole in their covering (or expose them to a little more light) and then increase light more and more until they don't appear to be stressed any long and the graft is healed.
You will probably see tiny little roots growing from the graft as the vascular tissue heals together. This is normal and they will fall off as the plant grows.
9. Harden and dampen off the plants are you would normally.
10. When planting: I usually plant my tomato plants deeper, to encourage rooting.
You do NOT want to do this with a grafted plant. The graft needs to above the soil level or the scion (the top plant) will root and it will destroy all the benefits of having the graft there.
Importance of Pruning Grafted Plants
As with standard tomatoes, it's a good idea to prune your plants - especially if you are growing a type that is very vegetative (produces lots of leaves or stems). By removing the leaves, you force the plant to redirect its energy to producing fruit rather than vegetation.
Want to Learn More?
I highly recommend this
video from Extension.org and this PDF from Johnny's Seeds. Or just Google "tomato grafting" and find a treasure of information!
I hope you found this information useful. I'll be posting in the next couple of days about how my little graftees are doing in their infirmary. Cross your fingers for me that I don't kill the little guys!
