I have mentioned before that my big garden experiment this year is grafting tomatoes. It is essentially the same thing that grape growers do. Some varieties of tomatoes have hardy rootstocks that promote vigorous growth, are more disease resistant, and can tolerate greater fluctuations in temperatures, while increasing yields 25% – 30%. Plus, it was something new to try. I am hoping for increased yield from our small garden and that the wild temperature fluctuations we have are better tolerated; 30+ degrees variance within a single day is common.
The rootstock I selected has a funny name, DRO138TX. It is supposed to encourage increased fruit production over foliage growth compared to more common rootstock varieties. My uncle is using Maxifort, so we might be able to compare progress over the season. Rootstock varieties do not produce tomatoes you would want to eat by themselves.
The basic procedure is to start the seeds of the rootstock variety and desired eating variety. The rootstock grows quicker than heirloom tomatoes so the heirlooms should be started a few days earlier. When they reach the appropriate size, about 10-12 days later for me, the tops of both the rootstock and heirloom are cut off with a very thin and sterile blade. The top of the heirloom (scion) is then attached to the rootstock with little silicon clips (as I showed in Field Trip). After that the plants are put back in their pots and covered with a large humidity dome. This is then kept out of the light for a few days and then gradually reintroduced to UV light. After about a week the plants should show signs of fusing together and starting to grow again. I then started removing the domes for longer periods of time to allow the plants to adjust to a less humid and hot environment.
Grafting will also alter how I plant tomatoes in the garden. Typically I would plant the tomatoes about 10 inches deep, covering a lot of the growth to that point. With grafted tomatoes you cannot cover the area of the graft or it will start re-growing the rootstock variety and stealing energy from the tomatoes you want to eat. I plan on using straw mulch to help keep some of the moisture in the soil this summer, something I have not had to do before because I planted the tomatoes, and ran the irrigation line, deep enough to not really worry about that.
So far most of the plants I grafted are doing well. Because some of the heirloom varieties grew very slowly they were too small to survive the process. Fearing this, I did not graft all of the heirloom plants I have. Because I now have extra heirloom and rootstock plants I might try another technique, side grafting, and grafting two varieties onto one rootstock so I can harvest two types of tomatoes from one plant. I have not started this yet, other than having the plants about ready.
I will update progress this summer as the tomatoes grow. I will have some grafted and some ungrafted tomatoes of the same varieties in the garden so I should be able to see if there is a real difference in growth and production. Although grafting created some stress when I initially did it, because the plants were all droopy and did not look happy, things seem to have worked out.