Grafting heirloom tomatoes for field production
Because of an unexpected illness that involved emergency surgery, I was unable to satisfactorily complete this project in 2009.
Goals: The plan was to provide three cooperating farms with equal quantities of grafted and (for comparative purposes) ungrafted heirloom tomato seedlings. Batches of rootstock and scion material were planted at weekly intervals, with the intention of grafting, healing, hardening, and distributing these batches, also at weekly intervals, to the cooperating farms.
Updated information: At just about the worst possible time—when the second batch had just been grafted—I was taken ill. Batches 1 and 2 did not survive, and Batch 3 was never grafted.
Actual progress: However, I did gain several valuable learning experiences:
a) I found that the scion material I chose for this project (heirloom tomatoes, particularly Brandywine Sudduth) grew faster and therefore had thicker stems than the rootstock material, which is Maxifort. This made topgraft matches difficult and sometimes impossible.
b) One consequence of the growth interruption that the grafting process imposes on the grafted plants is that while the grafted plants are healing and hardening, the non-grafted plants continue their development uninterrupted. The result is that the grafted and ungrafted plants are not equal in size. To compensate for this, I should have planted the ungrafted seedlings about a week later so they all end up of equal size when they are ready for transplant to the field. I also found that small labels with dates were not the easiest way to differentiate between all the different batches of grafted and ungrafted seedlings.
c) The healing chamber I built was much too large, which made it harder to maintain the necessary humidity. At the same time, I found that the grafting process is much more forgiving of mismatches and other errors than I expected.
Plan for 2010: The project will be started over this year, taking advantage of last year’s experience to make a few small modifications that will fine-tune the project. These are:
1. Replace Brandywine Sudduth with another red Brandywine strain with the hope that the stem diameter mismatching will be less of a problem. My experience last year with the Brandywine Quisenberry strain suggests that this will be a suitable replacement.
2. Replace Maxifort rootstock with Beaufort rootstock. I found that Maxifort’s root development is so vigorous that it outgrows 72-cell capacity, and rapidly requires a 3.5- or 4-inch pot if it is not to become rootbound before it is ready to be transplanted out into the field. A phone conversation with a scientist at De Ruiter Seeds (the breeder of Maxifort, Beaufort, and Multifort rootstocks) suggests that Beaufort, while still vigorous, is less aggressive than Maxifort.
3. I have built a smaller healing chamber that will comfortably accommodate all the grafted seedlings I need to protect, and which will be easier to keep properly humidified.
4. I will adjust the seeding dates for grafted and ungrafted plants so the field-ready transplants of each will be of equal size. Also, I will be using a simple color-coding system to clearly and visibly differentiate between the batches of grafted and ungrafted plants.
I am excited to have the opportunity to run this project, and despite the disappointment from having to abandon last year’s attempt, I feel confident that what I learned last year will make for a more successful outcome in 2010.