To graft or not to graft?

Do the advantages compensate for the extra cost?

Do the advantages compensate for the extra cost?

Actually, I’m not planning on grafting my vegetables myself. Spending time grafting annuals for a small home garden is not efficient for my situation. However, everywhere I turn — in catalogs and gardening magazines — the big buzz is about the advantages of planting grafted vegetables.  All the catalogs want to sell me these higher priced darlings.

If you use your favorite search engine to learn about the advantages of grafted veggies, you will get many, many results. A quick perusal on my part this morning was instructive. Apparently, the Japanese, especially greenhouse operations, have been grafting melons, squash, tomatoes, eggplants, and peppers for quite some time. Fruit production is supposed to be higher, as is the length of productivity — more fruits over a longer period.

For those unfamiliar with this ancient horticultural technique, grafting usually involves putting together two different cultivars of the same species. Fruit growers have been doing this for centuries. They look for a tree with a vigorous root system and less-than-spectacular fruits and a tree with great fruit quality but perhaps weaker roots. They take a cutting from the top of the tasty plant (called a scion) and plug it into the lopped-off top of the plant with vigorous roots (called the rootstock). When done correctly, the two pieces grow together nicely, leaving just a bit of a scar line where they join. The grafted fruit tree scion generally becomes able to produce more, healthier fruit, because it is growing on the vigorous rootstock.

Often, rootstock plants are more resistant to diseases than the tasty fruit plants, so when the rootstock is able to impart this advantage to its grafted top, fruit production improves. This propagation process makes perfect sense to me for long-lived perennials and trees. But for annuals in a home garden? I’m just not sure, which is why my 2013 garden will feature an experiment.

Tomato growers are hyping grafted heirloom plants as the solution to heirloom tomatoes’ notorious susceptibility to diseases, most of which linger in the soil for years. They claim that an heirloom tomato growing on disease-resistant rootstock will give growers much more vigorous plants, and prolonged crops of tasty Brandywines, Cherokee Purples, etc.

For some situations, this may be true. For example, if your garden space is so small that you can’t manage to rotate your crops each year, grafted veggies may help you. When you rotate crops, you avoid growing members of the same plant family in the same spot every year. I am blessed with a large garden area. I only grow the same plant family in the same spot after growing other plants there for the previous two years. This may not eliminate every vestige of lingering disease spores, but I think it helps a lot.

Squashes are members of the cucurbit family.

Squashes are members of the cucurbit family.

For those who may have forgotten, squash, melons, and cucumbers are all members of the cucurbit family. Tomatoes, peppers, eggplants, and potatoes are all members of the Solanaceae family, and peas and beans are legumes. Rotating where you grow these family groups makes it harder for their diseases and predators to lay in wait for them.

I have also read research that suggests that stressed plants produce more chemicals that make them less appealing to bad bugs and diseases. Grafting does stress plants, in that it requires them to allocate resources to heal the graft wound. Maybe this revs up the plant’s vigor?

The only way to learn more is to try some of these new-fangled plants, so I have ordered two grafted plants: a Brandywine and a Goliath. I have never had much success with seed-grown Brandywines in my garden. I usually get a few nice fruits, then the plant is overwhelmed by disease. I usually pull them out of the garden before the hybridized, disease-resistant tomatoes are halfway done. If the grafted Brandywine I plant this year really performs better, I will be a believer in the concept, although I’m still not sure it is enough of a return on investment to justify the cost.

The other grafted variety I’m trying is Goliath. This hybrid, disease-resistant tomato has always produced magnificently for me from seed-grown plants. I cannot imagine that grafting will improve its productivity in my garden, but it will be interesting to see.

Of course, I must have control plants to measure against the grafted ones, so I’ll also grow Brandywine and Goliath tomato plants from seed as usual. I’ll plant them at opposite ends of the trellises to minimize any cross contamination. May the best tomato win.

Fans of grafted tomatoes wax positively poetic about how disease-resistant rootstocks will prevent diseases from overwhelming tasty, disease-susceptible heirlooms. I am a doubter for my garden, because the root systems of all my tomatoes are always vigorous, and <knock on wood> I don’t have a nematode problem in my garden soil.

Most of the diseases that hit my tomatoes correlate with weather — hot humid summers breed fungal plagues — and insect infestations — spotted cucumber beetles, stink bugs, and other sucking insect predators insert diseases into plants when they suck out their juices. Unless the act of grafting in itself is the key to such improved vigor that even insect-introduced diseases are repelled, I doubt I’ll see much, if any, difference between my seed-grown controls and grafted test subjects.

Similarly, many of the soil-born wilts reach leaves when they are splashed up off the ground by watering or heavy rain. If you use organic mulch around your tomatoes, as I do, eventually soil-based fungi will find their way onto lower leaves, then work their way up from there. I don’t see how a disease-resistant rootstock will save a grafted heirloom in that scenario.

One more point for those who may have read about my tomato-planting technique in previous posts. I always dig a deep hole, maybe 8 inches below ground level, so that I can plant tomato seedlings deeply. The newly buried length of stem almost instantly begins to sprout roots, which may explain why my tomato plants always have vigorous, plentiful root systems.  However, for the grafted plants, I won’t be able to do this.

If I buried the grafted plants so that the graft line was below soil level, the buried stem of the scion (top part) would sprout roots. Because those roots would be from a plant that is less disease-resistant, any advantage conferred by the graft would be negated. This is another reason I’ll be surprised if the grafts win the productivity race. Their root systems will almost certainly remain smaller than their seed-grown competitors. If roots are the key piece of this puzzle, my money is on the seed-grown, deeply buried plants.

I’ll keep you posted as the season progresses. I’ve ordered all my seeds and plants, and I’ll be prepping my greenhouse soon for seed production mode. It will be most interesting to see the results of this experiment.

Have you ordered your seeds yet? If not, get busy. Seed sales are up as more folks are trying to grow some of their own food. To get the best selection, ordering soon is your best option.

Don't forget the herbs and flowers when you order your veggie seeds. A diverse garden is always healthier.

Don’t forget the herbs and flowers when you order your veggie seeds. A diverse garden is always healthier.

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