Posts Tagged vegetable garden crop rotation

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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Garden Clean-Up Bonuses

Black Swallowtail caterpillar

Decades of vegetable gardening in the Piedmont of North Carolina have taught me the value of post-growing-season clean-up. Our warm and muggy climate offers many opportunities for harmful insects and diseases to make themselves at home. And in the last decade, I’ve noticed that climate change has made our winters much less reliably cold. Prolonged cold spells, say, two weeks when the highs never top 45 degrees Farenheit, and nightly lows lingering in the teens and twenties just don’t seem to happen anymore.

Without those long cold spells to kill overwintering insects and diseases, my best weapon against them is garden clean-up. So as soon as I can manage after our first killing freeze, I remove every speck of dead vegetable plant and annual flowers and herbs from the vegetable garden area. I am not sufficiently dedicated in my composting techniques to be certain it gets hot enough to kill loitering diseases on my dead veggie leaves, so I bag them up and take them to the dump. It’s the only way I can be sure the bad guys don’t gain an easy foothold in my garden.

I’ve found that it’s best to do this as soon as possible, so that any evils lurking among browned tomato vines and limp cucumber leaves are removed before they multiply. It’s hard on my aging hands and back to laboriously cut off every strip of tomato tie attached to the trellis. And my nose inevitably gets sneezy as dried bits of vegetable matter released from yanked stems float on the breezes and all over me. But the effort is worth a few aches. I’ve seen what happens when I wait until spring to remove the remains of the previous year’s garden. Disease and bug problems are always much worse.

Here’s a shot of a piece of the garden with its cleaned trellises:

Fewer places left for pest diseases and insects to hide

The white flowers are the Sweet-Alyssums-that-would-not-die. That’s what I’m calling these “annuals” that I grew from seed last spring. Pollinators are enjoying them on warm days. The deep green plants are crimson clover, which I sowed about six weeks ago. They serve as a winter cover crop on my beds.

In addition to fall clean-up, I also rotate crops to reduce pest problems. You should never grow members of the same plant family in the same spot two years in succession because it allows disease and insect pests of those families to prosper at the expense of your crops. The Solanaceae family is the trickiest. That includes peppers, tomatoes, eggplants, and potatoes; they all share genes and pests. Likewise, you must be mindful not to plant cucumbers, melons, gourds, and pumpkins in the same area two years in a row, since they all belong to the Cucurbitaceae family. Ditto for beans and peas (Leguminosae).

I’ve been working for the last couple of weeks to cut, pull, and bag all the dead vegetable matter and their ties. Wonder Spouse helped me with the taller parts of the trellises that I can’t reach — thanks, Big Guy. Yesterday while I was finishing up, I found the caterpillar in the above photo dining on one of my Bronze Fennels. I had noticed that my fennels were looking chewed on, but I hadn’t spotted the culprit until yesterday.

I confess I was surprised to find a Black Swallowtail caterpillar still alive and eating my plants. But I was also delighted; I plant Bronze Fennel in my garden specifically for these caterpillars. Black Swallowtail larvae dine on members of the carrot family, including Queen Anne’s Lace, parsley, carrots, dill, and fennel. They also like the herb rue.  During the growing season when I find one of these caterpillars chewing on a dill or parsley plant, I relocate them to the fennel. This way I can maintain plenty of my favorite herbs and also get to enjoy the beauty of the butterflies when these caterpillars metamorphose.

My favorite caterpillar reference (Caterpillars of Eastern North America by David L. Wagner) says that Black Swallowtails are increasingly rare in the northeastern part of the US, because fields and agricultural lands have largely been replaced by concrete and forest. Members of the carrot plant family don’t generally grow in such places, so there are no food plants for this butterfly.

I’m happy to report that this species is a common visitor of flowers in my summer gardens, and I’m happy to ensure their food supply by offering up Bronze Fennels for their consumption. I suspect the caterpillar in the above photo is about to morph into its chrysalis form for overwintering. I found one of its siblings already metamorphosed, tucked against a rusty trellis stake nearby here:

Black Swallowtail chrysalis

Sweet dreams, garden friends. May your winter musings make next year’s growing season the most richly vibrant one yet.

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