Nematodes, marigolds, and crop rotation

Marigolds as a cover crop: they are not only useful, but also beautiful and
attract butterflies and bees.

This summer, for several reasons, I skipped most of the summer crops and planted a cover crop of marigolds. I'd also planted a lot of marigolds around the tomatoes earlier in the season--about 3 marigolds for every tomato plant.

This is my experiment to see if I can reduce the root-knot nematode populations in my gardens.

First, as I've been preaching in my talks, just planting marigolds around the tomatoes does not prevent nematode damage. Here is the result...

Tomato roots are stunted and filled with nematode
damage even though the plants were surrounded
by marigolds.

The marigold roots have no nematode damage and
even have some mycorrhizae fungus intertwined.

While the marigolds can shun the nematodes, they need to be a cover crop that is turned under to reduce the nematode population in the soil. Having a cover crop also means that the soil gets a rest from the stress of growing a crop.

So here's my scheme: After pulling the marigolds and weeds, I dig out the garden soil about six inches to form shallow rows, then I add layers of fresh grass clippings, marigolds that were pulled last week, freshly clipped or pulled marigolds and then enough compost to bring the level back up to the original level. Then I chop the rows repeatedly with the shovel to break up the marigolds into smaller pieces. After that I add the original garden soil on top of the mixture.

We have an abundance of grass clippings right now because we were out of town for a few weeks. We had someone mow the front lawn while we were gone, but the back yard was a jungle.

The original garden soil has plenty of earth worms.

After smoothing the soil I sprinkle a light layer of grass
clippings and then cover with pine needles and
then irrigate with rain barrel water.

There's a very good reason why rain barrel water is important for this process: it doesn't contain chlorine that would impede the microbes that are needed to break down the grass clippings and marigolds. This is a form of in-the-ground composting. I will give these beds a few weeks before I plant the cool weather crops.

The walking onions need to be walked to another spot!
The onions are in the pot next to the garlic chives.

Crop Rotation

When you plant the same crop in one place year after year, it causes several problems, but here are the two biggest problems:
- It depletes the soil of the same nutrients over and over.
- Its soil-borne enemies, such as root borers, are already in place to attack it the next time.

Crop rotation by plant family helps to combat these problems, especially in organically managed gardens. For instance, if you plant parsley in one bed, plant a crop that is not in the carrot family there for at least the next two seasons.

This is easy enough to do if your crop lasts only one season, but with a perennial crop like walking onions or garlic chives, it's a different strategy. After my walking onions had been in place for at least six years, this year, they started to deteriorate. I usually use them for only for their greens, but when I dug them up, something had been eating their bulbs. So it's time to clean them up and walk them to an entirely new bed. I think I'll move them to the herb garden behind the chives. I need to plant some more chives there as well.

The garlic chives have only been in place for two years, so they are still looking good, but I'll thin them out to start some in a different location--maybe even a pot.

This year I grew lime basil and at this point in the season, the leaves are extremely citrusy and will probably not be useful for "normal" pesto. We'll see what we come up with maybe we'll think of something interesting to do with it.

How does your garden grow?

Green Gardening Matters,
Ginny Stibolt

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Old gardeners' tales

Old gardeners' tales are rampant, even these days.

Companion planting advice as shown in this graphic is freely passed along as gospel of the garden. But most of the companion planting pairings (compatible or incompatible) have not been verified with scientific methods.  Nevertheless, books have been written about plants with human emotions such as "love" or "hate" used in their titles.
  
Don't fall for these old gardeners' tales.

In my research for "Organic Methods for Vegetable Gardening in Florida," I found that the more important thing to keep in mind is the botanical family of the plants so your crop rotation from one season to the next includes different crop families for at least two rounds. This keeps the specific pests guessing and allows the soils to be replenished.

One of my go to resources for garden myths is Linda Chalker-Scott's website, The Informed Gardener. She's an urban extension agent in Washington State and she has access to the professional journals where she researches various gardening traditions to find if the science proves them to be true or not. She's also published two books listing some of the most common myths.

I planted a row of tall sunflowers away from other gardens.

I planted two seeds in each pile of compost.

Sunflowers are one of the exceptions

Sunflowers (Helianthus spp) are one type of plant that kills or stunts its neighbors. So when you grow them, it's best to plant them away from other plants and dispose of the dead plants at the end of the season so that you can take advantage of their built in herbicide such as using them for a path mulch.

While the danger of frost here in north Florida is not over, it's becoming less and less likely. So I planted two types of sunflowers this week. I'd been piling leaves and other dead stuff raked from the lawn before our first mowing in a line along the back edge of the raised septic drain field. The soil is extremely sandy up there, of course, so I needed the pile of dead stuff to hold the moisture. Then I nestled shovelfuls of compost along the row of leaves. Finally, I planted two seeds in each pile of compost.  These are tall sunflowers with supposedly easy-to-harvest sunflower seeds to eat. The directions stated eight inches apart. I think my planting falls into that range. After the seeds were planted, I covered them with a pine needle mulch.

I also planted some shorter, multi-headed sunflowers at the back of the herb garden for a change. I'll plant basil somewhere else. I'll let you know how they do.  Meanwhile, read my article from a few years back for more information on sunflowers and how this American native became Russia's national flower. Sensational Sunflowers.

Sunrise the other morning from our front yard highlighted a buttermilk sky.

I wish you beautiful sunrises and now that it's daylight savings time, maybe you'll see a few more.

Green Gardening Matters, 
Ginny Stibolt

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