Have you determined about how many seeds you'll need to get decent coverage of your garden? You won't need to sow the seeds as heavily as you would, say, grass seed. The chemicals are present in the living root systems, which are capable of spreading quite a bit.

What kind of spacing is recommended for this to be effective? Maybe somewhere around 6 inches or less? How many square feet in the area you're intending to cover?

Forgive all of the questions; I'm just curious. ;-)

i THINK i recall.. that there can be millions of nems in a given teaspoon of soil ... and they are not all bad ...

more facts please

ken

But you are right in that there are many different species, and not all of them are bad. However, some areas are plagued with that pesky root knot nematode, that's for certain. With few other options available to us, growing a crop of marigolds every other year or so is a viable option. It's been done in certain developing countries for hundreds of years.

It's sure something that I would experiment with, at least in my veggie garden. Luckily, I don't have much of a problem with plant-parasitic nematodes in my clayey soil.

For those who don't know how this works, here's a brief explanation. Plant-parasitic nematodes require a living host plant in order to survive; some species are very specific, by the way. Some marigolds can cause the decline in nema numbers because they (the plants) cannot be used as host plants. They don't 'repel' or kill the nematodes directly. There is also a chemical that some marigolds produce that inhibits the hatching of eggs from certain nematode species, so we have allelopathy going on, too.

For it to work, marigolds must be planted as a cover crop in the exact location you wish to grow vegetables at some point. After two of three months (or more) in the ground, the nematode population will have declined. Circling your veggie garden in cheerful marigolds does nothing to get rid of these pests, nor does planting a few here and there. You can't, for example, surround your perennials or woody landscape plants with marigolds and hope that you'll kill off the nematodes. A spacing of 6 to 12 inches is typically recommended.

Unfortunately, your marigold crop will have to become a part of a cyclical planting rotation, as long as you wish to grow susceptible host plants in the same area.

Please don't forget that some marigold species have proven to increase nematode populations. And remember that marigolds are spider mite magnets (among other pests). Your crop of marigolds will need watering and fertilizing just like any planting.