HI gardeners,

I'm gardening in an area of Florida that has a big problem with soil borne nematodes that make the roots look like the picture I attached. All knotty. The plants struggle, especially cucumbers, melons and zucchini/squash, but it also affects tomatoes, peppers, basil, eggplant etc....basically everything I like to grow :-(

So this summer, I planted the whole garden with 'golden guardian' marigolds (supposed to be bred for nematode reduction).

My question is....do the marigold roots kill nematodes? Or just repel them? Also, do I need to now dig the whole marigold plant into the soil, and cover it up with cardboard, like a green mulch? Do the marigold leaves have any affect? Or do I just pull them out now that I'm prepping the beds for fall planting?

I'm actually doing a squarefoot type raised bed system, with weed mat between my soil mix and the native soil (which is basically just beach sand)....For my soil, I'm using peatmoss, compost and vermiculite mix. So far it has not been too successful.

I'm actually thinking of going to containers if this season doesn't work!

Thanks!

I found the following from the University of Florida, which may be helpful: http://edis.ifas.ufl.edu/ng045

In summary, it says that marigolds produce a substance, alpha-terthienyl, that inhibits the hatching of nematode eggs. In addition, if the marigold is resistant to the nematodes, they won't have anything to eat and cannot develop and produce the eggs of the next generation. The article has a chart listing the relative resistance of different varieties of marigolds. Hope this helps.

Muddyfeet, I realized well into the summer that some of the problems I had with my garden were probably from nematodes. In researching what to do, I read that the marigold roots deterred them, the whole plant had to be chopped and incorporated into the soil and other sites talked about crop rotation with marigolds. I was a little confused as to exactly WHAT to do with marigolds!

I had some seeds for 'ground control marigolds'--supposedly the appropriate type for nematode suppression--but it was too late in the year to sow them.

After further investigation, I fully weeded the empty beds, dug in crabshells/compost and sowed mustard greens. (crabshells for the chitin, compost to boost beneficial microbes and mustard b/c brassicas, when chopped up and turned into the soil, release biocidal compounds effective against certain pathogens and pests-read nematodes )

I won't know if this was any help until later on in the fall/winter. Anyhow, it's what I came up with and thought I'd share.

Good luck!

Hey Muddyfeet

Are you near the Gulf Coast?

Way back in the 1960's when I first started gardening organically I remember reading about using non hybrid Marigolds to control the non beneficial nematodes in soil and that meant planting and growing the Marigolds and not pulling the plants after frost killed them but to leave them, roots and all, in place. Work the whole plant into the soil for the most benefit.

Crushed eggshells are supposed to encourage the "good" nematodes which in turn eat the root knot nematodes. I usually add a handfull of crushed shells to each tomato planting hole.

I save my eggshells all year. I rinse them, let them dry on paper towels and crush when dry. I save them in a paper lunch bag for spreading in gardening season.

Brownrexx,

Do the marigolds kill the beneficial nematodes in general?

I have seen it written that the yellow color attracts bugs, and when the flowers go into the soil after they have died for the next year is why we should plant them near tomatoes...

Does this make sense?

I have read a few articles on Marigolds and nematodes and it seems that they don't affect all nematodes but mainly the root knot nematodes which are bad guys. However not all varieties of marigolds will help and it is suggested that the marigolds be planted as a cover crop and tilled into the soil before planting the veggies. This is just not practical for me in PA with a relatively short growing season compared to warmer states.

I will continue to use the crushed eggshells with my tomatoes and use marigolds for an attractive addition to my garden but I do not expect them to solve nematode issues.

The non hybrid Marigolds repel Nematodes, all Nematodes good, bad, or indifferent. So planting Marigolds can aid in repeling Nematodes which can mean that the beneficial Nematodes that could control your harmful Nematodes will not be there to do that.
This is a choice you make, plant Marigolds to repel all Nematodes or develop a large enough population of parasitic Nematodes to control the few that harm your plants.

Thanks for all the responses! That was a great article gardendmpls, I'll bookmark that for sure.

So, to answer my question - I will be digging all the marigolds into the soil, stems, leaves, flowers and all, and letting it all rot down over the next month to be ready to plant in the fall. Looks like this would help too. I bet a few handfuls of bloodmeal would help break it all down.

I haven't found a good source of crushed shells in Florida (go figure!?) (I read shrimp shell meal is good - like this product - http://www.groworganic.com/shr...hell-meal-50-lb.html) But they are in California, and I'm loathe to have a 50lb bag of anything shipped that far. I do save all my egg shells and blend them to go in my compost. (good idea to add them directly to the planting hole!)

Yes Latitude33, we are on the gulf coast near Port Charlotte, South of Sarasota...but a little inland.

My next solution is to totally raise my raised beds off the ground, give them a cedar base will holes drilled in, and make them into containers....and working lots of compost into the soil mix to reduce nematodes that way. The nematodes love the sandy native soil and heat that we have here. The weed mat does nothing to discourage them from invading my nice soil mix.

Some people use crushed oyster shells as an alternative to egg shells. You can buy that relatively cheap wherever they sell chicken feed because it is used as a calcium supplement for laying hens.

We buy ours at a store called Tractor supply but I don't know if you have those. Agway also sells it.

Thanks, we have a tractor supply here, I'll try it!!

The last bag I bought for the hens had fairly large pieces. If I were using it for the garden, I would probably use a meat tenderizer mallet on the bag to crush the pieces smaller.

Nenatodes are microscopic and you could get more distribution with smaller pieces I would think.

Did anyone else read that it was the tall French marigolds that were most effective for the nematodes?
Another thing you could try would be solarization of the soil, and then adding compost next season to re-establish the good guys. And that is a lot easier than changing your planting beds. What have you got to loose?