People
have asked me why I grow Marigold plants in among my vegetable patch. Well,
the short answer is that they stop bugs dead in their tracks. The
long answer is that I need them to kill nematodes. Nematodes are
microscopic white worms that have infested the soil that I grow all of my
vegies in. The mongrel nematodes attack the root system of my tomatoes
and capsicums and wreak havoc with all of my carrots and beetroot in the warmer
months as well as attack and a whole heap of my vegies. 
If
you have an attack of nematodes in the garden you will notice a reduced vigor of your plants. In hot weather it’s
particularly noticeable. What they do is
cause:
Nodules
on the roots,
Stunted
root systems and plants, and
Deformed
root vegetables.
The
loss of vigor is because your plants are having their water and food supply
reduced as the roots are being attacked.
For
those who are attempting to minimise the amount of crap that you spray onto
your vegies, Marigolds are brilliant. The way it works is that the root
of the Marigold produces a chemical that kills nematodes in the soil.
The nematodes are attracted to the marigolds rather than the other veggies and
latch onto the roots and that is the end of them. They do not reproduce
because they are rendered sterile and the cycle is broken and your soil becomes
healthier. As a bonus, Marigolds also deter aphids, squash bugs, thrips,
tomato hornworms, and whiteflies.
If
a whole area is infested I plant the whole bed out and dig them in as a green manure
crop when they are mature, or if the garden bed is not infested, I plant as a
precautionary measure a couple throughout crops as they grow. Frogs also
love them.
