Marigolds: Do they keep the critters away?

A question came to me the other day, and I wanted to share it with you all:

Hello Kelsey,

Love your blog on Energize Clinton County!!

I have a garden question - I've heard that marigolds help keep insects from vegetable garden plants. Really?

Thanks,
Kim
Sardinia, OH

Okay, so this is a really good question. Good, but tricky. Every year we have customers that come in to buy marigolds, specifically to keep insects/rabbit/deer away from their vegetable garden. They come year after year, always requesting a flat of this age-old, yet pungent, plant.

The evidence that these plants ward off insects isn’t firm, however. French marigolds (the variety commonly sold) are said to release a nematode repellent into the soil. Nematodes, worm-like creatures, destroy plant root-systems. There is research suggesting that certain species find the compound released by marigolds to be toxic. And in this respect, having marigolds can be helpful.

I also spoke with Tony Nye at the OSU Extension Office in Clinton County and was told that marigolds may be useful for keeping beetles away from bean plants. However, there is not a lot of evidence saying that marigolds are effective for other insects. Aphids, for example, are sometimes even attracted to marigolds. (Tony Nye did, however, mention another plant, Nasturtiums, that is said to deter not only beetles, but aphids and squash bugs as well.)

In regard to marigolds, I would say that their scent is a distinguishing characteristic. Many say that their odor disguises the scent of vegetables, either confusing insects or preventing them (and possibly rabbits/deer) from perusing around your garden.

Honestly though, despite conflicting evidence, marigolds are a cheap experiment. They are inexpensive (we are now selling them at Swindlers for only 49 cents apiece), hardy, and easy to find. We are trying them out in the ECC vegetable garden, and will have a better idea of their effectiveness as the season continues. My advice, try them out. No promises, but they certainly are cheap and easy. And as always, let us know if you have any success!

Some sites I found helpful while researching this question:
http://www.vegetablegardener.com/item/4695/meet-the-magnificent-marigold
(Fellow blogger, appears to be a well-researched post)
http://www.aces.edu/dept/extcomm/specialty/marigolds.html
(Alabama Cooperative Extension System—article written by horticulture student and associate)