Four Flowers You Want To Trap Insects In Your Vegetable Garden

One of the interesting things in the vegetable garden is the existence of “trap plants” we can use to both attract and identify pest infestations as a form of companion planting.

We say these plants act as “insect traps” for the rest of the garden.

For example, beans and eggplant are beloved of spider mite and white flies so if you want to know if these pests are a problem in your garden, check these two plants first.

Or, if you’ve had a problem with these pests in the past, do plant these plants so they’ll both attract the pests (taking them away from other plants such as tomatoes) and give you an easy  place to spray insecticidal soap for control purposes.

This means you can actually put some eggplant and bean plants next to other plants that have had insect problems in the past to use as “traps” and infestation early warning signals.  A few plants scattered here and there through the garden works really well instead of concentrating these two plants in a section all by themselves.

Trap-cropping has several things in its favor in the home garden.

The first is that it works and has a great deal of scientific study behind it. The second thing is that it’s easy to do.

Trap-cropping is a simple system with limited plants to use.

The plants listed below attract the indicated pests. Period.

This means the insects prefer to eat the trap crop (most do anyway) instead of your preferred plant.

This gives two positive results –

  • the first is that your preferred plant isn’t being eaten and
  • the second is that the majority of pests are all in one place, making it much easier to kill them.

Because this is what you’re going to do – kill the pests attacking the trap crop.

Differences To Note

I note much of the research has been done on commercial farms where the trap crop is a row or two on the outside or running between rows of the desired crop.

It is on a much larger scale than backyard gardens so there are a few more details to be aware of and techniques to be used along with trap-cropping.

Diverse Planting In The Home Garden

This means plant a lot of different kinds of plants – vegetables, herbs and annual flowers in the same area.

Insects are less likely to build up into total crop-devouring numbers when there aren’t large mono-cultures. (All the same kind of plant.)

Did I mention to include flowers in the vegetable garden?

These will attract a great many beneficial insects as well as provide some beauty in your garden. And a cutting garden of your favorite flowers will fit right into a vegetable garden as both flowers and vegetables are constantly being cut and pruned.

My advice about which flowers to plant would include:

  • marigolds,
  • geraniums,
  • asters and
  • zinnias

All of these plants have been shown to attract insects.

Also include your favorite flowers for cutting. Don’t be restricted by what’s “good” for the garden but instead consider what’s good for the gardener.

Commercially Used Combinations You Can Use in the Home Garden

These suggestions are gleaned from commercial vegetable production research and studies and are recommended for big growers. I suggest home gardeners can take advantage of these as well.

Again, a trap crop will attract the pest first but it won’t “protect” the main crop in any way.

You do have to control the insect but at least you know where it’s more likely to be first. Check these trap crops regularly for the beginning stages of insect infestation.

When you see them on the trap crop, control immediately before the insect moves to your preferred crop.

  • Chevil attracts slugs. Plant with everything as it’s a favorite slug food.
  • Chinese cabbage seems to attract more Cabbage webworms, flea hoppers and mustard aphids than regular cabbage. Plant this form next to your regular cabbage.
  • Dill and Lovage are preferred foods of the tomato hornworm so mix these herbs into your tomato plantings.
  • Hot cherry peppers are used as trap crops for regular sweet bell peppers to attract pepper maggots. Plant all peppers in the same area but check those hot cherry types first for problems.Peppers also attract aphids probably more than any other vegetable – check this crop first and plant it next to any other plant you want to protect.
  • Marigolds deter root-knot nematodes in the soil so plant next to legumes (peas, beans) that are a main food crop of this pest. (Contrary to Internet advice, I haven’t seen research they actually “work” in any other way. But it never hurts to grow flowers in a vegetable garden and who knows….)
  • Nasturtiums are beloved and eaten by aphids, flea beetles, cucumber beetles and squash vine borers. Plant them either next to or among your cabbage and squash plant families.
  • Radishes are eaten by flea beetles and root maggots more than cabbage so plant radishes between your cabbages.
  • Tansy is a great food source for Colorado potato beetles so plant it next to your potato crop.

Remember though

Trap crop plants don’t deter insects, they attract them. This makes it easier for you to find/control/eliminate the bad guys.

Do You Think Traditional Companion Planting Really Works?

If you’re looking for companion planting information, you’ve landed on the right page. The information below has been gleaned from many antique books in my collection and from old copies of way too many magazines to even begin to list.

I do not vouch for any or all of these bits of garden pest protection lore but pass them along to you to try.

I do know many gardeners who swear by any and all of these companion planting techniques to protect your garden from pest problems.

To be honest, I do not use any of these techniques myself and I’m unable to find any scientific proof that they work.

Having said that, I do use commercial techniques that are tested and that do work.

If They Work…

Please understand the effects of each of these garden pest protection plants is very localized (i.e. small area) so if you want to stop ants for example from putting aphids on a tree, you’ll have to surround the tree with petunias. A petunia located a few yards away is ineffective.

A bit of pennyroyal in one part of the garden will not deter pests from entering another. Chives in the herb garden may protect those plants next door but not a yard away. The companion plants have to be companions – kissing cousins so to speak – to be effective.

The research on plant hormones I’ve read suggests that if leaves are touching, there may be a transfer of the hormone and the plant will develop some resistance but if you expect something to work without actual physical contact, there’s no scientific proof it works.

But If You Believe In Companion Planting For Garden Pest Protection:

Here are a few of the tradition combinations for you to use and experiment within your own garden.

  • Ants (carrying aphids) then plant pennyroyal, spearmint, southernwood, tansy,
  • Aphids plant pennyroyal, spearmint, southernwood, tansy, garlic, chives, coriander, anise, nasturtiums, and petunias.
  • Asparagus beetles apparently do not like tomatoes
  • Borers dislike garlic, tansy, and onion
  • Cabbage maggots are stopped if you plant alternating rows of mint, tomato, rosemary, sage.
  • Cabbage moths apparently do not like mint, hyssop, rosemary, southernwood, thyme, sage, wormwood, celery, catnip, and nasturtiums.
  • Carrot Fly dislikes rosemary, sage, wormwood, salsify, onions, coriander
  • Chinch bugs don’t like soybeans so surround your lawn with them. Right.
  • Colorado Potato Beetle doesn’t like green beans (me neither), horseradish, dead nettle, and flax.
  • Cucumber Beetle is repelled by radish and tansy
  • Cutworms are driven to distraction by tansy
  • Eelworms are repelled by big stinky marigolds
  • Flea beetle wormwood, mint, catnip, tomatoes
  • Fruit tree moths of all sorts don’t like southernwood
  • Groundhogs castor beans and human urine (human urine only works if you urinate down their holes)  although the latter is enhanced by imbibing products made from hops
  • Japanese Beetles garlic, larkspur/delphiniums, tansy, rue, geraniums
  • Leafhopper petunias and geraniums
  • Mexican bean beetle marigold, potatoes, rosemary, summer savory, and petunias
  • Mice don’t like mint (mice hate fresh breath)
  • Mites are repelled by onion, garlic, and chives
  • Moles don’t like spurge, castor plants and castor oil, fritillaria bulbs
  • Nematodes stinky marigolds, salvia, dahlia, calendula, asparagus
  • Plum curculio is supposedly repelled by garlic – don’t ask me how you get it into the tree but I’ve read this more than once. (maybe all copying from one source)
  • Rabbits don’t like onions or the onion family (garlic/chives etc)
  • Rose chafer geraniums, petunia and onion family
  • Slugs don’t like rosemary, wormwood and that might be the only two plants they won’t’ eat
  • Squash bug don’t like tansy and nasturtiums
  • Pumpkin beetle doesn’t like nasturtiums (and nasturtiums don’t like it either)
  • Tomato hornworm is deterred by borage, marigolds, and basil.
  • Whitefly won’t go near nasturtiums, marigolds, nicandra
  • Wireworms apparently don’t like mustard and buckwheat.

My Take On Companion Planting

Companion planting is a mixed bag of garden information with some gardeners saying there are effects from these techniques and others equally adamant that there are few if any measurable effects other than wishful thinking.

My own sense of it is that when the hordes of locusts or Japanese beetles come out of the sky, planting a marigold next to a tomato isn’t going to help much under this level of problem.

And for the record, the only thing I’ve read about marigolds (that works) is that the big old-fashioned ones secrete a hormone from their roots that “deters” the root-knot nematode.  But the fragrance doesn’t do a darn thing.

Not having seen real research other than this, I consider companion planting mostly a waste of time unless it makes you feel better.

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