Marigolds deter hornworms
Some plants will deter insects in the vegetable garden. This is one form of companion planting. Companion planting–growing plants singly or together–to repel insects, fight disease, or enhance the growth of another plant is a technique that many gardeners have used for generations. Some companion plants have been scientifically proven to deter insects; some companion planting combinations are anecdotal or attributed to “garden wisdom.”
Repelling insects by creating effective crop combinations uses plants’ natural fragrance, oils, compounds, and colors to chase pests away. For example, some aromatic compounds may mask the scent of companion plants: the aroma of garlic will chase away bean beetles and potato bugs. And the color of some plants will confuse some insect pests and send them on their way before they can do any harm.
One way to get started with companion planting is to draw on the science and wisdom of gardeners. Try some of these combinations and draw your own conclusions based on your observations and planting successes. Keep a record of what works and let others know.
The companion plantings in this chart are aimed at deterring pests from the garden. Note that there are also companion plantings that will attract beneficial insects to your garden.
| Plant | Insects and Pests Deterred | Plant Near |
|---|---|---|
| Asters | Most insects | Sunflower, plant around the garden |
| Basil | Flies and mosquitoes | Tomato; avoid planting near rue |
| Borage | Tomato worn, cabbageworms | Tomato, cabbage family crops, strawberry |
| Calendula | Asparagus beetles, tomato hornworms, most insects | All vegetables and herbs |
| Catnip | Flea beetles, spittlebugs, ants, Japanese beetles, weevils | All vegetables |
| Celery | White cabbage butterfly | Leek, tomato, cabbage, cauliflower, bush bean |
| Chrysanthemum | Most insects, nematodes | Tomato; avoid planting near lettuce |
| Dead Nettle | Potato bugs | Potato |
| Eggplant | Colorado potato beetle | Green bean, lettuce |
| Flax (Linnum usitatissimum) | Potato bugs | Potato, carrot |
| Garlic | Japanese beetle, aphids, other insects and blight | Tomato, eggplant, cabbage family plants; avoid planting near peas, beans, and other legumes |
| Geranium | Cabbageworms, corn earworms, Japanese beetles, most insects | Interplant with vegetables, especially cabbage |
| Horseradish | Potato bug | Potato, horseradish needs a permanent home |
| Henbit | Most insects | |
| Hyssop | Cabbage moth | Cabbage family, orchards, grapevines; avoid planting near radishes |
| Marigold | Nearly all insects including Mexican bean beetles and nematodes | Potato, tomato, pepper, eggplant, roses |
| Mint | Cabbage moth and ants | Cabbage, tomato |
| Mole plant(Euphorbia lathyrus) | Moles, gophers, mice | Space around the garden every 5 feet as a barrier |
| Nasturtium | Aphids, squash bugs, striped pumpkin beetles, whiteflies | Beans, cabbage family plants, cucumber |
| Onion family | Most pests, Colorado potato beetles, carrot rust flies | Most vegetables except peas, beans, sage |
| Petunia | Bean pests, Mexican bean beetles, potato bugs, squash bugs | Beans, squash, potato |
| Pot Marigold | Asparagus beetles, tomato worms, general garden pests | Asparagus, tomato, most vegetables |
| Peppermint | White cabbage butterfly | Cabbage |
| Radish | Cucumber beetles, squash borers | Beans, carrot, cucumber, kohlrabi, parsnip, onion, squash |
| Rosemary | Cabbage moth, bean beetle, carrot fly | Beans, cabbage family plants, carrot |
| Rue | Japanese beetle | Avoid skin contact; do not plant near cabbage family plants |
| Sage | Cabbage moth, carrot fly | Plant with perennial vegetables; avoid planting with cucumbers and rue |
| Salsify | Carrot fly | Carrot family plants |
| Southernwood(Artemisia abrotanum) | Cabbage moth, black aphids | Cabbage family plants or make a southernwood-water solution to spray cabbage |
| Summer Savory | Bean beetles | Beans, onion |
| Tansy | Flying insects, Japanese beetles, striped cucumber beetles, squash bugs, ants | Squash, potato; avoid planting near collard |
| Thyme | Cabbage worm | Eggplant, cabbage, potato, tomato, almost all vegetables and herbs |
| Tomato | Asparagus beetle | Asparagus, dill, borage |
| Wormwood(Artemisia absinthium) | Carrot fly, white cabbage butterfly, black flea beetle | Do not plant wormwood in the vegetable garden, but leaves used to make a spray will deter insects. |
Anything for squash bugs?
Squash bugs may be deterred by companion plants with strong oils or odors–garlic is one possible deterrent. Squash bugs can be controlled by exclusion–covering the crop with row covers, hand-picking, garlic spray, insecticidal soap, and neem oil.
Finding ants on a lot of leaves of various plants in garden, I believe they are eating leaves.I have already put ladybugs in garden, what else can be done ?
Ants often climb up into plants when they area attracted to insect excrement (called honeydew because of sugars). If the leaves feel sticky–that is honeydew; use a strong stream of water to clean leaves and wash away any insects–aphids, whiteflies and others. Ants will protect aphids from predators so that they can harvest the honeydew. Here is a link to an article on ant control: https://harvesttotable.com/tag/ants/
HI Steve, knew you at Westmont ! I was looking up this info and there you are!
Hi Rebecca. Great to hear from you. It’s a fitful Spring in the Sonoma Valley this year–cool then warm then cool. Hope all is well and Spring has come to your garden.
Here is an insect deterrent plant I discovered by accident: cilantro/coriander deters squash bugs. I have a patch in my garden that has grown and reseeded cilantro for years. last year I planted my acorn and yellow squash next to this patch. as long as the plants were growing/flowering I saw not one squash bug. as soon as they seeded and dried out I had to start fighting those nasty stinky bugs.
Thanks for this great tip!
Is there anything that deters squash vine borers?
The adult squash vine borer is a narrow winged moth with a 1-2 inch wingspan; eggs are brown, flat, oval and are laid singly on the stems near the base of the plant. To control squash borers you can: (1) exclude the moth from laying eggs by placing row covers over the plants–this can exclude pollinators so you would either have to grow parthenocarpic varieties which do not need pollinator or hand pollinate the flower; (2) search for and destroy the eggs or wipe the stems often to remove the eggs; (3) spray the stems .with insecticidal soap twice a week.