It is just about that time- time to plant the summer garden! While many are still harvesting cool-season crops like lettuce, kale and cabbage, the time for tomato and squash has yet to come. Whether you are a first time gardener getting ready to jump into an exciting new hobby or a long time enthusiast that’s gearing up for another year, planting the garden is an exciting time of anticipation. No matter your “experience level” consider a pest management plan before you plant. You might already know to choose resistant varieties, but do you know about companion plantings? They are a good addition to your pest management tool box.
Companion planting by definition, is using different crops in close proximity for pest control, pollination, providing habitat for beneficial creatures, maximizing use of space, and to otherwise increase the harvest crop productivity. So what does this mean for the home gardener? The benefits of companion plants includes providing cover for shade loving plants, repelling harmful insects, attracting beneficial insects, or by providing necessary soil requirements for other plants.
While the term companion planting may be new to you, this technique has been used for quite a while. Have you ever seen marigolds interplanted with okra or squash? What about planting basil near tomatoes? All of these are examples of companion planting. Marigolds have long been the garden superhero when intermixed in our vegetable gardens. While both African and French marigolds produce biochemicals from their roots that are toxic to root-knot nematodes, the benefit is greatest when these pungent plants are tilled into the soil the year prior to planting tomatoes in that spot. That being said, there are a lot of gardeners who swear that marigolds will repel beetles, nematodes and even some animal pests. I just say that they are pretty, they add diversity to the garden, and can attract butterflies to our garden which is always a plus. Another example of this is to plant dill and basil near the tomatoes. This can be for more than making bruschetta a bit easier; both crops have been documented to reduce the pressure from tomato hornworms.
While many gardeners focus on eradicating all insects from the vegetable garden, it is important to remember that there are far more beneficial insects than those that cause harm to our plants. Planting carrots, fennel, parsley, and cilantro can actually attract beneficial insects like praying mantis, lady bugs and spiders by providing shelter for them and other beneficial or parasitic insects. These “good guys” are protectors of the garden, seeking out harmful insects and eating them! Other good bug attractive plants? - thyme, rosemary, yarrow, chamomile, and cover crops like clover and buckwheat. [See native plant, mountain mint, above with Scoliid wasps]
Companion plantings are also used to actually attract harmful insects. Plants like nasturtium are more appetizing to aphids than many vegetables in the garden; luring these tiny but harmful pests away from our “cash crop”. In several experiments by Alabama Extension, we have seen that planting these crops that are more appetizing to the harmful insects greatly reduces their numbers on the harvest crop we're trying to protect. This also allows us to direct insecticides where the larger group of pest are feeding (on the trap crop) and reduce the need for insecticides on the harvest crops; like tomatoes and squash.
Lastly, we can use companion planting to create micro-climates in an otherwise over-heated garden. This is a technique we use outside of the vegetable garden as well, like planting blueberries, azaleas and camellias under the filtered shade of pines and oaks. This provides them with needed cover which minimizes afternoon heat. In the vegetable garden, plants like lettuce, kale, broccoli and other cool season crops can be planted on the garden's east side where they can be shaded by taller plants in the afternoon. Afternoon shade can delay their tendency to bolt as the days heat up and lengthen the harvest season.
With a little planning, we can better plant our garden to naturally avoid some pest and disease problems. Remember to check last year's garden notes to prepare for cyclical problems and avoid surprises where possible. Though planting these companions helps, there is still a need for a balanced IPM program using cultural, mechanical, biological, and chemical (natural or synthetic) controls to keep crop plants healthy and productive. For more information on companion planting, vegetable gardening, and other gardening questions, contact your local Alabama Extension Office. Check out or website, www.aces.edu for more information and publications.
Written by Hunter McBrayer, Urban Regional Extension Agent, of the Alabama Cooperative Extension System (ACES). He is housed at the Marshall County Extension Office, which is based at the Marshall County Courthouse in Guntersville, AL.
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