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MASTER GARDENER: Companion planting tips for insect control

Three of my favorite companion plants are versatile marigolds, aromatic alliums and stalwart nasturtiums. I've been planting these reliable, easily maintained and multi-purposed plants for many years in my gardens: ground, raised bed and container. 

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Last month, I wrote about companion planting in a vegetable garden with specific herbs and flowers to lessen potential problems with harmful pests and related diseases.

Three of my favorite companion plants are versatile marigolds, aromatic alliums and stalwart nasturtiums. I've been planting these reliable, easily maintained and multi-purposed plants for many years in my gardens: ground, raised bed and container. 

Native to the Andes Mountains, nasturtiums have been widely cultivated as an ornamental flowering plant and edible herb. However, controlling the plant pest population is most likely the first reason to add this plant to your vegetable row.

Nasturtiums can do this in two ways: by deterrence and by trapping. For either purpose, (or both) start your nasturtiums a few weeks ahead of your vegetable plants, ensuring their size and development are ready to take a stand in the battle against vegetable pests.

Mature nasturtiums are effective at confusing certain pests. Their aromatic and peppery scent can actually mask the odor of your vegetables and cause insects to overlook them.

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Squash, cucumbers, and other gourds can be overlooked by certain beetles, worms and whiteflies because they are distracted and redirected to nasturtiums.

The colorful orange, yellow and red flowers are an excellent choice for drawing aphids off your tomatoes, beans and brassicas (also called cruciferous vegetables) such as Brussels sprouts, cabbage, cauliflower, collard greens, kale, broccoli and turnips.

Once your nasturtium has done its job and is heavily infested with aphids, remove and dispose of it, but not in the compost pile. It is good practice to replace it with another mature nasturtium until your vegetable harvest is finished.

More benefits of the spicy and vibrant nasturtium include attracting pollinators and predatory insects. Nature's predatory insects are the best defense against harmful pests. Invite them to your vegetable rows by planting companion nasturtiums.

Both the trailing and the bush nasturtiums make an attractive and effective ground cover that also helps to prevent water from splashing back on the lower tomato and pepper leaves. This helps to ward off fungal diseases that spread from the soil to your vegetable plants.

Knowledge regarding companion plants and insect control has grown, and I am eager to plan more diversified and intentional pairings. While doing this, I will keep in mind some insects use visual cues, such as leaf shape or color, to find their target plants.

If one has a whole plot full of the same plant, insects may find it more easily and damage ensues. Insect-controlled gardens are more likely if one has a variety of plants with different heights, colors and textures.

Having more knowledge regarding specific harmful pests, their life cycles and how best to prevent or deter them in a garden will enhance vegetable production and gardening enjoyment.

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To learn more about other best practices, and the science of gardening with companion plants visit the link below.

These local garden articles will reach you each week throughout the gardening season, but gardening information can be found year-round by clicking on "Yard and Garden” at the University of Minnesota Extension website, www.extension.umn.edu, or by visiting our Facebook page at www.facebook.com/Beltramicountymastergardeners.

Local Master Gardeners will respond to questions via voicemail. Call (218) 444-7916 and leave your name, number and question.

Related Topics: GARDENING
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