Are Your Plants Competitors or Companions?

Like other living organisms, plants compete for sunlight, nutrients, water, space, etc. This form of competition can be both detrimental and beneficial.

Though they appear to be an agreeable bunch, the plants in your yard might be biologically bullying each other.

Like other living organisms, plants compete for sunlight, nutrients, water, space etc. and this competition is the basis for allelopathy. This form of competition can be both detrimental and beneficial.

Many allelopathic plants release toxic chemicals through the root sytem, by leaching or root exudation, or through vaporization. These toxins inhibit growth and prevent germination of surrounding plants allowing the allelopathic plants to reign supreme and have maximum reproductive success.

Negative Effects of Allelopathic Plants

Sometimes allelochemicals remain persistent in the soil long after the removal of the allelopathic plant, causing soil sickness and wreaking havoc on plants that try to take root next. This inhibiting allelopathic behavior can be seen locally with understory plants beneath pecans and oaks. Other examples of plants with allelopathic properties include black walnut, goldenrod, fescue, perennial rye, bluegrass and garlic mustard weed.

Benefits of Allelopathic Plants

On the other hand, many selective allelopathic plants are wonderful companion plants. Some work to our advantage by suppressing weed growth. Allelopathic plants will actually quell certain weeds that might choke out other plants. Others work to protect each other and boost each other’s growth and success.

In addition, since allelopathy can aid in repelling pests, both insects and weeds, companion planting is often used in herb and vegetable gardens. These plant partners are also said to enhance each other’s flavors.

Another benefit of allelopathic chemicals, besides making edible plants tastier and keeping pests at bay, is that there is a reduced — or even eliminated — need for pesticides. These chemical interactions act as natural pesticides, perfectly conducive for organic gardening. One common companion plant, basil, repels insects and benefits a wide array of plants such as bell peppers, tomatoes, asparagus, beans, cabbage and oregano. Aphids, an all-too-familiar garden pest, are also repelled by basil and other aromatic plants like chives, garlic, mint and petunias.

So if you’ve done all you can to help your plants thrive and they’re still not doing so hot, don’t beat yourself up. They could be at the mercy of a silent killer. And if your plant is under attack, being eaten alive by pests, don’t douse it in pesticides. Instead, consider giving it the companion it needs.

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