Your Garden … Kate Russell: Some weeds can be beneficial for soil in your Gilroy garden

Weeds can attract, distract, or repel insect pests

By Kate Russell

Kate Russell

Weeds are nearly always classified as undesirable. But what if we have been wrong about weeds all along? What if weeds could provide benefits to our Gilroy landscapes and gardens? It ends up, sometimes they can!

Weeds grow faster, go to seed earlier, and are more durable than nearly all of our garden and landscape plants. And yet, we battle them day after day, year after year. Those days may be (partly) over.

Recent research has shown that some weeds actually have a good side. Weeds can attract, distract, or repel insect pests. Weeds can also be used to reduce erosion, improve soil structure, add nutrients to the soil, and attract pollinators and other beneficial insects.

Weeds can be used as trap crops. Trap crops are planted earlier in a season to lure pests away from popular garden plantings. Trap crops may be left in place to attract natural predators, or they can be removed from the area once they are thoroughly infested. Because the pests prefer these weeds, your plants are less likely to contract the diseases carried by those pests or be damaged by insect feeding.

Some examples of weeds as trap crops include:

• Clover planted around cabbage family crops to reduce damage by cabbage root flies

• Weeds in the sunflower family, such as dandelions, goldenrod, and ragweed, lure leaf-footed bugs away from tomatoes

• Weeds from the cabbage family, such as mustard and hairy bittercress, protect collard greens, Brussels sprouts, and others from flea beetles and harlequin bugs

• Nasturtiums are said to attract aphids and whiteflies

On the flip side, tick-trefoil (‘Desmodium’) has been shown to repel moths whose caterpillars damage several different edible plants.

Since weeds grow so rapidly, with so little help from us, they are a natural when it comes to erosion control.  Some of these beneficial weed species can enrich the soil and reduce compaction. Weeds in the legume family, such as clover, vetch, and black medic, are good choices for erosion control because they add nitrogen to the soil. You can allow these weeds to stay in place, as a ground cover, or you can dig them in as a green manure, adding nutrients and improving soil structure.

Many weeds that sprout in our Gilroy gardens produce attractive flowers filled with pollen and nectar. These resources attract a wider variety of pollinators and other beneficial insects, increasing biodiversity and improving the overall health of your landscape.

While allowing weeds to grow around seedlings is still a bad idea, and we need to keep trying to eradicate invasive weeds, perhaps we can relax our stand on some weeds growing in and around our garden and perennial landscape plants.

Due to COVID-19, Spring Garden Market has been canceled. Alternate ways of making the plants available to the public are being investigated. Information will be posted at www.mgsantaclara.ucanr.edu/events/spring-garden-market/ when available.