Fall weed control

By Mike Lorenc, Conservation Garden Park

Weed. The four-letter word for those of us trying to maintain a nice landscape. Fall is here so the time to think about combating those weed pests is…(looks at watch..) right..  now.  Groaning aside, now is the time to take action as Autumn offers some unique opportunities to reduce the pain of weeds next season.

Disrupt the weed food cycle.

The most difficult weeds that we deal with are the kind with deep, extensive root systems. These perennial weeds include dandelion, mallow and field bindweed (morning glory). In the fall these weeds are sending most of their energy to the roots for winter storage, which makes the perfect time to disrupt their growth cycle. If you opt to use an herbicide, 2, 4-D (commonly called Weed-B-Gone) can be sprayed on lawn weeds now.  The pesticide follows the sugars in the plant which are being sent to the root system for winter storage.  This means herbicides will move deeper into the root system now than at other times of the year—providing a more thorough kill.  For those using organic techniques, hand pulling and getting as much of the root as possible will help disrupt the transfer of energy to the deeper parts of the root system, weakening or killing the weed.

Fertilizing to feed plant roots.

For the same reason that using pesticide in fall kills deep in the roots, fertilizing in the fall does the same thing in reverse. By adding fertilizer, you’re helping the plants create more energy that can be stored in the roots through the winter for on-demand access in the spring. Deeper, stronger roots improve water efficiency and help the plant out-compete weeds.  Make sure to use a fertilizer that is lower in nitrogen (promotes leaf growth) and higher in phosphorus (feeds root system).

Deadhead weeds.

As much as possible don’t let your weeds go to seed, and sometimes that means to deadhead the flowers off before the seeds form. Pulling them would be ideal, but if you only have a small amount of time, off with their (flower) heads. This will buy you a couple of weeks to take the weeds out before they regrow their seed heads, eliminating a source of fresh weed seed.


Now is a great time to mulch those flower beds to reduce the chances that weed seed in the soil will grow into weeds next season. A couple of inches of mulch prevents light from penetrating down to the soil, reducing or eliminating germination. As a result, early season annual weeds never get a foothold in your landscape, which means fewer weed pulling sessions all season long.

Plant new plants.

Planting new plants may not seems like weed control, but it is. Increasing the general density of your garden bed works to close the gaps in the canopy making it harder for drifting seed to reach the soil. And even if they do gain purchase in the soil, a more densely planted bed will out-compete weeds by taking up the water and nutrients and blocking out the light to new seedlings.

To learn more about landscaping in Utah, visit our website: http://conservationgardenpark.org