Garden Tips: Weed wars — to hoe or not to hoe

This spring I decided to use weed control fabric in my little vegetable garden. It is a small patch and hoeing is not burdensome, but by mid-summer the plants are so big that hoeing around them becomes impossible.

That is why I decided to use landscape fabric to control the weeds this year.

I bought a roll of spun-fiber fabric from a big box store. Within several weeks of putting the fabric down in the garden, it was being pushed up by the very healthy weeds underneath. Apparently the fabric is so thin that it does not block out light or weed growth. Why bother?

I then tried to use a mulch of overlapping sections of wet newspaper to block the light. A newspaper mulch worked well for me before in another region of the country, but not here. The paper quickly dried out and blew all over my yard the next day. Rats!

In desperation, I laid down a second layer of better quality woven landscape fabric that actually blocks out light. It is working much better, but I have put a lot of work into trying to control weeds in this little patch. It would have been easier to just leave the soil bare and do my best with a hoe, which is what I plan to do next year.

I am not the only one with weeding problems. Yesterday I noticed a local gardener out weeding a landscape bed that has been overtaken by Equisetum, also called scouring or horsetail rush. This plant is native to the Pacific Northwest and flourishes in areas where the soil stays wet or moderately wet. It our dry shrub-steppe region it is usually only a problem when it is introduced into landscapes via nursery stock grown elsewhere.

Equisetum reproduces via spores, tubers, and rhizomatous roots. It is a primitive plant that has no true leaves. In local landscapes it typically appears as green leafless stems topped with spore-producing cone-like structures. Equisetum may also produce sterile stems with whorls of leaf-like branches that makes it look somewhat like a bottle brush.

Equisetum thrives in wet sunny spots. However, once established it will tolerate less favorable conditions and is nearly impossible to eradicate. Because it does not have leaves and the stem has a ridged waxy surface, it is resistant to most herbicide applications.

The typical recommendation for control of Equisetum in home landscapes is persistent pulling or hoeing. Good luck with that.

One study in Quebec, Canada, revealed that “hoeing 16 times had no impact on removal.” Its persistence is due to its 3- to 6-foot deep tubers and extensive rhizomes that provide stored carbohydrates for regrowth time and after time.

The Thurston County Noxious Weed Board indicates that “depleting the food reserves in the rhizomes” by “complete removal of the tops about two weeks after each emergence for three to four years has provided effective control.”

Yikes, only a dedicated, unrelenting gardener is likely to have success using this method.

Some sources also indicate that heavyweight light-blocking landscape fabric or black plastic placed over the soil for three to four years may kill out a patch of Equisetum, but it might still escape around the edges.

If all else fails when controlling Equisetum in the landscape, WSU recommends the use of dichlobenil, known as Casoron, a granular pre-emergent herbicide that is applied directly to the soil surface. They recommend application in late winter or early spring when there is precipitation available to move the chemical into the soil.

Note: Casoron should not be used on sandy soils like those found in many parts of our area.

The war against weeds has just started — more to come.

This story was originally published June 23, 2017 at 10:19 AM with the headline "Garden Tips: Weed wars — to hoe or not to hoe."