Maine news, sports, weather from Portland Press Herald / Maine Sunday Telegram, Portland, Maine

July 22, 2012

Maine Gardener: Eradicating weeds takes patience, persistence and hard work

By TOM ATWELL

The weeds have been terrible this year. With all the wet weather in May and June, followed by temperatures in the 90s, they have been persistent and profuse.

We have had dock -- broadleaf and curly, with the botanical name Rumex -- invading our raspberries and the nearby grounds. Purslane, chickweed and clover have been all over the vegetable garden recently.

And then there are violets, which probably aren't a weed -- but they sure do like to crowd out the tomatoes and peppers. And we are still getting a few dandelions, but they were more of a problem in the spring.

It could be that it just seems like weeds have been much worse and I have been paying more attention. Nancy has in the past done most of the weeding, but in this, my first year of semi-retirement, I committed myself to doing a lot more to keep the weeds down.

I got some unexpected help in March. A really heavy box with two containers of Preen showed up at the newspaper office, and I brought it home. 

One container was Organic Preen Vegetable Garden Weed Preventer, which contains processed granules of corn gluten meal. This is a byproduct of making corn syrup, and for some reason the corn gluten meal prevents sprouting seeds from producing roots.

The Preen label did not say it could be used on lawns early in the spring to prevent crabgrass, but there are corn gluten meal products sold for that purpose.

Following the label directions, I put this down in the area where I planted a new bed of strawberries and the early rows of peas. The label says this will keep weeds down for four to six weeks, and it really did the job. I could have bought another container and put more down, but by late May, I wanted to plant cucumbers and squash in between the pea rows, and I feared the corn gluten might prevent them from sprouting.

I haven't used the Preen for flower beds yet.

In my battle to keep weeds at a minimum, I contacted the Weed Science Society of America. The person who answered the phone directed me to an article that Robert Norris, a professor emeritus at the University of California-Davis, wrote for the society: "Never Let 'Em Seed."

After reading the article, I no longer wonder how the purslane keeps coming back to our garden. Norris conducted research and found that a single purslane plant can produce 2 million seeds.

Chickweed is lazy compared to that, producing only 25,000 seeds per plant.

And those seeds stay in the ground, creating what Norris calls the "weed seed bank."

"Seeds 'in the bank' can remain viable for quite a long time and sprout when conditions are right," Norris wrote. "That means it will take several years for you to reach your weed-free goal."

He said some weed seeds die in two or three years, but others can last decades.

"On average, though, the bulk of your weed seed bank will be depleted in about five years if no additional seeds are added," Norris wrote. "That means diligence is the key. Never let one weed go to seed, or you will be back to square one."

Norris discounted the weeds you get from seeds dropped by birds and by windblown weeds such as dandelions. Birds drop few annual weeds, and you should be able to handle the wind-blown weeds with little trouble.

So, since this is the first year of my diligent weeding program, I may see some results by 2017.

Norris noted that weed fighting in the vegetable garden is easier than fighting weeds in perennial gardens. Weeds in perennial gardens are often perennial as well, which means they keep coming back even if you don't let them go to seed. While you do have to keep them from going to seed, you also have to be diligent about removing their shoots and tubers so that, eventually, they will die and you will no longer have to deal with them.

(Continued on page 2)

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