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Controlling Perennial Weeds

without resorting to the use of chemicals

January 23, 2000
Perennial weeds can be difficult to get control of, once they have become established. They are tough and durable, and can withstand conditions which would kill most other plants. Like most weeds (and other plants), perennial weeds produce an abundance of flowers... and thousands of subsequent seeds. Unfortunately they also reproduce and spread by fleshy underground roots and rhizomes. Attempts at pulling up perennial weeds may seem successful at first, but the cold reality is that the plant will regrow from any (and every) portion of the root which remains in the ground. That #@^&*!! dandelion out in the middle of your lawn, is probably the best example of these perennial pains....
The most effective way to rid yourself of a perennial weed is by carefully digging up the entire root system. This is usually only appropriate when there is a need to do other digging and cultivating in the area. There is no reason to dig up your entire lawn in pursuit of dandelion roots, and it is ill advised to do too much digging around your perennial plants. Because of their ability to regenerate from even a very small piece of root, perennial weeds should be dug and destroyed prior to using a roto-tiller in the garden. Roto-tilling will chop their thick roots into a multitude of new plant starts, so it is definitely worth the extra effort to get as many of these roots out of the soil before you till!

Lawn weeds

As for those weeds in the lawn... Probably the best weed control of all is a healthy, well fed and watered lawn. Regular mowing is equally important to prevent the weeds from flowering and producing seed.
When you grab your trusty weed extractor and head out to pull perennial weeds like dandelions out of your lawn, you will probably have only temporary success. These weed pullers reach down into the soil a couple inches, and with a quick motion grasps the tap root and pulls the weed out of the ground. Unfortunately, even though you may succeed in getting most of the plant's roots, the tip of the root is usually snapped off, and remains in the ground to begin regrowing into a new weed which will pop up in a week or two.
The plant world is to a large extent, governed by the rule of "survival of the fittest". Although your weeding efforts may seem futile because of the weeds ability to regenerate, each time you remove that weed you weaken it, and temporarily retard its growth. With the weed in this "root cutting" state, your lawn grass will begin to regrow in that space. With subsequent weed extractions, your healthy lawn grass will easily crowd out the weeds, and become the "survivor". Keeping your lawn mowed at about 2 1/2 inches tall will further weaken the weeds because as you mow, you are also removing much of the foliage from the weed, and consequently, much of it's ability to attain food. If your lawn has reached the point of neglect that the weeds are thriving, and the patches of grass are thin, brown and sparse, you are probably facing a lost cause. You will probably be better off to use a shovel to dig and remove each weed, and then start a new lawn from scratch.

Vegetable garden

The principal of "choking out the competition" also applies in the vegetable garden, but to a lesser extent. Hopefully, as you prepared your vegetable garden plot, you were able to remove most of the perennial weeds as you dug and cultivated. If you were successful in this effort, your concerns will only lie in removing new weed seedlings as they sprout. Healthy vegetable plants also help out by shading the soil, preventing any waiting weed seeds from germinating. Complete your weed defense with a good, thick layer of mulch between each row, and your weeding in the vegetable garden should be kept to a minimum.

Hard core weeds... blackberries etc.

The most difficult of the perennial weeds to eliminate are the woody vines and shrub weeds like blackberries and scotch broom. The only way to beat these killer weeds (aside from chemical warfare) is hard work, pure and simple. Again, we are faced with the weed's power to reproduce by seed in addition to it's ability to spread new stems underground, which can emerge from the soil twenty feet or more away from the parent.
You will not get rid of your blackberry vines (or other woody weeds) in the first or second year, but you can begin to get a handle on the problem, and eventually become the victor. It will take diligence, commitment, and a good pair of leather gloves. Begin the battle by cutting all of the stems off, as close to the ground as possible, and then dig up or pull as much of the plant's root system as possible. As new stems emerge, again attempt to dig up as many of the roots as possible.
At this point, figure out what your particular plans are for this space, and begin to implement them. For example, you can direct a pathway constructed of black plastic covered with a layer of gravel or bark, so that it wanders through the weedy area. Not only will the finished path inhibit the weed's growth by blocking the light and air from the weed, but the foot traffic along the path will constantly trample, damage, and destroy them. You will have to be prepared for the chance that you may periodically do a little more digging in the path to eliminate renegade growth, but with each new season it will take far less effort than the prior year.
If your plan is for a perennial flower bed, take the time to dig in, and get every root you possibly can before you begin your planting. Because you will not want to disturb your new flowering plants by re-digging around them, it might be helpful to wait a month or two between the initial weeding operation, and the time when you set your new plants in the garden. Any weeds which survived your first eradication efforts, will probably pop their little heads up out of the soil during this waiting period. Being the ever-vigilant gardener that you are, you will take note, dig and destroy them.
Sod may be planted as a control measure in these weeded areas, but only after you have made a reasonable attempt at eliminating all of the woody weeds and their roots. Periodically you may have problems with stems that manage to work their way through the turf. Cut these back to the ground as soon as you see them, so they always remain a leafless stub. Eventually, the new grass will have a strong enough foothold to choke out the offending plants on their own. Once the lawn is established, your regular mowing will do any further weed trimming for you.

Just an odd tip or two

It is sometimes possible to kill woody weeds (like blackberries) by driving a few COPPER nails into the stem or trunk. This is not a foolproof method, and may only kill a portion of the plant, but I have had good success in the past. If you can find the copper nails to use, it is worth a try!

In areas where the ground freezes solid for a prolonged time (for a week or more), there will be a period immediately after the thaw, when the roots of woody weeds have very little hold into the soil. During this period the soil is in a loose, unpacked state. The ground 'heaves' or rises up when the water in the soil freezes solid. When the temperature again rises above freezing, the ice melts and flows back into the soil. This leaves the soil temporarily in this heaved state, with voids where the frozen water had been. If you can handle working in the cold, you will be amazed at the ease of which you can tug these woody weeds out of the ground (roots and all, I might add...). Please use care when you try to do any hand pulling of this nature. Even though it will be considerably easier for you to pull these big weeds out of the loosened soil, it is still strenuous work, which will probably tax a couple muscles you didn't even know you had, so be very careful and don't overdo it.
Normally you shouldn't be walking on the soil when it is in this expanded stage, because it can become seriously compacted and caked. Serious caking may necessitate adding organic matter to the soil in order to rejuvenate and rebuild the tilth (texture). A patch of ground which is covered with brambles and blackberries however, is of no practical use. With that in mind, I guess that the rule about not walking around on heaved soil can be disregarded.

GO TO: General Weed Control
GO TO: Controlling Annual Weeds

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