Weeds in Your Yard - a Basic Primer

“One man’s trash is another man’s treasure”. That is a very old axiom that holds so true, and we could make a couple of slight changes to this and have it apply to some things around our yards. One person’s scary spider is another person’s fly-eating beneficial bug. One person’s annoying raccoon is another person’s close-up encounter with wildlife. And, very clearly, one person’s aggravating WEED could well be someone else’s wildflower. The dandelions we so universally despise in our well-manicured lawns might just be the salad in someone else’s dinner, and perhaps purposely grown for that reason.

In fact, a very high percentage of the plants around us, along roadsides or in landscape settings, are not native to North America, and were purposely brought to this country over the hundreds of years of immigration and settlement here. European immigrants, in particular, routinely brought with them the plants or their seeds for things they felt they could not do without. Perhaps not knowing what to expect in a new country they would call home they brought grasses for their livestock to forage from, agricultural plants to grow their own food, and herbs and ornamental flowers for their gardens. It would be very difficult for many of us now to find true “native” plants in our landscapes and gardens, the invaders have taken over so well.

This leads to the question – just exactly what is a “Weed”? We could apply a botanical definition, which might be that a weed is any plant in an environment where it does not belong. On the west coast eucalyptus trees dominate many hillsides and open fields, all of which are native to the Australian region of the world. These, technically, are weeds, which have the ability to become seriously invasive and dominant, choking out native vegetation. The islands of Hawaii have suffered tremendous loss of native vegetation over the past century or two, due to imported trees and shrubs that take over the lush environment there, at the expense of the native plants. Whatever biological forces may have controlled these plants in the habitat in which they evolved are lacking in their new homes, and they can grow and spread rapidly.

Most of our designated “invasive” weeds, however, likely snuck into North America, possibly as contaminants in sacks of grain, in soils of potted plants, or other containers. Their seeds could have been mixed in with desirable seeds and just managed to plant themselves and propagate once deposited on the soil. Again in the west the awful Yellow Star Thistle now covers tens of thousands of acres of open fields with solid stands of their spiny, toxic shrubbery, likely an import as a stowaway with other materials. Across much of North America that weed so often depicted in cowboy movies, the tumbleweed or Russian Thistle, grows in abundance after being imported many years ago as a contaminant seed in bags of grain. With the potential to grow in vast, solid stands with plants up to 6 feet in height this invasive weed is a serious problem and can be destructive to native vegetation.

The second definition of weed, though, is simply a plant where we don’t want it to be, and many times our desirable garden plants find a way to grow invasively outside of managed landscapes, and can become problems. Plants that may be attractive and planted intentionally in backyard ponds can escape to natural waterways and propagate quickly, causing major problems. An excellent example of this is the floating weed called water hyacinth, native to South America and quite lovely to look at, but now responsible for thousands of square miles of clogged waterways throughout much of the U.S. In the name of preserving our environment as much as we possibly can it behooves us not to intentionally import new varieties of plants and animals. Seeds should be removed from our clothing and shoes if we have been hiking in some country outside the U.S., and souvenirs should not be brought back with us unless sanctioned by the USDA as okay to import.

When it comes to the weeds you find in your gardens and lawns there are some lessons to be learned, and that is the hope of this short introductory article on Weeds. It is not our intention here to teach you how to do your own weed control, but given the many kinds of obvious problems caused by homeowners performing their own chemical weed control we hope we can keep you from making similar mistakes. One important lesson is to understand the basics of the weeds themselves. We classify weeds as either “broadleaf” or “grassy” weeds, and this really matters when choosing a weed control chemical, especially for use on your lawn. There also are some weeds that look just like grasses, but biologically are broadleaf weeds, so you have to watch out.

In general a Broadleaf weed is distinguished by the arrangement of the thick veins on the leaves. Picture in your mind a maple leaf, with a major vein running from the stem to the tip of the leaf, and side veins arising off of this central vein. Some of the common broadleaf weeds (and there are a great many kinds) are things like blackberry, poison oak and ivy, nightshade, thistles, dandelion, spurge, oxalis, etc. Grass weeds have all their thickened veins arising from the base of the leaf blade and extending all the way to the tip of the blade, running parallel to each other. Grass weeds are things like crabgrass, Bermuda grass, orchard grass, dallies grass, etc..

The imposter in this nice orderly system is a group of plants called the Sedges, such as nutsedge (also called nutgrass) and kyllinga. These are biologically broadleaf plants but their leaves and the veins on them are arranged just like grasses. Why does this matter? Well, chemical weed control products work on the biology of the weed, and there is just enough difference between the biology and metabolism of broadleaf and grass weeds that a chemical that is designed to kill a broadleaf weed may have no effect on a grass weed. A product like 2,4-D, commonly the active ingredient in so called “weed and feed” lawn products, will only kill broadleaf weeds, so if you use it to eliminate crabgrass in your lawn it will be ineffective.

Another characteristic of weeds is their growth cycles, and the two most important kinds are Annual and Perennial weeds. Annual weeds are those that grow from seeds in the spring, produce flowers and their own seeds that summer, and die by fall, with the next year’s crop of that plant being produced only from the new seeds. Perennial weeds are those that survive from year to year, even though they also may produce seeds to grow new plants. The perennial weed may have foliage that stays on it all year long as some of the shrubby weeds do, it may lose its leaves like poison oak or blackberries do and grow new leaves the next year, or possibly only the roots survive the winter with all new foliage growing the next spring, such as Bermuda grass does.

A very common example of an annual weed is crabgrass. Again, why does this matter to you? Well, if you choose a chemical to control this weed that is a “pre-emergent” it is designed only to stop the seeds from sprouting. If the crabgrass has already begun its growth in your lawn that pre-emergent herbicide will be ineffective and you will be disappointed. Similarly, if you have a perennial weed like Bermuda grass, whose roots survive the cold winters even as all the green foliage dies, you have a tough problem for control. The pre-emergent herbicide that can kill sprouting seeds is going to have no effect on the hardy roots of Bermuda grass, which could extend as deep as 8 to 10 feet in the soil.

Hopefully this basic information helps you to understand that some knowledge of the weeds themselves is needed in order to effectively control the problem. The other area that is important, should you choose to do your own chemical weed control, is the safety of your landscape and perhaps that of your neighbors. Most herbicides are not particularly toxic to people, being designed to affect a plant’s metabolism as they are. However, if used incorrectly some very visible problems can occur. Perhaps the example to start with is one of the most popular weed control products, and that is Roundup. This is a “non-selective” chemical that will control any kind of weed – annual or perennial, broadleaf or grass – if applied at the appropriate time. It also does not have the ability to distinguish between the “weeds” you want to eliminate and the desirable plants you want to keep. For that reason it is imperative that you READ THE PRODUCT LABEL for precautions and use directions, and adhere to these very carefully. Roundup is absorbed by the green parts of plants, including stems of such plants as roses or citrus, and you must avoid spraying these areas. If you casually spray the “weeds” in your lawn with Roundup you will also easily kill every turf grass plant that the Roundup landed on. It is very effective, but all it knows is that the plant is green.

While the spray is still wet Roundup, and many other herbicides, can also be transferred from place to place on your shoes, and if you walk on the wet weeds, and then walk over your lawn, you run the risk of creating a path of dead spots exactly where your shoes touched. If you spray weed control chemicals when there is any amount of wind blowing you also run the risk of having the herbicide drift onto nearby plants to kill them as well. You would be surprised at how far a few fine droplets of mist can be carried, even in a slight breeze. The good news is that this particular weed control product is going to stay where you put it unless you physically carry it someplace else.

Not so with a few other kinds of herbicides, including that 2,4-D we mentioned earlier. This and some other products are “volatile”, meaning vapors of the active ingredient can actually drift off of the treated site, particularly on hot, windy days. If 2,4-D is used and left on the soil surface, its vapors can relocate to other plants in your yard or even to neighboring yards, and cause injury or death to plants that were never intended to be killed. Other broadleaf weed products used on lawns can have the same effect, and if used under trees or shrubs on hot days can kill the plants above due to vapors drifting onto the leaves. Once again, read the label that comes with the product to note any precautions on its use. Many times the instructions will tell you to “water in” the product after you have applied it, to get it into the top layer of the soil. Once here it is far less likely to move on its own, and will provide that weed control you wanted in the first place.

The internet offers a great many websites, particularly from Universities, that will help to educate you on weed control. They discuss the various retail products available and often just what characteristics of each kind you need to know to prevent problems. It can be more than just embarrassing if your herbicide application causes the death of valuable plants in your neighbor’s yard. It could lead to legal squabbles as well. Always consider the option of hiring a licensed professional to do the weed control for you. These companies have received a great deal of training in the area, they have been tested by the state to ensure they know how to apply weed control products effectively and safely, and they can help you maintain your lawns and gardens weed free.

You cannot overlook the fact that while herbicides, in general, have a low toxicity to people and pets, they still are toxic materials that need to be used correctly. This may be another good reason to consider hiring a professional to do most of your weed control for you, as they are equipped with the proper application equipment and safety equipment, and you won’t have to bother storing all this stuff yourself. But, for the do-it-yourself homeowner the most important advice is to read the Label for the product. By following the instructions provided by the manufacturer you can enjoy the benefits the products provide. Children and pets should be kept away from any plants you spray until the spray has dried, and whoever does the application should wear, at a minimum, shoes and socks, long pants, long sleeves, safety glasses, and waterproof gloves. Excess spray material should never be dumped into rain gutters or storm drains, but used up correctly or stored for the next application.

Source: BugBattalion New York