America’s most weeded – dandelion

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By David Graper

SDSU Extension Horticulture Specialist

Dandelions (Taraxacum officinale) are probably one of the most noticeable and common lawn and field weeds of all. Just about everyone that has a lawn has fought to get rid of this weed at one time or another. And, right now we are in the middle of dandelion bloom season. They are very adaptable to the types of soils in which they will grow, can tolerate repeatedly being mowed off to within a couple inches of their lives yet seem to thrive in countless lawns and other non-cultivated areas throughout the northern Great Plains, most of the United States with related species found all over the world. This low-growing member of the Aster (Asteraceae) family produces bright yellow-orange flowers on hollow stems about 3 to 8” long, depending on where it is growing. Each plant may produce a few dozen flowers over the course of a growing season with peak bloom usually in early summer but flowering can continue into mid-summer or even into the fall. Each of those individual flowers may produce dozens of individual seeds, each equipped with a silky little parachute of white fibers that are designed to allow the seed to be carried off by the wind or when blown by a child.

Dandelion is a perennial weed that develops a deep taproot within just a few weeks. Only basal leaves are produced because the flowering stems do not possess any leaves. All parts of the plant contain a white, bitter sap. The leaves are elongated, and grow to about 1” wide and 5 to 6” in length with distinctive serrations and dissections in the leaf giving them a jagged appearance, similar to the teeth of a lion, for which it is named. As plants age over several years, leaves may become more upright, particularly if they are growing in tall grass, or among other plants or in shadier locations. But in a lawn situation, the leaves tend to remain fairly close to the ground.

One of the amazing things I have noticed about dandelions is their ability to come back after mowing. Even though I might try to time mowing when there are at what seem to be a maximal number of flowers sticking up in the grass of our lawn, the next day there appear to be nearly as many in their place as before. Those flower stems must grow very rapidly – perhaps mowing off the other flower stems on a plant somehow stimulates the remaining flower stems to grow that much more quickly. Individual flowers are open for only a few days. One positive benefit those yellow flowers have is that they do serve as a significant pollen and nectar source for pollinating insects in the spring, when few other plants are yet blooming.

Controlling dandelions can be a challenge. Once plants are a year old or more, they have likely stored up significant food reserves in their fleshy tap roots so they can withstand stressful conditions for some time. However, they are not that competitive against a thick, dense lawn. A dense lawn makes it more difficult for new dandelion seedlings to get established and the grass blades block sunlight from the leaves of the dandelion plant. Raising the mowing height to at least 2 ½” is also helpful in promoting healthy grass and increasing the competition for dandelions and other lawn weeds.

Most people think about trying to control their dandelions in the spring when they see them in bloom. However, this is not the best time to try to control them, particularly if they plan to use a broadleaf herbicide to do it. Dandelions are in their most active growth stage in the spring and are actually somewhat resistant to the herbicide at that time. Yes, you can curl up the flower stems and the leaves a bit but will probably not really kill that many dandelion plants at that time of year. Another larger concern is that there are so many other broadleaf plants actively growing at that time of year too, most with lots of soft, succulent foliage that will easily take up the herbicide. The result is “collateral” damage to trees, shrubs, perennial flowers and often garden vegetable plants. The new growth will become twisted and the new leaves will be misshapen and pinched. Since there are no stated safe levels of herbicide residue in garden vegetables like tomatoes or potatoes, the fruit produced from drift damaged plants may not be safe to eat. Dry, granular weed and feed products that contain a fertilizer as well as a broadleaf herbicide may be somewhat safer than a liquid herbicide because it is less likely to drift. But the efficacy of a weed and feed product may not be as good, particularly if it is not applied correctly. Be sure to follow the label directions for whatever product you decide to use.

Fall treatment of dandelions is a much better option for a number of reasons. First, dandelion plants are much more susceptible to the effects of the herbicide in the fall. They are actively storing carbohydrates in their roots which makes it easier for the herbicide to be translocated to the roots as well. Secondly, plants of all ages will be susceptible. Spring treatments will not affect the seed that is flying around at that time of year. Once that seed lands, it starts the next generation of plants that will have avoided the spring herbicide application. So, the next spring, dandelions will still be there in the lawn. Treating in the fall is much more likely to break the cycle of new plants growing up from seed because there are usually only a few flowers forming in the fall. Secondly, most other broadleaf plants are shutting down for the year in the fall. In fact, it is not a bad idea to wait until you start seeing the leaves of your trees and shrubs turning their fall colors before you treat for dandelions and other broadleaf weeds. Once the leaves on your trees start turning color they will be much less likely to absorb broadleaf herbicides from drift and have it translocate to other parts of the plant. The vegetable garden is also shutting down for the year, particularly if you delay your herbicide application until after the first frost. While most garden vegetables will be damaged by the frost, dandelions are cold tolerant enough that they can withstand freezing temperatures and still be susceptible to control with herbicides. If they are still green, you can probably still spray, but it will be best to do it on a day when the temperature is above 50°F.

Hand digging of dandelions is another method of control, but really only feasible in a small yard, garden or flower bed situation. There are a number of different types of dandelion diggers available, most of which are designed with a narrow shaft with a broader, forked tip that can cut the root or pry the plant up out of the soil. Keep in mind that that fleshy tap root may go down a foot or more into the soil. An older plant can be difficult to dig out. The tap root may be a ½” in diameter, 12” long and may even have a few branches off the main root. If you do not dig it all out, there is a good chance that new shoots will develop around the remaining portions of the root and the dandelion will regrow, often with several smaller plants taking over where the larger, original plant once grew. Dandelion digging a few days after a good rain can make it easier to get most of the root out. It can also be rather therapeutic and you can work on it over several weeks, eventually clearing out the dandelions in your lawn or garden. I would advise wearing gloves to protect your hands though, that dandelion digger can cause some blisters after a few hours work. Hand digging is probably the only good option when dandelions are growing in a flower bed too, since you should avoid truing to use herbicides amongst other plants.

Dandelions are not all bad however. I have fond memories of taking a basket out into the pasture back home on my parent’s dairy farm in Wisconsin to collect dandelion flowers for my grandmother to make dandelion wine. I recall how she put them in a big crock to ferment with a dish towel over the top. I do not remember how the dandelion wine tasted however, probably not very good to a young child of eight or so. Dandelions can also be eaten, particularly in the early spring when they are not too bitter tasting. The young leaves as well as the crown of the plant can be used in salads. The leaves are often blanched to reduce the bitter flavor. The roots can be dried and ground up to make a coffee substitute. The roots are sometimes used as a component of root beer. Dandelions are credited with various medicinal properties as well.

A question from a gardener in Iowa

Q I planted some asparagus last spring. It came up this spring. Do I just leave it and let it go to seed or do I cut it back?

A The only time you should cut back asparagus is in the fall after the top growth has frozen. You can probably take a few harvests now, if the shoots are at least the size of a pencil. Then let all the new shoots grow up to make carbohydrates that will be stored in the plant crown for the winter and next year’s growth.

A question from Brookings, SD

Q I bet/hope you can tell me what is going on with my lawn! Last summer there was some rather lush grass here. Obviously, it didn’t winter too well. Now there is no grass and all the dirt appears to be “popping up.” (See photo.)

A First of all, it looks like the grass did die out, it was probably a bit weak under the shade of the trees there. I believe what you are seeing “popping up” are nightcrawler mounds. They are probably happily feeding on the dead roots of the grass plants that died. You could try using a stiff rake to knock down the mounds which will at the same time prepare a seedbed to replant that area. I would suggest a grass mix that contains fine leaf fescues like creeping red fescue, chewings fescue or sheep fescue. I would avoid ryegrass since that is not as hardy.

A question from Clay County, SD

Q I have a neighbor who has featured tulips in her yard for years. She has early, mid and late tulips and has divided them and continued several kinds of tulips for year. She has standard management of the tulips. This year, first time ever, she sees drooping tulips in several kinds of mid season tulips. This did not show up in the early ones. Tulips are in several locations around her yard in the country. It isn’t herbicide drift. She’s a farmer and would be aware of this condition. Question is if this condition is occuring in other areas this spring with the extra moisture. The stems seem unable to fully support the bloom. Thoughts on this environmental or viral? condition?

A I suspect that this is an environmental problem. The excess soil moisture may be limiting oxygen in the soil that is not allowing the roots to function like they should. On top of this we have suddenly been experiencing above normal temperatures, so the plants are not able to take up enough water with the sudden need for more water, even though the soil is wet. This problem should subside on its own.

A question from Minnehaha County, SD

Q All my asparagus spears have become thumb sized. No longer am I seeing nice thin green spears. I seem to have all male plants. Are the plants too old?

A This article at https://bit.ly/2IzFIbS may provide you with some information that you will find useful. Typically, thicker spears mean that the plant is becoming more vigorous and healthy, not too old. Thinner spears indicate a weakening plant. Male plants tend to have thicker spears because they do not use their energy to produce seed. I grow a variety called ‘Purple Passion’ that produces spears as thick as my index finger. The spears are very tender, even though they are quite thick. They also have an attractive purplish color. We like to chop the spears up and add them to salads or steam them, but the purple color fades once the spears are cooked.

Dandelions are generally quite easy to control with a fall herbicide treatment to the lawn. iGrow photo
Asparagus ready to harvest. iGrow photo
Lawn with nightcrawler mounds. iGrow photo
Tulips. iGrow photo
Fall is the best time to control broadleaf weeds like dandelions. iGrow photo
Dandelion diggers can be used to help control dandelions. iGrow photo