Field Horsetail Biology and Control methods
This perennial plant belongs to the Equisetaceae, Equisetum or horsetail family. Equisetum comes from Latin, equus meaning horse and seta meaning brittle, referring to the barren stems that supposedly resemble a horse’s tail.
Some other common names are joint grass, mare’s tail, horse pipes or snake grass. There are several members of this family that are native to the northwest.
Members of the Equisetaceae family are prehistoric plants, as are ferns, which may provide a clue as to why and how they have been around so long. This plant spreads by spores located on the cones and has an extensive creeping rhizome system that penetrates to great depths in the soil.
Field horsetail, Equisetum arvense L. is a perennial with aerial stems and underground tuber-bearing rootstocks which has dimorphic stems: a fertile cone-bearing stem which arises in early spring is flesh-colored and ½ to 1 foot tall with cones ¾ to 1½ inches long; a sterile or vegetative stem arises after the fertile stem and is 1 1/5 to 2 feet tall with many whorls of slender, green jointed branches.
Giant horsetail, Equisetum telmateia Ehrh resembles field horse tail but is much more robust with sterile stems over 1½ feet high and cones which are 1½ to 4 inches long.
Smooth Scouring Rush, Equisetum laevigatum A. is a tenacious perennial plant with deep, spreading rootstock. Stems are rough (high silica content), jointed and hollow. Leaves are scale-like appendages located at stem nodes. Fertile stems have a terminal spore-producing cone. Field horsetail produces whorls of branches at each stem node while Scouring Rush is coarse with evergreen stems and very apparent bands at the base of each collar. Field horsetail is adapted to wet areas, while Scouring Rush can establish either along stream banks or in relatively dry soils. Field horsetail is a noxious weed that has survived millions of years to become one of the most tenacious weeds today. It is toxic for horses, sheep and cattle when consumed. Horsetail is difficult to eradicate despite a gardeners best efforts. It spreads by spores carried by the wind every spring and by its tubers. It thrives in wet soils, which is why it is commonly found near rivers, lakes roadsides and ponds or poorly drained ground. This perennial weed has a deep and extensive root system and easily survives cold winters;
Some steps to help eradicate this thug of weeds
Wear your gloves and dig up a small horsetail plant with a spade, making sure to get all the roots. Even the smallest piece of rootstock will grow into a horsetail plant. without delay collect it in a plastic bag, knot it securely and dispose of appropriately. Not on the compost heap!
Chop or mow horsetail weed to ground level if the plant is large or covers a vast area. Put the foliage in a plastic bag and dispose of appropriately.
Break the thick stem or slash it with a sharp knife or shovel in several places. Make sure the gashes are deep enough and bruise the plant. Douse the plant in commercial weed killer that contains glyphosate,( I know, but it is effective, and I am going against my principles, but as a spot weedkiller I’ll excuse myself this is the last result) pouring directly over and around it. The weed killer will penetrate the gashes and eventually kill the horsetail plant. Treat any new growth promptly, and reapply the herbicide later in the season, or early next season to eradicate it permanently.
A much more ecologically friendly approach, is to pour vinegar directly over the horsetail plant and the soil around it on a dry day to eradicate it from your lawn. Horticulture vinegar is stronger than household vinegar and kills young plants immediately. Reapplication may be required the next day and for a few days after for mature plants .
The long-term control of Equisetums has been very difficult due to their tenacious root systems and high silicone content. An integrated control approach can help alleviate the problem. Improve drainage and encourage growth of a healthy perennial grass cover. Cut or burn fertile stems prior to spore formation to reduce spread potential. Porous landscape fabrics or black plastic mulch effectively prevent Equisetum growth. Smother the horsetail plants as an alternative to applying weed killer to it. Spread a plastic sheet or a 1/2-inch thick cardboard over the mowed plant and poke holes in it to allow mulch to penetrate. Spread a thick layer, at least 5 to 6 inches, of pine bark or mulch over the sheet; leave it for four to five months. The plants will compress under the weight and eventually die due to lack of oxygen.
(Sawdust or bark mulches are ineffective. Deep cultivation can be effective in the short term. Be aware that rhizomes cut into very short pieces will regenerate. Shallow cultivation and dragging the rhizomes are not advised.)