The recent dip in the temperature likely prompted you to reach for a jacket. But the change in the weather has also instituted some subtle responses in the plant world.
Just like us, they're getting ready for winter.
Like most natural organisms, plants have their own ways of surviving the winter. Annuals produce seeds that insure survival of the species; deciduous trees move nutrients out of their leaves, which makes them change colors and then drop to the ground.
Herbaceous perennials extract sugars and minerals from their leaves before they freeze and die back. Lest you think this is a course in plant physiology, some of the most difficult weeds that you battle in your garden are herbaceous perennials, and this physiology lesson will help you defeat them.
Killing the leaves on these pesky weeds might make you feel good, but it does little to eradicate them. Mow them off, cut them off or even burn them off with your flamethrower and they come back. Only when you kill the roots will you get the upper hand.
Fall is the time to attack. Ever since the plants started growing in the spring, the dominant movement has been from the bottom up. With recent temperature drops, the movement has reversed as plants are storing next year's nutrients in their roots.
Your challenge is to get weed killer from the top of the plant to the roots.
One of the prime targets this time of year is field bindweed. Bindweed is native to Eurasia and ironically, it was sold as an ornamental in the United States in the early 1800s. It had spread throughout much of Utah and beyond by the end of that century.
Field bindweed's Latin name, Convolvulus arvensis describes it well. It is derived from convolere meaning "to entwine," and arvensis meaning "of the fields."
This weed goes by many different aliases including morning glory, wild morning glory, creeping Jenny, creeping Charlie, cornbind, greenvine and lovevine. It is so widespread that it reportedly goes by 84 different names in 29 different languages.
While addressing a weed by the correct name might not seem important in your social circle, you need to determine if you are referring to the right plant, because controls are specific to certain plants.
The Weed Science Society of America has designated an approved common name for each weed. This is in addition to the Latin or scientific name of the plant.
For example if you refer to Convolvus arvensis as morning glory, you are calling it the wrong name. True morning glory is Ipomea, a shallow-rooted annual that dies with the frost. If a label indicates a herbicide controls morning glory, it may not control the field bindweed.
For home landscapes, look at one of three herbicidal options:
If you have bindweed or other broadleafed weeds in your lawn, apply a lawn weedkiller to the infested areas. Do not spray the entire lawn unless weeds are present.
For easy-to-kill weeds, use a product called 2,4-D. For more persistent weeds — such as bindweed — try Trimec, MCPP or dicamba. Other active ingredients that help control bindweed are triclopyr and carfetrezone. The later is available at independent nurseries as "Weed Free Zone."
In non-lawn areas where you have desirable plants, carefully use glyphosate (Roundup) at the strength recommended for perennial or woody plants. Mix in a nonionic surfactant to improve control. Glyphosate does not move through the soil, but it kills any plant it contacts, so prevent drift or overspray. To improve control, till the treated area two to three weeks after application.
In areas where you are not growing desirable plants or in annual flower or vegetable beds, consider mixing glyphosate and broadleaf weedkiller. Use them at the recommended rate and stay away from desirable plants. Using a mixture of the two increases their effectiveness.
Spray the weeds while they are green and actively growing. My final advice: Be patient, persistent and systematic.
One plant can produce 500 seeds that can remain viable for 50 years. The root system can spread 20 to 30 feet from the original plant and may penetrate the soil as deep as 20 feet. These roots build up food reserves that allow the plant to survive for as long as three years.
The war against the weeds is not won with one battle. Good luck in your fall campaign.
Larry Sagers is the horticulture specialist at Utah State Extension Thanksgiving Point.