So far, we’ve had a mild, dry winter. Just a little rain or snow and a little increase in temperature could help initiate weed growth. This time last year, the wet weather gave us a bumper crop of weeds. If last year’s weed crop got away from you and produced seed, you made a deposit into the seedbank.
The seedbank contains the viable seeds held in the soil from previous seasons, waiting for the right moisture and temperature conditions to sprout and grow. Many plants have seeds that can remain viable in the soil for one to five years. A few very persistent weeds have seeds that can remain viable in the soil for 10 or more years.
Provided the weeds are not state of Nevada listed noxious weeds, you could just leave them growing. Keep in mind this course of action may make you very unpopular with your neighbors, as the weeds do not respect property lines or fences. It may also increase the fire hazard potential on your property.
Start scouting now for weeds that have begun to grow. These little seedlings are easy to control. They do not have a substantial root system yet, so they are easy to pull or hoe. Many will not resprout after being pulled or hoed, so you will have just controlled your infestation.
Another option to control weed infestations is by the use of herbicides – pesticides that kill plants. There are two basic types of herbicides used for weeds: post-emergence and pre-emergence. Post-emergence herbicides kill plants that have sprouted and are actively growing. Pre-emergence herbicides target germinating seeds, providing a chemical barrier to their growth. As the seeds begin to sprout, they encounter this chemical barrier, and cell division in the young root system is inhibited. This results in seedling death before the plants ever emerge from the soil.
Pre-emergence herbicides are applied to the soil and stick to the soil particles. They will stay in place unless the soil is moved by wind or water. They must be watered in, either by irrigation or precipitation, to be activated in the soil. It is not recommended to apply them when the ground is frozen, as they will not be activated by frozen water.
Planning your pre-emergence herbicide application to coincide with a major rain event is the best way to ensure effectiveness, but predicting meaningful rainfall in our area is difficult at best. You want to apply when there will be enough precipitation to activate them, but not so much precipitation that they are washed by rain water to unintended areas, or worse, to the storm drains and into our rivers.
It is important to put some planning into your pre-emergence application. Pre-emergence herbicides are not selective and will inhibit all seedling growth. In areas where you are planning to establish plants from seed, such as a lawn or garden bed, you need to be very careful what product you choose. You need to be sure that the product will remain active long enough to prevent weed seeds from sprouting, but not so long that it will interfere with your planned seeding. Remember to read, understand and follow label directions.
For more information on identifying and controlling nuisance weeds, mark your calendar to attend University of Nevada Cooperative Extension’s free Gardening in Nevada class on Feb. 20 from 6-8 p.m. at Bartley Ranch Regional Park, 6000 Bartley Ranch Road, Reno. Visit www.growyourownnevada.com for more information.
Melody Hefner is the Urban IPM and Pesticide Safety Education Program Assistant for University of Nevada Cooperative Extension. Have a gardening question? Ask a Master Gardener at firstname.lastname@example.org.