Timing of Herbicide Application is Critical

A guest blog by Noel Jinings, Education and Compliance Officer with Flathead County Weed Control Department

For the most part, the snow has melted.  The sun is shining more often and the spring rains are frequent.  All of this means we are finally seeing things get green again!  It’s the time of year when we all get really excited to start planting flowers, getting our gardens started, and getting back out into our yards.  Another thing to think about as soon as the green starts to appear around the Valley is treating weeds if you are planning on using herbicide. 

Unfortunately, many people don’t think about noxious weeds until the summertime when they are all flowering and obvious.  This is when I get the bulk of the complaint calls and questions about what herbicide will work on the given weed or weeds.  Inevitably people are extremely disappointed to hear that at this point, it’s too late for herbicide.  In general, once a noxious weed has flowered you have missed the opportunity to treat it that year and it will go to seed and reproduce. 

When treating weeds with herbicide, timing is extremely important to the success of the treatment.  Many of the noxious weeds of concern in Flathead County respond best to a late spring herbicide treatment.  This is because the rosette is well developed, but the plant hasn’t yet started to put its energy into developing flowers and seeds.  This is the point of development when most of our weeds are most susceptible to herbicide treatment.  If you apply herbicide too soon, before the leaves reach maximum development, you reduce the amount of chemical contact with plant tissue.  The more surface area contacted by the herbicide, the more of the herbicide that will be absorbed by the plant and the greater the control. 

Although spring is generally the most effective time to spray herbicide for greatest management success for many of our most common noxious weeds, there are always exceptions.  If you have questions regarding timing for specific species call Noel Jinings with Flathead County Weed Control District at 406-758-2161

Additionally, the Weed District has many resources available to assist you in making your herbicide treatment as successful as possible.  We have truck mounted and backpack sprayers available for rent by the day or over the weekend.  We also have a vast amount of literature available to assist you in identifying weeds present, choosing the appropriate herbicide, calibrating spraying equipment, etc.  Additionally, we can assist you in developing an integrated weed management plan because herbicides are not always the only or best management option.