Thursday, April 17, 2014

Supergermination of Annual Weeds Possible by Irene Shonle

The torrential rains of last fall combined with an above average snowpack this winter mean that we can expect a banner year for weeds, especially annual weeds.  (Of course, it also means we should have a fabulous wildflower year, too.)
Cheatgrass, also known as downy brome, is the weed that is most likely to be found in abundance this year.  Cheatgrass can outcompete most native plants and even many grasses, because it germinates so early; it is a state-listed noxious weed (List C).  Later in the summer it becomes a fire hazard and a nuisance as the seed heads lodge in socks and fur.  Cheatgrass can produce 13,000 seeds per square yard (meter).  When conditions are just right, almost all of these seeds will germinate, creating a larger-than-usual crop of weeds.   
Alyssum simplex (also known as Alyssum minus) at early stages of flowering -- a great time to tackle it
Small-flowered alyssum, that tiny upright weed that turns the hillsides a yellow green in the spring, will also respond to the moisture, but perhaps not quite to the same extent.  Other annual weeds that might respond enthusiastically include scentless chamomile and field pennycress.

This supergermination might sound like it’s really bad news, but it all depends on whether you can get out there to deal with them before they go to seed.  If you can, this spring will be a golden opportunity to deplete most of the seeds in the seed bank.  That means that in future years, there will be almost no new weeds!   If possible, prioritize working on these weeds in May and early June, especially if you don’t have extensive patches to deal with.  If your populations are large, try tackling the most important areas first; these probably will be the areas closest to your house, or where you want to grow flowers.  The flip side is that if the weeds go untreated, we will have extra seeds going into the soil and weed populations will increase.

The key here is in the timing – you have to get out there almost as soon as the seeds germinate.  If you catch them before there are any seeds present, you can hoe, till, or pull the weeds.    It’s possible to take care of huge swaths of weeds in just an hour using a stirrup hoe.  Kind of makes you feel like the Valiant Little Tailor of Grimm’s Fairy Tale fame, who “killed seven with one blow.”  There’s no need to bag the plants if seeds have not been set (anytime through early flowering); they can just be left to decompose on the ground.   It’s also possible to use an herbicide, but you would need to apply it very early; many annuals don’t respond to herbicides later in their growth cycle
Cheatgrass seedlings before flowering and seed set -- easy to take care of with a hoe
If you don’t quite catch them before they set seed, controlling the weeds becomes a little more of a nuisance, but is still doable.  Pull the weeds and seal them in a plastic bag, then throw them away.  Since this can quickly turn into quite a lot of bags, it’s easy to see why getting them earlier is a good idea.
Pulling and bagging cheatgrass

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