Making Room for Native Pollinator Plants by Controlling Weeds – July 2015
Gardens can get weedy. Sometimes that’s a good thing–even weeds can provide pollen and nectar for bees and other pollinators. But if you spent last year preparing your planting beds and the fall or spring seeding your pollinator friendly plants, the last thing you’ll want to see are weeds crowding out your flowers!
Weeds can quickly overgrow a pollinator garden, especially if they go to seed. What were once small weeds seem to triple in size overnight following a summer rain, and what seemed like a manageable situation can quickly become overwhelming.
Ideally, try to remove weeds when they are young. If an area is overgrown with weeds, prioritize removing those most at risk of going to seed. Depending on your pollinator garden’s size, that may mean hand weeding, hoeing or mowing. These can be fairly easy when working around shrubs but more difficult when managing weeds within a perennial wildflower planting. If you are in the latter situation, consider running a high mower through the area, with the blade at least six inches off the ground before weeds have gone to seed.
Some gardeners use mulches to retain soil moisture and create a weed barrier around plants. However, this technique can be problematic for the roughly 3,000 species of ground-nesting bees in North America. Please avoid plastic mulches unless using them to solarize an area for future pollinator plantings. Wood chip mulches can have mixed effects: very thick layers of mulch can be hard for ground-nesting bees to get through, though some will nest under thin layers of mulch.
Preparing a site to minimize future weed pressure is a key part of establishing a successful pollinator garden. Depending on weed pressure, this may mean an entire season of weed control before planting pollinator friendly seeds or shrubs. One effective, organic way to prepare a site for planting is solarization, where bare, moist ground is sealed with plastic. The moisture activates the seed below the plastic, while the heat kills any growing weeds. Depending on where you live, the temperature under the plastic can reach between 99 and 140°F. In order for this technique to be most effective: (1) use clear, thick, UV resistant plastic; (2) check the plastic for holes throughout the summer; (3) remove the plastic when the temperature underneath becomes more favorable than that outside; and (4) avoid disturbing the soil prior to seeding in the fall or spring.
Solarization is a safe and effective weed control method; depending on climatic conditions where you are, you could even start implementing it now! And if it’s too late in the year to solarize in your part of the continent, why not keep it in mind for next year?
If you’d like to learn more about soil solarization, please check out these resources:
Establishing Pollinator Meadows (The Xerces Society)
Soil Solarization for Gardens and Landscapes (University of California)
To read previous months’ tips, please click here.