Pre-emergent Herbicides and Mulch

Wiese Acres perennial alyssum

Even though temperatures have been 20 to 25 degrees below normal, most of my gardens still have about 18 inches of snow on them from the massive blizzard of April 14 and 15, and what isn't covered with snow is still the winter brown, the calendar says it is spring.  I am confident that at some point Mother Nature will look at her calendar and say "Oh, shoot, I missed spring.  I better get busy."

So, anticipating spring work right around the corner, I will begin to publish the Wiese Acres blog on Tuesdays and Thursdays of each week.  The beginning of spring is the beginning of a season of mostly outdoor work.

As soon as I can get in the gardens, I will be cleaning the old foliage off, sprucing up the mulch a bit, and spreading some Preen.  Preen is a pre-emergent herbicide that works quite well to keep those pesky elm and maple tree seeds, as well as wild lettuce, pigeon grass, dandelions, and other weeds from germinating in the mulch.  It doesn't keep them all down, but it sure helps. 

I also use Preen in some of the beds, but I wait until after the perennials and any favorable self-seeders have gotten started. That means I don't suppress as much of the spring flush of weeds in those beds, but it keeps the later population in check.  It's a price I gladly pay to have some self-seeded Bells of Ireland, rose mallow, poppies, snow on the mountain, and a few other annuals that add so much to the perennial beds.   If you want seedlings to be safe from the pre-emergent herbicide, you need to wait until they have at least one set of "true" leaves - leaves that really look like the plant rather than the rounded leaves that emerge first when the seed germinates.

I don't use the combination pre-emergent herbicide combined with fertilizer.  Most perennials beds, in our clay soil, don't appreciate extra fertilizer.  They get all they need from the nutrient rich clay and the composting foliage and mulch they get each year.  In sandy soil, they tolerate additional fertilizing better, but even then, they prefer to get it from additional organic matter such as compost, decaying foliage or mulch.

There are brands of pre-emergent herbicides other than Preen, but I prefer Preen because it is easy to apply and stays where you put it quite well.  I also like that I can buy it in large containers at a lower price at some of the warehouse selling clubs, like Costco and Sam's Club. 

Preen does market a corn gluten based product that is safe for use on vegetable, fruit, and herb gardens.  I find that it isn't nearly as effective as the Preen I use on the mulch, so I save my money and just pull weeds in the edibles gardens.

Happy Spring (whenever it gets here).