By Adam Austing, University of Minnesota Extension Educator
As we enter February, many Minnesota gardeners find themselves wishing they didn’t have to wait until April or May to get back in the garden. Cold fall temperatures usually shut down our growing season by October, which we’re more than halfway through our wait to get back to working in backyards and gardens! But some of us are just too impatient to let nature work its course. Luckily, there are a few things we can do to squeeze every day out of our growing season.
One of the simplest ways to warm up the soil in the spring is to use soil warming mulches. Plastic mulches can be laid in your garden one or two weeks before planting. The soil surface needs to be smooth and level for these mulches to work well. These work by absorbing the sun’s heat and transferring it to the soil it’s making contact with, so air pockets due to uneven soil will reduce the effectiveness of the plastic mulch. Clear plastic is an exception to this rule. Clear mulches allow the sun’s energy to move through the plastic and heat the soil. As the soil warms, the clear plastic will work to trap heat and moisture instead of it being released into the atmosphere.
Plastic mulches do not come without some issues. The habitat in soil underneath plastic is not as good for soil-dwelling organisms as soil covered with plant material or compost. This could potentially reduce soil health and productivity in minor ways. Also, petroleum is a major component of plastic mulch, so it’s recommended that you throw away the plastic after each growing season. Annually needing to purchase new plastic mulch and then throwing it away is not ideal for many people.
There are many alternatives to using plastic mulches to extend the growing season. Biodegradable paper mulches and photodegradable plastic mulches are available, but are often less effective than plastic and come with their own sets of challenges. Landscape fabric or other permeable materials can help increase yields, but aren’t as effective at raising soil temperatures in early spring. There are also many types of structures, covers, and other ingenious ways people have fought the cold temperatures of Minnesota springs and falls. Many of these can be viewed at extension.umn.edu/planting-and-growing-guides/extending-growing-season.
February is a great time to start preparing for spring. Now is the perfect time to trim many trees and cut back perennials. You can make plans for your garden, make sure tools are clean and ready to go, and evaluate how you can be more successful than you were last year. We’re also getting very close to the time to be starting seeds indoors. A guide to growing plants indoors can be found at extension.umn.edu/planting-and-growing-guides/starting-seeds-indoors.