3 Easy Tips to Extend Your Growing Season

If you’re a northern grower like me, about this time of year you’re chomping at the bit to get gardening, but it’s too early to get planting straight in the garden. These are my three favorite techniques to get a jump start on the growing season.

Start seed indoors

Photo by Laurie Neverman.

Figure out the average date of last frost in your area by checking with your local extension office or researching online. Then check the seed packets of your desired crops to see which ones are best started inside before setting outside as transplants. Count back from your average last frost date the appropriate number of weeks to determine your indoor planting schedule. *Note: Don’t forget to check whether your seeds need to be stratified to improve germination. Stratification is the process of placing seeds in cold storage for a time to mimic the natural freezing process.

For instance, many slow growing herbs and flowers suggest starting indoors 10-12 weeks before last frost. Tomatoes and peppers may suggest 4-8 weeks before last frost. Vine crops may be started inside 1-2 weeks before last frost (if the plants get too large they do not transplant well and are more likely to get transplant shock and be set back).

Build a Greenhouse or Cold Frame

Basic cold frame made from a recycled patio door. Note wooden braces in the front to keep the door in place. Photo by Laurie Neverman.

I have a small greenhouse attached to the southeast corner of our home. Since the greenhouse was built, I transition plants from inside, to the greenhouse, to the cold frames to out in the garden. The greenhouse has allowed me to significantly reduce the time the plants spend under grow lights. Our greenhouse is a simple wooden frame covered in multi-wall polycarbonate, and is built into the hillside as part of our retaining wall so it is earth sheltered. Many different sizes and types of greenhouses are available, depending on your space and budget. A greenhouse may or may not have supplemental heat. (Ours does not, although I can open the door to the house, and I sometimes place jugs of water in it to absorb the heat from the sun and release it at night.)

A cold frame is a box, typically with opaque walls and a clear cover. It can be simple, such as an old storm window over a rectangle of straw bales, or a custom built wooden frame and cover, or a pre-packaged unit. Most home built units are lower in the front and higher in the back to allow more sun to reach the plants, and sized to accommodate whatever used windows are available. The fronts should be at least eight inches tall so that you have room to accommodate some plant height. We have two cold frames sized to fit old patio doors. *Note: Make sure any old windows you use do not have lead paint on them. Obviously, that’s not something you want around your food.

Cold frames are unheated (except for by the sun). Their primary advantages are to protect from the wind and overnight cold temperatures. When using them (as when using a greenhouse), be careful to vent to avoid overheating on sunny days.

Create Microclimates with Dark Groundcovers
and Water Filled Containers

This melon patch has a cold frame and water jugs blocking the wind from the north and black fabric to heat the soil. Photo by Laurie Neverman.

A microclimate is a small area with a climate that differs from the surrounding area. In the case of season extension, you generally want to warm the air and soil just where you’re planting, and shelter it from excess wind and temperature fluctuations.

Covering the ground with plastic or other dark material raises the soil temperature so you can transplant earlier. Clear plastic warms the soil well, but can promote weed growth. Black plastic mulch is commonly used, as it is cheap and blocks weed growth. I’ve been using landscape fabric for years. Recently, IRT (Infra-Red Transmitting) plastic mulch has become available, which block visible light but allows infrared light to pass through. Preheating the soil promotes better germination rates and easier transplanting.

I always use landscape fabric in my melon patches. Depending on the season, I may also do it for other heat loving crops such as cucumbers, tomatoes, summer squash, and eggplants. You may wish to preheat the soil for corn, but once it’s growing it prefers cooler roots.

Another inexpensive microclimate option is a homemade version of the well-known wall-o-water products. Fill empty plastic jugs with water, and use them to create a wall around a transplant (for instance, around a hill of melons) or at least in the direction of prevailing winds. I use gallon jugs from milk and vinegar; I’ve seen others use two liter soda bottles. These will typically last a season or two before ending up in recycling.

These basic tips can help you add weeks to your spring growing season without breaking your budget. To learn more about Laurie Neverman's garden, visit The Common Sense Homestead Garden on YourGardenShow. You can also visit her blog at Common Sense Homesteading, where she focuses on using common sense to be more self-reliant, with an emphasis on home food production.