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How to Start Seeds Outside in March for Cool Weather Vegetable Crops

Mar 01, 2023 ● By Tiffany Hinton
someone pulling out radishes from their garden.

Photo credit: Megan Holly Photography

Are you ready to get your garden started early this year and enjoy just-harvested cool weather veggies? If so, a great way to jump start your spring backyard garden is by directly sowing crops like kale, spinach, radishes, lettuce, peas and more in an easily constructed, temporary and affordable low hoop house.
In March, the days grow longer and the sun angle is higher in the sky, allowing the spring sun to start warming the soil. This a great thing for early spring gardeners, because warmer soil temps and sunnier days will allow cold seeds (also called cole crops) to germinate and begin to grow, even if there are still a few nights with frost or a light freeze. Using a low hoop house or floating heavyweight frost cloth over the planted beds will allow them to grow even when the temp drops overnight. Community Sponsored Agriculture (CSA) growers and local greenhouses use this technique to get an early start growing their crops for the start of farmers market and farmstand season.   

Photo credit: Megan Holly Photography

Construct the Hoop House

Two simple methods to plant seeds earlier in the season are cost-effective and easy to add to your backyard garden. Both methods can be done for under $100. A hoop house will help to warm the soil and also protect the seeds and tender young plants as they sprout.
The first way to construct a low hoop house using half- inch PVC pipe cut into 10-foot lengths that will flex to create an arch. The PVC ends can be pushed into the ground directly or fixed to an existing raised bed using pipe hanger straps. Place the PVC arches approximately three feet apart to form a tunnel, then drape the PVC with heavy plastic drop cloth or heavyweight frost cloth. Secure with clamps or zip ties to create a simple and low-cost low hoop house for the seedlings to easily grow with protection from the overnight cooler temperatures and any late season snow.
Another option is to use the floating cloth method to protect tender seedlings and create a greenhouse effect. This methos works well for raised beds and can also be used for seeds directly sown into the ground. Once you’ve planted the seeds, carefully place the floating row cover cloth over the ground and secure the edges to keep it from blowing away. You can use landscape staples, small rocks or bricks that will also work well. You can purchase floating row cover cloth online in a variety of weights for spring sowing and also for protecting tender crops in summer from sunscald, insects, birds, heavy rain or late-season frost. Johnny’s Seeds sells frost cloth in 10-foot by 50-foot packages that can be cut to size using scissors for under $40. Gardener’s Supply Company is another good source, and if you need a larger amount, check out Greenhouse Megsatore.

Select the Right Seeds

The second thing to consider for spring planting success is choosing seeds that will germinate in cooler temperatures and can be directly sown. These include kale, spinach, radishes, peas, and several varieties of lettuce. Look through the seed catalogs for additional crops that can be direct sown before the frost in the culture section of the plant description. Local independent garden centers and nurseries, like Jung Garden Center in the Madison area of Wisconsin, also have garden experts who can assist with selecting seeds that will thrive in the early season.   

Photo credit: Megan Holly Photography

Don’t Forget the Compost

Third, consider adding a 2-inch layer of mushroom compost (or your own backyard-produced compost) from your local independent garden store to the planting bed. Compost provides two bonuses. First, it will naturally create heat as the material continues to decompose back into the soil, creating a nourishing environment for the plants throughout the season. Secondly, planting the seeds directly into the compost layer avoids the need for any tilling, preventing soil disturbance and saving the gardener the work of turning hard, pre-thaw soil in late Spring.  
If you are interested in learning how to build the low hoop house from PVC or looking for professional help with your garden design and plan for this summer, Tiffany Hinton, owner of Cultivating Guts, offers personal garden consultations. Hinton will be hosting a live, full day immersion retreat on Earth Day, April 22, where she will be sharing knowledge and guiding others in hands-on sessions on garden planning, biodynamic gardening and raised bed building among other topics.  Visit for more information.