Missouri gardeners who want to get a head start on spring plants or who want to extend their growing season can do so with a greenhouse. With the right heat, ventilation and watering systems, a greenhouse allows you to have control over temperature and water, regardless of what the weather is doing outside. A greenhouse also allows you to shelter plants from wind, deep frost and outdoor pests like deer and rabbits.
There are several greenhouses options for the home gardener. A cool-season greenhouse is one option for Missouri gardeners who want to grow vegetables like broccoli, cabbage, kale and peas through the winter. This type of greenhouse uses water-filled plastic barrels on the north wall; the barrels collect heat during the day and heat the greenhouse at night. If you need to maintain a warmer temperature, you can supplement your greenhouse with gas, wood or electric heat in the winter.
Even though Missouri is in the south-central United States, winter temperatures can drop as low as zero to minus 20 degrees F, according to the USDA Hardiness Zone Map. If you plan to use your greenhouse to nurture a warm-season crop like tomatoes through the winter, you will need to have a supplemental heat source to keep your greenhouse in the optimal temperature range. Additionally, Missouri's winter storms can cause ice and snow buildup on your greenhouse that must be removed.
The average date of last frost in Missouri falls between April 1 and April 30. Occasionally, there may be a late-spring frost that can harm unprotected seedlings after April 30. A greenhouse can allow you to start your seedlings earlier, without worry of frost. Once the danger of frost has passed, you can either transfer your growing seedlings to the ground or continue to grow them in the greenhouse.
The heat of Missouri's summers can be harnessed to grow heat-loving plants like cucumbers and tomatoes, herbs like rosemary and sage, and flowering vines such as mandevilla and passion flower. However, summer gardening in the greenhouse is not a hands-free process. You must open vents and turn on fans so the air can circulate and prevent the greenhouse from getting too hot. You also may need to water some plants more often.
According to the National Climatic Data Center, Missouri's first frost date generally falls in mid- to late October, depending on the zone you live in. Fall in Missouri is a good time to move some plants indoors to keep flowers and vegetables thriving throughout winter. If you have plants that are dormant in the winter but cannot withstand a deep freeze, you can transfer them to the greenhouse.