The cold and dreary weather of January is depressing for most gardeners. However, planning for and starting vegetables and flower transplants from seed can help alleviate some of the doldrums. While most plants can be directly seeded into the garden, many plants benefit from being started inside then transplanted outside.
The first step is to determine what to grow. There are many options available to assist you with selecting this year’s varieties. You should always obtain your seeds from a reputable source such as garden centers and seed catalogs. If choosing seeds from a business that does not specialize in plants, pay special attention to the package date to make sure the seed was packaged for the current year. Though most seed remains viable for about 3 years, germination decreases as seed ages.
Now you need to determine the date to plant your seeds. You need to know two pieces of information: the target date for transplanting outside and the number of weeks needed to grow the transplant. The target date for transplanting cool-season crops such as broccoli, cabbage, and cauliflower is April 10 but can vary a week either direction depending on the weather. Warm-season crops like tomatoes, peppers and most annual flowers are usually planted around May 10. While the time from planting the seeds to transplanting to the garden varies depending on the species, 6 -8 weeks is a good estimate.
Do not use garden soil to germinate seed as it is too heavy and may contain diseases. Use a media made especially for seed germination. There are many options for containers you can use to start seeds but whatever you use should be sterile and free from harmful chemicals.
While there are many commercial containers available, I have found that 16oz plastic containers that cottage cheese or sour cream come in work well for larger plants and yogurt containers are great for smaller plants. Remember to add a few holes in the bottom for drainage.
The seed must be kept moist in order to germinate. Water often enough that the media never dries. Using a clear plastic wrap over the top of the container can reduce the amount of watering needed. Remove the wrap after the seedlings emerge.
Most plants will germinate in either darkness or light. All plants require adequate amounts of light once emergence occurs. South-facing windows may not provide enough light so fluorescent fixtures can be used to provide additional light. Additional light produces stronger plants. Young plants do not react to day length, so lights can be left on as long as desired.
The temperature best for germination is often higher than what we may find in our homes especially since evaporating moisture can cool the germination media. Moving the container closer to the ceiling (top of a refrigerator) can help but a heating mat is best for consistent germination. After plants have germinated, they can be grown at a cooler temperature; 65 to 70 degrees during the day and 55 to 60 degrees at night. This will help prevent tall, spindly transplants.
Seedlings will need some fertilization for best development. Use a soluble houseplant fertilizer and apply at about half the recommended strength a few days after seedlings have germinated as young seedlings are easily damaged. After that, fertilize according to the recommendations on the fertilizer label.
Plants grown inside will often undergo transplant shock if not hardened off. Plants are hardened off by moving them outside and exposing them to sun and wind before transplanting. Start about two weeks before transplanting and gradually expose the plants to outside conditions. Increase the number of hours and degree of exposure over the two-week period.
More details can be found in our guide sheet G6570 Starting Plants Indoors From Seeds online at https://extension2.missouri.edu/g6570.
Jim Crawford is a field specialist in agricultural engineering at the University of Missouri Extension, Atchison County.