COLUMBIA, Mo. – It is hard to think about gardening when the weather is cool. “However, now is the perfect time to start seeds of certain garden plants indoors so they will be ready for transplant when warmer weather arrives,” said University of Missouri Extension horticulture specialist David Trinklein.

By kick-starting the growing season, you will have flowers and produce earlier, said Trinklein.

Starting your own transplants is a good way to trial new varieties that might not be available in garden stores yet, he said. By growing your own, plants will be at the ideal size when it is time to move them to the garden.

Most vegetables take 6-8 weeks from the time you drop the seed until they are ready to transplant to the garden. The exact time depends on species and growing conditions.

“There are references online or available in book form that will tell you how long it takes to produce a transplantable plant of a specific species,” Trinklein said.

Germination

The germination medium needs to be loose, well-drained and finely textured, Trinklein said. You can purchase pre-mixed germination media, or you can create your own using peat moss and vermiculite or perlite.

You can buy cell packs designed specifically for starting seeds, but empty egg cartons or similar containers also work well, he said.

Planting depth varies by species. The rule of thumb is to cover seeds about three to five times their diameter, Trinklein said.

Each species has specific requirements for germination. For some it is light, for others it can be temperature. Most seed packets list germination requirements.

“For most seeds, germination happens when three conditions are met: adequate moisture, appropriate temperature and oxygen,” Trinklein said.

Accurate temperature control helps the immature plant emerge from its seed.

“One way to control temperature is to place electrical cables under the germination trays to keep the medium at a constant 78 degrees,” Trinklein said.

Germination time varies. Cabbage, broccoli and cauliflower, for example, take only a few days until seedlings peek through the medium. Something like a tomato might take 5-10 days. Germination time for flowering plants ranges from 5 to 21 days, depending on the species, he said.

Growing seedlings

When seedlings can be handled, it is time to transfer them to a growing medium. Young plants need light, nutrients, proper temperature and moisture. One of the biggest problems with growing transplants indoors is temperature.

“We set our home thermostat for our comfort. Most plants prefer it much cooler at night,” Trinklein said.

The ideal temperature for seedlings is 60 degrees at night and 75-80 degrees during the day, he said. Plants will show spindly growth if it is too warm at night.

Seedlings will need fertilizer in careful doses because young roots are tender. Trinklein recommends half-strength fertilizer for the first few waterings.

“Applying a full-strength fertilizer solution to a young seedling would be like feeding steak and potatoes to a 6-week-old baby. You don’t do that,” he said. “Seedlings need to be nurtured along carefully.”

Moving plants outdoors

As the time for transplanting approaches, get them ready through a process called hardening, Trinklein said.

“About two weeks before transplanting, expose plants to cooler temperatures and give them less water and fertilizer,” Trinklein said. “This will toughen them up for the move to the garden.”

Photo

https://extension.missouri.edu/sites/default/files/legacy_media/wysiwyg/News/photos/20250224-seeds-1.jpg
Get a head start on the gardening season by planting vegetable and flower seeds indoors. Photo by University of Missouri Extension field horticulturist Donna Aufdenberg.