As cold temperatures and snow and ice persist, late winter has many gardeners missing their time planting outdoors. But this period is the perfect time to start planting certain vegetable seeds indoors. The William T. Kemper Center for Home Gardening shares the following advice on seeding indoors in late winter.

Seeds to start

Cool season vegetables that will be transplanted into the garden later in March can be started indoors in late winter. These cool season vegetables include:

• Cauliflower
• Broccoli
• Brussels sprouts
• Cabbage
• Kale
• Chard
• Kohlrabi
• Bok choy
• Mustard greens
• Lettuce

What not to plant

 It is too early to start seeds of most summer crops, such as summer squash, tomatoes, and melons. The seedlings will get large and leggy if grown indoors for too long, and will not transplant as well. Most summer vegetables are either sown directly into the garden when the threat of frost has passed, or are started indoors in early spring.

How to

Supplies: Starting seeds indoors only requires seeds, a well-draining soil mix, and some kind of containers for the seeds to grow in. Although plastic cell trays are the easiest to use, small cups, egg cartons, empty K-cup pods, and the bottoms of empty milk or juice cartons can all work just as well. 

Soil: You can buy potting soil mixes that are specially formulated for starting seeds, but this is not necessary. Regular potting mixes are just as suitable for the job, although we recommend trying to find one that does not include added fertilizer, or only a small amount of fertilizer. 

Fertilizer: Seedlings need very little, if any, fertilizer when they are just starting out, since they already have all the nutrients they need to start growing packed within the seed’s endosperm or food stores. Using a coarse screen to filter out large pieces of wood or clumps of peat from your regular soil mix can help to make a more uniform, fine growing media. 

Don’t forget

Pre-moistening the soil mix is a step you don’t want to skip. This makes the whole process of planting seeds much easier. 

Labeling your seeds is also a must. Once the seeds are planted, a spray bottle or very gentle stream of water can be used to keep the soil moist. The containers with the seeds can be placed on top of a heating mat to increase the soil temperature and speed up germination, but it is not required.

More information

More detailed instructions can be found on our website.  Check out other guides, tutorials, and seasonal tips at gardeninghelp.org.

Justine Kandra
Horticulturist