As the buzz of the Winter holidays settles down and seed packets start being displayed in local stores, enthusiastic gardeners may find themselves eager to start the next growing season. 

January is the perfect month to plan and organize your sowing and harvesting schedules, and order some seeds, so you’ll know which crops and flowers you’ll have when Spring comes.

How and When To Start Seeds Indoors

When is The Best Time to Start Seeds?

Seasonality is the most important aspect in a gardener’s life. If you start seeds too early, you might get weak and leggy plants. If you start seeds too late, your harvest may be delayed and you’ll find yourself dealing with cold-loving crops unable to mature in warmer weather.

If you want your plants to be in their best health during the harvesting season, you may sow your seeds indoors when temperatures are still cold so they’ll have time to grow and harden off before they are ready for transplanting outdoors when it’s finally warm.

As a general rule, seeds must be started 4-6 weeks before the last frost. Use this website to calculate the expected frost dates in your area. Don’t forget to check the labels on the seed packets indicating how long each crop will take to germinate and be ready for transplanting.

Temperature is the most important factor for seed germination and eventual plant health. The ideal soil temperature for seeds to sprout is between 20°C to 30°C (68°F to 86°F) [1], while air temperature should be at 18°C to 20°C (64°F to 68°F) [2]. For gardeners living in the USA, always consider your Hardiness Zone to help you decide the best time to start plants from seeds. 

How and When To Start Seeds Indoors

Which Seeds Can Be Started Early?

Some cold-tolerant crops such as Asparagus, Bean, Beet, Carrot, Corn, Cucumber, Garlic, Kale, Lettuce, Melon, Onion, Pea, Radish, Spinach, and Squash [3] can be directly sown in the ground when the soil is dry enough in early Spring.

Some annual flowers take a long time to germinate, and can therefore be sown in the ground early so your garden will be in full bloom by Summer. Examples of these are Aster, Calendula, Geranium, Pansy, Sunflower, and Zinnia.

Summer herbs and vegetables which have a long growing season such as Basil, Broccoli, Cabbage, Cauliflower, Celery, Eggplant, Leek, Mustard, Okra, Parsley, Pepper, and Tomato can be started indoors as early as 7-10 weeks before the last frost.

I developed a free tool to help you calculate sowing, germinating, transplanting, and harvesting dates along with spacing and light requirements for a long list of vegetables, fruits, herbs, and flowers. Check out my Seed Starting & Planting Calculator here

Download the Seed Starting Guide for Free
Organic Weed Management methods ebook