Vegetable Garden Basics: When to Start Seed Indoors

As days get longer, it’s natural for gardeners to start thinking about seeds and possibly starting seeds indoors. In Minnesota, many warm-season vegetables need to be started indoors and planted in the garden as transplants in order to flower and fruit in our relatively short growing season.

But when is a good time to start seeds? That depends on several factors: the type of seed, how large you want your transplant to be before it’s moved outdoors and how much time you want to devote to caring for seedlings.

What Seeds When

seed starting2First, there are a variety of seeds that do best if started right in the garden. Cucumbers, beets, carrots, peas, green beans, potatoes and melons all do best if planted in the garden directly. You can also plant lettuce and greens like chard and kale directly in the garden, though they can also be started indoors and set out as transplants to get an earlier harvest.

The first seeds to start indoors are onions (if you choose to grow them from seed rather than sets), leeks and celery. All of these should be started before March 1. In early to mid March, start brassicas like cabbage, broccoli, peppers and lettuce. You’ll notice tomatoes are not on that list. Hold off until early April for tomatoes. They do best if they are started later and set outside in late May or even early June.

The seed packets will tell you the best time to start seeds. This is typically expressed as weeks before “last frost.” This is the last day where on average frost can occur. For much of Minnesota, that day is around May 10 — earlier in the southern part of the state, later in the north.

If you are looking for more information on seed starting, check out this overview of the process or this very complete discussion from the University of Minnesota. A couple of years ago, we did a three-part series on starting seeds indoors, we’ve also discussed winter seed sowing.

Are you starting seeds indoors this year?


  1. Deb Young on February 20, 2015 at 1:45 pm

    Yes, I will be starting seeds indoors again this year. I have done so for the last 4 or 5 years. Interesting about not starting tomatoes until April 1; I have not heard that before. May be why start to go bad a few weeks before I can get them in the ground.

  2. Mary Lahr Schier on February 20, 2015 at 10:54 pm

    Deb — I had lots of problems with tomatoes when I started them in March. Also transplanting them later helps them really take off when they get in the ground!

  3. scott sueker on March 6, 2015 at 5:56 pm

    Do you think global warming has affected outdoor 1st planting dates? I live in Hibbing and am a recent transplant from the Cities. Everyone here swears by June 10th as the earliest outdoor date. I have put my 1st plants out 2 weeks before that for 2 years now with no ill affects. Is that June date an “old wives tale” now?

    • Mary Lahr Schier on March 10, 2015 at 12:56 pm

      Scott — Sorry for the slow reply. I’ve been away from the site a bit. The advice I’ve heard is to stick with the old dates because you never know when we could get a freeze. (Witness what happened in 2012, for example, really, really warm March, then a freeze in April.) In 2014, I did not plant out tomatoes until after June 1, and I’m south of the Twin Cities. That said, I would guess there are lots of vegetables and flowers that could safely be planted outside in northern Minnesota in late May.

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