How do I know when to start seedlings indoors?

Seedlings started inside

Growing plants from seed is fun and can be an antidote for the winter blues and cabin fever. It can also save you money and allow you to grow unique varieties that aren’t readily available at garden centers.

Read the Packet

One of the best sources of information about starting seeds indoors can be found right on the seed packet.  No matter which company your seed is from, you will find information on the label about days to germination and harvest, depth to plant, optimal soil temperature for germination, seed spacing, and how many weeks before the last frost to start indoors.

In Zone 5, where most New Hampshire residents live, the last frost is typically in late May. That means you can anticipate planting your tender flowers and vegetables in the garden after Memorial Day. Of course this isn’t a hard and fast rule and you should always pay attention to long-range forecasts.

cabbage seedlings

If you want to start tomatoes, the package will direct you to start the seeds indoors six to eight weeks before the last frost. If you want to plan to transplant your flowers and vegetables into the garden on May 27th, then you would start your seeds between April 1st and April 15th. Cucumbers can be started four to six weeks before planting date, while peppers and eggplant may require at least 10 weeks of time indoors.  

No Early Birds

Although you may be anxious to get your seeds going, don’t be too hasty. Plants that are started from seed too early will probably be of poor health and quality by the time you’re ready to plant them in the garden. Instead of rushing to sow, get out your seed packets and make a garden plan!

UNH Cooperative Extension Master Gardener volunteers share information about home, yard, and garden topics with the people of New Hampshire. Got questions? Master Gardeners provide practical help finding answers to your questions through the Ask UNH Extension Infoline. Call toll free at 1-877-398-4769, Monday to Friday, 9 a.m. to 2 p.m., or e-mail us