Planting vegetable and flower seeds indoors to get a head start on garden plants is a good idea if you like gardening, have limited funds, or want a large volume of plants. If you only need a few plants and you’d like quick and easy, buying transplants at the garden center may be best for you.
There is a therapeutic effect to planting seeds and watching them peek their heads out of the dirt and grow into plants you can put in the garden. Gardening relieves stress and gives you a sense of well-being.
Last Frost Date
So, if you plant seeds, you’ll need to know when to plant them so that they are ready to plant out into the garden at the optimum time. The last frost date in Billings is somewhere between May 16th and May 30th. Start thinking about planting cool season crops when soil temperature averages at least 40° F(4° C) and warm season crops when the average is 50° F (10° C) or more http://www.weekendgardener.net/vegetable-gardening-tips/soil-temperature-030803.htm
Plant Hardiness Zones
Montana has seven plant hardiness zones, so if you live outside the Billings area consult the USDA Agricultural Research Service Plant Hardiness Zones linked below. The last frost dates may change depending on your zone. The frost-free growing season is around 125 days. Last frost date is September 18th in Billings.
Plants grown indoors will only be happy in their small pots, cells, or flats for about 8 weeks. By then they will have used up the nutrients and be struggling for water. If you can’t plant them outside yet, repot them into larger pots. Large yogurt and cottage cheese containers are great for this. After hardening off, most cold weather plants can be put into the garden a couple weeks before the last frost date.
Warm Season Plants
Warm season plants need warm soil temperatures to thrive (55 and above), so wait until after the last frost date and check the soil with a thermometer. Counting back from the maturity date and adding a couple of weeks for the seeds to germinate should give you a general idea of when to plant seeds. The back of the seed packet should tell you how long the seeds need to germinate and the maturity date.