Getting Started with Nightshades and Alliums - Megen Hall
After writing last month's article on building your own seed starting workstation, I have been propelled into the second gear of garden planning. I just got my seed order and my Stella Natura calendar and have begun the process of organizing my planting schedule. There's still plenty of time before crops can go in the ground in the Northeast Kingdom of Vermont, but there are a few that need to get started long before the snow melts, such as nightshades and alliums. Starting seeds indoors, whether under lights or in a greenhouse, is necessary if you want them to reach full maturity in climates where the growing season is short, or just get a jump on planting even where the season is long. To establish your seeding dates, you want to determine when to put your plants in the garden or greenhouse and count backwards to from there.
Nightshades, such as tomatoes, peppers, and eggplant, should only be planted outside after all danger of frost has past and once soil temperatures have warmed. Planting into a heated greenhouse or an unheated high tunnel will allow for earlier planting dates, but resist the urge to start your plants too soon. Soil temperatures will still need to be taken into consideration when figuring your dates.
Nightshades can be started indoors 6-8 weeks before their planting date. They can be seeded approximately 4 seeds per inch and ¼" deep into channel trays filled with moistened potting soil. Cover your tray with a propagation dome or some other clear plastic tent to hold in heat and humidity during germination, and place on a heat mat. Bottom watering or misting with a spray bottle can be used to keep the soil evenly moist (not soggy). Optimal soil temperatures for germination are between 75-85 degrees Fahrenheit. Once seedlings emerge, remove the cover to reduce humidity. After the first set of true leaves appear, carefully transplant seedlings into their own individual cells. Repeat the transplant process as necessary; once the roots fill the cell, but do not allow the seedlings to become root bound.
Onions are dependent on day length for bulb production and can be direct seeded in some climates, but transplanting is recommended in regions with shorter growing seasons. In the North (latitudes north of 35º), choose long-day varieties and sow seeds approximately 8-12 weeks before transplanting into the garden. Onions can be transplanted as soon as soil can be worked. Seeds can be sown in 1" cells about ¼ - ½ " deep. As a rule of thumb, if you want larger onions, plant one seed per cell, for smaller onions, 2-3 seeds per cell. Optimal soil temperatures for germination are between 75-85 degrees Fahrenheit. When seedlings reach 5", trim to 1" to increase girth and allow plants to re-establish about 7 leaves before transplanting into the garden.
Nightshades and alliums are just a few of the crops that should be started early indoors, but there are some herbs, brassicas (such as Brussels sprouts), and others that require an early start as well. Check out our Vegetable Planting Guide (pdf) for the particulars on other crop types. You can also learn important tips and advice from our expert gardeners here at HMS with our new Seed Starting Video. Have fun getting started!