6 seed-starting tips

Over the next few weeks, gardeners everywhere will take on the challenge of starting their own seeds. Whether it’s sowing seeds of your favorite heirloom tomato variety, planting herb seeds, or starting a collection of annuals like sunflowers, cosmos, or marigolds, it’s one of our most favorite times of the year.

I hear from many seed starters each season with questions about the process and inquiries on tips for success. Today, I thought I’d compile some of the most frequently asked questions along with their answers, into one single article. Hopefully it will help you get started on your own seed-growing journey and serve as a guide to success.

How do you know the best time to start seeds indoors?

The proper timing for seed sowing is highly dependant on the variety of seed you’re sowing. Most seed packets will tell you when to sow your seeds based on when you can expect to plant them out into the garden. It may say “sow seeds indoors under grow lights 4 to 6 weeks before your last expected spring frost.” Here in Pennsylvania, our last frost date is around May 15th, so those seeds should be sown indoors between March 20 and April 3. For cold-weather crops that can go out into the garden much earlier, the packet might say to “sow seeds indoors 10 to 12 weeks before your last expected frost.” Those seeds will need to be sown much earlier.

Do I really need to use grow lights when starting seeds indoors?

I know you want me to say no, but the answer is yes. Grow lights will make a huge difference in your success. The level of sunlight present this time of year, even in the brightest window, just isn’t enough. Your seedlings will be stretchy and pale. You don’t need an expensive, fancy grow light for seed starting. Just a simple shop light fixture fitted with florescent bulbs will do for seed starting (but not for blooming plants). Keep the lights about 2 to 3 inches above the plant tops, raising them as the plants grow.

Should I soak my seeds in water prior to planting them?

As long as you keep your newly planted seeds moist, there’s no need to pre-soak them. I will say, though, that thick-coated seeds, like beans, will germinate substantially faster when soaked in tepid water for 8 hours prior to planting. It’s a step that won’t hurt seeds, no matter what you’re growing, but it certainly isn’t essential.

I’ve heard that I have to put seeds in the fridge for weeks before planting them or else they won’t grow. Is this true?

While some perennial, tree, and shrub seeds do need to be exposed to a period of cold in order to break dormancy and germinate (called stratification), most annuals and vegetables do not.

Do I need to pot up seedlings into bigger containers at some point?

Most seedlings benefit from being transplanted from their seeding tray into either a cell pack or a small pot for a few weeks prior to being moved out into the garden. Not only does the process give each seedling more room to grow, but it encourages a sturdy, healthy root system. When your seedlings start to develop their second set of leaves, it’s time to gently pry them out of the seed-starting flat, separate them, and move them into a fresh container of new potting soil. This is also when you can start to fertilize your seedlings with a liquid organic fertilizer diluted to half of the recommended strength. Fertilize once a week until the transplants are ready to go out into the garden.

What is the best way to acclimate seedlings to outdoor conditions?

Known as “hardening off,” the process of slowly acclimating transplants to the wild and unpredictable weather of spring should take about 10 days. Every morning, take your seedlings outdoors and then move them back inside in the evening. With each passing day, increase their exposure to full sunlight, until at the 10-day mark, they are in full sun all day long. Then you can start leaving them outside at night, too. If you’re growing warm-season plants that don’t tolerate frosts, like tomatoes and peppers, don’t keep them outdoors at night if a frost is expected. Cold-season crops, like cabbage, kale and broccoli, can be planted right into the garden after 10 days of hardening off.