Starting Seeds Indoors
It’s never too early to start thinking about spring! The long winter months are the perfect time to plan and prepare for the garden season ahead. As you dream about what you’d like to grow this year, consider starting seeds indoors. Our growing season is short, so giving plants a head start inside can make all the difference—especially when it comes to producing more… produce.
If you’re new to starting seeds, the process can feel a little overwhelming, but starting seeds is easier than it looks, and a little preparation goes a long way. Here are some helpful tips to get you growing with confidence.
When Should You Start Seeds Indoors?
Timing depends entirely on what you’re planting. Each seed packet includes valuable information, including how many weeks before your last frost date seeds should be started indoors.
Most seeds are started in early spring, but some benefit from an earlier start—as early as February. Early-start annual flowers include wax begonias, geraniums, pansies, dusty miller, and fountain grass. Vegetables like celery, leeks, and onions also need a longer indoor growing period to reach maturity in our climate.
Keeping a garden journal can be incredibly helpful. Write down what you plant, when you start seeds, what works well, and what doesn’t. For vegetables, pay close attention to “days to harvest” on seed packets to ensure your crops have time to mature before fall frost. This step is so important because no matter how well you THINK you are going to remember the details, you likely won’t. Writing things down helps you so that you don’t repeat the same mistakes twice!
Choosing and Storing Seeds
Now comes the fun part—buying seeds! This season, we’re excited to offer both Lake Valley Seeds and Seed Savers Exchange—two trusted sources known for reliable germination and excellent varieties.
Avoid buying more seeds than you can use within two to three years, as germination rates decline over time. If you’re planting older seeds, sow a few extras per container to account for lower viability. Store leftover seeds in an airtight container in a cool, dry place.
Also be mindful of space—your indoor “real estate” for seedlings may be limited, especially once lights and heat mats are involved.
Light Matters (More Than You Think)
The location of your seedlings is crucial. Avoid windowsills, which can be drafty and cold at night and surprisingly hot on sunny days. In Minnesota, weak winter sunlight and frequent cloudy days mean artificial lights are often the best option for indoor seed starting.
Grow lights should be kept on for 12–16 hours per day and positioned no more than 4 inches above the seedlings. Inadequate light causes plants to become “leggy,” with long, weak stems that won’t stand up well outdoors. A low-traffic area like a basement or spare room works well for a seed-starting setup.
If you’re only growing a few plants that don’t need an early start and you have a bright, south-facing window, that may be sufficient. Plastic humidity domes can help retain moisture and warmth, but they should be removed once seedlings reach the top.
Containers, Pots, and Soil
Start seeds in small, individual containers with drainage holes. Planting multiple seeds in a large container often leads to root damage when separating seedlings. (Onions and leeks are exceptions—they tolerate being grown together and separated later.)
Reusable plastic containers are fine, but be sure to disinfect them each year to prevent disease. Biodegradable pots are another great option, especially for plants that dislike transplanting, such as cucumbers and squash. These pots can be planted directly into the soil, reducing root disturbance.
Use a soilless seed-starting mix, which is lightweight and designed to promote germination. Because the mix settles after watering, fill containers to the top and moisten the soil before planting seeds.
Warmth, Water, and Feeding
Bottom heat—such as an electric heating mat—can significantly improve germination and root development by keeping soil temperatures consistent.
When planting, a general rule is to sow seeds at a depth twice the width of the seed. Some seeds require darkness to germinate; check seed packets carefully for specific instructions.
Keep soil consistently moist, but not soggy. Use a spray bottle to gently water from above, or place containers in a tray and water from below. Always drain excess water to avoid root rot.
Fertilizer isn’t needed until seedlings develop their first true leaves. At that point, a water-soluble fertilizer diluted to ¼ strength once a week is plenty. Use plain water the rest of the time.
When Seedlings Outgrow Their Pots
Sometimes seedlings grow faster than the weather warms up. If roots are circling the bottom of the container or plants are drying out quickly, it’s time to move them into a slightly larger pot.
Choose a new container that is only 1–2 inches wider than the current one. Moving seedlings into pots that are too large can slow growth and lead to overly wet soil. When transplanting, gently loosen the root ball and lift the plant by the roots—not the stem. A spoon works well for supporting seedlings as you move them.
After transplanting, water thoroughly and return plants to their lights right away. Expect a brief pause in growth while roots settle in—this is normal.
Hardening Off: Don’t Skip This Step
Seedlings grown indoors aren’t ready for wind, sun, or temperature swings right away. About 10–14 days before planting outdoors, begin hardening them off.
Start by placing seedlings outside in a sheltered, shady spot for a few hours on mild days, then bring them back inside. Gradually increase both their time outdoors and their exposure to sunlight each day. Avoid windy or cold days at first, and always bring plants in at night.
By the end of the hardening-off period, seedlings should be able to stay outside all day and tolerate sun and breeze without wilting.
In most years, mid to late May is a safe time to plant outdoors, but always watch the forecast—frost can undo weeks of careful work.