Starting Seeds Indoors: A Beginner’s Step-by-Step Guide
If you're anxious to get outside in the garden, but the temperatures are still too cold, why not go ahead and start seeds indoors?
Quick Reference: Starting Seeds Indoors
- When to start: about four to six weeks before your planned transplant date, which should fall after your last spring frost.
- What you need: fresh seeds, clean containers with drainage, a sterile seed-starting mix, and light.
- Light: 12 to 16 hours a day. A south-facing window is best, or use grow lights or fluorescent shop lights.
- Germination temperature: keep the air between 65 and 75 degrees Fahrenheit, with steady humidity.
- Move outside: harden off about ten days ahead, then transplant once all danger of frost has passed.
The ground is still cold, but the itch to garden shows up well before the soil is ready. Starting seeds indoors is how you scratch it. With a handful of seeds, a few clean containers, and a sunny window, you can have flowers and vegetables well on their way weeks before it is safe to plant outside. It is easy, it is economical, and it gives you a head start on the 2026 growing season. Here is how to do it right, from the first seed packet to the day your seedlings move out to the garden.
Why Start Seeds Indoors
Starting from seed gives you far more choices than a tray of nursery transplants ever will. You get access to harder-to-find varieties and organic seeds, and you can grow exactly the plants you want. It is also economical, since a single packet costs about what one greenhouse seedling does. Best of all, it lets you garden in the weeks when the weather will not yet let you outside.
What You Will Need To Start Seeds Indoors
Seeds. Fresh seeds give better results than older ones, so pull out the seed catalogs or go online and pick the plants you want to grow this year. One advantage of starting from seed is the range of choices, including harder-to-find varieties and organic seeds, and it is easy on the wallet. If you are new to it, start with these forgiving choices: zinnias, morning glories, sunflowers, nasturtiums, parsley, basil, tomatoes, and squash.
Containers. Plenty of things will hold a seed: trays, flats, egg cartons, cans, eggshells, and plastic containers all work, as long as they are well cleaned and drain freely. If you use a fiber or peat pot, wet it thoroughly before you add soil so the pot does not pull moisture away from the growing medium.
Soil. Use a commercial seed-starting mix. It is lightweight, sterile, and free of weed seeds, and it gives the loose, fine-textured, well-drained medium that delicate seedling roots need. Skip potting or garden soil, which is heavier and can carry weed seeds, insects, and pathogens.
Sunlight. Seedlings need plenty of bright, indirect light, roughly 12 to 16 hours a day. A south-facing window is best. If you do not have one, use artificial light to supplement or replace it, either grow lights or ordinary fluorescent shop lights. For a deeper look at what young seedlings need, the University of Minnesota Extension guide to starting seeds indoors is a reliable, plain-English reference.
When to Start Seeds Indoors
Timing is the part most folks get wrong. Always read individual seed packets for specifics, but as a rule, start seeds about four to six weeks before you plan to transplant outdoors, and make sure that transplant date falls after your last spring frost. Start too early and your seedlings get leggy and rootbound indoors. Start too late and you lose the head start. Consult the Farmers’ Almanac Frost Table to estimate the last frost for your region, then count back four to six weeks from there.
Frost dates run weeks apart across the country, so the calendar date that works for one gardener is wrong for another. The window itself, four to six weeks before transplant, does not change. Only the date on the calendar does.
These are general windows. Your own last frost can shift by a couple of weeks with elevation and local microclimate, so lean on the Frost Table and the back of the seed packet before you sow.
How to Start Seeds
Once your timing is set, the sowing itself is straightforward. Work through these steps in order.
- Read each seed packet first. Packets carry the specific instructions for that plant, including depth and any special needs.
- Fill containers to within 1/4 inch of the top with seed-starting mix and level the surface. Water the soil well, then let it drain completely.
- Using your finger or a pencil, make an indentation for the seed. The hole should be four times as deep as the seed is wide. Cover the seed with soil.
- Mind temperature and humidity, the two most important factors for germination. Keep the air between 65 and 75 degrees Fahrenheit. Water with a spray mister, or from below by setting containers on a drip pan filled with water and letting the moisture soak up through the bottom. Keep the soil moist but never soggy, since seeds rot if they get too much water. Cover containers with plastic to hold in humidity, ventilating daily, until the seeds germinate, then remove the cover.
- Check each packet for light needs at germination. Some seeds need total darkness to sprout, but most want plenty of light. Once they germinate, all seedlings need a healthy dose of light each day. If a windowsill is your light source, rotate the containers now and then so the seedlings grow evenly instead of leaning toward the glass.
Easy Seeds for Beginners
If this is your first time, stack the deck in your favor with seeds that sprout readily and forgive a few mistakes. The eight below are the same beginner picks gardeners have leaned on for years.
Many of these make good garden neighbors once they move outdoors. For a fuller look at which plants help each other, see our companion planting guide. And if potatoes are on your list this year, our guide to growing your own potatoes walks through that root crop start to finish.
Get Ready To Transplant
- Once a seedling grows one or two sets of true leaves, it is ready to move to its own pot. (The very first set of leaves is not true leaves at all, but a pair of food-storage cells called cotyledons.) At this stage you can switch to an all-purpose potting soil. Water the seedling well an hour or two before transplanting, and from here you can begin feeding a diluted organic liquid fertilizer once a week.
- About ten days before the seedlings go outdoors, start hardening them off so the tender plants can adjust to the change. When daytime temperatures reach at least 45 degrees, set the plants outside in a sheltered spot for a few hours, increasing their time outdoors a little more each day.
- Once all danger of frost has passed, transplant the seedlings into the garden. A cloudy day is best, since it keeps the plants from wilting. Water the outdoor soil thoroughly before planting to help prevent transplant shock. Dig a hole twice the size of the plant’s root ball, set the seedling in, and fill so the root ball is covered by 1/4 inch of soil. Water deeply each day for the first week.
Time the Move by the Moon
When you are ready to transplant, check the Farmers’ Almanac Best Days Gardening Calendar for the right Moon phase for the task. Remember, that calendar goes by phases of the Moon, not the weather, so you still want to be sure conditions are weather permitting before you set anything in the ground.
- Time your transplanting by both the Moon phase and the weather.
- The Gardening by the Moon Calendar lists this month’s Best Days to plant in your area.
Starting Seeds Indoors: Frequently Asked Questions
When should I start seeds indoors?
Start seeds about four to six weeks before your planned transplant date, and make sure that date falls after your last spring frost. Always check the individual seed packet, since some plants want more or less lead time, and use the Farmers’ Almanac Frost Table to find the last frost for your region.
What temperature do seeds need to germinate?
Keep the air temperature between 65 and 75 degrees Fahrenheit, which is ideal for most seeds. Temperature and humidity are the two most important factors for germination, so cover the containers with plastic to hold humidity, ventilate daily, and remove the cover once the seeds sprout.
How much light do seedlings need indoors?
Seedlings need roughly 12 to 16 hours of bright, indirect light each day. A south-facing window is best. If you do not have one, use grow lights or ordinary fluorescent shop lights, and rotate windowsill containers now and then so the plants grow evenly instead of leaning toward the glass.
What soil should I use to start seeds?
Use a commercial seed-starting mix, which is lightweight, sterile, and free of weed seeds. It gives delicate roots the loose, well-drained medium they need. Avoid potting or garden soil at the seed stage, since it is heavier and can carry weed seeds, insects, and pathogens. You can switch to all-purpose potting soil once you transplant seedlings into their own pots.
How deep should I plant seeds?
As a general rule, make the hole about four times as deep as the seed is wide, then cover the seed with soil. Read the seed packet for the exact depth, since some seeds need light to germinate and should sit at or near the surface rather than buried.
What does hardening off mean?
Hardening off is the gradual process of getting indoor seedlings used to outdoor conditions. About ten days before transplanting, and once daytime temperatures reach at least 45 degrees, set the plants outside in a sheltered spot for a few hours, increasing their time out a little more each day until they are ready to live in the garden.
Which seeds are easiest for beginners to start indoors?
Good first choices include zinnias, morning glories, sunflowers, nasturtiums, parsley, basil, tomatoes, and squash. They sprout readily and forgive small mistakes, which makes them a confident place to begin starting seeds indoors.
Dondra Vaughn
- Dondra Vaughn
My seedlings get very leggie how do I fix this