Succeed with seeds! Here are my 10 tips and tricks for starting your vegetable seeds indoors. Over the decades, I've learned some valuable lessons—from when to start seeds to avoiding common mistakes.
The Hindi word for seed is " bija" which translates literally as "containment of life". An apt description for these tiny miracles that contain everything needed to make a new plant. This time of year we are up to our elbows in dirt, starting more seeds indoors each week.
Why would you want to start your own seeds? Three big reasons: There is a much wider range of varieties available as seeds, things you would never find in a six-pack at the local garden center. You will know how they have been raised —organically instead of bathed in a wash of chemicals. You can time the plants to be ready for when you want to plant them.
Before we talk about starting seeds indoors, recognize that some seeds prefer to be direct planted in the soil and do not want to be transplanted. Check the Almanac's chart on which seeds can be started indoors and which are better direct seeded into the ground outdoors.
10 Tips to Succeed With Seeds
To succeed with seeds we need to follow a few simple rules:
- Disinfect any recycled pots, flats, or trays. You don't need to buy new pots and can use just about any kind of container that is at least 2 inches deep to start your seeds—s long as it has holes for drainage. If you don't clean your seed pots, you may experience “damping off” from the mold (or leftover pathogens) and your seedlings will wilt. Clean with soap and water, plus an added step for sanitization (either with a bleach solution or the sun).
We use wide shallow boxes called "community flats" to start rows of seedlings.
- Read your seed packets. They have a wealth of information—germination temperature, light requirements, depth to sow, and when to sow.
Don't start seeds too soon! This is a beginner's biggest mistake. Timing is everything. Count backwards from your frost-free date the required number of weeks stated on the package to have your plants ready at just the right time. If the soil is too cold, some plants just won't make it. As a general rule, most plants are ready to go outside four to six weeks after you start the seeds. See the Almanac's Planting Calendar which includes when to plant seeds indoors, based on your local frost dates.
Also, as any reading of the seed package will show you, not all seeds should be planted at the same time. Some vegetables are cool-weather crops and some are warm-weather. Before you get started, it might be helpful to write out a schedule, or group your seed packets by planting date/weekend.
- Use a soil mix designed for seed starting. To avoid soil-borne diseases and fungi look for a soil-less mix. We use a compost-based seedling mix with excellent results. Regular potting soil or plain garden soil are too heavy.
- Label everything! Many emerging seedlings look alike. We cut labels from recycled plastic containers.
- Light is key. Once your seedlings have emerged, place them where they will receive bright light for most of the day—greenhouse, sunporch, or south-facing windows. If you don't have such a spot try a grow light or an ordinary shoplight fixture with fluorescent bulbs.
No matter what you hear, most homes simply do not have enough light for health, robust seedlings. Grow lights truly do make a difference and they don't have to be expensive. Suspend a large fluorescent shop light from chains about a few inches above the seedlings. Once seedlings appear, keep the lights turned on for 12 to 16 hours per day. Raise the lights higher as the seedlings grow.
Likewise, we recommend adding heat mats which really help with germination. Most seedlings like the temperature to be in the about 65- to 75-degree range to germinate. Sometimes the top of your refrigerator will do but a simple heating mat will do the trick.
Hang the lights so they can be adjusted to keep them 4 inches above the plants as they grow.
- Transplant seedlings into individual pots when they get their "true" leaves. What is a true leaf? A seeling first develops two small cotyledon; they look like tiny leaves but they're actually a food source for the sprouting seedling. The seeding will then develop two real leaves that look different; these leaves are photosynthesizing. (Eventually the cotyledons will fall off.)
- Handle seedlings with care and replant them deeper into their new pots—up to their seed leaves. Many plants—like these tomatoes—will form new roots along the buried stem.
However, don't plant too deep. See your seed packet for instructions. The general guideline is to plant seeds 2 to 3 times as deep as they are wide.
If your plants outgrow their pots before time to plant them outside, move them into larger containers to keep them growing. You don't want to plant outside too early.
- Fertilize and water, especially if you are using a soil-less mix that has no nutrients added. Feed the plants weekly with a water-soluble, organic fertilizer. We use fish and kelp emulsion. A little stinky but it does the trick!
Avoid over-watering seedlings. One method is to water from the bottom of the container. Then seedlings to soak up water through the container drainage holes. Add water slowly for 10 to 30 minutes until moisture has reached the top of the container.
- Stroke your plants or set up a fan to gently blow on them. Studies show that plants grown in a still environment are weaker than those subjected to a gentle breeze.
- Harden off your transplants by gradually exposing them to the great outdoors before planting them out. "Hardening off" prepares seedlings for the transition from indoors to outdoors. Do not rush this! Give them one hour outdoors the first day, and increase the hours every day for 6 to 10 days. If it's very rainy, you may need to slow down your timetable.
Give seed starting indoors a try! It is a garden variety miracle!
For more information about hardening off and transplanting, see the Almanac's Learn-to-Garden Hub.