This guide covers the basics of seed starting. We recommend seeking out other resources: talk to local gardeners, find your local Master Gardeners, and read gardening books for your region! We recommend Nancy Bubel's classic guide The New Seed Starter's Handbook for anyone learning about starting plants from seed.
When do your normally have your last frost of the year? In Central Virginia our average last frost is April 15. Knowing this date is essential to planning your garden. Use the planting dates chart in this growing guide to help you plan, but also seek out resources with dates specifically for your region.
Map your garden: measure the space you have and place your rows, beds, and paths. Gardeners often make 4 foot wide raised beds between 12 inch paths, but we find it's easier to reach across 3 foot beds and kneel in 18 inch paths. Notice shady areas, soggy areas, and which way is south. Plan to plant tall crops on the north side, where they won't shade other plants, or plant shade tolerant crops on their north side. Think about where your water will come from and how far your hose or sprinkler can reach (or how far you're willing to haul).
You may want to make a map for every season. A gardener can often grow 3 or more crops each year in the same space. For example, plant spring lettuce, followed by summer green beans, followed by fall spinach. Most variety descriptions indicate days-to-maturity: this tells you when you can expect to begin harvesting and helps you predict when the crop will be finished. Some crops get planted once a year, while others, like lettuce and cilantro, are best planted several times a season (this is called succession planting). Don't plant any one crop in the same place every year: we recommend a four year rotation to reduce plant diseases. Incorporate cover crops (good choices might be buckwheat in the summer, oats in the fall, and rye mixed with vetch or clover in the late fall and winter) into your rotation to recharge the soil and prevent erosion.
You can get soil sample testing kits from your local Cooperative Extension office, local Master Gardeners, or a garden center. Find out about free and inexpensive soil testing services in your state. Do this early in the spring, so you'll have plenty of time to get the results and amend your soil before planting time.
Some seeds should be started indoors in the spring in pots or trays, and then moved into the garden as small plants (seedlings) when the soil is warm enough. You can grow healthy, sturdy seedlings in a sunny window, but rotate your plants every few days so they don't lean towards the window and become leggy. Fluorescent lights can help your seedlings get enough light, but turn the lights off at night to give the growing plants a rest! You can also start seeds in a cold frame or greenhouse if you have one.
We start most spring seedlings 4-6 weeks before the recommended transplanting date (tomatoes, sweet peppers, eggplants, broccoli, cabbage, kale, and collards). Onions, hot peppers, and celery need longer, 8-10 weeks. Don't start your seeds indoors too soon: if the seedlings get very large they'll suffer more damage when you move them outside.
Start your seeds in a good organic seed starting mix from a local store or make your own soil mix. Purchased mixes are sterile, light and hold moisture well. Use a large container to mix water into your soil mixture until it is moist, but not soggy. Fill nursery flats, small pots, or other containers nearly to the top with your seed starting mix (the best size is 2-3" deep and at least 3" wide). Make sure your containers have drainage holes!
Use your finger or a stick to make holes in the soil for the seeds. The holes can be quite close together, because you'll move your plants into larger containers before they're very large. For large seeds, makes holes about a half inch deep. For smaller seeds, an eighth to a quarter inch is plenty. Place 1 to 3 seeds in each spot. (It's good to sow extra because not all your seeds will come up. Pull out any extras once they sprout, or very gently move them to an empty spot.) Cover the seeds with fine soil and press down gently. If you added enough water when you mixed the soil, you won't need to water again for at least a day.
Water gently and sparingly, just enough to keep the soil moist but not soggy. It may be several days or even a couple weeks before you see your first seedlings break through the soil. It's important not to water too much during this time (or your seeds could rot!).
The first leaves you see are called the seedling leaves or cotyledons. Most garden plants have two seedling leaves that open up at the same time, but corn and other grasses only have one. Your plants will start growing larger, true leaves after the seedling leaves appear.
Make sure your seedlings always have plenty of light, moisture, and space to grow. When they have 2-3 true leaves it's time move them into larger flats or pots (this is called potting up). Don't give them too much more room too quickly: seedlings grow best and it will be easier to keep them evenly moist if you choose slightly larger containers, not enormous ones.
This is a good time to make sure your plants are getting the nutrients they need to keep growing until it's time to move them to the garden. We do this by potting up into fine, fertile compost. You could use a mix of compost and soil or a purchased potting mix. Moisten your potting soil first and fill the container nearly to the top. Use a narrow trowel or a popsicle stick to make a deep hole, and while holding the soil aside, slide in the seedling. It's best if the seedling roots are a bit spread out and generally point downwards. Gently press down the soil around the base of the plant, avoiding mounding soil against the stem. Give each plant a bit more water and you're done!
A couple weeks before you expect to transplant, begin hardening off your plants by moving them to a cold frame or setting them outside for several hours each day.
It's important to add organic matter to your soil before you plant. Compost and partially decomposed leaves are good sources of organic matter. Organic matter improves the structure of heavy clay soils and helps sandy soils to hold water. Adding organic matter is especially important where topsoil has been lost, such as in a new subdivision.
If you can find a good source for it, composted animal manure is a wonderful organic amendment. Composted manure adds fertility to your soil, but it also improves the soil structure and adds slow-release nutrients that will be available for years to come.
Use your soil testing results to decide which amendments to apply. When you use only as much lime, fertilizer, and other nutrients as necessary, you minimize nutrient runoff into surface and ground water, optimize the health of your plants, and save money.
There are many tools for preparing the soil for planting. Your goal is to mix in any amendments and to loosen the soil, so plant roots can grow easily and water can seep in.
Double digging is a technique where you turn the soil using a shovel, to the depth of two shovel lengths. If your soil is already quite loose you may only need to turn the top layer. A broad fork can also be used to turn and loosen the soil. A roto-tiller is a machine that turns the soil. These can easily be rented, but are quite heavy and may be unwieldy to operate. Farmers may use a plough or disk on the back of a tractor to loosen their soil.
Use a rake to remove clumps from the tops of your beds, especially if you will be sowing seeds directly into the soil. You can also use a rake to mix amendments into the top few inches of soil.
To avoid stressing your tender seedlings, transplant them into your garden in the afternoon on an overcast or drizzly day. Thoroughly moisten the soil before you plant. Use a garden trowel or shovel to make a hole that is deep enough for the roots of the plant. While pressing the soil aside, gently place the plant so the roots are spread out and directed downwards (dig a deeper hole if necessary). Press the soil down firmly around the base of the stem.
Give the plants plenty of water just after transplanting and continue giving them lots of water until they're established (growing well). It's the best thing you can do to reduce damage from transplanting (transplant shock). Place mulch around the plants to help keep the soil moist and prevent weeds from coming up.
Some seeds, like peas, beans, and corn, should be sown directly into the soil outside, but wait until the soil warms up before you sow! Watermelon, melons, cucumbers, and squash are often sown outside, because their tender roots can be easily damaged by transplanting. Know how far apart you want your plants to be and sow 3 or 4 seeds at each spot. It's important to sow extra because seeds sown outside are less protected and could be eaten by birds or other critters. Be diligent about keeping the seeds moist until they germinate! Once your seedlings have put on 2 to 3 true leaves, pull out any extra plants (this is called thinning).