Cucumbers can be started early indoors or direct seeded in the garden. For an earlier crop, sow cucumber seeds indoors 4-5 weeks before they can be planted outdoors. Cucumber seedlings can be planted two feet apart in the garden after the soil has warmed to at least 70 degrees Fahrenheit. Plant the seeds directly in the garden after the soil has warmed. Cucumber seeds will not germinate if the soil temperature is less than 50 degrees. They can be spaced as closely as 8 inches apart if the plants will be given a trellis to climb on.
Eggplants do not like cold temperatures and the seed will not germinate in cool soil. The time to plant seeds for eggplants is about 8 weeks before the weather has settled into consistently warm temperatures. Sow the seeds indoors in flats.
Lettuce is a cool weather crop that can be direct seeded in the garden as soon as the soil can be worked. To get an even earlier start to the lettuce crop, the seeds can be sown in flats 3-4 weeks before they are transplanted to the garden. Plant lettuce seedlings 6 – 12 inches apart in the garden.
Melons have a tropical ancestry, and the plants grow best in warm weather. Melon seeds can be sown indoors one month before they can be transplanted into the garden, or direct seeded in the garden a week or two after the last spring frost date. Handle seedlings carefully as they do not like to have their roots disturbed. Seedlings can be transplanted two to three feet apart. To plant melon seeds directly in the garden, plant 3 seeds every 18 inches, and once the seedlings sprout, they can be thinned to one plant every 18 inches.
Okra seeds can be planted directly in the garden or given a head start indoors. The time to start okra early indoors is 4-5 weeks before all danger of frost has passed. Okra seedlings should be planted about a foot apart. As far as okra is concerned, you will know when to plant seeds directly in the garden when the soil has warmed up to at least 70 degrees Fahrenheit. Plant okra seeds about two inches apart, thinning the seedlings later to 12 inches apart.
Onions are often grown from tiny bulbs called sets, but onions can also be grown from seed. Plant onion seeds indoors in flats 6-8 weeks before the seedlings are to be planted out. Or plant onion seeds directly in the garden as soon as the soil can be worked. When you want to plant seeds for onions in the garden, they should be planted two per inch, and then later thinned to 2-4 inches apart.
Peas grow very quickly from seed and there is no need to start pea plants indoors. Plant pea seeds directly in the garden as soon as the soil can be worked, spacing the seeds 1 to 1 ½ inches apart. Peas prefer cool soil, so spring and fall crops are suitable in most areas.
Peppers grow more slowly and in most climates the plants should be started indoors so their fruit has time to ripen before the end of the growing season. Pepper plants do not like cold soil. Sow pepper seeds indoors eight weeks before planting out the little seedlings, and do not plant them outdoors until the soil has warmed and summer weather has settled in. Plant pepper seedlings 12-18 inches apart in the garden.
Pumpkins and winter squash are vigorous plants that grow well when the seeds are planted directly in the garden. Plant pumpkin or winter squash seeds in the garden after the threat of a spring frost has passed, planting seeds in groups of two or three, with each group planted at least 18 inches apart. Once the seeds have sprouted, they can be thinned to one robust seedling every 18 inches. If you have a short growing season, you may start pumpkin winter squash seeds indoors no more than 3-4 weeks before planting out the seedlings. These vining plants grow quickly, and they are also sensitive to transplant shock, so take care when transplanting seedlings and do not allow them to become overgrown in their pots.
Summer squash also grows very quickly and can be planted directly in the garden. You will know when to plant seeds for summer squash as soon as the soil has warmed up to at least 62 degrees Fahrenheit and there is no longer a threat of frost.
Tomatoes are most likely the number one vegetable garden plant that is started early indoors. If you grow your own tomato seedlings you have a much wider choice of varieties than you will find for sale at garden centers. Tomato plants cannot handle cool temperatures or frost, so the seedlings must not be planted outdoors until all danger of frost has passed and the soil has warmed to at least 70 degrees. Tomato plants that are planted while the soil is still cool will grow slowly and are also vulnerable to blossom end rot.
Sow tomato seeds indoors 5-6 weeks before the seedlings can be planted out. The timing for when to plant seeds for larger seedlings is a bit longer. To grow larger tomato seedlings, start the seeds 7-8 weeks early, and transplant the seedlings into larger pots after they have developed their first set of true leaves. Plants that will be staked and determinate varieties can be spaced 14-20 inches apart in the garden, while indeterminate varieties that will not be staked should be given more room to sprawl. Plant tomato seedlings that are not staked one to three feet apart.