New to Gardening? These 7 Seeds Are the Easiest to Start Indoors

Seed starting can be a finicky business, but these 7 veggie and flower all-stars are a cinch to start indoors in late winter or spring. If you live in a climate with a short growing season, starting seeds indoors allows you to grow crops that take a long time to mature. Another advantage of an early start indoors is an earlier harvest, and in some cases, a longer harvest for plants that produce flowers and fruit through the growing season.

Gather your seed-starting supplies, such as quality seed-starting soil mix, seed-starting trays or pots, a source of bright light, and seeds from this list to get started.

Time It Right

Timing is everything when it comes to starting seeds. The plants in this list are quick and easy to start from seed, but if your timing is off, even the most robust, healthy seedling will languish. Pay close attention to the “when to start” section for each plant below.

Starting too early causes seedlings to grow tall and lanky with weak stems. On the other hand, starting cool-season crops, like broccoli, too late exposes them to the summer heat, in which they struggle and produce poor results. No matter the type of seeds, the key is to determine the average last frost date in your area and then do some simple math to properly time when to start them.

 1. Broccoli

A cool-season crop that is harvested in late spring or early summer, broccoli needs an early start indoors to be ready for harvest before the heat of summer hits.

When to start: Sow seeds indoors 6 to 8 weeks before the average last frost date in your area. Seedlings are ready to transplant outdoors about 3 weeks before the average last frost date. Although broccoli tolerates cold temperatures, cover the transplants when temperatures below 25°F are predicted.

Planting details: Cover seeds with about ½-inch of fine potting soil. Seeds germinate quickly, often emerging just 4 to 7 days after planting. 

Growing tip: Space broccoli transplants about 2 feet apart in the garden. The young seedlings will grow quickly and need ample space to expand foliage that will support tender flower stalks.

2. Kale

Kale is another cold-hardy cool-season vegetable that benefits from an early start indoors, which allows you to begin harvesting in late spring or early summer.

When to start: Sow the seeds indoors 6 to 8 weeks before the average last frost date in your area. Transplant seedlings outdoors about 4 weeks before the average last frost date.

Planting details: Cover seeds with about ½ inch of fine potting soil. Expect seeds to emerge 4 to 7 days after sowing. 

Growing tip: Kale performs poorly when daytime temperatures consistently exceed 80°F.  To keep it growing as long as possible in summer weather, plant it in a spot where it gets afternoon shade.

3. Peppers

Mild peppers like bell peppers mature faster than hot peppers, such as ghost peppers, but the seed-starting process is the same for all peppers. Start this warm-season crop indoors for a plentiful summer harvest.

When to start: Sow seeds indoors 8 weeks before the average last frost date in your area. Peppers are highly cold-sensitive and often one of the last vegetables to be planted in the garden. Make sure to wait until nighttime temperatures remain consistently above 50°F to 55°F to plant transplants in the garden.

Planting details: Cover seeds with about ¼ inch of fine potting soil. Seedlings will emerge in 7 to 10 days. 

Growing tip: When seedlings are 2 inches tall, transplant into a deep pot and grow under a strong light source until transplanting outside. 

4. Tomatoes

One compelling reason for starting your own tomato plants is that the number of tomato varieties available from seed is much larger than the handful of varieties available as transplants at garden centers. If you would like unique and hard-to-find varieties, starting them indoors is the way to go.

When to start: Sow seeds indoors 6 to 8 weeks before the average last frost date in your area. Tomatoes are very vulnerable to cold, so wait to move them outside until nighttime temperatures are consistently above 55°F.

Planting details: Cover seeds with about ¼ inch of fine potting soil. Seedlings will emerge in 6 to 12 days. 

Growing tip: Hardening off, or the process of gradually acclimating young seedlings to the rigors of growing outdoors, is essential for tomatoes. When the seedlings are several inches tall, and the temperature is at least 50°F, set them outside for a couple of hours in a shaded location. Continue this indoor-outdoor transition, extending their outdoor time a couple hours each day for a4 to 5 days before planting the seedlings in the garden.

5. Basil

Starting basil indoors from seed allows you to begin harvesting this essential kitchen herb in early summer. The more basil leaves you harvest, the more leaves the plant will produce.

When to start: Sow indoors 4 to 6 weeks before the average last frost date in your area. Basil is cold- sensitive and struggles in temperatures below 50°F. Put off planting it in the garden until the daytime temperature reaches 70°F.

Planting details: Cover seeds with about ¼ inch of fine potting soil. Seedlings usually emerge 10 to 14 days after sowing. 

Growing tip: If you have started basil indoors and the weather is still too cool to plant it outside, keep growing it indoors in a sunny window or under grow lights.

6. Zinnia

An annual cutting flower, zinnias flower from early summer until fall when started early indoors. Harvesting the flowers spurs the plant to produce more flower buds, so pick them frequently.

When to start: Sow seeds 4 to 6 weeks before the average last frost date in your area. Wait to transplant them in the garden until daytime temperatures have reached 70°F, as young plants are cold-sensitive (established plants can handle cool weather).

Planting details: Cover seeds with about 1/4 inch of fine potting soil. Expect seedlings to emerge in 5 to 7 days. 

Growing tip: Encourage zinnia plants to develop branches, which will lead to more flowers, by pinching the central stem back by about 2 inches when the transplants are about 8 inches tall.

7. Cosmos

Cosmos is a warm-climate annual native to Mexico whose seeds need a soil temperature of at least 65°F to germinate. To get a head start on the growing season, start the seeds indoors for a flower that will continue to bloom until the first frost.

When to start: Sow indoors 5 to 7 weeks before the average last frost date in your area. Transplant them outdoors after hardening off the seedlings, and the temperature remains consistently above 60°F.

Planting details: Only cover seeds lightly, as they need light to germinate. Seedlings emerge 5 to 14 days after planting. 

Growing tip: Plant cosmos about 12 inches apart in the garden so they can grow together, supporting each other.