Learn when to start seeds indoors, what plants you should pick, how to care for them, and how and when to transplant them outdoors.
It’s easy to cure an early case of garden fever: follow these tips on how and when to start seeds indoors. Growing your own seedlings also saves money and gives you the opportunity to enjoy unusual heirloom varieties.
“It’s kind of fun to start things indoors,” says Richard Jauron, a recently retired horticulturist at Iowa State University. “If you’re looking for a specific variety, you may not find it locally at a greenhouse, so you can buy the seed and start it yourself.”
Selecting Seeds
Deciding what to grow from seed is up to you, but Richard notes some things aren’t worth the bother. Begonias, for example, have tiny seeds that are hard to germinate and slow to mature. It’s much easier just to buy those plants at the garden center.
Fortunately, there are plenty of easy and readily available candidates, including flowers such as marigolds, zinnias, petunias and impatiens, and vegetables such as tomatoes, peppers, cabbage, kale and broccoli.
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When to Start Seeds Indoors
Determining when to start seeds indoors depends on where you live. Those who live in hot climates—Zones 8 or 9, for example—may be able start seeds as early as December. Northern gardeners, like those who grow in Zones 3 or 4, should wait until March or April to start most seeds, depending on the plant’s germination period.
Don’t fret if you have to wait a little longer. Extra time offers the perfect opportunity to order seeds—preferably as early as possible to get the best selection. Check out our favorite seed catalogs. Seed packets often include recommendations on when to plant indoors based on your average last frost date.
Richard cautions not to start growing too early. “Something like cucumbers or squash germinate and grow quickly, so start these inside three to four weeks before they can go outdoors,” he says. Tomatoes need five to six weeks indoors; peppers require seven to eight weeks. Here’s more expert advice for growing tomatoes indoors.
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How to Get Started Growing Seeds Indoors
Richard starts vining vegetables in peat pots, which are biodegradable cells made of compressed peat moss that can be set directly in the ground without disturbing roots. For most other plants, he recommends plastic trays that have been washed with warm, soapy water and disinfected with a 10% bleach solution to prevent spreading disease. You can also make your own newspaper pots.
Fill the tray with a commercial seed-starting mix of peat moss and vermiculite, and then sow the seed at the depth recommended on the packet. “For the seed to germinate, it needs good seed-to-soil contact,” Richard says. “And make sure they’re not too crowded.” Properly spaced seedlings are easier to transplant later.
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Boost Germination With Heat
When you start seeds indoors, warmth and humidity aid germination. “You need to keep the seed consistently moist,” Richard says. After sowing, he waters the tray before stretching clear plastic food wrap across the top and securing it with tape. (Some trays are sold with clear plastic domes to create this greenhouse effect.) He then places it by a heating vent, or you can also use a heating mat specifically for plants.
“As soon as the seedlings come up, take off the plastic, put the trays under lights and let the germination medium dry out—not completely dry out but just enough to dry out somewhat—then water again,” Richard says.
Light is very important. “If you put the seedlings in a window, even a sunny window, they’re not going to get enough light, so they stretch and get very spindly,” Richard says. “I typically use an ordinary fluorescent light with two 40-watt tubes. The light needs to be very close to the seedlings when they come up, typically within 4 to 6 inches.”
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When to Move Seedlings Outdoors
Once the seedlings develop a second set of true leaves, Richard transplants them into cell packs filled with potting mix. “I just use a knife and dig them up really carefully by hand,” he says.
When it’s time to take plants outside (see the seed packet for guidance), start by acclimating them to the conditions. This process, called hardening off, can be done by placing plants outside in the shade for a few days, gradually moving them to increase the amount of light they receive every few days.
“I like planting in the morning or in the evening, not during the heat of the day when the plants might suffer a little bit,” Richard says. “Water them well and they should be OK.” If seedlings appear a bit pale, he suggests adding a water-soluble fertilizer when watering, and wait for your plants to flourish.Learn the best time to water plants.
Top Plants to Start from Seed
These popular blooms and veggies are easy to grow start from seed.
Flowers
- Aster
- Bachelor’s button
- Calendula
- Cosmos
- Phlox
- Salvia
- Sunflower
Vegetables
- Beans
- Broccoli
- Cauliflower
- Cucumber
- Eggplant
- Lettuce
- Squash
- Tomatoes
- Peppers
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Insights, advice, suggestions, feedback and comments from experts
I am an expert and enthusiast assistant. I have access to a wide range of information and can provide assistance on various topics. I can help you with questions related to starting seeds indoors, selecting seeds, caring for seedlings, and transplanting them outdoors.
Starting seeds indoors can be a fun and rewarding way to grow your own plants. It also allows you to have more control over the varieties you grow and can save you money. Here are some tips and information on starting seeds indoors:
Selecting Seeds
When deciding what to grow from seed, it's important to consider the ease of germination and maturity. Some plants, like begonias, have tiny seeds that are hard to germinate and slow to mature, making it easier to buy those plants from a garden center. However, there are plenty of easy and readily available candidates for starting seeds indoors, including flowers like marigolds, zinnias, petunias, and impatiens, as well as vegetables like tomatoes, peppers, cabbage, kale, and broccoli.
When to Start Seeds Indoors
The timing for starting seeds indoors depends on your location and the specific plant's germination period. Those living in hot climates (Zones 8 or 9) may be able to start seeds as early as December, while northern gardeners (Zones 3 or 4) should wait until March or April. It's important to consider your average last frost date when determining when to start seeds indoors. Seed packets often include recommendations on when to plant indoors based on your average last frost date.
How to Get Started Growing Seeds Indoors
To get started, you'll need containers or trays for planting the seeds. Vining vegetables can be started in peat pots, which are biodegradable cells made of compressed peat moss. For most other plants, plastic trays that have been washed with warm, soapy water and disinfected with a 10% bleach solution can be used. You can also make your own newspaper pots.
Fill the containers with a commercial seed-starting mix of peat moss and vermiculite, and then sow the seeds at the recommended depth. Good seed-to-soil contact is important for germination, so make sure the seeds are not too crowded. Proper spacing will make it easier to transplant the seedlings later.
Boost Germination With Heat and Light
Warmth and humidity aid germination, so it's important to keep the seeds consistently moist. After sowing, you can cover the containers with clear plastic food wrap or use clear plastic domes to create a greenhouse effect. Placing the containers near a heating vent or using a heating mat specifically for plants can provide the necessary warmth.
Once the seedlings emerge, remove the plastic cover and place the trays under lights. Ordinary fluorescent lights with two 40-watt tubes can be used, and the lights should be positioned within 4 to 6 inches of the seedlings. Sufficient light is crucial to prevent the seedlings from becoming stretched and spindly.
Transplanting Seedlings Outdoors
Once the seedlings develop a second set of true leaves, they can be transplanted into cell packs filled with potting mix. Carefully dig up the seedlings by hand and transplant them into the cell packs. When it's time to move the seedlings outdoors, start by acclimating them to the conditions through a process called hardening off. This involves placing the plants outside in the shade for a few days and gradually increasing the amount of light they receive. It's best to plant them in the morning or evening, avoiding the heat of the day. Water the seedlings well after transplanting, and if they appear pale, consider adding a water-soluble fertilizer when watering.
Starting seeds indoors can be a rewarding experience that allows you to grow a variety of plants. By following these tips and guidelines, you can increase your chances of success and enjoy the process of nurturing your seedlings until they are ready to be transplanted outdoors.
I hope this information helps you with starting seeds indoors and growing your own plants! Let me know if there's anything else I can assist you with.