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How to Start Seeds Indoors and Transplant into Your Garden

Categories: | Author: George | Posted: 2/20/2009 | Views: 18157
How to Grow Vegetables and Flowers from Seed

In Northern climates, like zone 5 in Ohio, frosts can occur as late as the end of May. But why wait to plant? There are some very good reasons to start seeds indoors; start planning now to enjoy these benefits:

  • Save money!
  • Share the fun and fascination with the family!
  • Grow vegetable and flower varieties that aren't available from local stores!
  • Take advantage of seeds that you saved from previous years!

This article also contains links to over 40 seed and gardening supply nurseries, stores and vendors.

 Here are some great seed starting and vegetable gardening resources:



First, you need to learn the last frost date for your area to determine when to start the seeds (Google the date for your area). For Medina, Ohio where I live, the last frost date is approximately May 25.

Next, determine when you should start each vegetable or flower indoors. Start dates are determined by how long a seed takes to germinate and when it needs to go into the ground relative to the last frost date. A great resource for finding these dates is the Seed Starting Calculator at www.johnnyseeds.com. Just plug in the last frost date and the calculator will provide the start date for a wide variety of seeds.

For example, in my area I should start tomatoes April 6, peppers April 13, cucumbers May 4, and squash May 11.

Note: If you're planting under row covers, cold frames, or high tunnels you can pull-in the average last frost date since the transplants will be protected from mild frosts.

Seed Starting Dates Based on May 25th Average Last Frost Date
Plant Name Start Indoors

Harden-Off Date

Basil April 20th June 1st
Broccoli March 30th May 11th
Cucumber May 4th June 1st
Kale March 16th April 27th
Onions February 16th April 27th
Parsley February 23rd May 4th
Peppers April 13th June 8th
Pumpkins May 11th June 8th
Spinach March 2nd April 13th
Tomatoes April 6th June 1st
Impatiens March 23rd June 1st
Marigold April 6th June 1st
Petunia March 16th May 25th
Rudbeckia March 16th May 25th


What You'll Need to get Started

  • Seeds
  • Planting containers and medium
  • Lighting
  • Warmth
  • Fertilizer


 If your using common seed varieties, you can probably find them last minute at a local nursery or store. However, if you want something on the unusual side, start looking now. Your best bet may be to order from an online catalog like Johnny's Seeds, Seed Savers Exchange, Bountiful Gardens, Fedco Seeds, Harris Seeds, or Park Seed (see the end of this article for additional seed vendors.)

Planting Containers and Medium 

Plastic trays for starting seeds are available from your local nursery, box stores or mail order. I've listed some planting tray, heat mat and seed starting supply links at the end of this article.

For a growing medium you have a wide variety of options, including sterilized seed starting mix, peat pellets and custom organic mix recipes. In this article I'll focus on the easiest solution, peat pellets. Another option, soil blocks, is covered in our 2011 The High-Yield Vegetable Garden article.

If you want to make your own mix, OEFFA (Ohio Ecological Food & Farm Association) has some recipes listed in a corresponding article.

Peat Pellet / Soil Block Quick Comparison
Planting Medium Pros Cons
Peat Pellets Neat, clean and easy to use. Easy to water and transplant.  Netting around pellets does not easily decompose and may restrict root growth. Pure peat medium is not ideal for all plants.
Soil Blocks Allows you to customize the growing medium. Air prunes roots to minimize transplant shock. Requires special tool. Difficult to water.

Self Water

Allows for custom medium. Keeps soil at the right moisture level. A bit pricy. Awkward to add a warming mat to the system.



 If you have a nice sunny South-facing window space available in the house, this may be your best choice.

An alternative is to use fluorescent lighting, which is a great solution for basement gardening. You can purchase a four foot fluorescent fixture and bulbs from local stores or online. A four foot-two bulb fixture is good. The best light spectrum is provided if you use one cool-white and one warm-white bulb (this actually provides a lot more of the necessary light than the "grow" lights!) Make sure that the fixture is compatable with the size of the bulbs. For more information see the TGH article about How to construct a grow stand for seedlings.

Another option is to buy a grow light system (see the product list at the end of this article.)


Most seeds prefer to germinate at a temperature between 75-85 degrees. One option is to keep the seed containers on top of a refrigerator inside the house during germination. For basement gardens you can speed up germination by using a starter kit that includes a plant heating pad or heat mat. The heating pad is especially important if you're growing plants like peppers and tomatoes in the basement, where temperatures can be in the 50s. Seeds can rot in the medium and hot weather plants may suffer from stunted growth if planted in a cool location.

Pepper Comparison: With and Without a Heating Mat


These pepper plants were both germinated in a cool basement (about 59 degrees). The plant on the left was not warmed by a pad. Notice the weaker growth and yellow foliage. The pepper on the right was germinated and raised with a heating pad.


Seeds were planted March 1st, photo was taken on April 13th.



A standard soluble houseplant fertilizer should do the trick diluted to half strength. I prefer to mix an organic vegetable fertilizer in with the planting medium or add it to the water because synthetic fertilizers build up salts in the soil that can harm the seedlings.

Planting the Seeds

OK, so you've purchased seeds and supplies and picked out a good location in the house. The calendar date is circled--it's time to start the seeds!

 Using a seed starter kit that includes sterilized trays, inserts, growing cubes and a greenhouse dome is the easiest way to get started.  


Most of these kits use peat-based growing cubes. You simply add warm water to the peat pellets and they expand to form a seed container; pour off excess water and cover with the greenhouse dome. Detailed directions are supplied with the kit. Easy and clean! 


Add warm water. Once pellets are fully expanded, pour off excess water.


Fluff the top of the pellets to make room for seeds. A toothpick is a good tool for this operation.


Add seeds (in this case Bhut Jolokia Ghost peppers).


Cover seeds with peat.


 During the first week, the seeds should require little or no watering--prop the dome open a bit to provide air circulation (yes, even seeds need some air) and prevent mold. Once the seeds have germinated you can remove the greenhouse dome. Since seedlings need less heat than the germinating seeds, this is a good opportunity turn off the heat mat and move the plants to a sunny window in the house. Good humidity is a benefit, so if the seedlings are placed in a dry location, consider placing a humidifier close to the plants. Note: if you are keeping hot weather plants in a cool area, keep the heating pad plugged in; they want temperatures in the mid-70s to grow properly.

Seedlings also benefit from a slight breeze to help them develop thicker stems, so consider placing a small fan so that the plants experience some air movement.

One challenge with starting seeds is keeping the peat pellets or starter mix moist; not too wet or too dry until the plants are ready to go outdoors. Even if there is moisture on the clear dome it does not mean that the "soil" is moist enough, especially while the heat pad is turned on. Check the soil moisture daily and water with warm water as needed.

The Burpee kit shown above uses a wicking system to keep seedlings at the correct moisture level.

Broccoli germinated in 3 days in heated tray, 5 days in Burpee tray

Keep the pots moist, but do not over-water! Fertilize a couple days after germination, then about every two weeks. If you're using fluorescent lights, adjust them to within about 2" above the seedlings. Leave the lights on for 16 hours per day. A common mistake is to place the lights too far above the plants. I hang the fixtures from chains so I can raise and lower the lights to accommodate the plants; for more information see the TGH article about how to construct a grow stand for seedlings. 

If your seedlings start to outgrow the starter pots, transplant them into larger peat pots—these can be planted directly into the garden when the weather permits. If you've started your seeds really early, you may need to move them into plastic landscape containers to give them room to grow.

Hardening Off the Seedlings

Once outdoor temperatures warm up, you'll need to harden-off the seedlings before planting them in the ground. This process acclimates the plants to wind and sun. Acclimate plants by first placing them in a bright shady location where they are protected from drying winds, such as a porch or under a tree.  Bring the plants indoors each day. Gradually increase the number of hours the plants spend outdoors. 

After 7-14 days the hardened seedlings should be ready for planting into the garden as weather permits. Plant on a cloudy day or late in the evening to ease the transition.

I've had good luck bypassing the hardening-off procedure by transplanting into a garden or planter that is protected by row cover fabric. See the TGH article on Row Covers & Plastic Mulch for a Vegetable Garden for some ideas.

Cool weather plants like broccoli, onions and spinach can deal with cold snaps, and even a bit of frost, and can be brought outside 2-4 weeks prior to the last frost date. (Add a row cover and you can transplant even earlier!)

Note: You can start the seeds earlier if you have a cold frame or row cover to protect the plants once you move them outdoors. Consider adding a soil warming cable if you want to get peppers, tomatoes and other warm weather plants outside early, otherwise the plants will not grow significantly until the weather warms into the 80s. (See our How to Use Soil Warming Cables to Start Vegetables Early article for more information.)

Watching the seeds germinate and then grow into plants is fascinating and fun. And when it comes time to plant the garden, your plants will have a huge head start, meaning more bloom time and larger harvests! Good Luck!

Seed Starter Kits, Heat Mats and Supplies


Seed and Gardening Suppliers

Johnny's Select Seeds

Seeds, tools & information


Bountiful Gardens

Seeds, supplies & information (bio-intensive)


Fedco Seeds

Seeds & supplies co-op


 Seed Savers Exchange

Heirloom seeds


Abundant Life Seeds

Seeds (biodynamic)


 Thyme Garden Herb Company

Herb seeds & hop rhizomes


Nichols Garden Nursery

Seeds & supplies


Turtle Tree Biodynamic
Seed Initiative

Seeds (biodynamic)


Raintree Nursery

Fruit & nut trees, berries


Baker Creek Heirloom Seed Company

Heirloom seeds


Botanical Interests



Companion Plants

Seeds (culinary, medicinal, aromatic)



D. Landreth Seed Company

Heirloom & vintage seeds, garlic, roots, bulbs


Willhite Seed Inc

Seeds & supplies


Dixondale Farms, Inc



Earthwave Living Company

Self-sufficient home supplies


West Wind Seeds



Grandpa's Orchard

Fruit trees


Home Harvest Garden Supply

Ferry-Morse seeds


 J.W. Jung Seed Company

Seeds, bulbs, plants & supplies


Montana Bird and Garden

Outdoor furniture, gazebos, DYI greenhouse


Musser Forests

Nursery stock, seedlings, transplants


Nature's Crossroads
Earth-Friendly Seeds

Mid-west adapted seeds


Northern Greenhouse Sales

Woven poly products


Ohio Earth Food

Organic supplies


HTG Supply

Grow lights & hydroponics


Phoenix Tears Nursery

Goji (wolfberry) plants


R.H. Shumway Seedsman



Sandy Mush Herb Nursery

Plants (herbs, perennials, trees, shrubs)


Select Seeds

Heirloom seeds & plants


Sierra Gold Nurseries

Fruit trees


Southern Exposure Seed Exchange

Seeds, garlic, perennial onions


Sow True Seed

Open pollinated seeds


Summit Year-Round Spray Oil

Garden chemicals


Territorial Seed Company

Seeds, plants, garlic & supplies


Terroir Seeds

Heirloom seeds


Tomato Growers Supply



Tomatofest Heirloom Tomato Seeds



Vermont Bean Seed Company

Seeds, garlic


High Mowing Organic Seeds

Organic seeds


 Haris Seeds

Seeds and supplies


Park Seed 

Seeds and supplies


Earth Tools

BCS walk behind tractors


Lehmans Hardware

Garden tools & hardware








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