Starting seeds indoors: Jump-start your garden today

In some parts of the U.S., vegetable and flower seeds can be successfully planted directly into the garden. But in many areas, the growing season is too short to allow this.

Cool spring soil temperatures and cold weather can prevent seeds from germinating or kill young seedlings. If you wait until the weather warms, the plants get off to a late start only to be zapped by fall's first frost; they don't get a chance to bear a full crop or to put on a full floral display.

There are three solutions for home gardeners:

  • Buy all of your vegetables and flowers as plant starts, once the weather warms.
  • Extend the growing season outside with coldframes and rowcovers.
  • Start your own seeds inside while the wintry weather lingers.

The first choice is best for beginning gardeners who are working on a small scale. The second option is nice for committed gardeners who want to test the limits. Starting from seed, however, is easy, is cheaper per plant and allows a greater variety of choice among both ornamentals and crops than buying nursery plants.

I'm eager each (early) Spring to get my seeds going. On March 1st, I began seven types of flowers and my basil seeds. (As of March 5th, the basil has sprouted, as have a couple of the flowers.) In two weeks, I'll start tomatoes and a few others, and the squash, cucumbers and more flowers will follow. How do I do it, and how do I know when to start? Here are my tips:

When Should I Start My Seeds?

In order to decide when to sow your seeds, you need to find the average last frost date for your region. In Oregon's wet and unpredictable Willamette Valley, published last frost dates range from March 23 to May 14. Based on my own experience, I pick the latter end of this range and count backward from May 1st.

Seed Schedule
Click for full version of our 2009 seed-starting agenda.

I start my tomato plants six or seven weeks before this date. Slow-to-germinate flowers get an eight-week head start. Squashes and cucumbers don't transplant especially well, but I germinate them inside to protect them from marauding slugs. I move them outside two weeks later before they've developed much of a root system.

What Should I Plant Indoors?

To determine what to plant indoors, read your seed packets. Many will list instructions for both inside and outdoor seed sowing. Knowing which to do will depend on your climate. With flowers, I often do both. I'll start a limited number indoors for “insurance” and then sow the remainder of the packet directly in the garden once true Spring arrives.

Some crops should not be started indoors because they don't transplant well or because they need an impractical amount of room. I would not recommend starting the following inside:

  • Root, tuber or bulb crops (beets, radishes, turnips, onions, potatoes, carrots, etc.)
  • Leafy greens (lettuces, spinach, cabbage, chards)

These cool season plants can withstand planting directly outside even before the weather fully warms. Likewise, things you are going to plant in large numbers should wait until they can be sown into the garden soil. The following are usually grown in sizable quantities:

  • Corn
  • Peas
  • Beans

If you are worried about your short growing season for crops like corn, look for varieties that have a short days-to-maturity period.

Tomatoes and peppers, broccoli, eggplants, cauliflower, melons and squashes can all be started successfully indoors. Herbs and flowers, too, benefit from the controlled environment of indoor seed starting. Let's get started!

How Do I Start Plants From Seed?

The two most important factors for seed germination are temperature and humidity. The seed contains all the nutrients the plant needs to germinate, so it doesn't need fertilizer or fertile soil.

Note: Fertilizer may actually prevent some seeds from sprouting. Generally, I avoid fertilizing until plants have grown their first set of “true leaves”, which look different than the first pair that emerges.

To start my seeds, I used the bio-dome from Park Seeds, a device that looks like a plastic greenhouse dome with a styrofoam tray. The tray holds little soil-less planting plugs called bio-sponges. Each plug has a hole in it for the seeds. I don't normally advocate one product over another, but I really like these.

Bio-SpongeSeed Packets

Seeds sprout best in a light soil; don't use potting soil or garden dirt at this first stage! You can buy seed starting mix or make your own from peat moss, sand, and compost.

Note: Take care if using vermiculite; it can be a respiratory hazard. I prefer the little soil-less planting plugs because they're mess free and they pop out easily for transplanting, doing minimal damage to the roots, but other methods work fine too.

Any device that keeps the environment moist and fairly warm will work. You can cover trays of soil with saran wrap or a dry-cleaning bag — poke plastic forks into the soil to hold the plastic layer up off the growing sprouts. Commercial peat pots, yogurt cups or milk cartons (poke drainage holes in the bottoms) or pots made from newspapers (avoid colored ink) all work fine, too.

Set your pots in a tray, tub or rimmed cookie sheet so you can water from the bottom, letting the moisture soak up through the soil. This helps keep the moisture level constant and prevents dislodging seeds with a fountain of water. Do not let the soil dry out! Little tiny seedling rootlets need constant moisture.

Seed Sizes

Seeds vary widely in size. I like to use tweezers to place them exactly where I want them. In general, seeds should be planted approximately four times deeper than their diameter. Some seeds need light to germinate and should be scattered just on the surface of the soil. Again, read those packets!

I usually put two seeds into each hole. I use three if I think the germination rate will be low. You can test your germination rate by placing ten seeds between layers of moist paper towels in putting them in a Ziploc bag in a warm place. This is a good idea if you have saved the seeds yourself or they are several years old. Do this 2-3 weeks before you want to actually start your seeds.

Bio Dome

As you're planting, take good notes! Make a planting diagram and jot down how many days it takes each type of seed to germinate. Some germination times are given as huge ranges (5-20 days). The happier the seed is (warm and wet), the speedier germination may be.

Plant Labels

If you are using individual pots, mark them with labels or masking tape, unless you know for sure that you will recognize what the leaves of your young plants will look like. There's nothing worse than getting your plants mixed up. This is especially important if you are starting different varieties of the same crop! Free plant stakes can be made simply by cutting up a plastic yogurt tub. Store your leftover seeds in a ziploc bag or glass jar in the refrigerator.

Seeds in the WindowNow that the seeds are snug in their beds, cover them to retain moisture and put them in a warm place. A temperature of 70 degrees Fahrenheit (21 degrees Celsius) is ideal, but in March our house is nowhere near 70 degrees! I like to set my mini-greenhouse on a heating pad (a wet/dry safe heating pad set on low) to maintain a more constant temperature, since our thermostat drops to 54 degrees (12 Celsius) at night. Some people recommend putting the seed tray on top of the refrigerator. If your house is more temperate, the heat source is unnecessary. I have often started seeds without a heat source, but peppers and eggplants seem especially fussy about the temperature.

What Happens After the Seeds Sprout?

Once the seeds have germinated (keep them moist!), they'll need light, nutrients and air. Give them some ventilation and move them to a very sunny window, supplemented with artificial light. There is no need to buy an expensive grow light or full spectrum light. For these purposes, a basic 48″ fluorescent shop light is all you need.

Tip: The type I own has two tubular bulbs per light; they're available at home improvement stores for less than $20. The critical thing is to hang them in such a way that they can be raised as the plants grow; I use a link-type chain that can be doubled-up on itself to different lengths.

As your plants grow, keep the light about 6″ from their tops. If the light is too far away, the plants will grow spindly as they stretch for it. This can be rather tricky if you are starting different types of seeds at the same time, because they will grow at varied rates. You can lift the shorter ones with shoeboxes or phonebooks to alleviate this difficulty. Once all the seeds in your tray have germinated, remove the cover completely. Too much humidity at this stage can encourage mildew and harm the seedlings.

As you water, fertilize with a weak solution of water-soluble all-purpose fertilizer. I make mine about one-quarter the strength called for. Watch out for crystallized salts forming on your soil surface — that's a sign you're over-fertilizing and need to cut back. Turn the lights off for your plants at night (they need a dark cycle to grow properly) but leave the heat on (temperature fluctuations can stunt them).

What About Transplanting?

When the seedlings first sprout, they will usually have a pair of first leaves that look nothing like the true leaves that come later. (Many crops are dicots, but not all.) Watch closely, and soon after they have two sets of true leaves, it's time to move the teenage seedlings into their first real apartment. Water your seedlings thoroughly an hour or two ahead of time, and then, working carefully and quickly, remove each seedling into its own pot.

At this point I generally use an all-purpose potting soil. Scooping them up from below, try your best to get all their little roots, and handle their tops as little as possible, and always by the leaves, rather than the stem. A damaged leaf can be replaced; a damaged stem often dooms a plant at this stage.

Kris' Tomatoes

Depending on how long your plants will be living inside, you may perform only one transplant, or you may need two. For my tomatoes, I'll move them into 4-inch plastic nursery pots first, then into gallon-sized pots before they go outside. Everything else gets one transplant, then into the garden.

Once your seedlings are thriving, it's tempting to treat them a bit too carelessly. Being started inside in a safe environment, they can't stand the shock of an immediate change in their conditions. Basically, they are weak, coddled little things. Expose them gradually to the out-of-doors by setting them outside on nice days for a few hours, being sure to bring them inside at night and making sure they don't get sunburned or blown over. Some gardeners like to have a fan blow on their indoor starts, saying it strengthens the stems to withstand windy outdoor conditions. I can't vouch for that, but I do think it helps prevent mildew.

Happy Planting

Wow, that seems like a lot of work when I write it all out. But it's not really! Watching my garden plants grow from tiny seeds is a thrill every year. I love trying new things each spring and learning from my successes and failures. I hope these tips get you well on your way to learning what works best for you. Happy gardening!

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Jon
Jon
11 years ago

Unfortunately, in some areas, this is a great way to get your house raided by police on suspected drug charges.

RJ
RJ
11 years ago

I find it helps to keep an attitude of “everything’s an experiment!” and try enough different seedling/gardening projects that some can fail and I can still feel successful and rewarded.

This year I’m going to try Belgian Endive, my expectations for success are quite low!

Janet
Janet
7 years ago
Reply to  RJ

Ever grow the plant that closes its leaves like crazy when you Tickle It? My kids love growing TickleMe Plants. They are like pets!

http://www.ticklemeplant.com

Janet
Janet
7 years ago
Reply to  RJ

I really do love my pet TickleMe Plant as well

Beth @ Smart Family Tips
Beth @ Smart Family Tips
11 years ago

Thanks so much for this post, Kris! I’ve been eagerly awaiting it. I’m ready to plant my seeds, but because this is my first year starting from seed, I was looking for some guidance.

Well written, clear, and very informative. Much appreciation.

The Personal Finance Playbook
The Personal Finance Playbook
11 years ago

Great post, Kris. I am going to file this page away and keep it for when my wife and I start a garden.

Becca
Becca
11 years ago

Oh how I wish I had the space right now, by next year I will. You write in a very reader friendly way and describe this process the best I have seen! You and J.D. both are gifted writers and this blog is a joy to read everyday.

John
John
11 years ago

What a great article and the steps are very easy to follow. I have never tried this before, but I might give it a shot in the future.

Tom S.
Tom S.
11 years ago

What a timely post! I just bought my seeds yesterday. I also picked up seed starter “dome” similar to what you wrote about.

Katharine
Katharine
11 years ago

LOVE the gardening posts – we just planted our beans and peas on the 1st too. It makes it feel like spring around here!

Just one comment on growing (or not) lettuce indoors. I saw this article about growing lettuce indoors that looks like it might work:
http://www.motherearthnews.com/Grow-It/Growing-Lettuce-Indoors-Small-Space-Gardening.aspx

We haven’t tried it yet but I think we’ll do it next week.

Bill
Bill
11 years ago

I’ve already started 16 tomatoes. I’m in the process of switching to only heirloom’s so I can harvest the seeds but I still have some hybrid seeds. One thing for new people to remember, you need to “harden off” the seedlings. Meaning you can’t take the indoor starts and just toss them out into the garden. You need to move them out for a couple of hours at a time. Full direct sun will kill them.

eddie
eddie
7 years ago
Reply to  Bill

he mentioned that

David S
David S
11 years ago

This is a great post. I try to start seeds indoors, but usually with mixed results. Your article will make a great reference tool.

geraldine vatan
geraldine vatan
11 years ago

Hello,

I read your post with interest and then I got confused about which plants to start indoors. You mention that you started your own lettuce indoor and then you discourage to do that because they don’t transplant well! Is there a typo somewhere?

Thanks for the clarification,

GV

J.D.
J.D.
11 years ago

@geraldine (#11)
Good catch. We currently have an indoor herb container. These is for herbs we’ve been using over the winter. Kris planted some lettuce seeds in this container, but it’s for our use later this spring, and not for transplanting. We shouldn’t have mixed the two projects together in this post because it’s confusing (even for me!). Thanks for pointing this out!

Schizohedron
Schizohedron
11 years ago

Free plant stakes can be made simply by cutting up a plastic yogurt tub.

A diamond of an idea in a post filled with gems. I always have a few of these tubs kicking around.

Luci
Luci
11 years ago

@Jon: Now that sounds like the voice of experience… 🙂 Maybe it’s because I’m still pretty new to gardening or maybe I’m just a little dense, but is there any way Kris could clarify her transplantation method? “Scooping them up from below, try your best to get all their little roots, and handle their tops as little as possible, and always by the leaves, rather than the stem.” I just can’t picture this process in my head for the life of me. I feel silly for asking, but maybe there’s someone else reading this who’s just as confused as I… Read more »

stephanie
stephanie
7 years ago
Reply to  Luci

if you’re worried about damaging the tiny roots, do what i do. I plant my seeds in little waxed dixie cups that fit into the holes of my starter kit and simply label the cup with any info I need. Then the bottom easily peels off from having been wet and you can push the plant up from the bottom to transplant it without having to pull on the plant from above, which can rip the immature roots. You can dust away a bit of the dirt if it’s packed or solid or the roots are balled, but you shouldn’t… Read more »

Camille@TheFinancialWoman.com
11 years ago

What a nice, detailed article. Every year, after killing yet another tomato plant, I vow to never try again, but you did inspire me, and homegrown tomaotes are the best!

Kris at GRS
Kris at GRS
11 years ago

Luci: Here’s a little more detail to help explain the transplanting: If your seeds were started in a flat of soil, then use a plastic spoon to carefully dig around the root area of your seedling and then scoop the entire “soil + root” area into your next-sized pot. By supporting the weight of the seedling from below (on the spoon), you minimize the chance of ripping the poor little thing loose from its roots. If you have started your seeds in flimsy plastic pots, you can often loosen the soil by pushing the pot up from the bottom. Then… Read more »

Luci
Luci
11 years ago

@Kris: Thank you so much! That helps me tremendously. I guess sometimes I just need to have things explained to me twice–definitely obvious that I’m a gardening n00b. 🙂

Mel
Mel
11 years ago

Folks that are off the grid can’t always spare electricity to power grow lights — me included! I do have a green room and have had moderate success starting transplants indoors, but my starts still need more light. Large south facing windows and reflectors just aren’t enough and we are making plans to install skylights. The skylights will drastically increase the temperature of the room, though the increased light will hopefully be much appreciated by my plants. I’ve heard that there is a correlation between heat and light and that the hotter it is, the more light the plants will… Read more »

green crop circles
green crop circles
11 years ago

Kris,

This is the post I have been waiting for!!! Very well-written with good pictures. I am very excited to start my garden. I’m doing SFG this year.

I know there is some controversy on vermiculite and I have been reading that you have to choose “asbestos-free” to be safe. Anyway, on a related note, I know you do some version of SFG but what kind of soild do you use? Did you follow Mel’s Mix? Why/Why not? I am getting ready to put soil on the frame. I appreciate your input.

-Charlotte

The Arabic Student
The Arabic Student
11 years ago

I planted some tomato and cantaloupe seeds about a month ago and they were doing nicely until last week when they all started wilting. Now they’re all lying down completely which can’t be a good thing. Mold started to grow on the containers about a week after I planted the seeds, so I figured I was watering them too much. I started watering them less. Now I’m not sure if they’re dying from not enough water or from the mold. Can mold kill the plants? I only saw it on the outside of the containers, but I assume it was… Read more »

MeThinkingLoud
MeThinkingLoud
11 years ago

Hi,
Would like to know how tips to avoid bringing bugs and insects in doors when we move the garden to indoor.

Diatryma
Diatryma
11 years ago

Peppers are in soil– regular potting soil, too wet because I decided to really soak it after filling the cells, and I basically broke all the rules. I have twenty-four seeds in right now, seven each of Northstar and Buran peppers and ten California Wonders. Tomorrow, I’ll start messing with the mylar, the light, and the space heater.

It’s very haphazard, but seeds are cheaper than plants.

Ben-David
Ben-David
11 years ago

Now that you have the dome and the tray – STOP buying the “sponges”. It’s a lot cheaper to fill the trays with regular planting/seedling mixes, rather than keep buying the sponges. Go to your garden center and buy one of the following: milled sphagnum moss milled peat moss compressed coco fiber All of these are inert, weed-free, moisture-holding material that is great for seed-sowing. If you buy large bales of peat, you may have to sift it to get finer-textured stuff for seed sowing – save the coarser bits for use in the bottom of hanging pots or as… Read more »

Lynn
Lynn
11 years ago

This will be of great help. I am seeding this weekend. Earthbound Farms is giving away free organic heirloom lettuce seeds in celebration of their 25th anniversary. I buy EB Farms lettuce, it’s wonderful!
http://www.ebfarm.com/

$5 Dinner Mom
$5 Dinner Mom
11 years ago

Very timely! Thanks! I’m attempting square foot gardening this year and was nervous about starting seeds indoors. I appreciate the step by step!

And I got those free seeds for lettuce from EB Farms that Lynn mentioned!

Erin

CarrieK
CarrieK
11 years ago

Here in the Pacific NW is helps to take a look at Steve Solomon’s Growing Vegetables West of the Cascades. We don’t need as much compost here (too wet) and he has a really easy, inexpensive fertilizer recipe. I started tomatoes, lettuce, broccoli, various herbs and celery inside yesterday. Wish me luck! Thanks for all the help and encouragement Kris 🙂

Emily
Emily
11 years ago

Great article! Last year was the first time I tried starting plants from seeds. I used the shop light and everything. My favorite part was scratching the gardening itch when there was still snow on the ground!

I keep track of all my gardening exploits on my blog, and I recently organized a coherent chart that explains “when to plant what.” You can check it out at http://www.mysquarefootgarden.net/color

Irving Isler
Irving Isler
11 years ago

I love that GRS goes Gardening frequently. There’s something very poetic about the mirroring of growing plants, flowers and fruits and vegetables with investment, savings, and fiscal responsibility; both can be fun and rewarding – and if done properly offer a lifetime of rewards without any guilt.

Tim
Tim
11 years ago

Why don’t you show us pictures of the real herb garden, the one under lock and key and alarm in the basement or in the shed out back. ;o)

Chiot's Run
Chiot's Run
11 years ago

I started my onions several weeks ago. I start so many seeds indoors, it really does save money. You also get earlier harvests.

http://chiotsrun.com/2009/03/01/starting-onions-from-seeds/

DDFD at DivorcedDadFrugalDad
DDFD at DivorcedDadFrugalDad
11 years ago

Great post!

I love the early harvests!

Brian
Brian
11 years ago

Great post. I do have one question. I have three cats and they go bonkers over any green leaves. How do you keep your cats from eating the seedlings?

Katie
Katie
11 years ago

Thanks for all the great information! I found your blog more informational and helpful than anything else I could find on the web. I’m starting seeds indoors for the first time this year and wasn’t really sure where to start or when I need to start planting. Your info helps so much! Thank you!

southerngirl
southerngirl
11 years ago

Oh gosh, folks! There’s a whole ‘nuther world of starting plants from seed outdoors! No lights, no hardening off of plants, no dirt inside!

Check out the WINTER SOWING forum on Gardenweb!

http://forums2.gardenweb.com/forums/wtrsow/

And start saving your milk jugs and 2 liter bottles for next year. You will need them!

These folks start sowing seeds outdoors in jugs and bottles in DECEMBER and up through March. Plus, they have great free seed exchanges.

Grab a cup of coffee and hit that link. You will be amazed.

Note: This is for all regions of the country, not just the South….

Lynn
Lynn
11 years ago

Thanks Southern Girl!

Chelsey
Chelsey
11 years ago

Hi Kris, Thank you for this great post! I just came back to it again, because I’m about to start my very first garden and I was looking for guidance on starting seeds indoors (especially from someone following the Square Foot Gardening technique). I do have one question for you. For space reasons, I am going to have to set my seedlings on two different shelves rather than a table. Do you have any suggestions for lighting that wouldn’t require me to buy 8 different fluorescent lights? Our windows all face west and our neighbor’s house is taller than ours,… Read more »

Tim
Tim
11 years ago

This is a great article with great information for every gardener. I have been growing for 10 years now and still learned some new information from this article. I get all my seeds from Urban Farmer Seeds at http://www.ufseeds.com

Jenni
Jenni
11 years ago

I was so excited to see this article until I realized that eventually the seeds have to go outside. 🙁

I live in an apartment in the middle of Los Angeles, with no yard (although there is a beautiful avocado tree right outside my window). If you are ever looking for post ideas, a post on how to grow a small garden (herbs? maybe even some kind of produce?) indoors or in pots would be much appreciated!

Or maybe I’ll just have to wait until I move out of the city and buy a house… someday …

mom
mom
6 years ago
Reply to  Jenni

My daughter lives in LA condo and grows annual herbs in pots on the window sill– basil, parsley, rosemary, etc ;(something like mint wouldn’t do as well–they like to be in the ground.) You can replace them if they tank on you. It is easier if you get transplants and not try every thing by seed if you are a beginner. Most herbs and veggies need 6 hrs of sun. Also a selection of veggies can be grown in large containers (12″ or larger). They just don’t get as large as veggies grown outdoors; they need good potting mix as… Read more »

Nicholas
Nicholas
11 years ago

Thanks for this advice. Unfortanatly i have already started radishes in my house. Oh well ill just have to see what happens and see if they grow. But i have also started Pumpkins too and i am so excited. The package says they get to be 70 inches around. But i also live in colorado springs, CO so i had to start indoors because lastyear nothing grew much fruit because of a short growing season. Thank You!

-Nicholas

RyansDad
RyansDad
11 years ago

Thanks for the post and the info! I hope my indoor/ outdoor garden will turn out well!!

Jeff
Jeff
10 years ago

I know you don’t like recommending one product over another but what seeds would you recommend and where do you recommend to buy them from?

Maureen
Maureen
10 years ago

Old house. Put trays on table in front of window that faced North. Guess it got some East and West as well? There were 2 front windows facing West. All seedling grew beatufilly without grow lights. New house. Put trays on bench in bow window area; lots of light. One side faces South and somewhat Eest (lot on an anagled street. 2 front ones face(think) South and the other one faces West. Seedlings did not do well. Could this area be too cold with all the windows? Other house was brick; this is vinyl. Could you advise? I really can’t… Read more »

sam
sam
10 years ago

when can i start the cucumbers seed indoor im in new jersey thank you

Shannon
Shannon
10 years ago

Is it bad to plant seeds in late May????

carol
carol
8 years ago

What I need to know is: can I start my veggie plants indoors then when they show the first leaves put them in the green house? I want a head start getting plants going in pots. My unheated green house doesn’t get warm enough yet to germinate plants like tomatoes.

Terri
Terri
8 years ago

Great article. This is my first attempt at starting plants from seeds indoors. This was my first search page I pulled up and I have no need to go looking any further. Thank you for such clear instructions.

stephanie
stephanie
7 years ago

What a lovely and informative post! You are clearly very experienced! Do you use a specific potting soil for tomatoes (once they are mature and in their permanent homes, or a general soil for all your veggies? I live in AZ and seem to be able to grow almost anything I want but have utterly failed at tomatoes! I’ve been serial killing them for 2 years with no fruit. Any suggestions or direction toward helpful posts would be greatly appreciated!

Fred
Fred
7 years ago

I have read and looked at many post of seed starting and gardening.
You have done a great job with the details of starting a garden indoors.
One question, If more than one type of plant is in your seed starter, what do you do when one kind grows faster than another. I read that it is best to keep your light very close to your plant to prevent the plants from getting leggi. Thanks

Caitlin | The Siren's Tale
Caitlin | The Siren's Tale
6 years ago

This is a fantastic ‘how to’! Thank you for explaining all the steps, why they’re needed, and how to approach them. Much appreciated 🙂

Lisa
Lisa
6 years ago

This will be my first year attempting seeds indoors and not just buying them from a store and putting them in the garden fully bloomed. This is such a great article since I had no idea where to start. Thank you!!

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