Seed Starting Indoors (The Complete Guide)
Itās time to start thinking about Spring, garden planning, and seed starting. Spring may be a ways off for your but that should not stop us from getting excited about the prospect of green and growing things. Seed starting indoors is the best way to get a head start on the upcoming growing season.
Iām not going to say seed starting indoors is easy, because itās not. So if you see ā10 Easy Steps” referring to seed starting donāt believe it. Well okay, the actual process of putting some seeds in dirt is easy, but once the young seedlings start sprouting, they take a good amount of time for care daily.
My advice to those of you who have never done seed starting is to start with one or two trays your first time. In trying to keep it as simple as I can, I am sharing my tried and true, step-by-step instructions for seed starting indoors.
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Indoor Seed Starting Supplies:
- Seed Starting Chart available in the Gingham Gardens Free Gardening Printables Resource Library. With this handy chart, you can keep track of your successes and failures, so that you can refer back to it next year.
- Seeds ā did you collect your own seeds last fall? If not, most garden centers and big box stores have their packages of seeds out. For mail order, I like Botanical Interests (wins the prize for most gorgeous and informative seed packet, plus great seeds), Select Seeds, and Johnny’s Seeds. Iāve found that these seed companies have more a variety than the big box stores. Please note: if the seed packet says to direct sow, itās not a good idea to try and start those types of seeds indoors.
- Seed Starting Potting Mix ā if youāre trying to do this on the cheap, donāt skip a good seed-starting mix, and definitely don’t use regular garden soil. Most soil mixes made for seed starting are light and fluffy and consist mostly of peat moss.
- Seed Starting Pots or Containers ā I do not like peat pots, they dry out way too fast. Iāve used both plastic and peat pots and I have much better success with plastic. I use pots that are big enough to allow the roots a little room, so I don’t have to transplant the seedlings into bigger pots before moving them outside.
If youāre just starting out, you can use yogurt containers, or plastic or styrofoam cups. Just make sure to poke drainage holes in the bottom of your container. Even though you will see them all over Pinterest, I would not use egg cartons to start seeds. Just like peat pots, they dry out too quickly.
Also, egg cartons are too small and the seedlings will have to be transplanted early on. The same thing with toilet paper rolls – the cardboard wicks the moisture out of the soil and away from your seedling roots.
- Plastic trays to hold the pots ā I like the ones with the domes. The dome acts like a little greenhouse and it helps to retain heat and moisture to give your seeds a good start.
- The BEST Seed Starter Cell & Tray Sets – This style is hands down the Best Containers and Trays for Seed Starting that I’ve ever used. They come in packs of 10 and include a watertight base tray, clear plastic dome lids, a seedling poker thingy for planting the seed, a gadget to assist with transplanting, and plant labels.
They are available in both small and larger sizes and work perfectly for starting smaller batches of seeds. These seed starter cell and tray sets are strong and sturdy and will last for several years. The first year I used them, they quickly became my favorites.
- Proper Lights ā sorry a window with direct sunlight is just not enough light. Youāll end up with leggy seedlings that will flop over. My setup consists of cheap shop lights with hanging chains. There are all kinds of fancy light setups available and if you have the money to spend go ahead and try them. The 48″ shop lights available at big box stores work just fine.
- Fluorescent bulbs – I just use the cheap ones, really nothing special and I’ve started many, many seeds indoors and had great success with just the regular fluorescent lights. Last year, I started switching over to LED bulbs because I needed to replace some of my old fluorescent bulbs.
I use a mix of cool and warm bulbs. I don’t think it matters to your seed-starting efforts, but in the long run, LED bulbs are cheaper to operate. A fancy grow light is not necessary.
- Shelving ā this is the shelving unit I use. Because the width on this one is 48ā, it works perfectly for the 48ā shop lights. Itās very easy to hang shop lights on it and to be able to adjust them. There are lots of DIY seed starting set-ups on Pinterest, but I really love this style because of the ability to hang the shop lights and I donāt have to worry about water on the shelves when Iām watering. Itās definitely an investment upfront, but Iāve been using mine for several years.
- Power Strip with a timer, or a separate timer. I never remember to turn the lights off and on, so very early on in my seed-starting venture, I knew I would need a timer.
- S-hooks to hang the shop lights.
- Chains to hang the lights (if your lights donāt already come with them).
- A small fan (I use a clip-on oscillating one).
- Fertilizer (I use Fish Emulsion for my veggies, and just watered down MiracleGro for my flowers).
- Plant Tags and paint marker.
- Watering can and spray bottle.
Here’s a Pin to save to your Gardening Board on Pinterest for later reference. There are more pin collages to share at the bottom of the page. Thanks for pinning!
Getting Started
If youāre a beginner, start small and choose 5 or 6 flowers or veggies to start with. Some really easy seeds to start indoors are tomatoes, cucumbers, marigolds, zinnias, and nasturtiums. Don’t start them too early though.
When to Start Seeds Indoors – Timing
So this step requires a little math, but don’t worry, it’s easy.
First of all, youāll want to know the last frost date for your zone. Daveās Garden website has a cool page where you can enter your zip code and it will tell you when your last frost date is. Check it out here. Don’t know your gardening zone, you can look that up here.
You can find charts online that refer to “when to start seeds inside,” but they don’t take into consideration what gardening zone you are in and when you can plant outdoors and those are important factors to consider.
Next, look at your seed packet and it should tell you when to start your seeds. For example: I live in Zone 4b so my last frost date is somewhere around May 1st. The seeds that Iām starting say to sow indoors 8 weeks before the danger of frost has passed. So counting back 8 weeks from May 1st, I come up with March 6th. I will start these seeds sometime in the first week of March to have a few days to harden them off before planting them outdoors. This is a great way to utilize the Gardening Calendar that’s available in the Free Gardening Printables Library.
Read Seed Packets
There is a lot of important information on the back of your seed packet. Some companies are better than others at including information in their seed packets. Seed packets will also start the number of days until you should start seeing seed germination. So, read your seed packets.
I go through my seed packets and divide them up according to the number of weeks before the last frost date that I need to start them. Then I record the dates along with the plant names on the handy Free Printable Seed Starting Chart.
Please note that not all seeds are suitable to start indoors, they either grow too fast, or they are picky about having their roots disturbed. The seed packets will say if the seeds should not be started indoors.
Light Station for Indoor Seed Starting
Again, don’t try to start seeds in a sunny window. In most locations, there is no guarantee how much sun or bright light your seedlings will get in a window. Although natural light sounds good, it just isn’t very realistic. You’ll have much better success with an artificial light source.
Find a place where you can access each of your shelves. You’ll have to be able to move your seed trays around for watering and be able to make light adjustments. Also, think about your floor, it will most likely get water and maybe even some soil on it. Youāll want to have chains attached to your lights so that you can adjust the entire light as your seedlings grow. I highly recommend a timer, because your seedlings will need 14 – 16 hours of light per day.
I have my light setup in an unfinished part of our basement. The floor is concrete, so I don’t have to worry about spills. The entire setup is in a very small area that isn’t necessarily convenient, but it works. I say that to tell you to just use the space you have even though it might not be perfect.
Adjusting your lights ā Keep the lights just a couple of inches from the tops of the seedlings. You want them close enough so the seedlings donāt stretch for the light and get leggy.
As your seedlings grow, your lights will have to be adjusted frequently. If you have several trays of seedlings, they will need to be repositioned so that each plant grows straight and gets ample light. Your seedlings will need 14-16 hours of light per day.
How to Start Seeds Indoors – Steps:
Mix the Soil
Follow the instructions on your bag of seed starting mix to prepare the soil. Most mixes need to be mixed with water. Donāt get your mix too soggy, or your seeds will rot before they have a chance to germinate. I use a bucket and alternate pouring seed starting mix in and water, and stirring between each layer.
Add Soil to the Pots
Fill your pots with soil, leaving a little room at the top for the seeds and soil to cover them. Gently tamp the soil down to eliminate large air gaps.
Planting the seeds
Follow directions on the seed packets as to what depth to plant the seed. A good rule of thumb is the smaller the seed, the more shallow it needs to be planted. Some teeny tiny seeds donāt even require a covering of soil. I usually plant 3 – 4 seeds per pot. I use the eraser end of a pencil (or the little gadget that comes with my favorite trays) to make a couple of indentations in the soil surface, as deep as the seed should be planted. After the seeds have been dropped, go back and cover them with soil. Once I have a tray planted, I use a spray bottle and just lightly mist the soil. Use a plant tag to label your seedlings.
Covering your newly planted seeds
Cover your trays with plastic domes, or plastic wrap to create a greenhouse effect. Some instructions say to remove the cover when you see the first signs of green, but I usually wait until the seedlings almost reach the top of the plastic cover. Once the lid is removed, make sure to check the seedlings every day. I start watering with a spray bottle and just mist the soil. Once the seedlings are bigger and their roots are established, I water them with a small watering can. Typically, when the seedlings are covered with a humidity dome, the soil will retain enough moisture so you don’t have to water them.
Heat Mats
If you have your seed starting set up in a basement, garage, or any place where the temperature is too cool, you might want to consider using a heat mat. The seeds will germinate quicker and the heat mat will serve to keep them at a consistent temperature.
Fan
As soon as all the domes come off, I set an oscillating fan on low and set it to blow on the seedlings. The breeze from the fan mimics the wind and makes the little seedlings strong. Good air circulation will also help prevent any fungal diseases.
Fertilizer
When your seedlings get their second set of leaves, it’s time to start giving them a little fertilizer. I start with a very weak mix of fertilizer and water. The next time I fertilize, I will add a bit more fertilizer to the water. I only fertilize my seedlings once a week.
Thinning Your Seedlings
I hate thinning my seedlings. To kill those sweet little seedlings that Iāve nurtured and brought to life just pains me. So I have to keep telling myself that itās better to have one strong plant than to have a bunch of scrappy weaklings. I’ve learned over the years to not sow as many seeds in the first place, but with some of the tiny ones, it’s difficult not to over-sow. To thin, I simply snip the weakest seedlings with a pair of tiny scissors and leave two or three to thrive. Don’t pull the seedlings out because the roots of the seedlings you want to keep will be damaged.
Bumping Up Your Seedlings
Are your seedlings looking crowded? Are the roots growing out of the bottom of the container? It may be time to bump up those babies to larger pots. If you have too many plants growing in one pot this is a good time to separate the seedling masses and pot them up in their own individual larger containers.
Hardening Off
Once your plants are ready to go outside, it’s a good idea to harden them off. After being in a controlled environment, they need to adjust to being outdoors. To harden off, simply sit your plants outdoors for a couple of hours at a time each day, extending the time a little each day to toughen them up. Start out by putting them in a shaded location and increase their sun exposure a little each day. However, don’t leave the plants in full sun or they will fry. I’m lucky to have a pop-up greenhouse (similar to this one) where I can harden off my baby seedlings.
Transplanting Outdoors
Now that your seedlings have been hardened off, it’s best to place them in their new home in your garden on an overcast or cloudy day. Be sure to give them a good drink of water, once they are planted. It’s normal for hardened-off plants to wilt a bit when they are first transplanted, but they will soon acclimate to their new homes and will be off and growing.
Seed Starting – Problems
How to Control Fungus Gnats
Sometimes fungus gnats can be a problem with seed starting indoors. I’ve never had them damage my seedlings, but I understand if there’s a large enough infestation, they can. I haven’t tried it, but I’ve read that sprinkling a little cinnamon on the surface of the soil will keep them away. I’ve had very good luck controlling soil gnats with these little sticky things.
How to Prevent Damping Off
If your seedlings suddenly wilt and look mushy or discolored, chances are they have damping off. There’s nothing you can do to remedy the situation, but there are ways to avoid it. Damping off can be prevented by using clean containers, new potting mix, a heating mat under the seed trays, good drainage, using a fan, and adequate light. If you would like to read more about damping off, here’s an article by the University of Minnesota Extension. I have also been reading that using a small pebble gravel (like the stuff used in fish tanks) will prevent damping off.
It’s incredibly gratifying to grow flowers or vegetables from seed. After the initial purchase of your lighting, shelving, trays, and pots, the cost is minimal. You can start small and add on every year. I encourage you to give Seed Starting Indoors a try.
If you want a much simpler method of starting seeds outdoors during winter months, check out my post on Winter Sowing.
Thanks a bunch for stopping by today to learn about seed starting. Do you start seeds indoors? Are you going to give it a try? Leave a comment and let me know. Or, if you have questions, leave a comment and ask. I would love to hear from you and be able to help with your gardening questions.
Happy Gardening,
Julie
Other posts on Gingham Gardens that you will enjoy:
Flower Gardening 101
DIY Garden Journal & Planner
Vegetable Gardening 101
Flower Garden Design
How to Jump Start Summer Blooming Bulbs
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Greetings,
I have learned another from you. This is my first year with indoor seeds. I have had a great germination rate. What minimum wattage for grow lights do you believe is necessary? Mine are full spectrum but 20watts. I’m hearing I need at least 600w and that is why I’m loosing my seedlings.
Hi Mel – thanks for stopping by Gingham Gardens. I have never even thought about the wattage or lumens of lights before for my seed starting setup. I use regular old shop lights, some of the bulbs are fluorescent and some are LED. I have some other plant lights that I purchased from Amazon that I use for other plants. I would love to help you further though. Would you please email me – [email protected] and tell me more about your seed setup, what seeds are you starting, what kind of soil are you using, how long are you leaving the lights on, how close to your seedlings are the lights, how wet are you keeping the soil and at what point are you loosing seedlings. I’m happy to help. Good luck, Joanna
Great information! I always struggle with the hardening off phase of the process. Could you go into detail on how you use your portable greenhouse to successfully harden off your seedlings?
(i.e.- How long you keep plants in the greenhouse before they are ready to be planted outside? Do you use a shade cover on the greenhouse during the day? What do you do at night? What do you do for heat in chilly weather? What do you do for ventilation and how often do you open and close the zippers? Where do you place your greenhouse in your yard, a sunny or shaded location?)
Any advice would be appreciated. š
Hi MaryAnn – thanks for stopping by Gingham Gardens. I think the key to hardening off new seedlings is patience. I strictly use my greenhouse as a shelter for my seedlings during the hardening off phase. My seed starting set up is in my basement and I cannot fathom bringing all my seed trays back inside and down the stairs every day during the hardening off process. That’s why I use my greenhouse. To answer your other questions about greenhouse gardening, you can check out this post. Good luck and happy gardening, Joanna
why am i having so much trouble to start mine i am doing all these things listed. last year i had no trouble at all the dont think the seeds are very old.
Hi Lisa – I can help you troubleshoot your seed starting difficulties if you send me an email. I will watch for it. Joanna
I have a question about the heat mats. At what point do you turn your heat mats off? Once the seeds have germinated or when the seedlings are bigger? I have read differing opinions on this.
Hi Kay, thanks for stopping by Gingham Gardens. That’s a really good question and yes there are many differing opinions. That’s because there really is no right or wrong answer. It totally depends on your situation. If the area where you are starting seeds is cooler, then leave the mats on. For example, my seed starting set up is in our basement in the utility room where it’s a bit chilly, so I leave the heat mat on until my seedlings are well established and a couple of inches tall. Also, read your seed packets and they will tell you the best temperature for the seeds to germinate. If the seed packet says 70-75 degrees and your room is only around 65, then you know you’ll need to provide some warmth for your seedlings. I don’t use heat mats for all my seedlings, just those that need warmer temps to germinate. Good luck and happy growing, Joanna
Iām just thinking of setting up a seeding shelves, and trying to see just what I need. What is the watts or leds on your fluorescent bulbs, lumens? Do you have two set of light on each shelve? Do you put your geraniums, bulbs(cannas, ele ears, caladiums)under the light too?
Hi Lynn – sorry for the delay in getting back to you. I use 2 sets of shop lights (that’s 4 bulbs) on each shelf. Honestly I have no idea what the watts or leds are of my bulbs. I started several years ago with cheap fluorescent bulbs and then started replacing those with LEDs, so I have a mix. This year I replaced 2 old fluorescent bulbs with 2 of the pink plant light bulbs. I don’t have room for my geraniums and bulbs on my seed starting shelf, but you can certainly do that. Don’t overthink the light part. If you can afford it, I would just go for all of the pink plant bulbs, I can’t do that right now, so I’m fine with the mix and the seedlings don’t seem to mind either. Happy seed starting, Joanna
Hi Joanna! I’m starting seeds for the first time this year and am wondering about the heat mats. Any recommendations? And would the thermostat be necessary?
I love this article! So helpful.
Thanks!
Sandy
Hi Sandy – I’m so glad you’re starting seeds. I have this heat mat (it’s huge and a bit spendy, but I’ve had it for several years and it fits one shelf on my 4′ shelving unit. Not all seeds require heat mats and you can usually tell from the seed packet. I also have several of these smaller mats. These links are affiliate links. I’ve never used a thermostat with my heat mats. Good luck and let me know if you have any more questions! Joanna
Thx very much for your expertise. I get very excited in April because itās time to start seeds indoors. I have grown lights (two) one behind the other. I also have house plants some (geraniums and red clover) that will eventually go outside. I end up with some seeds that donāt germinate because my set up is in a storage room off my basement apartment. I did buy a heat blanket last year and those baby seeds turned out fine. But…I canāt buy more due to finance and room to put it. It is frustrating to say the least.
When the seeds germinate I get very excited. I live in zone 3 outside of Toronto so our day for outdoor planting is May 24th weekend. Our winter is too long. Now with this covidviris I have something I love to keep me home.
Iāve now told you my story and vented a little. By the way, I live with my eldest son and family and they tolerate me and my advice very well. I get to do the back garden and my daughter-in-law does the front.
Take good care,
Helena
Hello Helena – so good to hear from you. I’m glad you are well and keeping occupied with your seed starting. Soon, very soon, you will be able to get outdoors and into your beloved gardens. Hang in there! Joanna
Iāve tried so many times to start seeds indoors with no luck. After reading your article that was so thorough Iām armed and ready to try my luck again. We are dealing with the coronavirus spread right now and this is just the thing to brighten my day! Thank you
Hi Terri – seed starting is not the easiest gardening task. But, you can do it! Learn from your mistakes and don’t give up. Yes, I agree that gardening and dreaming of gardening is the perfect thing for us right now. Good luck and let me know if you have any questions. [email protected]
Very much enjoyed your sequential explanations. As I was reading through the steps to seed starting, I knew this was my kind of blog when I read the paragraph on best containers. The list of items included with the packs of 10 trays with domes was a seedling poker thingy for planting the seed. Such appropriate language only women understand.
Hi Linda – thanks so much for stopping by and taking the time to leave a comment. I’m happy you find my descriptions amusing. Lol! Come back soon! Happy gardening, Joanna
I enjoyed reading your information, glad you explained why not to use egg cartons.Just soon as I get more cash, I will be able to get the lights to hang,and found some plastic flower container,s go dumpster hurting.Thankyou so much for explaining things.
Youāre so welcome, Ginger. Thanks for stopping by and taking the time to comment. Stop back soon!
Such great info! I’ll be printing it off! Thanks for sharing at the To Grandma’s House We Go DIY, Crafts, Recipes and More Link Party. I pinned this on Pinterest! Hope to see you next week.
I am so looking forward to Spring this year and I have already mentioned to my husband that we need to start our seeds this month. Thanks for a great article. Visiting from Celebrate Your Story.
Donna – thanks so much for stopping by and reading up on seed starting. Good luck!
You are so ambitious! I know that seed stating is a lot of work. I don’t have the time to be so diligent so I wait until I can sow them in the ground. š Thanks for sharing with SYC.
hugs,
Jann
Youāve given some great advice. We bought grow lights one year but I think we had them too high so the plant I was trying to keep going kept getting leggy. What kind of plants to you grow? Flowers or vegetables or both?
Joanna, you inspire me with your knowledge and how much you love gardening. We have had really cold temps in the Deep South. Our ground is really cold right now. I canāt wait to get my hands outside in the dirt. I should plant seeds, but I donāt I hope to start the Gardens Galore Link-up Party by mid-March! Have a wonderful weekend!
Thanks for stopping by, Pam. I love Gardens Galore and look forward to itās return.
My luck growing plants from seeds is hit or miss. It’s really hard, but like you say, very satisfying! I have some seeds in a container outside right now. Its been cold at nights but the days are still warm in the sun. I hope they survive and grow into flowers soon. Thanks for all these great tips!
Thank you for stopping by, Ann.