Starting seeds indoors is surprisingly easy, if you know a few tricks and invest in a few simple tools. I spent my first few years gardening buying my starts from nursery stores. That cost adds surprisingly fast each year, though, and eventually, I decided to learn how to start seeds indoors. After many failures and partial successes, I’m totally hooked.
Not only does it save a lot of money in the long run, it also makes gardening that much more rewarding. You have the freedom to start any variety of seed you like, rather than being dependent on what your local garden stores have in stock. Plus, not being reliant on a garden store or plant nursery to have your garden chock full of healthy, beautiful plants is an incredible feeling. I also love that each spring, I have beautiful, healthy starts to give to my garden-loving friends and neighbors.
This is mainly for people who want to start vegetables indoors, but everything here applies to a lot of flower varieties, as well.
What You Need to Start Seeds Indoors
Now, I know I said starting your own seeds saves money, and I’m all about finding ways to do things on a shoestring budget. But, to have any success, you do need to invest a little bit upfront. Don’t worry. If you’re smart about it, it shouldn’t cost that much more than buying a new round of starts for your garden, and almost everything that you need is totally reusable.
Here are the basics you need to invest in to start seeds indoors:
- Timer (optional)
- Heat Mat
- Seed Starter Mix
- Seeds (of course!)
Most seedlings need way more light than you probably think. Like, 14 – 16 hours a day of full, bright light. In most areas, that’s just not possible to achieve without supplemental lights. Trust me, I’ve tried growing my starts in sunny windows. It just doesn’t cut it. You’re likely starting vegetable seeds during late winter or early spring, when days are still fairly short, too.
Especially if you plan on starting sun-loving plants like tomatoes or basil, you’ll find that they get really leggy, tall, and spindly. Without enough light, your sprouts will grow too tall too fast in search of more light and eventually be unable to support their own weight.
You don’t need to invest in any ultra-specialized plant lights (although they are awesome, if you do – I invested in a 600W grow light, shown above, and find it well worth it). A couple of basic LED lights that you can buy from Amazon or Walmart for $10 or $15 bucks will do the trick. You’ll want something that you can get put directly above your seedlings for hours at a time without generating so much heat that it will burn them, so avoid typical halogen light bulbs or any lights that generate a lot of heat.
Clip lights or standing lights are also a great option. They’re easily adjustable and you don’t have to worry about mounting or hanging them. Make sure that the lights can illuminate a large enough area to give all of your seedlings even light.
This is a collection of plant lights I’ve accumulated. A couple of long LED bulbs are an inexpensive way to get started growing seeds indoors.
You don’t strictly need a timer for your lights, but it makes things a lot easier. There are all sorts of options out there, from very simple mechanical on/off timers for less than $10 to more expensive smart plug systems.
I recommend using a timer if you can. New seedlings need a lot of light, and it’s super easy to forget to turn your lights on during this crucial period and end up with leggy seedlings.
Seeds need fairly warm soil temperatures, around 70 – 80 degrees F, to germinate. That’s not to say that seeds can’t ever germinate at lower temperatures. Some plants, like sugar snap peas, will sprout just fine in much cooler temperatures.
But if you plan to start warmer-weather plants indoors, you will have a much lower rate of germination without a heat mat. There’s also a much higher chance that nothing will ever sprout. A basic heat mat should cost you between $15 and $30 (you don’t need anything fancier or more expensive). Considering how much more successful it makes the seed-starting process, it’s a good investment that should last you for many, many years. You’ll only be running the heat mat for a week or two until you see the first little sprouts, but it makes a huge difference in your rate of success here.
Make sure that you get a heat mat specifically designed for seed starting, as they do great at keeping the soil at the perfect temperature, and are resistant to having a little water spilled on them.
Your seeds need something to grow in, and I recommend putting together a system with three components:
- Small containers with drainage holes at the bottom, where you’ll actually plant the seeds.
- A larger container or tray to put those smaller containers inside of, to catch excess water.
- A lid to keep in moisture while your seeds are germinating.
I’m a big fan of these plastic trays in the image above. You can pick them up at most garden stores or online for a few bucks. They come with clear plastic lids, as well as 6-cell inserts for seeds. With enough cells for 72 starts, one tray is more than most people need to get enough starts going for a small to medium sized garden. If you’re a fan of DIY, you can also make seed containers for free from egg cartons.
Depending on how big you want your plants to get before you transplant them outside, you’ll need some 3” to 6” containers as well. Once you’ve been gardening or growing houseplants for a while, you’ll inevitably accumulate a collection of miscellaneous nursery pots (never throw out a pot unless it’s totally damaged beyond repair). If you don’t have a random assortment of little plastic pots, then you can check your local garden store or online stores for some thin plastic “nursery pots.” You can also easily recycle other miscellaneous containers, like yogurt tubs or soda bottles, into pots – just make sure you poke drainage holes in the bottom.
You can also buy commercial seed-starting kits with ready-to-go pellets of fertilizer. These have worked fairly well for me in the past, and are a great low-hassle way to start seeds indoors.
Seed starting mix
Seeds need a pretty specific environment and set of conditions to germinate, and that includes the growing medium. First, seeds and sprouts are susceptible to diseases and are easily out-competed by weeds that might be found in your outdoor soil, so it’s important to give them a sterile start until they get established. They also need a very loose medium to make sure that they can break through to the surface after they germinate.
You can start seeds in some potting mixes, but I recommend starting out with a commercial seed starting mix. It’s designed to give you a high rate of success. Once you get the hang of things and have some success, start experimenting with other potting soils (or with making your own seed starter mix).
Seeds (of course!)
You can find packs of common vegetable seeds at most grocery stores these days. Those seeds are great, especially because they’re so easy and convenient to pick up when your doing your other shopping. But, you’ll definitely find that the quality and options are somewhat limited. You can find much better quality seeds online, or by asking friends and family if they have any favorites that they can share. You can also try harvesting seeds from around your house.
How to Start Seeds Indoors: Step-by-Step
Once you’ve gathered everything you need, and set up your grow area, getting your vegetable seeds started is actually a really easy, simple process:
- Set up your grow area
- Prepare the seed starter mix
- Fill your containers
- Plant your seeds and label your containers
- Cover, place on heat mat, and check daily
- Remove the heat and the cover once sprouts appear
- Repot once they have their first true leaves
- Repot again as needed until you can transplant them outside
1. Set up your grow area
Figure out where your little seedlings will live, and get your heat mat and light ready to go. You can start seeds indoors pretty much anywhere that you can easily access to check on them, such as a windowsill or an unused kitchen shelf. Pets love to chomp on seedlings, so consider putting them somewhere protected from dogs or cats.
Ideally, your light should be adjustable so that you can keep it consistently a few inches above your plants as they grow. You can also raise up your tray on books or boxes if needed to bring it closer to the light.
2. Prepare the seed starter mix
Seed starter mix is weirdly hydro-phobic. Most mixes contain peat moss, which holds onto water really well once it’s wet. When it’s dry, however, it actually repels water. If you just dump your seed starter mix into your pots and water it from above, you’ll have a mess as the water just kinda floats on top and runs off.
The best way that I’ve found to get the mix hydrated and ready for planting is to dump some into a bowl, and gradually add water while you mix it in. A spoon or garden tool works here, but I find that putting on a plastic glove and just mushing the water into the mix by hand works best.
The mix should be damp, but not sopping wet. You should be able to pick up a handful of it and squeeze out just a few drops of water. It’s a little hard to show in a photo, but you can see above that the mix is releasing a little bit of water when squeezed, but it’s not dripping wet.
3. Fill your containers
Press the damp mix into your containers, and pack it down lightly. You want each container to be full, but not tightly packed. You’ll probably find a little bit of water and mix dripping out through the drainage holes at the bottom, so make sure you do this over a bowl or tray.
Once the containers are full, I press my finger about half an inch down to make a hole for each seed. Check the packaging for specifics on how deep seeds should be planted. Some seeds need to be closer to the surface to germinate, while others like to be at least 1/4 inch deep.
4. Plant your seeds and label your containers
Before I plant anything, I prepare labels so that I can keep track of what’s what. I find that tape and a sharpie work well, or (clean!) popsicle sticks broken in half. Really, anything that won’t fade or rub off too easily.
I usually plant 2 – 3 seeds in each cell, in case not all of the seeds actually germinate. I might even plant 4 or 5 for seeds that I know have a low germination rate. You ultimately only want one plant per cell, so you’ll have to thin them out a little bit if more than one seed sprouts.
Once you’ve dropped your seeds into the holes, add enough soil to cover the seeds and lightly press it in.
5. Cover, place on heat mat, and check daily
Place your inserts onto the main tray, and turn on your heat mat. Keep the tray covered, and check it at least once a day. Add water to keep the seed mix slightly damp. Make sure that your seeds never completely dry out.
You don’t need to have your light on for the first couple of days, but I usually turn it on pretty early, before any sprouts have appeared. It’s easy for sprouts to pop up and grow too leggy before you even notice them. Keeping the light on will make sure that they’re getting all the light they need from the moment they sprout.
6. Remove the heat and the cover once sprouts appear
You should see sprouts in a week or so, and sometimes as quickly as 2 or 3 days. Once most of your seeds have sprouted, they no longer need the heat mat or the cover. In fact, at that point, they’ll prefer slightly cooler temperatures, lower humidity, and unobstructed light. Make sure that you water them at least daily – these delicate little sprouts will easily be killed by drying out even for a couple of hours.
7. Repot once the seedlings have their first true leaves
When your sprouts first appear, they’ll have a set of “leaves” called cotyledon. These “seed leaves” typically look different from the plant’s regular leaves. After a few days of growth, you’ll see true leaves appearing. These leaves should be recognizable as the actual plant you’re growing, whether it’s distinctive coriander leaves, or tomato leaves. Once these leaves have appeared, your plant is ready to be transplanted out of its little seed pod and into a slightly larger pot.
You don’t want to leave your seedlings in the seed trays too long. They’ll be growing quickly and will outgrow those containers. They’re also very prone to drying out and dying while still in those containers, as they don’t hold much water. I’ll typically plant my seedlings up into a 2” or 3” pot (anything bigger is too much for those tiny little plants).
Prepare your new container by filling it about halfway with soil. Leave a slight indent in the middle where your plant will go.
Lightly squeeze the container around the plant to loosen the seed starting mix, and use a small spoon or garden tool to carefully scoop out the plant and as much seed mix as you can. You can see in the image above this plant was already starting to outgrow the little seed starter cell – its roots are extending down all the way out of the bottom of the container. Gently place it in your new container and fill in around it with soil.
Repot again as needed until you can transplant them outside
Your starts should really take off once they have space to spread their roots in a larger pot. Keep them growing under your plant lights until you’re ready to move them outside. If you see roots starting to grow out of the bottom of the pot, or the plant just looks too big for its container, pot it up again into a 6” or so nursery pot.
Make sure that you harden your plants off by gradually exposing them to sunlight and outdoor conditions before you plant them in your garden.