With your seeds ready and supplies set up, it’s time to sow seeds! I’ll walk you through how I sow seeds indoors to produce plants for my outdoor garden.
This is part of a series, Indoor Seed Starting for Beginners | Sow Indoors Grow Outdoors, where I walk you through the process from seed to garden. It’s all the information I wish I had when I was getting started.
How to Sow Seeds Indoors Step-by-Step
This is an excerpt from the ebook, Seed Starting for Beginners: Sow Inside Grow Outside, sharing everything you need to know to start your own garden plants from seeds indoors.
If you would like the entire ebook with all the printable lists in one handy file, you can download it instantly here.
The main reason we sow seeds indoors in late winter and spring is to get a jump start on the main growing season. Many plants take longer to fruit and flower than our frost-free garden days allow, so to get around this, we begin the seed sowing indoors instead.
Getting the supplies ready is the most time-consuming part, but thoughtful preparations will definitely pay off. With good quality seeds and the right setup, seed starting (and the ongoing process of caring for the new plants), is not just functional, it’s very enjoyable as well. As I mentioned in the best reasons to start plants from seed indoors, there’s nothing like indoor gardening to hurdle past the winter blues. It’s basic survival for those of us in cold climates.
Indoor seed starting is often suggested for vegetables, especially ones like tomatoes that can’t take cold spring weather, or greens like broccoli that take a long time to grow, but there are lots of other options as well. You can also start herbs, flowering annuals, and perennials. Always check the details in the seed catalog or on the seed packet first, and, unless some special germination conditions are required, most seeds can be started indoors.
- Plants by Life Cycle
- Annuals are plants that flower or fruit in the first year, including many flowers, herbs, and vegetables. Sunflowers are a good example.
- Biennials have a two-year biological cycle. They grow leaves the first year, and flower, seed, and die in the second year. Foxgloves are an example of this.
- Perennials are plants that live on for several years. They can flower or fruit year after year.
- Direct sowing means sowing the seeds directly in the garden (in-ground or containers) where they will live out their happy plant lives.
- Indoor sowing means we start the seeds indoors. We may grow them until it is time to plant them in the garden, giving us a jump start over direct sowing, or continue growing indoors, if it suits the plant species.
With so many options, we have to dial it back down to what we have room for and what’s most important. This is your opportunity to grow things your local garden nurseries don’t offer including multitudes of heirloom vegetables plants and other unusual plants, or plants that are too expensive to buy as mature plants. This will help you narrow down your options to make the best choices.
Indoor Seed Sowing Preparations
1 Order Seeds
This is the part many of us love: poring over the seed catalogs and online shops and narrowing down our choices. There are so many wonderful plants to try. For the sake of your finances, you may want to team up with some friends to share orders as we rarely need all the seeds in one pack and they do lose their viability within a few years.
This explains how to choose the best seeds for your garden.
2 Get Your Supplies Ready
If you’re new to this, you may need to purchase some supplies first, or sort through your basement or shed to find what you need. I strongly suggest getting your whole grow light setup ready first, and then do the seed sowing on another day. It takes the stress out.
This shares exactly what supplies you need to get started.
Once you have everything assembled, you will need to wash and sanitize your seed trays, pots, containers, and plant tags. I wash mine in a tub of mild dish soap, rinse thoroughly, and then soak in a solution of 1-part bleach and 9-parts water for two minutes. Rinse thoroughly and allow to dry before use.
3 Plan Your Sowing Schedule
Each seed type requires a different amount of time to get started indoors (germinate, become a seedling, and start maturing) before it’s ready for planting outdoors after last frost. I created this streamlined printable sowing schedule so you can combine different seeds into sowing groups every two weeks.
Print out the schedule, grab your seed packets, and layout your personalized schedule. Read all the seed packets and watch for any seeds that may require special care in advance like pre-chilling, pre-soaking, or scraping the seed coats. Pre-requirements like pre-chilling may take days or weeks depending on the seed type.
Every plant type grows at different rates and reaches different heights. When we’re using grow lights, we need the lights about 2 to 3-inches above the tops of the seedlings. But, with every plant type growing differently, suddenly some will be too close to the lights and others will be too far.
So, what’s the solution? Whether you use the soil block method or sow the seeds in pots, at some point you will be moving the seedlings around to keep everyone is happy.
I group same-type plants together in my soil block trays. If I see a height problem coming up, I group my soil blocks by size in smaller trays, and place wood blocks under whichever ones need to be higher up than others. The lights stay where they are, and the plant containers are adjusted individually as needed.
Having more than one shelf of lights also helps. Taller plants may all end up on one shelf, and shorter plants on another.
4 Prepare Your Sowing Plan, Tags, and Notes
It’s worth the effort to keep track of what you sow (the seed name, seed company, date, container, number of days it takes to germinate, number of days to maturity) so you can track progress and learn about all the growth stages as they unfold before you.
Free Printable Seed Starting Notes
You can make your own seed sowing notes or print out this one:
It shows examples of my notes and provides a preformatted page that you can print out as many times as you like.
Tags and Labels
The other important part is tags or labels. Each seedling needs an identity tag all along the way. At the start, I mark the actual seed tray, because I use soil blocks in a grid system, so it’s easy to label the actual tray with marker, just like cells in a spreadsheet. This shows how I do it.
If you are using pots, you can use masking tape and a Sharpie. Plastic or wood plant markers can work too, but they are hard to manage early on because there is not much space between the grow lights and the seeds. There’s more here on choosing tags.
5 Read the Tips for Success
This article gives a good overview of the seed sowing process and points out several things to watch for.
6 Prepare Soil Blocks or Pots
Okay, it’s time! You’ve got everything setup, your seeds are ready, you have a sowing plan, your tags are written, pots are clean, sanitized, and labelled.
I assume you have planned out what you’re sowing so you know how many soil blocks (or pots) you will need.
Combine Seed Starting Mix with Water
I use a bucket or tub or large tray and rubber gloves.
- Pour your seed starting mix in the bucket.
- Gradually add warm water and combine.
- You want the mixture moist but not soaking wet.
- The test is: grab a clump of the mixture in your hand and squeeze.
- It should hold together in a clump without any water dripping out.
- If it crumbles, you need more water. Work slowly so you don’t over-water it.
If you do over-water it and run out of seed starting mix, you can squeeze out the excess water and allow it to dry out for a while before using the soil blocking tool.
Create Soil Blocks
Have your seed sowing trays ready and labelled. You can also prepare the soil blocks for future weeks. They store nicely and can be re-damped as needed.
- Press the soil blocking tool into the mixture.
- Make sure each cell block is packed with the mixture.
- Place the tool over your seedling tray and release the blocks.
If you are using pots instead of soil blocks, fill each pot with seed starting mix and press it down. Dip the pot in a bucket of water. The mix will sink down. Top it up and wet again. You want it filled, leaving about an one-half to one-inch free at the top.
7 Sow Seeds
At last! Grab a white plate or dish and your seeds. This makes it easier to see the seeds. Have your seed starting note sheets and a pen ready. Be sure your seedling trays or pots are already labelled.
Open your seeds, working with one packet at a time, and pour them out onto the plate. It can be startling how tiny or odd some seeds are. If you need to, use tweezers to handle them.
I sow one seed per soil block. This goes against the habits of many other gardeners. My reason is: I’ve tested the seeds for viability, I know the germination rates are going to be good, and I do not want to thin out the seedlings later. Thinning seedlings is a fine motor skill I’m not very good at, and, to me, it wastes seeds. Instead of growing far more than I need and getting rid of a bunch, I grow just what I need with a few extras in case something doesn’t germinate.
Double check the sowing instructions on the seed packet. In general, seeds are sown at a depth twice their width. Some are really tiny and placed on the surface of the growing medium; others need darkness to germinate and are sown just below the surface.
If you’re using soil blocks, the soil blocking tool has created a little indent in each block for the seed to be placed. Sometimes, this indent is too deep for the seed, so I use a dibber or pencil to push some seed mix into the hole, add the seed, and then bury it with more mix.
After each seed type, stop, put the leftover seeds safely away, jot down any notes needed, and then carry on until all your seeds are sown. Be sure everything is tagged, and, if something gets mixed up, write down whatever you know. While you may not recognize a seedling in its early days, eventually the plant will be identifiable!
When you’re done, make sure the sowing mix is still moist, particularly the tops where the seeds are. They must have contact with warmth and moisture to germinate. If you need to water, aim the watering can spout at the base of the soil blocks and use warm water. Never water the seeds directly or they can wash away. You can also use a plant mister with warm water.
While most seeds do not need light to germinate, there is no problem having the lights on from this stage onward. Place them so they are 2 to 3-inches above the surface and set the timer so they run for approximately 14 hours a day (12 hours is fine at night if they will also get indirect light during the day).
Take photos if you like. If you’re growing some fast-germinators, they could pop up within days. It’s very cool.
It’s important to check your seeds daily so they are never allowed to dry out.
This explains the care and maintenance of your future seedlings.
And, in two weeks, it will be time to sow your next group of seeds.
Seed Starting for Beginners | Ebook
Everything you need to know to start your own garden plants from seeds indoors.
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64 pages | color images | PDF format for Acrobat Reader | Includes handy printable checklists
~Melissa the Empress of Dirt ♛