Gardening Guide: Starting Seeds Indoors 🌱

Photo by Andrej Lišakov on Unsplash

Starting seeds indoors is a great way to get a jump start on your garden, especially if you have a limited growing season. Here are our top 15 tips that provide a crash course in seed starting:

1. Know the needs of your seeds: This may sound like a no-brainer, but you should only start seeds indoors if it's already well known that they are suitable for indoor starting. Some plants don't appreciate being transplanted, and others grow so quickly after being sown directly outdoors that the effort to start indoors just isn't worth it, so do your research before you start. The best place to get information is right from the seed supplier, so always read the seed packet.
2. Start the seeds at the right time: Once you know which seeds can start indoors, you then need to understand when to start them.  There is a delicate balance here: you usually want to avoid re-potting the seedling, but at the same time, starting seeds in too large of a pot can lead to moisture issues. As mentioned previously, your best bet is to follow what it says on your seed packet.  A garden planning tool like plannt.ca can help you turn all of your different seed instructions into one clear schedule.
3. Hedge your bets: Depending on the age and variety of your seeds, you may need to throw a few extra seeds in the cell in order to guarantee yourself a few seedlings.  There's nothing sadder than a seed cell that's still empty after weeks, so don't be shy!
4. Choose the right containers: Only use containers that have drainage holes to prevent water from pooling.  Plastic seed trays molded with a grid individual cells are a great option. Biodegradable paper fibre pots can be a good choice as long as they don't get too soggy and weak over time.  I personally avoid the "peat pellet"-style pots that are wrapped in netting.  I have found that the netting doesn't break down very well, and you end up having to pick up trash in your own yard!
5. Know your depth: Use containers that are deep enough to allow for good root growth. Keep seed planting depth in mind when choosing the container.  A general rule of thumb is that planting depth should be 2x the width of the seed itself.  Very tiny seeds like chamomile or oregano can simply be scattered over the surface of the soil.
6. Plan out the neighbourhood: If you're using trays with connected cells- think about what types of plants you're putting beside each other.  A big tomato is going to need the light to be moved further away sooner than a stout little lettuce plant will.  If half of the things in your tray will need to be re-potted and the other half are staying in the tray- will you have enough space on your growing shelf to host a half-empty tray?
7. Don't forget what you're growing where: Use labels, draw a map, color code the trays- it's up to you!  Don't let your tray layout become lost to the sands of time.
8. Use a proper seed starting mix: It is not recommended to start seedlings in potting soil because it is usually too coarse and dense.  In fact, many seed starting mixes are specifically referred to as a "soilless medium".  Invest in a good quality soil mix that is specifically designed for seed starting. Avoid using garden soil or compost, which can be too heavy and may contain weed seeds or diseases.
9. Select the best: Once seedlings get a few sets of their "true" leaves, they begin competing for resources.  If you have multiple seedlings per cell in your tray, you need to make some tough choices.  It's a hard truth, but not everyone makes the cut.  Don't worry though- certain seedlings are quite delicious.  Think of it this way: you're not thinning seedlings- you're farming microgreens!  (Advisory: Always check if the plants you intend to eat are indeed edible).
10. Let there be light: Seedlings need plenty of light to grow strong and healthy. Place them on a sunny windowsill or use grow lights. Keep the lights on for 12-16 hours per day, and make sure that the plants are not too close to the lights to prevent overheating.  If you notice that your seedlings are getting very "leggy" and tall, your light source is either too weak or too far away.
11. Keep the soil moist: Seedlings need to be kept consistently moist, but not waterlogged. Check your seedlings regularly to maintain this balance.  If you must water from the top, water the soil gradually to avoid displacing seeds, and avoid getting water on the leaves. If all of your cells are contained by a solid flat tray, you can water all of the seedlings from the bottom at once (much easier!)
12. Bring the heat: Different plants have different temperature requirements for germination and growth. Generally, most seeds germinate best at around room temperature. A heat mat for starting seeds is not necessary, but a clear plastic lid (humidity dome) can create a "greenhouse effect" and kick-start germination by warming the soil and preventing moisture loss.  Remember to remove the dome once most of your seedlings have emerged.
13. Give em a tousle: Good air circulation helps prevent disease and encourages strong, sturdy plants. Use a small fan to provide gentle air movement, or, once in a while, run your hands over the seedlings to ruffle them up a little bit.  Just a little bit!
14. Repot: if any seedlings begin crowding out their neighbors or it's clear that their roots have reached the bottom of the cell, it is a good time to repot them.  Be gentle when transplanting and never upsize to a pot more than 2" larger in diameter compared to the current container.
15. Fertilize: you don't need to, but you can.  It is a good idea to fertilize seedlings when you repot them to kick-start their growth.  Typically, liquid fertilizer will be more effective than granular for seedlings since you want the nutrients to reach them ASAP.  Typically, at the time of starting seeds, you want to focus on strong root formation instead of flowers, so keep that in mind when you research fertilizer options.

As always, gardening is a personal activity, and it's up to you to find what works best for you through trial & error.  You may try some of these tips out to find that you prefer to do something differently, and that's the beauty of it.  I wish you a successful seed starting adventure!