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Seed starting 101 is to help guide to grow from seed!
There’s something so enchanting about watching a seed germinate.
Watching that little seed grow into a large plant is one of the rewarding aspects of home gardening. Sowing your seeds can sometimes be challenging though, and baby-ing a seed into a transplant takes a little practice.
If you’d like to plant a garden then seed starting 101 will help you grow your own transplants.
Learn seed starting mistakes to avoid, tips for direct sowing outdoors, growing seedlings indoors and troubleshooting problems. Seed starting is very rewarding, here are some tips so you can grow healthy garden plants.
Here are some seed starting tips for how to plant seeds
3 ways for seed starting
- Direct sowing
- Growing your transplants
- Buying transplants from your local garden centre/nursery
There are many benefits to growing your own transplants; it saves money ($2-3 for a pack of seeds versus $2-3 for each transplant). There can be some start up costs though with pots, trays and starter soil. Some gardeners even invest into a grow light set up, which makes it not cheaper but great in the long run. It’s cheaper still to direct seed, however for time and space efficiency, it helps to grow transplants for many vegetables and fruits because otherwise they would take too long in your garden. For example if you sowed broccoli into your garden you’d be waiting 6-8 weeks for your broccoli to grow to the same size as a transplant grown inside then moved to the garden.
Things you need to grow your own transplants
- Seed trays with drainage holes and without. If you’re using soil blocks or directly into the tray you’ll want that tray to have drainage holes and another without them so water doesn’t get all over your table. If you have pots you just need the trays with no holes.
- Pots OR things like the potmaker (uses newspaper to make pots) OR a seed block maker (expensive to buy but again, this tool will last you years and has the benefit of not washing plastic pots covered with spiders every season/replacing the cracked ones).
- Soil: Seed Starter Mix
- Spray bottle and/or watering can
- Optional: Grow lights (I use Sunblaster) and an indoor greenhouse or shelving unit to put a grow light on each layer.
- Large table with a south facing window if no grow lights
- Optional: heating mats for under the seed trays. Although they warm up the soil they are a costly addition and I’ve found that seeds sown inside germinate quite rapidly anyways.
Growing Seedlings vs Direct Sowing
Some crops will grow better than others in the ground because they are so tiny and don’t benefit transplanting. These tend to be the non-fruiting types and the ones that grow roots instead of just leafy greens. Others can handle the pots so long as they don’t get root bound.
Crops that are better directly seeded in your garden:
- Certain herbs like chives, cilantro, dill… I’ve found to be better direct seeded
- Pole and Bush Beans*
- Swiss Chard
- Mustard greens
- Asian greens/bok choi
- Leaf Lettuce
- Spinach, arugula, mache, claytonia, other greens..
* these apparently don’t like to be transplanted as they are sensitive to root disturbance, but I’ve successfully transplanted them before.
Crops grown better as transplants:
- Summer squash/zucchini
- Winter squash
- Many herbs like: Basil, oregano, thyme, savory, and marjoram…
- Many of the Brassicas: Cauliflower, Brussel Sprouts, Broccoli, Cabbage. Some like bok choi and mustards you can grow transplants but I’ve found them to grow better directly seeded outside.
- Celery and celeriac
Crops that can be direct seeded or grown as transplants with about the same success rate:
- Certain Brassicas: Kale, Kohl Rabi, Cabbage
- Head Lettuce
What is a true leaf?
The first ‘true’ leaves aren’t the first green ‘leaves’ that you see on your seedlings! Those are called the cotyledons and they’ll eventually fall off the plant. The cotyledons come first then you’ll see a second set of greenery that will be your first ‘true leaves’. They will also look different than the cotyledons. Observe your seedlings but be mindful of this when certain plants say they to be transplanted at certain leaf stages; for example transplanting tomatoes with at least 4 leaves.
General Sowing Tips
- Always use seeds that are healthy, stored properly and relatively new. Most seeds can last a few years if stored is a cool dark place.
- If you have old seed you can totally still use it, it just means you’ll have a lower germination rate. Pre-germinating your seeds can help use up your old seed without wasting them. Place seeds in between two pieces of damp paper towel and let them pre-sprout. After they’ve sprouted transfer them to your potting soil.
- Soil temperature needs to be warm and moist before planting. Many cool season crops can be direct seeded in cooler soil than your warm season crops, but if it’s too cold they might have a slower germination rate or not sprout at all.
- Make sure you have adequate light, both indoors and out otherwise your plants won’t grow.
- Understand the requirements for each crop family in terms of nutrients, ph levels and if they need boosting throughout the season. Most seed catalogs will have this info for free. You’ll need to amend your garden beds before the growing season starts.
Indoor seed starting tips
Indoor seed starting kit with LED grow lights & stand from Gardner’s Supply
- Make sure there’s plenty of airflow and air circulation. Lack of airflow increases fungal problems like dampening off (which can kill your seedlings in one night; you’ll notice a thin weak stem and a collapsed plant). Adding a fan can help and making sure the door is open.
- Make sure that you disinfect your seeding trays and pots before using them (unless it’s your first year using them from the store) because they could have disease in the soil from the previous year. Use 1 part bleach to 9 parts water.
- Don’t overwater! You want the soil lightly moist but not damp. Too much water promotes fungal problems and an increase in gnats laying eggs there. If you have fungal problems or gnats sprinkle of cinnamon or sand can help, as can watering with a little hydrogen peroxide in it. There are some pots and trays where you water from the bottom instead of the top too. Using a spray bottle to water helps to prevent overwatering.
- Some people add domes over there seeding trays to add some humidity and heat to your seedlings. You want the soil moist but you also don’t want it too dry.
- Read each seed packet and know when you need to start your seeds. In general the larger seeds like squash need to be in large pots than a cabbage.
- Buy seed starting mix or make your own soil mix. The key here though is to make sure you’ve heated your DIY soil mix so there’s no disease or pathogen spores etc that could ruin your seedlings. Seed starting mix has nutrients in there for little seeds to grow, so don’t just use potting soil unless you add some fertilizers for the seeds to grow.
- You can use a south facing window or use grow lights (I use Sunblaster). You can see our indoor seed starting set up here.
- Seeds germinate better with warmer soil. As many of us are starting seeds in the winter months, don’t use soil that was sitting in your car for a few days then sow directly into it without it warming up. You can also buy heating mat for under your trays, but I’ve found so long as the room is warm, your seeds will germinate fine. Don’t start your seeds in a garage or cold basement unless there’s added heat and light.
- It helps to sow more than one seed in each section but don’t let them grow for too long together as they need the space. Re-pot them into a larger containers or pinch off any plants that look weaker and grew slower. Less vigor isn’t good for the productive garden!
- Keep your seedlings growing healthy with some homemade compost tea, or buy some fertilizer from the store. Usually a boost every week or 2 suffices. I often use worm castings.
- To avoid your plants getting ‘leggy’ (tall, thin and floppy) it helps to be closer to the light source. If they are thin and tall they are seeking the light! If you’re using grow lights have it lowered and raise it as the seedlings grow. Some people say that brushing your hand over your plants will also help thicken the stem as it ‘simulates’ wind and they will grow stronger in response.
Here’s a detailed post I wrote about fixing seed starting problems like leggy seedlings, gnats & mold
Outdoor sowing tips
- In the springtime soil and air temperature is the most important for your direct seeding.
- You can sow crops before the last frost but they have to be the cool season crops, definitely not the warm season ones (you can gamble your last frost date but you might lose your crops).
- Always make sure you harden off your transplants before putting them in the ground. This means slowly get them use to the outside temperatures, wind and general elements so they aren’t shocked with the change.
- Soil temperature can slow down germination by a lot depending on what crops you’re growing and how cold it is. This might change your sowing schedule off by a week. This also means it might have been better to hold off a week to direct seed if they’re germinating slowly anyways.
- Warm season crops definitely need warm soil. You can put them outside sooner if they’re hardened off transplants and you’re transplanting into a greenhouse or other small tunnel for added warmth.
- Many new transplants benefit from some protection in the springtime, even the cool season ones. Mini hoop tunnels, small cloches, or frost fabric are worth the investment to increase your growing season.