Now that you have all the supplies you need for a successful growing season, let's get to the good part and start planting those seeds!!
- Prepare Potting Mix
Pre-moisten your soil, you want it to be moist but not dripping wet. Less is more…you can always add more water but you can’t take it away. It’s easy to put your potting mix in a rubber maid container and adding water and mixing it through there, you can always fasten a lid on the container if you have left over and it will stay moist and you can use up when you seed other seeds.
- Fill Flats/Containers
Fill seed flats to the top with soil, tapping the whole tray firmly against the table as you go so the soil settles and there are no air pockets trapped in the tray cells. Do not pack down. Leave a small amount of space at the top.
You can also use a soil-blocking method but you’ll need to get a tool to make the soil blocks. If you want to do this, the method doesn’t change other than seeding in to the blocks rather than containers.
Label the tray or cell with the variety name and date sown so you can keep track of the variety and whether or not germination is happening in the correct timing.
- Plant the Seeds
For small seeds simply drop a seed or two in to each cell. For larger seeds that are planted in larger containers, make holes in each cell using your finger, a pencil, or a dibbler. A general rule is to plant the seed to a depth twice its size. I often plant melon and cucumbers by pushing the seed down to my first knuckle. Cover the tray with a light dusting of fine vermiculite or seed starting mix, making sure all seeds are covered.
Always use warm water, not COOL. You can either water from the top or the bottom. The soil is usually moist enough at first to not need too much water in the beginning especially when the dome is on but if it is not sufficient give it a gentle watering. If watering from the bottom, set freshly sown trays into a plastic tub with an inch (2.5 cm) of water in the bottom and let them soak up the water from below. Remove once the soil surface is evenly moist.
Cover trays with a clear plastic dome and set onto a 21°C (70°F) to 26.5°C (80°F) heat mat or in a warm corner of the house, consistently above 65°F (18°C). You can set seeds on top of your fridge if you do not have heat mat, be sure to check on them constantly as once they emerge, they need to be in sunlight. But the top of your fridge can often generate enough heat to warm the soil for good seed germination. Keep the soil moist but not overly wet to prevent damping off.
Check trays daily, once the plants emerge you can crack the dome open and start getting airflow in there. It may be a bit difficult managing if you have multiple varieties of plants that have different requirements so if you’re able to consider this when planting that will help with successful germination.
You will now move the tray off the heat mat to a bright space, such as a greenhouse, or under florescent lights. If using lights, make sure they are suspended a few inches above seedlings and put them on a timer, making sure to give plants 16 hours of light a day. As the plants get taller, be sure to keep raising the lights so that they are 2 to 3 inches (5 to 7.6 cm) above the tallest plant. When the seedlings are young you may want to cover them with the dome again for a few hours to keep them from drying out.
We talk a lot about true leaves, the first set of leaves that come up on emergence are not true leaves but cotyledons, they are part of the seed or embryo of the plant.
- Continue to Water
Check seedlings daily and water when the soil appears dry, remember to water gently.
- Bumping Up
When seedlings outgrow their trays, either repot them into larger containers, or if the weather is warm enough, start transitioning them outdoors. This is usually about the time they develop a couple sets of true leaves; the leaves you see upon emergence are cotyledons. Once the seedlings appear to be over-crowded, or have developed their second and third set of true leaves, it is time to separate them and transplant them into little containers of their own, (about 1 ½” – 2”) large. Pick the plants up by the leaves, not the stem or roots when you are transplanting. Make sure the containers you are using have holes for good drainage. If you transplant seedlings into a container that is too large, you won’t see much new top-growth, however, the plant will be busy growing roots to fill the container.
- Air Flow
As your seedlings grow, use a fan on them for a few hours a day to stress them a little. Also, allow them to dry out a bit by missing a watering and a fertilizing once a week and put them in a cool spot at night. Your plants will be a lot stronger and more able to survive better on their own outside. This isn’t totally necessary but can be a good thing if you’re comfortable managing this.
- Hardening Off
It’s important to “harden off” young plants before putting them into the garden, otherwise they will be shocked by the sudden change in temperature. Usually towards the end of May to beginning of June you can start this process. It can take seven to ten days to harden them off well, don’t rush this process. Set trays in a sheltered spot outside, increasing the amount of time they are out each day. Start with a one to two hour period the first day and increase it one hour a day for the rest of the week, you can even cover them early on to protect them more. This helps the young plants acclimate to outdoor temperature fluctuations. Once all danger of frost has passed they can be planted into the garden.
Almost all seedlings will grow into better, bushier plants if you pinch off their top growth after they’ve grown their second or third set of leaves. Pinching plantsis a form of pruning that encourages branching on the plant. This means that when you pinch a plant, you are removing the main stem, forcing the plant to grow two new stems from the leaf nodes below the pinch or cut. Pinch right above a set of leaves.
Keep in mind ALMOST ALL seedlings will respond well to this but some won’t, you can google this but for example don’t pinch tomato seedlings but basil and coleus responds well to pinching. Don’t pinch anything that grows a single stem with a flowering head like cauliflower or broccoli.
- Planting Out
Make sure the plants are thoroughly moist a few hours before transplanting. This will help the soil stay on the roots. The best time to transplant is on a cloudy day, late in the afternoon. This will allow the plants to acclimatize a bit before the hot sun is on them. Try and take as much of the soil as you can when you transplant and backfill well. Some plants can be planted deep (tomatoes) and some plant at the same depth as they are in the pot they are grown in (peppers). Make sure to water well.
If you are just super excited to get everything in the ground just remember the May 24 date is an average for the last day of frost and we definitely get frost after that date so understand what you have and be prepared to cover with sheets or cardboard or drag containers in to the garage. Never cover with plastic as that draws in the cold. Many plants such as petunias, verbena, alyssum, dianthus, foxglove (foxy), snapdragons, gazanias, centaurea (batchelor button), rudbeckia (gloriosa daisy), sweet peas, chrysanthemum, cosmos and pansies can take a little cold and frost.
When you have a couple sets of true leaves you can start to fertilize but less is more is still the idea at this point. I like to use a water soluble fertilizer such as a 10-52-10. Add fertilizer to tepid water, as directed, and fertilize about every third watering. A high middle number (phosphorous) will encourage a good root system; a high first number (nitrogen) will encourage too much leaf growth and the third number (potassium) will allow for better uptake of food and water from the soil and is good for the over-all health of the plant. At this point, don’t over-fertilize and don’t over-water.
Once you bump up your plants you can start on a stronger fertilizer such as an all-purpose fertilizer (10-10-10).
About a week after your plants have been planted outside, give them a good fertilizing (like a Miracle Gro 15-30-15 for all your blooming plants and an all-purpose 20-20-20) for all your leafy plants. Continue to do so, according to directions, throughout the summer and you will have strong, healthy plants right through the season.
We’ve been using an organic fertilizer for years because it actually seems to be the most forgiving in that we don’t see plants being burnt if the solution is a bit strong and it seems to be working great for us. We also like water soluble because it just is so much easier to use and utilized by the plant right away.
One thing we watch for with seedlings is called Damping Off, it is caused by a fungus or mold that thrive in cool, wet conditions and can affect a lot of vegetables and flowers. It is most common in young seedlings, once the plants mature enough to have a few sets of true leaves and a well developed root system, they are better able to naturally resist the fungus or mold that causes damping off. There is a critical period of growth between planting and maturity when special care needs to be taken to protect sensitive seedlings so you want to get them through that stage quickly and this is where the heat mats and lights are pretty beneficial. It’s equally important to make sure your trays are sterilized and your potting mix is new and sterilized or a soilless mix.What to look for:
- Seedlings that fail to emerge from the soil.
- Cotyledons (the first set of leaves produced by a seedling) and seedling stems are water soaked, soft, mush and mat be discoloured gray to brown.
- Seedling stems become water soaked and thin, almost thread like, where infected.
- Roots are absent, stunted or have grayish-brown sunken spots.
- Fluffy white cobweb-like growth on infected plant parts under high humidity.
I would say the biggest mistakes people make revolve around watering, either under watering or over watering…mostly over watering. The other mistake would be starting too early.This might sound ridiculous but gardening is really all about trial and error and conditions are never the same from one year to the next so don’t get discouraged…just keep growing and altering your methods and enjoying the process!!