Starting Plants from Seed
by Sharon Carr, Rideau Lakes Horticultural Society
Sowing Seeds Indoors - You need 7 things for sowing seeds indoors:
- A sterile container that is 2 - 3 inches deep and has drainage holes. Any household container is good and commercial seed trays are really easy to use. It is essential that the container be sterile so use a javex and water solution to wash anything that is not new.
- A plastic cover for the container to keep the humidity high. If you don’t have a commercial seed tray you can just cover it with a regular plastic wrap or put the container in a plastic bag - use toothpicks to keep the plastic away from the surface.
- A sterile soil less seed starting mix (e.g. Pro-mix). Regular soil is too heavy for the roots to develop easily.
- A heat and light source. If you have a nice bright south facing window sill you may not need a separate light. If you need more light than the window, any fluorescent light will do - you don’t need special “grow lights”.
- A water soluable fertilizer (transplanter is very good) that will help root growth once the seedling has started. There are no nutrients in most soil less mix.
- A spray bottle
- Seeds. Don’t worry if your seed packet is a couple of years old, this just means that the percentage of seeds that will germinate is likely to be less than in a fresh packet. Just sow more seeds for a better chance of germination.
Now you’re ready to start …
Pre-moisten your soil less mix in a separate bucket. If you try to water dry mix it will just run all over. The mix should be moist enough to make a loose ball in your hand and then crumble easily.
Fill your container with moistened mix tamping it in gently until the mix is level with the top. Spray mist to settle the mix.
Follow directions on the seed pack to sow seeds with respect to depth and whether to cover or not. Vermiculite works very nicely as a seed cover if your seeds need to be covered.
Cover the container with clear plastic and place it in a south-facing window or under an adjustable fluorescent shop light or grow light. The light should be 4-6″ above the container. This will keep the plants from reaching up too much to the light and getting leggy. You can raise the light as the plants grow to keep it 4-6″ from the seedlings.
Do not let the mix dry out. Water from the bottom to help prevent “damping off” a fungal condition that will kill the seedling. A good way to do this if you are using a commercial seed tray is to keep two seed cells out of the tray and water from this point to a depth of about 1/2″. After 15 or 20 minutes drain off any water that hasn’t been absorbed by the other cells. If you’re using other kinds of containers something like a roasting plan will work really well to hold your containers and let you water from the bottom. Spraying the plants with “No Damp” will also help to prevent plants from rotting at the surface.
Germination occurs when you see the first set of “natal” leaves. These are not true leaves. When you have germination, remove the cover so the seedlings can get more light and begin to grow.
Once the first set of true leaves has appeared, give your new seedlings a weak solution of transplanter fertilizer (about 1/4 strength) every week.
If you’ve had too many seeds sprout close to one another they’ll start to compete for the space and the nutrients in the transplanter. This is the time to thin them out by cutting the extra seedlings off at the base. Don’t pull them out or you’ll disturb the roots of the seedlings you want to keep.
When the seedling has grown a few sets of leaves it will probably need to be transplanted to a larger pot - again with soilless mix. Be very careful when you handle the seedling that you lift it by the leaves only - never the stem. Leaves will grow back if they come off, the stem won’t.
Before putting your new plants out for the summer you’ll want to “harden them off” by putting them out on warm days out of direct sun to get them used to the outdoors - a greenhouse or cool sunroom is also excellent for this. This helps the plant from experiencing too much shock when they’re moved outdoors.
Some easy plants to start from seed: marigolds, sunflowers, petunia, zinnia, cosmos, rudbeckia, coreopsis, celosia, calendula, ageratum, aster, salvia, brachycome, bachelor buttons, forget-me-nots, lobelia, delphinium and morning glory.
Sharon Carr was the seminar presenter at the Garden Coach seminar “Starting Seeds Indoors” in February 2006 and 2007. The fruits of her labours will be on display when she hosts the “Mid-Summer Garden” tour on July 22.