Starting Seeds Indoors
There are numerous benefits to starting seeds indoors.
- Starting seeds outdoors, requires the soil to be warm enough for seeds to germinate. Sowing seeds indoors, early in the season before the soil has warmed, enables you to start producing earlier.
- Indoor sowing/growing conditions are easier to monitor and control. Seeds can be keep evenly moist and soil temperature manipulated using heat mats or by simply placing seed trays in a warm, draft free location.
- New seedlings can be started in pots mid summer when the garden beds are most likely full. These seedlings can replace mature plants as their production slows.
Choosing a container
Seedling pots can be purchased from garden centres or you can make your own. Food and drink containers can be repurposed as seedling pots as long as you make some holes for drainage in the bottoms. Yogurt pots, bottoms of drink/soda bottles, berry punnets and fast food containers all work well. Avoid porous containers such as cardboard or paper rolls as it can be difficult to maintain an even soil moisture.
I find dark coloured, plastic containers work well as they take in heat and retain moisture. The container size you choose will depend on how big your seedling will get before planting out and how well it transplants. I recommend using larger 10cm containers for pumpkins, squash, cucumbers, zucchini and melons (sensitive to transplanting). Most other seedlings can be potted in smaller containers (5cm), then repotted to larger ones as required.
If using containers which have previously held soil or plants, they should be sterilised prior to using. This prevents diseases such as Damping Off, passing to your seedlings. Containers can be sterilised using bleach mixed at standard cleaning concentration.
Choose a sterilised medium for planting to avoid transmitting plant diseases to your seedlings. Garden stores sell sterilised seedling mix which is a fine, soil based product and coir which is soil-less, light and holds moisture well (and my preference).
Seeds need humidity, warmth and moisture to germinate.
Humidity: Place seed containers in a tray lined with rocks. Pour water over rocks until just covered. Cover seed containers with plastic and keep warm. Once germination occurs, remove any plastic coverings immediately.
Moisture: Keep seeds moist but not wet. Wet seeds rot, dry seeds will not germinate.
Warmth: Spring seeds need gentle warmth (ideally from the bottom) to germinate, most require darkness.
Once seeds have germinated, plastic coverings should be removed as humidity can cause disease. The growing medium should be kept moist but not wet or soggy. It is generally best to water from below into the tray, allowing the medium to soak up the water like a sponge. After watering, remove any excess water from the seedling tray.
Seedlings need a lot of light otherwise they become leggy (lanky and drawn out). Grow lights are ideal, but expensive. The screened side of a window sill works well, just ensure the seedlings do not get too hot. Approximately 1 week after seedlings have emerged, provide them with a little food in the form of a weak, water-soluble fertilizer. Repeat weekly.
If seedlings outgrow their containers before conditions are ready for planting out, you might try transplanting them to bigger pots. For the most part though, you want to plant them outside as soon as they become large enough to cope well with transplanting. This is generally four to six weeks after sowing, when they have at least two sets of true leaves i.e. the 1st set of leaves from base of plant are seedling leaves, not true leaves and will look different. It is very important that the weather is right for planting out otherwise the seedling growth will slow. For spring seedlings, wait until temperatures (night and day) are sufficiently warm enough.
Hardening off is a method of slowly introducing seedlings to the weather variations outside, toughening them up if you like.
To harden-off seedlings, leave the plants in their containers and place them in a shaded area with some indirect light for a few days. A covered porch is ideal. If a frost is predicted, bring the plants inside overnight. After a few days in the shade, place the seedlings in a sunny location for an hour one day, two hours the next and so on, increasing their exposure each day. At the end of a week, the plants are accustomed to the sunlight and wind and are ready to be transplanted to the garden.
Transplant carefully to minimise root disturbance. This is especially important for pumpkin, squash, cucumber, melons and zucchini. Plant at the same depth they were in the pot. Note: Tomatoes and capsicum can be planted up to their first true leaves. This encourages greater root growth for a stronger plant. Gently water soil to help roots settle.
Protect from snails: If possible, reduce snail numbers prior to planting out. Nightly collections or baiting a week before-hand are two options. Cloches, placed over seedlings in the evening will also protect young plants . Remember to remove cloches in the morning. You can make your own cloches easily by cutting a plastic soft drink/soda bottle in half and placing the top half over the seedling (lid removed).
If your seedling wilts slightly after transplanting, provide it with a little shade for a couple of days. Old sheer or lace curtain can be used for this purpose.