Starting Plants from Seeds Indoors
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Growing plants from seeds indoors takes minimal supplies – a container, lightweight seed starting medium, seeds and a light source. Trays with transparent covers are also handy to keep soil moist until plants are about 2-3” tall. A spray bottle can be used to water the containers without displacing the soil.
You can use a variety of containers, from paper cups with drain holes to plastic cell packs which have dividers for multiple plants. If you’re growing many plants, its best to use pots which when grouped, fit nicely in a tray. Since they can be planted right into the ground where they decompose, peat pots are great for growing crops that don’t like to be disrupted once they start growing. A tip for peat pots, though, is to cut off the upper rim when planting so the exposed pot doesn’t wick soil moisture away from the plant.
Starting seeds indoors is a handy way to get a jump on the season while outdoor conditions are too harsh for seedlings. In spring, that means starting your seeds about 6 weeks before the last expected frost date. The first of February could be your start date in North Florida. This is approximate as crops take different amounts of time to germinate or grow to a size strong enough to transplant. You should also work in some days to harden off the seedling (put it outdoors increasingly longer each day for it to become adjusted to the change in temperature and sun). In fall, you may want to start some cool sea-son crops early indoors where they are sheltered from the heat. Use our “Planting Guide for North Florida Vegetables” and our “Planting Guide for North Florida Culinary Herbs” for the appropriate range of months to plant transplants and seeds OUTDOORS for each crop.
Use a bucket to hold the seed starting mix while you moisten it with water. Dry mix repels water and is more difficult to wet once it is in a container. Fill the container with moistened seed starting mix, press lightly and leave room to water. Refer to the seed packet for the depth to plant the seed. Create a hole with a pencil tip or similar, drop a couple seeds in and cover with more medium. (The extra seed is planted in case not all seeds germinate but some gardeners would rather plant one seed and not have to thin any plants later. If you do need to thin plants growing together, it is better to snip off the ones you cull rather than pull them up and risk unsettling the roots of the keeper.)
Label your containers with the variety planted and the planting date. Keep your planted seeds warm to speed germination. A heat mat can be used, but that can cause the containers to dry too quickly. It is the water that starts the germination process. Once the seed starts taking in water and growing, it can’t go on hold to grow later – disruption in moisture will kill the seed. Although most seeds don’t need light to germinate, a clear cover will help retain the moisture and allow light to reach the plant once it has germinated. Light can be supplied by a full spectrum artificial source a few inches above the plants if sunlight is not available. LED lights have the advantage of staying cool.
Once the seedlings start to emerge, the cover should be positioned to allow a little air flow. The first set of leaves to emerge are called cotyledons. Up to this point all the energy for the plant has come from the seed. The second set of leaves are true leaves, capable of photosynthesis. When they emerge, you can remove the cover and begin watering with a dilute liquid fertilizer weekly.
When all danger of frost has passed for warm season seedlings, or conditions are cool for cool season crops, you can start the hardening off process by gradually introducing them to outdoor conditions and sun exposure. On the first day put them in a sheltered spot with no sun for 3 or 4 hours then bring them back inside. Add 2 or 3 hours each day to their time outside, bringing them back in at night. After 2 or 3 days put them in morning sun for the first part of the day, move into the shade in the afternoon and bring them in at night. After 7 days the seedlings should be able to stay outside all day in the sun but remember they can dry easily in their small containers. Leave them out at night if the temperature stays above 50° for spring crops. They can be planted in the garden after 7-10 days. Try not to plant at the sunniest time of day and water them in well. Now they’re part of your garden!