How to Start Seeds in a Greenhouse
A greenhouse is an excellent place to start and grow new plants from seeds. From flowers to vegetables to trees and shrubs, starting seeds in a greenhouse offers many advantages: the controlled environment, convenience of having everything in one place and protection from the elements. Does this Spark an idea?
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Things You'll Need
- Potting table or bench Seed starting potting soil Seed starting flats Plastic grow flats Plastic grow cells Indoor potting soil Liquid fertilizers Spoon Warming mat Spray bottle Water Bucket Plastic film or tray covers.
Instructions
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Preparation
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Measure the amount of seed starting potting soil that you want to begin with into a bucket. Now turn the soil as you spray water in until the soil is just damp.
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Add lukewarm water to the potting soil. Work the water in until the soil begins getting wet.
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Pull handfuls from the bucket and squeeze them to remove any excess water. Some should drip out, but not a lot. If you are not seeing water drip when you squeeze, you might not have enough water in it. Spread it out evenly in your starting tray, just about one inch deep.
Planting the Seeds
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A good tool is an unsharpened pencil. Mark the side with the depth to plant. Poke holes in the potting soil to the depth you need to plant the seeds. Spacing depends on what is being planted, but an inch apart is a good starting point. Make the holes in rows and columns.
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Drop one seed into each hole. Once all the holes have a seed, gently press the hole closed with your finger.
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Cover the flat with plastic wrap or a plastic cover. If the type of seed needs warmer soil temperatures than the greenhouse can provide, place the tray on a warming mat and keep it plugged in until the seeds germinate. Check every few days to make sure the soil isn't drying out. Mist with the water bottle if it is.
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Remove the cover when the green shoots appear. Keep the soil moist over the next few days as the remaining seeds germinate. Seeds that require long germination periods may need the covers to remain in place longer.
Planting the Seedlings
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Prepare regular potting soil as before, in a bucket or tub and adding water until well dampened. Squeezing it should just barely produce a few drops. Fill plastic cells with soil until you have enough to handle all your seedlings.
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Begin transferring the seedlings to cells when they have grown one set of true leaves. Using a small spoon, carefully slice into the soil around a seedling, then lift it out with the spoon.
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Transfer the seedling to a plastic cell. With practice, you can pick up a seedling with the spoon, use the tip of the spoon to press a space into the soil and slide the seedling off at the same time. Gently press the soil back around the newly potted plant.
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Follow guidelines for the type of seedlings you have. Generally, place the cells into a plastic flat and fill it with an inch of water. Once per week, fill the cells with a weak mixture of liquid fertilizer. Include a root starter fertilizer once the plants begin to be established in the cells, usually in about one to two weeks.
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Tips & Warnings
The depth you plant depends on the seeds. Some seeds require light to germinate, others darkness. Very tiny seeds may just need to be placed on top of the soil, while big seeds may need to go in deeper. Read the instructions for your particular plant. Some extremely fine seeds are so small you need a magnifying glass to see them. These seeds need special care for starting. Prepare your seed starting soil as described and put it in a flat. Next, add one-fourth inch or so of very fine sand and wet it with spray water. Don't make holes for these seeds. Instead, make a slight depression in the wet sand and try to put one or two seeds in each depression. Keep the sand damp until the seeds germinate. Plants that grow fast need to be moved to cells quickly. As soon as true leaves appear, get them moved before their roots intertwine. To steady a seedling as you move it, grasp it gently by a seed leaf. If you damage it, no harm done as they fall off soon anyway. Some people like to make a place in all the cells before they prick out the seedlings. Just use the spoon. Insert it about an inch and move it back and forth, making a slot about an inch wide and deep. Now you're ready to prick and plant.
Liquid fertilizer can damage your eyes. Wear safety glasses when mixing it. For young plants, always mix it at a ratio of one-to-five strength. Once most of the seeds germinate, remove their covers as soon as possible to prevent fungus. Keep the air moving in your greenhouse. Don't let it stagnate anywhere. Use fans to keep the air moving. This prevents fungus from getting a foothold.
References
- Photo Credit Lynn Blazyk, Rand G., Ewen Roberts
