Starting Seeds in a Greenhouse

Planting seeds can be a fun thing to do, especially if you are an avid gardener. This can be hard to do during the winter season or when there are weather fluctuations especially if you don’t have the right Greenhouse kit. This is true when the seeds require steady temperatures and controlled environments for them to germinate. Starting seeds in a greenhouse allow you to provide a stable environment for the seeds to germinate and allowing seedlings to grow.

When should you Plant Greenhouse Seeds?

Greenhouses are common because they allow you to control the humidity and temperature required for growing seeds. This means you can plant your seeds in a greenhouse at any time of the year. However, if you are planning on transplanting your plants to the outdoors once the weather is stable, you should start planting the seeds in the greenhouse 6-8 weeks before winter ends.

To get the best results, you should germinate the seeds in temperatures around 21-27 degrees Celsius (70-80 Fahrenheit) during the day and 10-13 degrees Celsius (50-55 degrees Fahrenheit) during the night. You should always monitor the temperatures, especially at night, when temperatures can drop. You can use seedling heat maps that will generate warmth in the soil. There are also fans, or you can also open windows if the temperatures get too hot.

Greenhouse Seed Starting

In greenhouses, seeds are started in individual plug trays or open flat seed trays. It would be best if you prepped the seeds according to specificity like soaking them overnight, scarified or stratified, and then planted in trays in the greenhouse. You can use a seed-starting mix to fill the trays.

Remove the plastic wrap, or plastic lid, once seedlings start to appear. Make sure the plant mix is always moist but not soggy. Fertilize every two weeks and snip excess seedlings with scissors. Water the seedlings after fertilizing. Once they are 6-8 weeks old, you can then transplant them to the outdoors or move them to larger containers.

When using open flat trays, the seeds are neatly spaced in rows to make it easy to thin, water, and fertilize the seeds. Once they produce their leaves, they can be transplanted into their pots and cells. Some experts may argue that using plug trays is better than using open trays because they hold and retain more moisture and warmth for the seeds. They can also stay longer without their roots intertwining. They can also be transferred easily into the garden when the time comes.

Other ways to start seeds in greenhouses are by using a cold frame, freestanding unit, or a mini-greenhouse to generate warmth.

Cold Frame

A cold frame is a shallow pit covered with a glass-topped lid. The backside is usually taller than the front side. This way, the sun rays can penetrate the interior and warm the trays, peat pots, or flowerpots. The temperatures inside the cold frame can only rise to 10 degrees above its surrounding temperatures. This kind of temperature is suitable for cold-tolerant plants like cabbage, broccoli, and peas, as well as flower seeds.

Hotbed Frame

You can turn a cold frame into a hotbed frame by heating it with manure, light bulbs, or heating coils. When using manure, you should dig the pit more than 30 inches deeper than the hole you would use for a cold frame. Add 6 inches of coarse gravel and tamp it down. You then proceed to fill the bottom of the hole with 18 inches of manure that is partially composted, like horse manure. Cover it with potting soil, about 4 inches. Wait until the temperature of the soil drops to 85 degrees before adding the seeds.

Indoor Mini-Greenhouse

This greenhouse comes in handy when you live in a drafty place or areas with low temperatures. You can either buy a mini-greenhouse, or you can create one of your own. To do this, you can use a clear plastic container with the lid acting as the greenhouse. You can also use plastic wrap to cover the container.

Freestanding Greenhouse

You can use shelves or benches as a freestanding greenhouse to start multiple seeds. To regulate the temperature, use fans, and heaters. You can also use fluorescent lighting to encourage seed growth. Make sure you disinfect the place you will use to discourage the growth of fungi, algae, and other pets.


You can create your own greenhouse at home, or buy a greenhouse, to start seed planting. You can use regular containers or trays to plant the seeds. Constantly germinate the seeds every one-to-two weeks to encourage plant growth. It would help if you also watered the seeds for germination. Follow the procedures mentioned above to ensure that your seeds grow then transfer them outside when they are ready to be transplanted.


Leave a Reply

Your email address will not be published.

For security, use of Google's reCAPTCHA service is required which is subject to the Google Privacy Policy and Terms of Use.

I agree to these terms.

This site uses Akismet to reduce spam. Learn how your comment data is processed.