Every gardener wishes to plant out earlier. How many times you had to postpone a start of growing season due to low temperatures outside? To speed up the process you can move your seedlings to a greenhouse. Let’s find out how much warmer is a greenhouse than outside.
The ideal temperature for growing plants should be in a range of 60-70°F (15.5-21.1°C). However, if you are germinating seeds or propagating cuttings, the temperature must be much higher – around 80° to 85°F (26°-29°C). As you know, meeting temperature requirements is vital for high yields.
There is a direct link between temperature and photosynthesis. If the temperature is cooler, rate of photosynthesis gradually falls down. Moreover, temperature is important for seed germination as well as fruit and flower development.
You need to plant seeds in soil that is warm enough so they can germinate. Therefore, the air and soil temperatures in your garden might still be cold. If you can’t wait to start your vegetables garden going, get a cold frame or greenhouse.
Both cold frame and greenhouse shield plants from winds and use solar energy and insulation to increase the temperature inside the structure. It results in the temperature inside the cold frame from 5 to 10 degrees warmer than the outside temperature.
So, how much warmer is it inside a greenhouse than outside?
An unheated expect by the sun greenhouse is 8 degrees warmer than outside. So, the temperature inside the greenhouse is 28°F (-2°C) when temperature outside falls to 20°F (-7°C). However, insulating and positioning a greenhouse properly makes it 20-30 degrees warmer than outside.
Learn how to heat a greenhouse in winter without electricity in just 10 easy steps. However, if you want to grow a wide range of plants during winter months, you need to heat it to at least 55°F (13°C). One of the easiest ways to heat a greenhouse in winter is to run an electric fan heater. Check out this guide to find out what is the cheapest greenhouse heater to run.
Why does a greenhouse get warm?
Greenhouse traps the sun’s heat. How? It’s very simple. Sun rays enter the structure through the greenhouse cover which can be glass or plastic. These rays heat objects inside the structure including soil, plants, frame and benches.
Then, plants and soil that have absorbed the sun’s heat emit the radiation inside the structure. In comparison to sun’s energy that can enter and exit the greenhouse freely, this energy does hardly get out. Therefore, it helps to trap the heat inside.
Although it makes a greenhouse warmer, it can lead to overheating. That is why to maintain stable temperature you need have ventilation. The warm air near the soil rises and you need to replace it with cool air from the outside. Vents will do exactly this – let hot air exit via roof and cooler air to enter via louvered vents at the ground level.
Does a greenhouse stay warm at night?
You will face a lot of debates around this question. You will hear that due to convection and heat trap a greenhouse is able to retain heat during the night. On the other hand, growers will warn you that temperature inside a greenhouse is the same as outside at night.
Most of the time whether a greenhouse will stay warm at night depends on your location and type of the structure. Many growers agree that temperature inside a mini or a walk-in greenhouse is the same as outside at night.
That is due to a temperature dip. Also, the temperature it is unlikely to be warmer in a hobby greenhouse without any heat collection system. So, a solution here would be using thermal blankets at night or putting black barrels filled with water.
The science behind this is very simple. Place the bucket in a place that receives most sunlight and water will absorb the heat during the day. At nighttime the captured heat emanates from the water and warms the greenhouse. The larger the barrel, the more heat will be absorbed.
How much warmer is an unheated greenhouse?
An unheated greenhouse also known as a cold greenhouse is heated only by the sun. The minimum temperature inside the unheated greenhouse is 28°F (-2°C) when outside temperature falls to 20°F (-7°C). It means that an unheated greenhouse can get at least 8°F (5°C) warmer than outside.
That said, an unheated greenhouse keeps plants frost-free, so go ahead and use it in fall and winter. You can keep tender plants frost-free and start growing hardy vegetables like salads and herbs. In addition, a cold greenhouse protects plants from wind, rain and snow.
As you know there is a higher chance that a damp plant will freeze. That’s why if a tender plant is outside when it’s cold and wet, it is most likely to die. So, a greenhouse does a good job by protecting your plants from nature elements.
Want more information on benefits of growing in a greenhouse? Ask questions in the comments section down below!
Happy Growing 🙂
