Frosty Greenhouse

Can plants freeze in a greenhouse? 4 ways to prevent frost in the greenhouse

Yes, plants can freeze in a greenhouse.  An unheated greenhouse will generally be 5 degrees warmer than the outside temperature.  That means that a greenhouse will only begin to drop below zero in very wintry conditions.

 

Some plants are frost hardy and will be able to withstand subzero temperatures.  Frost hardiness will differ from plant to plant and variety to variety, so it is worth double-checking this before placing plants to over-winter in a greenhouse.

 

Sometimes frost will only form on plants exposed to the cold air coming in through the glass or plastic from above.  If a plant is sheltered within the greenhouse, under some shelving for instance or under some horticultural fleece, then this might be enough to create a warmer microclimate, raising the temperature enough to prevent the plant from freezing.

 

Another factor in plants freezing within unheated greenhouses is how damp the soil is that the plant is growing in.  A plant that is sodden wet will have a much greater chance of freezing as there is a higher concentration of water among the roots.

 

It is advisable to vastly reduce watering in the winter as the plant’s vascular system runs very slowly and therefore doesn’t require much water.  This will decrease the chance of freezing.

Do plastic greenhouses protect from frost?

Yes, plastic greenhouses protect plants from frost.  A plastic greenhouse will offer enough insulation to ensure that the temperature inside the greenhouse stays at least 5 degrees higher than outside.  Therefore, a plastic greenhouse will offer enough protection to your plants during cold winter weather.

 

Further protection will be required during extended, extremely cold winter weather.

 

One way of assuring that plastic greenhouses remain frost-free is to add some bubble wrap to the plastic sheeting to give an extra layer of insulation.

 

Secondly, avoid placing your greenhouse in a frost pocket in your garden.  You won’t know where your garden’s frost pockets will be until you have spent a winter at your property.  A neighboring tree should help to shelter your greenhouse from frost.

 

Placing some horticultural fleece over the top of the plants will create a micro-climate to help increase the temperatures surrounding your plants, rather than the overall temperature of your greenhouse.

 

One last thing to remember with plastic greenhouses is to pin or tie them down so that they don’t blow away in the wintry weather.  Plastic isn’t as heavy as glass and therefore needs to be secured to prevent it from moving suddenly, along with your plants!

Can you keep plants in a greenhouse during winter?

Plants can be kept in greenhouses during winter however, this will depend on the plant or variety.  Some plants are frost hardy while some can’t tolerate frost and require a consistently warmer temperature.

 

It is worth checking the frost hardiness of your plants before placing them in the greenhouse to overwinter.

 

Remember greenhouses can be both heated and unheated, so pay attention to the minimum temperature that your plants need to live.  If your greenhouse can’t maintain the correct temperature, then you may need to consider adding a heater to it or alternatively fetch the plants indoors to nurture them in the house.

Do mini-greenhouses protect from frost?

Yes, mini-greenhouses protect plants from frost.  A mini greenhouse will offer enough insulation to ensure that the temperature inside the greenhouse stays at least 5 degrees higher than outside.  Therefore, a mini-greenhouse will offer enough protection to your plants during cold winter weather.

 

Further protection will be required during extended, extremely cold winter weather.

 

One way of assuring that mini-greenhouses remain frost-free is to add some bubble wrap to the plastic sheeting to give an extra layer of insulation.

 

Secondly, avoid placing your greenhouse in a frost pocket in your garden.  You won’t know where your garden’s frost pockets will be until you have spent a winter at your property.  A neighboring tree should help to shelter your greenhouse from frost.

 

Placing some horticultural fleece over the top of the plants will create a micro-climate to help increase the temperatures surrounding your plants, rather than the overall temperature of your greenhouse.

 

A mini-greenhouse is light enough to allow you to move it around the garden.  As the sun doesn’t rise as high during winter, the light levels will differ during the winter when compared to summer.  It might therefore be wise to move the mini-greenhouse to a sunnier position in the garden.  This will increase the overall temperature of the greenhouse and therefore reduce the chance of frost forming within it.

 

One last thing to remember with plastic greenhouses is to pin or tie them down so that they don’t blow away in the wintry weather.  Plastic isn’t as heavy as glass and therefore needs to be secured to prevent it from moving suddenly, along with your plants!

How can I protect my plants in an unheated greenhouse?

There are many ways to protect your plants within an unheated greenhouse to prevent frost from killing your plants.

 

  1. Avoid frost pockets.  You won’t know where your garden’s frost pockets will be until you have spent a winter at your property.  A neighboring tree should help to shelter your greenhouse from frost.
  2. Bubble wrap.  One way of assuring that mini-greenhouses remain frost-free is to add some bubble wrap to the plastic sheeting to give an extra layer of insulation.
  3. Horticultural fleece.  Placing some horticultural fleece over the top of the plants will create a micro-climate to help increase the temperatures surrounding your plants, rather than the overall temperature of your greenhouse.
  4. Don’t overwater.  Another factor in plants freezing within unheated greenhouses is how damp the soil is that the plant is growing in.  A plant that is sodden wet will have a much greater chance of freezing as there is a higher concentration of water among the roots.  It is advisable to vastly reduce watering in the winter as the plant’s vascular system runs very slowly and therefore doesn’t require much water.  This will decrease the chance of freezing.

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