Winter in the Greenhouse

Answered by Harrod Horticultural Posted in Category Greenhouse

Dear Martin

In my greenhouse I have a number of trays/modules with hardy plants I have grown from seed in the last few weeks (clarkia, cornflower, buplueurm, ammi majus).  My greenhouse is unheated - will these plants be okay in there if it gets very cold?  What's the minimum temperature when I should start to get alarmed and move them if need be somewhere warmer?  Or can I just cover them with fleece?
 
In a similar vein, I have moved several tender plants (pennisetum, nemesia, and cuttings of pelargonium and penstemon into the utility room attached to my house.
I would quite like to have an electric fan heater to use if necessary as this room is unheated but I would like a heater which switches itself on when the temperature falls to a certain level (and off when it rises sufficiently of course).  I notice you are selling a greenhouse heater on your site - would this do this??  The room is small, 10' x 5', would it get too hot in what is a relatively confined space?
 
Would appreciate your advice.
 
Regards
 
Gillian

Dear Gillian

Many thanks for your recent message concerning the winter protection of your seedlings and cuttings. Although both venues – the unheated greenhouse and utility room – should be frost proof in all but the most extreme of weather conditions, it’s still good practice not to let the plants become stressed by exposure to low temperatures.

The answer, as you rightly say, is to introduce a safety net by way of a thermostatically controlled electric fan heater and luckily, we have a couple of models suited for just the kind of work you outline - the Tropic Electric Fan Heater and the Montana.

Both these products will deliver all the requirements you have; they are both mains powered, are thermostatically controlled by an integral sensor, have a fan-only setting for summer ventilation and both can also be switched between 1 and 2kw outputs to save on running costs and conversely give a heat boost during key propagation times. The key feature is the ‘frostwatch’ function which both heaters can boast; usually on the lowest setting, the heaters will maintain a temperature of 4-5 °C and switch off once this figure is achieved/exceeded. In the case of the small utility room, both heaters could be switched to the half power setting (1kw); alternatively, leave the heaters set on 2kw and they will only need to work occasionally to maintain the chosen temperature. 

You’ll probably have noticed that the Tropic is twice the price of the Montana; this is an indication that the former is a better quality model with improved components but essentially, both heaters will provide the same results – it’s just the Montana is aimed at gardeners on a budget.

The other solution is to use horticultural fleece to keep the hardy annual seedlings in the greenhouse frost free. This material is light enough to lay over the plants and although this will affect light transmission, it’s not essential in the dull days of winter. You’ll also avoid giving the plants too much heat which could lead to leggy growth as they search for light to match the heat they are getting; better to keep them in a dormant state but protected from damaging low temperatures.

Hopefully this information proves to be of help and you enjoy the flowering head start your autumn seed sowing and propagating should bring. Please don’t hesitate to contact me with any further questions or queries you may have and many thanks once again for your enquiry.

Kind Regards
Martin    

Dear Gillian

 

Many thanks for your recent message concerning the winter protection of your seedlings and cuttings. Although both venues – the unheated greenhouse and utility room – should be frost proof in all but the most extreme of weather conditions, it’s still good practice not to let the plants become stressed by exposure to low temperatures.

 

The answer, as you rightly say, is to introduce a safety net by way of a thermostatically controlled electric fan heater and luckily, we have a couple of models suited for just the kind of work you outline - the Tropic Electric Fan Heater and the Montana.

 

Both these products will deliver all the requirements you have; they are both mains powered, are thermostatically controlled by an integral sensor, have a fan-only setting for summer ventilation and both can also be switched between 1 and 2kw outputs to save on running costs and conversely give a heat boost during key propagation times. The key feature is the ‘frostwatch’ function which both heaters can boast; usually on the lowest setting, the heaters will maintain a temperature of 4-5 °C and switch off once this figure is achieved/exceeded. In the case of the small utility room, both heaters could be switched to the half power setting (1kw); alternatively, leave the heaters set on 2kw and they will only need to work occasionally to maintain the chosen temperature.  

 

You’ll probably have noticed that the Tropic is twice the price of the Montana; this is an indication that the former is a better quality model with improved components but essentially, both heaters will provide the same results – it’s just the Montana is aimed at gardeners on a budget.

 

The other solution is to use horticultural fleece to keep the hardy annual seedlings in the greenhouse frost free. This material is light enough to lay over the plants and although this will affect light transmission, it’s not essential in the dull days of winter. You’ll also avoid giving the plants too much heat which could lead to leggy growth as they search for light to match the heat they are getting; better to keep them in a dormant state but protected from damaging low temperatures.

 

Hopefully this information proves to be of help and you enjoy the flowering head start your autumn seed sowing and propagating should bring. Please don’t hesitate to contact me with any further questions or queries you may have and many thanks once again for your enquiry.

 

Kind Regards

Martin