Making your greenhouse ready for winter has both : –
- quick tips if you’ve been putting off these chores and planting bulbs instead
- planning help if you’re reading this in October
The focus is on a permanent structure, mainly wooden greenhouses and aluminium greenhouses. There are some similarities between greenhouses and cold frames which are glazed, regardless of whether they have wooden or aluminium frames. Whereas polytunnels have their own requirements, not least due to their greater “frame flexibility”.
Now whether the space is used for: –
- over wintering tender perennials,
- starting off seeds in autumn for early flowering of bedding and annuals,
- forcing bulbs for Christmas and early spring flowers,
- offering protection for salads so there are fresh leaves for your lunch
it is fairly obvious that taking steps to protect the structure will be necessary to get the most from the plants over winter and next year.
Storm proofing your Greenhouse
Whilst there’s no way we can 100% storm-proof garden buildings, by proactively making your greenhouse ready for winter, it is possible to minimise the risks of wind damage. That way, the greenhouses and polytunnels should at least come through ‘normal’ autumn and winter storms unscathed.
This is covered in detail in the relevant article, but a couple of tips are included here as it may be all you need to know.
Quick fixes
There are a number of easy things that can be done to minimize the chances of damage when high winds are forecast. For example: –
- close the windows, vents and door
- remove or put away clay pots and so on that could be blown against the greenhouse and break the glass
Making your greenhouse ready for winter should include a review of the glazing. And first up is to ask yourself, what type of glass is currently in use? If it is still horticultural glass then consider replacing this with safety glass. Clear styrene can be an economical alternative if there are budget restrictions. The last thing you need is a garden filled with shards of glass!
A note re Greenhouse insurance
Do take seriously the threat posed to your greenhouse by strong winds. If you spot a problem early it can often be easily mended. A few precautions and a good maintenance regime will reduce the risk of damage by storm force winds to greenhouses and polytunnels.
Check what insurance cover the greenhouses, cold frames and polytunnels have. They may not be covered for storm damage unless the buildings have been maintained and that there is proof of that maintenance. Record keeping – a ‘paper trail’ is vital, and remember that photographs, if dated stamped will count as evidence too.
Making your Greenhouse ready for winter – not just storms, but frosts too!
If you were able to clean out your greenhouse in the autumn, then the plants in the greenhouse will be in clean environment. But they may be in an unheated building rather than a warm glasshouse.
Did you know that the average interior temperature of an unheated and uninsulated greenhouse will be 2-3 degrees higher than it is outside? Good insulation can raise that to 4-5 degrees higher inside – and that’s before any heating is added!
With heated glasshouses, adding insulation will reduce the heating requirements, thereby reducing cost. We’re not quite all at the ground source heat pump stage yet, unfortunately, but solar panels are potentially a worthwhile investment.
It may sound obvious, but before insulating, check that opening windows and doors close fully and there are no gaps. If ventilators need to be opened during the day, open them once the morning chill has gone over, and close well before the sun dips low and has no heat left.
Discover where the cold spots in your greenhouse are – possibly in the corners. Have this in mind when organising which plants go where, as well as possibly increasing the insulation in those spots.
The degree of insulation required will depend on the particular plants. It may be that you have a wide enough variety to need separate areas. If so, an easy way to achieve this is by adding extra insulation on the inside of the frame and as a curtain at the end of the greenhouse furthest away from the door.
Greenhouse insulation material options
What should be used to add an insulating layer seems to be an increasingly difficult decision due to environmental as well as budgetary concerns. However, bubblewrap and horticultural fleece, with care, can be re-used over a number of years. Remember that even these will reduce the amount of light penetrating through – especially in polytunnels.
Of course, covering the whole greenhouse at night with roll-down blinds or by using thermal screens suspended above head height is much more effective. But this could take making your greenhouse ready for winter just that step too far!
If light is less important than heat, then consider using hessian and cardboard as insulators. For example, they could be used on the lower section. If there’s a gap behind, adding straw or paper will increase the insulation.
A large tub or trugs filled with water will help by absorbing the day’s warmth and slowly releasing it overnight.
Presuming your heat source is not from the ground up, then raising pots off the ground helps. Adding a layer of insulation underneath them may work, although if using something like cardboard, keep it away from direct contact with pots that will need watering.
Making your greenhouse ready for winter – what else?
There are tips for making sure your greenhouse plants are winter ready, on choosing the right greenhouse in the first place and on making sure your greenhouse is wind resistant in the articles below.
And if you’d like a gardening course on using your greenhouse to the full, learning more about your garden and gardening, why not ask about our bespoke Gardening Lessons, where your classroom is actually your own garden. We can help you learn gardening basics, carry out worm and other experiments and also show you how to plan an ornamental border or kitchen garden.
And for further gardening advice and inspiration, check out Plews Potting Shed blogs, including the selection below and our monthly Tipsheet – You could come and find us on Instagram Pinterest and Facebook too.
Related Gardening articles you may enjoy from our Award Winning Blog
Greenhouses
Your Greenhouse Plants Winter Checklist
Is Yours a Wind Resistant Greenhouse?
Greenhouses and cold frames – autumn maintenance
Do You have any Greenhouse Plans for this Year?
Choosing Your Greenhouse
Garden Visits
Winter Gardens Glasshouses and Indoor Plant Collections
Sub-tropical Glasshouse at Hall Place, Bexley
RHS Wisley Glasshouse
Giant Houseplant Takeover – Garden Rooms with a Difference
