HOW TO OVERWINTER GERANIUMS



People don’t seem to bother with overwintering geraniums anymore and this is probably down to two main reasons.

1. Geraniums are not as expensive as they used to be so the financial need is not as strong, and
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2. The old ways of traditional gardening practice aren’t being handed down through the generations as they once were.

Because Geraniums do not possess a storage organ such as a bulb or a tuberous root, they must be overwintered as soft, ‘green tissue’ that is either actively growing or semi-dormant. When preparing your plants you will need to choose the best quality stock so only select your healthiest looking specimens. Unfortunately, especially when they are grown outside, geraniums are at risk of infection from bacterial or viral diseases, and so discard anything that is showing signs of leaf spots, wilting, or have lesions on the stems

Although I remember my own grandfather wrapping up bare-root geraniums in old newspaper, I was too young to remember the details of his technique. However I have listed several ways below, all of which can be used to successfully care for your geraniums over-winter.

THE INDOORS METHOD

With all these methods timing is important, so don’t leave it too late and get caught out by an early frost otherwise your stock is likely to be only fit for the compost heap. You will need be looking at beginning preparation for over-wintering around October but keep an eye on the forecasts for overnight temperatures and don’t risk leaving them out if temperatures start to move towards 6 Degrees Celsius.
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With this method, and you will need to have a little bit of space put aside for it, lift your geraniums with as much of their root undisturbed and attached, and pot them on into 6-8 inch diameter pots using any good free-draining, multipurpose compost – you may wish to add some additional horticultural grit or perlite to the mix for extra drainage. Cut each plant back to about 1/3 of its original height, then water in thoroughly.

Bring the geraniums under suitable protected covering such as a heated greenhouse or a cool bright room and treat as you would do a normal houseplant i.e. water weekly - but not too much - and feed ½ recommended fertiliser dose monthly. Initially, they will need to be kept in a well-lit location to help to establish them in their new pots but after 3 or 4 weeks they can be moved into a less well-lit position should you require the space. If you do so they will require even less water and fertiliser, in fact tries to keep them just on the dry side.

Leave them where they are until it is time to acclimatise them for outside planting come the spring, when you can begin to start watering and feeding as per normal. However, do not leave them outside permanently until the threat of frost is over.

THE ‘OUTDOORS’ METHOD

Again, lift your geraniums with as much of their root undisturbed and attached, and pot them on into 6-8 inch diameter pots using any good free-draining, multipurpose compost – once more, you may wish to add some additional horticultural grit or perlite to the mix for extra drainage.
Move them to the protection of a greenhouse or cool conservatory and treat as before until they have established in their pots.
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Come November, reduce the watering until the compost it almost dry then prune back the plants back to remove all of the soft, green growth. Cover the prepared plants with a fleece to help maintain an even temperature during the day and help prevent frost damage over night. If temperatures start to dip below 4 degrees Celsius you may need to provide heat within the greenhouse (about 6-7 degrees) or bring the plants indoors until temperatures rise.

When kept in a greenhouse it is important to ventilate the greenhouse as often as the weather allows in order reducing the incidence of fungal rots. Inspect your plants weekly for fungal infection and remove and destroy any that showing the tell-tale signs. Leave them where they are until it is time to acclimatise them for outside planting come the spring, when you can begin to start watering and feeding as per normal. However, do not leave them outside permanently until the threat of frost is over.

THE ‘TRADITIONAL’ METHOD – or rather ‘a’ traditional method

Once again you will need to carefully lift your geraniums before the first winter frost, but this time you need to gently shake all the soil from the roots – trying to do so without damaging the roots. They will then need to be stored in a cool dark position such as a basement where the temperature will remain a steady 5-7 degrees Celsius. The plants can either be hung upside down. or as my granddad probably did, wrap them in newspaper and placed into an open crate.

Once a month the roots will need to be soaked in room-temperature water for about an hour or so. Allow them to dry and then apply the plants with a protective fungicidal dust. You will find that during the course of this ‘enforced hibernation’ most of the leaves will dry up and fall off, but this is perfectly normal.

Come the early spring the plants can be potted on into 6-8 inch diameter pots using any good free-draining, multipurpose compost, again you may wish to add some additional horticultural grit or perlite to the mix for extra drainage. Cut the plants back to about 1/3 of their original height, then water and fertilize as normal.

Move them to a protected, well-lit position to help them establish in their pots until the threat of late frosts are over. Now they can be put outside during the day, or under cool green house protection, for the next 2-3 weeks in order to acclimatise them, after which they can be planted into their final positions.

For related articles click onto the following links:
HOW DO YOU OVER-WINTER BEGONIA CORMS?
HOW TO OVERWINTER BANANA PLANTS
HOW TO OVERWINTER BRUGMANSIA
HOW TO OVERWINTER CANNA LILIES
HOW TO OVERWINTER GUNNERA MANICATA
HOW TO OVERWINTER LILY BULBS
RHS Pelagoniums

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