What Are Pelargoniums and Why Overwinter Them?
Overwintering pelargoniums involves protecting these popular summer-flowering plants from frost and low temperatures to ensure they survive and can be enjoyed again the following year. Many gardeners treat pelargoniums as annuals, discarding them after the first frost. However, with a little care and attention, these vibrant plants can be kept healthy through the winter months, saving you money and preserving beloved specimens.
- Protect pelargoniums from frost and cold.
- Overwintering saves money and preserves plants.
- Methods vary from dormant storage to keeping them growing.
- Timing is crucial for preparation.
Pelargoniums, often colloquially called 'geraniums' (though true geraniums are a different genus), are native to South Africa and are not naturally hardy in the UK climate. Their lush foliage and prolific blooms are a staple of summer bedding, hanging baskets, and containers. The decision to overwinter them stems from a desire to maintain these plants, often those with sentimental value, unique varieties, or simply because the gardener enjoys the challenge and reward of keeping them alive.
The primary reason for overwintering is to prevent the plant's death due to freezing temperatures. Frost can damage or kill the foliage and the delicate root systems if left unprotected outdoors. By bringing them into a sheltered environment, you essentially extend their lifespan and ensure a head start for the next growing season. This practice is particularly beneficial for 'collector's' varieties or plants that are difficult to obtain or replace.
Understanding Pelargonium Types for Winter Care
While the general principles apply, some pelargonium types might have slightly different needs. The most common are zonal pelargoniums (often sold as bedding geraniums), ivy-leaf pelargoniums (ideal for hanging baskets), and regal pelargoniums (known for their large, showy flowers). While all can be overwintered, the goal might differ slightly. For zonal and ivy-leaf types, the aim is often to keep them healthy and compact for mass planting next year. For regals, preserving their spectacular bloom potential is key.
It’s important to distinguish them from other summer bedding plants like petunias, marigolds, or fuchsias, which have entirely different overwintering requirements or are often treated as annuals. Begonias, for instance, are often lifted and their tubers stored, a different process to keeping pelargoniums as whole plants.
The core principle of overwintering pelargoniums is to manage moisture, temperature, and light to prevent disease and decay.
Methods for Overwintering Pelargoniums
How do you keep pelargoniums over winter? There isn't one single method; the best approach depends on the space available, the number of plants, and your willingness to provide care. The main techniques fall into two categories: keeping them growing in a protected environment, or storing them in a dormant state.
Method 1: Keeping Them Growing (Cool Conservatory or Greenhouse)
This method is ideal if you have a frost-free greenhouse, a cool conservatory, or a bright, unheated (but frost-free) indoor space. The aim here is to provide conditions where the plant remains partially active but growth is significantly slowed.
Preparation Steps:
- Pruning: In late autumn, before bringing plants indoors, prune them back by about a third to a half. Remove any yellowing or diseased foliage. Cut back stems to encourage a bushier plant in spring.
- Pest Check: Inspect plants thoroughly for aphids or whitefly. Treat any infestations before moving them indoors to prevent spreading. A dilute soapy water spray can be effective.
- Repotting (Optional): You can repot them into fresh, free-draining compost. If space is limited, you can gently shake off old soil and repot into the same size pot or slightly smaller. Alternatively, you can trim back the roots and reuse the existing soil.
- Watering: Reduce watering significantly. The soil should be kept only slightly moist, never wet. Allow the surface to dry out between waterings. Overwatering is the most common killer of overwintered pelargoniums.
- Light and Temperature: Place them in the brightest possible spot, ideally a south-facing window if indoors. Temperatures should ideally be between 5-10°C. Avoid placing them near direct heat sources.
Method 2: Dormant Storage (Cool, Dark Place)
This is a space-saving technique suitable for large numbers of plants or if you have limited bright space. The plants are kept in a state of near dormancy, requiring minimal water and light.
Preparation Steps:
- Pruning: Prune plants back hard, leaving only a few inches of stem. Remove all leaves.
- Uprooting: Gently remove plants from their pots. You can either pot them into very shallow trays of compost, or pack them bare-rooted into boxes or trays. If packing bare-rooted, ensure roots are not damaged and pack them snugly to retain some moisture.
- Storage Environment: Store them in a cool, dark, frost-free place such as a shed, garage, or cool cellar. Ideal temperatures are around 5°C.
- Watering: Water extremely sparingly. A very light sprinkle of water on the roots once a month may be sufficient, depending on humidity. The aim is to prevent them from drying out completely.
- Checking: Periodically check for any signs of rot or excessive drying. Remove any mouldy material immediately.
The key to dormant storage is minimal moisture to prevent rot.
Effective overwintering hinges on balancing the plant's need for rest with preventing decay.
Revive dormant plants by potting them into fresh compost in late winter or early spring. Water them and place them in a warmer, brighter spot to encourage new growth before the last frost.
When and How to Prepare for Winter
When should you start preparing your pelargoniums for overwintering? The timing is critical and depends on your local climate, but it's generally best to act before the first hard frost. Early autumn is the ideal period for this preparation.
Signs It's Time to Act
Watch the weather forecasts. As soon as temperatures consistently drop near freezing, especially overnight, it's time to bring your pelargoniums indoors or to their protected winter quarters. For most of the UK, this often means late September or October. Delaying too long can mean plants are already damaged, making recovery more difficult.
Pruning and Tidying: The First Steps
Before moving plants, a thorough tidy-up is essential. This involves:
- Cutting back: Trim back overgrown stems by at least a third. This prevents them from becoming leggy and encourages a more compact structure for the following year. It also makes them easier to handle and store.
- Removing foliage: Strip off any yellowing, damaged, or diseased leaves. This reduces the risk of fungal diseases taking hold during the damp winter months. Ensure you remove all fallen leaves from the pot surface.
- Checking for pests: Inspect plants carefully for common pests like aphids or spider mites. If found, treat them with a suitable spray before they can infest other plants in your home or greenhouse.
Potting and Soil Considerations
The compost used should be free-draining. If your plants are in old, depleted soil, consider repotting them. You can use a standard potting compost, perhaps with added perlite or grit to improve drainage. If you are opting for dormant storage, you can remove plants from their pots entirely and store them bare-rooted, or pot them into shallow trays with minimal compost.
Ensuring excellent drainage is paramount to prevent root rot.
Moving Plants Indoors
When moving plants, do so gradually if possible. If they have been in full sun, placing them directly into a dim conservatory might shock them. A few days in a brighter, sheltered spot outdoors before moving to their final indoor location can help acclimatise them. Clean the pots and the area where they will be stored to minimise the introduction of pests and diseases.
Ventilate regularly when plants are overwintering indoors. Opening windows or vents, even on cooler days, helps to reduce humidity and prevent fungal growth, a common issue in still, damp air.
Reviving Pelargoniums in Spring
Once the threat of frost has passed, typically from late March or April onwards, it's time to bring your overwintered pelargoniums back into active growth. This process requires a gradual reintroduction to warmer temperatures and increased light.
The Reawakening Process
For plants stored dormant, gently pot them into fresh, free-draining compost. Water them in and place them in a bright, frost-free location. You should see signs of new growth within a few weeks. For plants kept growing, the process is simpler: gradually increase watering as you see more active growth. You may need to repot them if they have become pot-bound or if the compost has degraded.
Pruning for New Growth
Once new shoots are visible, you can prune again to encourage a bushier habit. Pinch out the tips of new stems to promote branching. This is also the time to remove any dead or weak growth from the winter period.
The transition back to active growth needs careful management of water and light.
Feeding and Aftercare
As growth becomes more vigorous and temperatures rise, you can begin feeding your pelargoniums. Start with a balanced liquid feed. Once plants are established in their pots and showing good new foliage, you can switch to a feed higher in potassium to encourage flowering. Harden them off gradually before planting them out into their final positions in containers or borders after all risk of frost has disappeared.
This revived plant will be a testament to your efforts, providing colour throughout the summer. For those who also grow other popular garden plants, understanding the different needs of crops like sunflowers or sweet peas is important; for example, knowing when to plant sunflower seeds or how to grow sweet peas involves entirely different timing and environmental considerations compared to pelargonium care.