What Does Overwintering Geraniums Mean?
Overwintering geraniums refers to the process of protecting these popular plants from frost and cold temperatures during the winter months, so they can survive and be replanted or encouraged to grow again in the spring. This practice is particularly relevant for tender Pelargonium varieties, commonly known as zonal geraniums, which are often grown as annuals but can be preserved year after year with the right care.
- Geraniums need protection from frost to survive winter.
- Overwintering allows tender Pelargoniums to live for multiple years.
- Different methods suit varying amounts of space and effort.
- Successful overwintering ensures plants are ready for spring growth.
Many gardeners treat Pelargoniums as annuals, replanting them each spring. However, with a little effort, you can significantly extend their lifespan. This approach not only saves money but also preserves beloved specimens that may have sentimental value or unique characteristics. The goal is to keep the plant alive, dormant or semi-dormant, until conditions are favourable for renewed growth.
Hardy geraniums, conversely, are true perennials and are naturally equipped to survive the British winter outdoors. They die back to the ground in autumn and regrow from the roots in spring. When people refer to 'geraniums over winter', they are almost always discussing the tender Pelargonium types, which require intervention to survive freezing temperatures. Understanding this distinction is key to choosing the correct overwintering strategy.
The core principle behind overwintering is to shield the plant's roots and foliage from damaging frost and prolonged cold. This typically involves moving them to a sheltered location, reducing watering, and ceasing feeding. The specific method you choose will depend on factors such as the variety of geranium, the amount of space you have available, and your willingness to provide ongoing care.
Why Bother Overwintering Your Geraniums?
The primary motivation for overwintering geraniums is to keep your favourite plants alive and well for the following year. This means you don't have to buy new plants every spring, offering a considerable cost saving over time. It also allows you to maintain specific cultivars that might be difficult to source or are no longer readily available in garden centres.
Furthermore, plants that have been overwintered often establish more quickly in their second year. Having survived their first growth cycle, they can sometimes be more vigorous and quicker to flower than young, newly purchased specimens. This is especially true if you are overwintering plants that have reached a desirable size and shape, which would take time and expense to replicate.
Preserving Special Specimens
Some geranium varieties, particularly older or more unusual types, can be hard to find. Overwintering allows you to keep these unique plants going indefinitely, ensuring you don't lose them to a harsh winter. It’s a way of curating your own collection of plants that have proven their worth in your garden or on your patio.
The satisfaction of nurturing a plant through its dormant period and seeing it flourish again in spring is a rewarding aspect of gardening. It deepens your connection with your plants and enhances your understanding of their life cycles. For many, it's about more than just saving money; it’s about horticultural success and building a long-term relationship with their green companions.
Successfully overwintering geraniums transforms them from seasonal decorations into long-term garden investments.
Consider the space you have available and the time you can dedicate. While some methods require more attention, they yield a more robust plant. Others are more hands-off but might result in a slightly weaker start for the plant in spring. The choice often comes down to balancing effort against desired outcome.
Methods for Geraniums Over Winter
There are several effective ways to over winter geraniums, each with its own advantages and requirements. The best method for you will depend on your available space, climate, and how much effort you are prepared to invest.
Method 1: Bringing Plants Indoors (Pots)
This is perhaps the most common approach. Before the first hard frost, typically late autumn, bring your potted geraniums indoors. Find a cool, bright spot, such as a frost-free greenhouse, a bright windowsill in an unheated room, or a porch. Water sparingly, only when the compost feels dry to the touch, and stop feeding. Prune back any leggy growth or dead leaves. The key is to keep them cool but not frozen, and relatively dry to prevent rot.
Method 2: Storing Bare-Rooted Plants
This method is ideal if you have limited space. Carefully dig up the geraniums from their pots or borders. Gently shake off excess soil and trim back the foliage and roots by about a third. Hang the plants upside down in a cool, dark, frost-free place, such as a garage or shed, allowing them to dry out slightly. Alternatively, you can store them upright in boxes filled with dry sand, compost, or sawdust. Check them periodically and mist lightly if they seem excessively dry, but avoid dampness.
Method 3: Treating as Houseplants
If you have a bright, warm indoor space like a conservatory or a sunny windowsill in a heated room, you can continue to grow your geraniums through winter. Treat them as you would any other houseplant, ensuring they receive adequate light and water. They may continue to flower, albeit less profusely. This method requires more consistent attention to watering and light levels than dormant storage.
Method 4: Taking Cuttings
Another space-saving option is to take cuttings from your healthiest geranium plants in late summer or early autumn. Cut healthy shoots about 7-10 cm long, remove the lower leaves, and dip the ends in rooting hormone. Pot them in small pots of free-draining compost and keep them in a warm, bright place to root. Once established, these young plants can be overwintered in a frost-free environment and will provide strong specimens for the following year.
Inspect plants thoroughly for pests before bringing them indoors. A thorough clean of pots and pruning of affected areas can prevent problems from spreading to other houseplants.
Comparing Overwintering Options
| Method | Space Required | Effort Level | Outcome |
| Indoor Pots | Moderate | Moderate (watering, light) | Strong plants, potentially quicker to establish |
| Bare-Root Storage | Low | Low (periodic checks) | Plants may appear weaker initially, but recover well |
| Houseplant Growth | Moderate | High (consistent care) | Continuous growth and potential flowering, but needs specific conditions |
| Cuttings | Low | Moderate (propagation) | New, healthy plants, but require starting from scratch |
Each of these methods aims to protect the core of the plant from the harsh winter conditions. The choice between them is largely personal and depends on what works best for your circumstances.
Caring for Geraniums During Winter Dormancy
Once your geraniums are in their overwintering locations, the care required shifts significantly from their summer needs. The aim now is to keep them alive and healthy with minimal stress, encouraging them to enter a state of semi-dormancy or reduced growth.
Watering Requirements
This is arguably the most critical aspect of overwintering. Whether stored bare-root, in pots in a cool greenhouse, or in an unheated room, geraniums need very little water. The soil should be allowed to dry out considerably between waterings. Overwatering is the most common cause of failure, leading to root rot and fungal diseases. If stored bare-root, a very light misting every few weeks might be sufficient if the storage environment is very dry, but usually, no watering is needed until spring.
Light and Temperature
For potted plants or those grown on as houseplants, light is important. A bright windowsill or a greenhouse is ideal. If kept in very cool, dark conditions (like a shed), they will be more dormant. Temperatures should ideally remain cool, between 7-12°C (45-55°F). Avoid freezing temperatures, but also avoid the heat and dry air of a centrally heated house, which can encourage weak, leggy growth and attract pests.
Feeding and Pruning
During the winter months, stop all feeding. Geraniums do not require nutrients when they are not actively growing. Pruning should be minimal during dormancy, mostly confined to removing any dead or yellowing leaves to prevent disease. Any significant pruning is best left until the start of the spring growing season, when you can shape the plant and encourage new, bushy growth.
Check stored plants regularly for signs of rot or pests. Remove any affected parts promptly to prevent the problem from spreading.
Dealing with Pests and Diseases
Cool, damp conditions can encourage fungal diseases, especially if plants are overwatered. Ensure good air circulation around stored plants. Pests like aphids or whitefly can sometimes be a problem, particularly if plants are brought in from outdoors. If you spot pests, try to deal with them promptly using a suitable organic spray or by wiping them off manually. Early detection is key to managing infestations during the dormant period.
Bringing Geraniums Back to Life in Spring
As the days begin to lengthen and temperatures rise in spring, it's time to reawaken your overwintered geraniums. This transition period is crucial for setting them up for a successful flowering season.
Reintroduction to Growth
Begin by inspecting your plants. For potted plants, check the roots. If they have become pot-bound, it's time to repot them into fresh, free-draining compost. Use a good quality potting mix, ideally one formulated for containers or flowering plants. If storing bare-root plants, pot them into containers with fresh compost and water them in well. For cuttings, ensure they have developed a good root system before repotting.
Pruning and Shaping
This is the ideal time for a more substantial prune. Cut back leggy or overgrown stems to encourage bushier growth. Aim to shape the plant, removing any weak or spindly shoots. A good prune will stimulate new growth from the base and along the stems, resulting in a more compact and floriferous plant. Aim to reduce the plant's size by about a third to a half, depending on its condition.
Watering and Feeding
Once repotted and pruned, gradually increase watering. Start by watering thoroughly, and then maintain a regular watering schedule, allowing the top inch of compost to dry out between waterings. Begin feeding with a balanced liquid fertiliser once you see signs of active new growth. As the flowering season approaches, you might switch to a fertiliser higher in potassium to promote blooms.
Gradually acclimatise plants to outdoor conditions. For the first week or two, keep them in a sheltered spot outdoors, bringing them in at night if frost is still a risk. This hardening-off process prevents shock and prepares them for full sun and wind. For Pelargoniums, this is typically done after the last frost date in your area, which varies by region. By following these steps, your geraniums will be revitalised and ready to provide colour throughout the summer.