In brief: Dark storage is suitable for plants that need a genuine dormant phase. They stop growing in autumn. These include container plants such as angel's trumpet, fuchsias and geraniums. Move them into a cool, dark room such as a cellar, garage or shed before the first frost. The temperature should remain consistently between 5 and 10°C. Water the plants only occasionally to prevent the roots from drying out. Fertilising is not necessary.
How to overwinter plants correctly: understanding dark storage
Many garden plants are not hardy. They cannot survive frost outdoors. The solution is a protected winter location. However, not all plants need light. For some, darkness is the key to successful overwintering.
Dark storage means a cool, frost-free room without daylight. Typical locations include cellars, garages, garden sheds or dark outbuildings. This method replicates the plants' natural dormant phase in their native habitat.
You save energy and space. Overwintering in a bright location is often more involved. Choosing the right winter location can determine whether your plants survive.
Which plants belong in dark winter storage?
Not every plant can tolerate a dark winter location. The selection is clear. These are species that shed their leaves or die back completely above ground.
Classic candidates for cellars and garages
The best-known plants for this method include angel's trumpets. They lose their leaves in autumn. Fuchsias also go dormant. Geraniums, technically pelargoniums, are another classic choice.
Ornamental bananas shed their large leaves. Only the rootstock survives. Lantanas and hibiscus can also be overwintered in the dark. The decisive factor is a complete stop in growth.
Important note
Evergreen container plants such as oleander, olive trees and bay laurel do not belong in dark storage. They also need bright light in winter to maintain their leaves. A dark room would weaken them and cause leaf loss. A cool but bright conservatory or hallway is ideal for them.
Recognising the plant's signals
Observe your plants in late summer. They will show whether they are ready to go dormant. Growth stops. The leaves turn yellow and fall off. No new shoots develop.
This is the right time to move them into their winter location. Do not wait for the first frost. Bring the plants indoors when night-time temperatures are around 5°C. You can find the right autumn garden care in our garden tools category.
How to prepare plants for dark storage
Moving plants into their winter location requires preparation. Proceed step by step. This helps prevent pests and rot.
Pruning and health check
Prune the plants before moving them indoors. Remove all wilted leaves and dead shoots. Shorten long branches by around one third. This reduces the surface area vulnerable to fungal diseases.
Inspect the plant thoroughly for pests. Look out for aphids, mealybugs or spider mites. Treat any infestation while the plant is still outdoors. In an enclosed room, pests can spread explosively. You can find helpful products in our plant protection section.
The most common mistake is giving plants too much water in winter. The roots are cold and wet, but cannot absorb much water. This inevitably leads to rot. In this case, less is definitely more.
Checking pots and choosing a location
Remove old leaves and soil from the pots. Place them on wooden slats or polystyrene boards. This provides insulation against the cold floor. Make sure there is enough space between the pots.
Air must be able to circulate. Choose the darkest area of the room. Avoid locations next to heating pipes or appliances that give off heat. The aim is to maintain a consistently cool climate.
Expert tip
Label your pots with the plant name and the date they were moved indoors. After months in the dark, you may no longer recognise the species. A waterproof pen on a wooden stick is useful. Also note any specific care instructions. This makes winter checks easier.
The perfect conditions for winter storage
Temperature, light and humidity all need to be right. Create a stable microclimate. Fluctuations stress the plants.
Finding the right temperature
Five to ten degrees Celsius is ideal. Check the temperature regularly. A simple thermometer is sufficient. Temperatures below zero are not permitted. A garage can also freeze through.
Temperatures above twelve degrees wake the plants too early. They then produce long, pale, leggy shoots. These are susceptible to disease. Consistent cool temperatures keep the dormant phase stable.
Darkness does not mean complete blackness
Absolute darkness is not necessary. A small amount of subdued light from the hallway does no harm. However, avoid direct daylight. It could disrupt the plants' rhythm.
You can darken cellar windows with an opaque cover sheet. Make sure the sheet does not collect condensation. Moisture on the plants encourages mould.
Many people forget about humidity. The air in heated cellars is often too dry. This causes root balls to dry out more quickly. A bucket of water in the room or a damp cloth on the radiator can help.
Caring for plants during dark overwintering
The plants are sleeping, but they are not dead. Minimal care is still necessary. Check them at regular intervals.
Watering correctly during winter dormancy
Water very sparingly. The root ball should remain slightly moist, never wet. Push your finger two centimetres into the soil. If it feels dry, add a little water.
For most plants, a small amount every four to six weeks is enough. Use water at room temperature. Ice-cold tap water shocks the roots. Pour the water directly onto the soil, not over the plant.
Checking for pests and rot
Inspect your winter storage area once a month. Look for wilted leaves on the floor. Remove them immediately. They provide breeding grounds for fungi.
Lift a few pots. Do they feel unusually light? The plant may need some water after all. Does it smell musty? This may indicate root rot. If so, move it to a drier location immediately.
Additional advice
Use the winter months to maintain and clean your garden tools. Sharpen shears, oil wooden handles and check watering cans. You can find everything you need in our range of garden equipment. This means you can start the new season fully prepared.
Products That Make Overwintering Easier
The right equipment makes plant care easier. From storage to protection.
For valuable container plants or sensitive specimens, sturdy, insulated storage can be a sensible choice. A
For cleaning pots and tools before storing them, a mild yet effective cleaning product is recommended. The
is pH-neutral and removes traces of soil and algae without harsh chemicals. This helps prevent fungal growth.
For large, immovable containers outdoors or for covering storage areas, sturdy privacy screens are practical. The
Bringing Plants Out of Winter Storage and Back into the Light
By the end of March, the time has come. The days are getting longer. Carefully bring your plants out of the dark. A sudden change can stress them.
Choosing the Right Time
Wait until the hardest frosts are over. The Ice Saints in mid-May are a useful guide. However, start preparing earlier. From the end of March, initially place the plants outdoors for just a few hours in a shady, sheltered spot.
Gradually increase the time outdoors over two weeks. This process is called hardening off. It prevents sunburn on sensitive new shoots. The tender leaves are not accustomed to bright light.
Repotting and Fertilizing at the Start of the Season
After winter storage, it is the ideal time to repot. Check the root ball. If it is completely root-bound, move the plant into a slightly larger pot with fresh soil.
Only start fertilizing once the plant is producing vigorous new leaves. Use a balanced liquid fertilizer. Begin with half the recommended concentration. This is how to overwinter your plants properly and keep them healthy for the next gardening season.
Frequently Asked Questions
- Which plants can I overwinter in the dark?
- Dark storage is suitable for tender container plants that enter a pronounced dormant period. Typical examples include angel's trumpets, fuchsias, geraniums (pelargoniums), hibiscus, ornamental bananas and lantana. These plants often shed their leaves or die back completely. Evergreen plants such as oleander and olive trees, on the other hand, need a bright winter location.
- How often should I water plants in a dark winter storage area?
- Water very sparingly in a dark winter storage area. The root ball should remain only slightly moist and never wet. Check the moisture level every four to six weeks. For most plants, a small amount of water once a month is sufficient. Waterlogging quickly causes root rot because the plants evaporate very little water. In most cases, dryness is less harmful than too much moisture.
- What temperature is ideal for overwintering plants in the dark?
- The ideal temperature is between 5 and 10 degrees Celsius. This cool range signals dormancy to the plant and prevents premature growth. Temperatures below 0°C damage most container plants, even in the dark. Temperatures above 12°C can wake the plant too early. A consistent, cool temperature is more important than exact readings. Measure it with a simple thermometer.
- Can I fertilize plants while they are overwintering in the dark?
- No. Stop fertilizing completely during dark winter storage. The plants are dormant and do not absorb nutrients. Unused fertilizer builds up in the growing medium and can damage the roots. Only start fertilizing again when you move the plants into the light in spring and they respond with fresh growth. Then use a specialist plant fertilizer.
- When should I bring plants out of dark winter storage?
- Bring plants out of dark storage from the end of March to mid-April. Wait until no more severe frosts are expected. Initially place them outdoors in a shady, sheltered spot for a few days to harden them off. Cut back any dead shoots beforehand. Only then gradually acclimatize them to more sunlight. Bringing them out too early can cause damage from late frosts or sunburn.
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