We’ve had a mild autumn so far but who knows what we have coming our way this winter? Many gardeners love to grow exotics — some to feel as if they’ve been transported on holiday when they step into their own garden, others to push the boundaries of what can be grown in the UK. Hardy palms, agaves, bananas, tree ferns, oleanders, citrus, olives, tender salvias and cannas look brilliant in small gardens and do particularly well in the protected microclimate of a town or city.
However, it’s always good to play it safe and to get a plan in place to protect non-hardy plants before temperatures plummet. Plants will either be grown in containers or in the ground. If they are in containers they can be moved around for best protection (I use a sack trolley). If they get potted up every few years into larger containers (as they should), they’ll probably get to a stage where they can no longer be moved and will have to be protected in situ.
If you do move a pot, consider where you are going to move it to for protection. If you have a greenhouse or conservatory, happy days. If you are considering getting a greenhouse, overwintering exotics is one of its key functions and it’s a time of year when you will have some space for them. If you have a conservatory ideally it should not be centrally heated. The warm dry air and change in temperature between day and night in a centrally heated space can shock plants and do more harm than good. A shed can be perfect too, particularly one with windows to give plants some light.
If you don’t have a greenhouse or conservatory, place pots close together in the most protected spot you can find outside. For most plants light isn’t as important in winter as the ambient temperature and protection from cold winds will be. A shady spot such as a side alley or a basement well is fine. Also consider a corner of the garden where two walls meet or under a large, ideally evergreen, tree or shrub, to reduce the degree of ground frosts. Place pots on feet or bricks — anything to raise them a little off the ground to ensure drainage and air circulation, and to stop them freezing to the ground and cracking.
You could buy or make a temporary structure such as a polytunnel. These are easily made from a bent plastic pipe or a wooden frame clad with plastic sheeting or bubble wrap. Or make a simple lean-to against a wall. If you do use plastic, make sure that plenty of air can circulate around each plant to avoid fungal issues.
If tender plants are grown directly in the ground, protect them in situ. In milder areas, wrap plants with fleece (which can be bought in rolls) or use ready-made fleece bags. Secure them well with string or wire as they will easily get blown off in the winter winds.
Protect plants using hessian and fleece
GAP PHOTOS
Hessian sacking works well for the trunks of larger plants such as tree ferns — again, it’s important to make sure they can breathe. Never wrap plastic or bubble wrap straight onto a plant, as it can make them sweat and rot off. For colder areas, make a simple framework around the plant using chicken wire and stuff it with dry straw for insulation. This works particularly well with palms and tree ferns.
Here are the key plant groups that may need protecting.
• Read more expert advice about gardening
Bananas
Musa basjoo grows tall and has large leaves
ALAMY
The hardiest banana and most common is Musa basjoo, which develops a tall trunk and throws out huge dramatic leaves if protected in situ. If left it will die back into the ground like a regular perennial and in most areas will regrow from the base in spring. Less hardy bananas such as Ensete ventricosum ‘Maurelii’ (Ethiopian black banana) and other Musa varieties will need to be dug up, potted up, overwintered (ideally indoors) and planted out each year.
Tree ferns
Tasmanian tree fern is best in unpotted
ALAMY
There are plenty of tree ferns out there for the enthusiast. I lost a beautiful black tree fern (Cyathea medullaris) in the Beast from the East winter of 2018, when temperatures dropped well below freezing. Yes, I did everything I could to protect it, but sadly it didn’t make it. The hardiest is the Tasmanian tree fern (Dicksonia antartica), which to me looks plain wrong growing in a pot, so I would always plant into the ground and protect in situ. Protect the crown and croziers (new leaves inside the crown) by folding the leaves over the crown and then use fleece; in colder areas build a chicken wire and straw structure, again aiming to protect the crown primarily, more than the trunk.
• Why every garden needs fabulous ferns
Palms
The hardiest of all palms is Chusan
ALAMY
The Chusan palm (Trachycarpus fortunei) is the toughest and most hardy palm, yet still may need protection, especially when young (palms tend to get hardier the more mature they get). The dwarf fan palm (Chamaerops humilis) and Canary Island date palm (Phoenix canariensis) are commonly grown but not as hardy as the Chusan palm. Brahea armata (Mexican blue palm) is a beautiful grey-blue palm but will require protection in most gardens.
Olives, oleanders, yuccas, agaves, dasylirion and aloe
These plants vary in hardiness depending on species and variety. Many can cope with cold conditions but won’t survive prolonged periods of cold and wet. Only grow them where drainage is particularly sharp or in well-drained pots (add lots of grit). If you can move them, do. If not, protect in situ using fleece.
Citrus
Citrus trees need less watering and feeding
GAP PHOTOS/MATTEO CARASSALE – DESIGN: FLORICULTURA CHIARAVALLI, ITALY
Move into a light but cool space (a cool greenhouse is ideal), avoiding central heating. Reduce watering and feeding.
Cannas and gingers
Cannas and gingers work really well together in the garden with their exotic foliage and late-summer flowers. They are both perennial, so will die right down to the ground in autumn and the treatment for both is roughly the same. In milder areas, you can leave them in the ground. When the foliage goes black, simply cut the leaves off to about 15cm above ground and then apply a deep mulch of at least 10cm of organic matter (compost or straw is good).
• How to protect your exotic plants this winter
In cold regions, it’s best to lift them to be safe. Cut the foliage back to 5cm, then dig the plant up, shaking off the excess soil and letting them dry out for a week or two. Then place the root balls (not touching each other if there’s more than one) into a large cardboard box with punched holes, putting it somewhere dark that ideally won’t drop below 10C. Mist rhizomes occasionally (especially if shrivelling) to stop them drying out. You could, after they dry out, pot them up with a peat-free compost mix and keep on the dry side (again, water occasionally). They’re then ready to go next year — just water, and feed come spring to revive them, so they grow on and are ready to plant out after the final frosts in spring.
Comments are closed.