Protecting plants from the first frosts of autumn

The barometer was at its highest for months and while the days were sunny and warm, the nights became progressively colder.

Then it happened: last week we had our first frost. It was just a light one that day but the following morning we were greeted by a liberal sprinkling of dazzling white frost crystals, sparkling in the morning sun.

By Sunday it was all forgotten; the barometer plummeted, the rain came and with it much milder weather. When will it return? Who can tell? But return it will and next time it will be harder.

Last year we were caught out and lost several precious plants to a sudden cold snap. This year we have been planning ahead, lifting tender specimens and placing them under cover. We have rooted precautionary cuttings and begun mulching some of the plants which are on the border line of hardiness in our region and in our soil.

Lemons cannot be grown out of doors in central France and last year we lost two fine specimens in spite of providing fleece covers. It was the best we could do at the time: the plants were far too large to have in the house and the old metal and glass conservatory was full of office equipment; the log cabin was not yet built. This year we have a lovely new Lemon plant and have already moved it to the conservatory which, although unheated, will give sufficient protection for the time being. The conservatory is more than 100 years old and keeps much of the north side of our house dry and warm. We have replaced many panes of ancient broken glass and it should be cosier this year, in spite of a rusty door which fails to close completely. We have several dozen plants sheltering there, ranging from recently potted cuttings to established specimens in substantial pots. Bedding Geraniums have been gathered together in trays of home-made compost.

The recently built log cabin classroom is the second building which will be pressed into support of tender plants. It is a large structure with a covered, but open sided patio area occupying 25% of the floor space. By using this patio, some protection can be provided in reasonably light conditions. I also propose building a bench in the cabin by a large, south facing window for cuttings currently rooting in the tunnel under the loft skylights in the main house. I have installed electric heaters which, because of the superb insulation of the thick wooden walls, will keep the temperatures up at minimum expense. If Garden Design Academy students or other guests need to use the cabin before the spring, I trust they will understand that in this household of gardeners the plants always come first!

Over most of our garden the soil has a light, sandy texture. The drainage this provides in winter is very helpful to plants which might otherwise rot at the roots. We leave Gladioli and Dahlias in the ground without problem for instance, something which would have been risky in our previous garden in England. In one bed in the rear garden we have many plants from the Mediterranean, north and South Africa and from South America, including Salvia argentea and Aloysia citrodora, which have overwintered each year without problem. Just in case, I have recently sown home-produced seed of the Silver Clary and taken cuttings of Lemon Verbena, but I hope not to needthem and give the plants away next season.

A couple of cultural techniques have proved of value when overwintering half-hardy plants. I do not prune tender plants until the frosts have gone, allowing the foliage and stems produced last season to protect the shoots and buds which will grow next year. This is especially true of late-blooming plants which would have little chance to regrow if pruned after flowering. Cistus, Convolvulus cneorum, Lagerstroemia and Lavatera are examples of plants which I delay pruning until the spring.

We use leaf mould, generously collected and left in vast heaps around the outskirts of town by the local authority, both as free compost and as winter protection for tender plants. Delicate roots are given a liberal mulching and if heaped up around and over stems, these too benefit from the protection this provides. Where taller branches need similar treatment we use hay, straw and the stems of ornamental grasses, secured with twine if necessary. Our Olive bush was buried in Miscanthus stems last year and came through temperatures down to -17°C.

I love this region of France for its seasons, bringing daily changes to the plants we grow and to those growing wild in the countryside around us. By taking a few precautions, plants which a more reasonable gardener would never attempt, sail through the winter and provide a wider range of gardening experiences than if our choices were more conservative.