Andy's Adventures in Gardening: Frost, friend or foe?

After what seems like weeks of soggy wet weather the temperatures plummeted, and I awoke to find the garden transformed into a winter wonderland etched with frost. Milky sunlight slowly made the leaves and grass sparkle as shades of the softest blue filtered through an opaque sky. Probably my first thoughts should have been for those plants I’ve left unprotected from a few degrees of frost, but the beauty of the winter landscape was too much, and I headed out to admire the short-lived handiwork of the frost’s icy fingers.

A few years ago I worked on a book on The Winter Garden with the late Jane Sterndale-Bennett. Two things I remember vividly from that experience: Firstly Jane’s use of good, basic evergreen shrubs to hold the winter garden picture together. Yes, she loved her winter treasures, but plants like euonymus, elaeagnus, ligustrum and evergreen prunus were her winter garden basics. Secondly, I remember the raptures of Robin, the designer of the book; over pictures of frost edged hellebore leaves, which she described as “fabric”. Since then I always look at frosty shrubs and evergreen perennials, and imagine them as tapestry, brocade, garden embroidery. In some ways I think this frosted detail shows them at their best.

One of my favourite plants on a frosty morning is the evergreen Viburnum davidii. It has the most incredible forged metallic foliage on any day but etched with frost it is surreal. It looks like a tropical plant straight from a Rousseau painting; I expect a snow tiger to pounce at any moment.

I love the ruby foliage of any of the leucothoes in frosty weather. In winter they turn ruby and crimson, overlaid by a white sugar coating in the early winter morning light. Pittosporum ‘Tom Thumb’ is even deeper in colour; shining purple black in the winter months; it’s curious how the frost crystals seem even longer on the edges of these small leaves. Equally dark and dramatic, but this morning like metallic ribbon at ground level, the black grass-like Ophiopogon planiscarpus ‘Nigrescens’ shines amongst the grey frozen leaves of Cyclamen coum.

I know many consider them as retro, old fashioned or rather vulgar I must admit I’m a great fan of cortederia, the pampas grass. Not the big, tall untidy varieties but the shorter more weather resistant Cortederia selloana ‘Pumila’ which grows to around 2 metres (6 feet) when in flower. I think it’s a great plant for its curled grass foliage, even though I hate handling and cleaning it, and its plumes are really stunning in autumn and winter on a frosty morning. Visitors to the garden in summer raised their eyebrows and declared they thought it was only now planted outside houses to indicate a different type of adventure? I have to admit I just love it for its ornamental qualities – honestly!

I always say that there is just nothing appealing about a potentilla in winter. Left untrimmed they are just a mass of brown stems and faded flowerheads waiting for a short back and sides. However a frosty morning changes my opinion completely; rarely do you see anything quite so beautiful as that complex bronze silhouette sparkling in the sunlight.

The low, horizontal cold light of a winter morning really lights up the white bark of birch trees in the garden. The small multi-stemmed Betula utilis var. jacquemontii we planted on the rock bank by the pool is really starting to have a presence in the garden, and it looks stunning now the leaves have fallen. This is a proper multi-stem grown from a single plant cut back as a sapling, rather than several whips planted close together. We have carefully cut out any branches which cross over in the middle of the tree and confuse the silhouette and conceal the stems. This has to be done in early winter as soon as the leaves have fallen, or in summer when in full leaf. If you prune in late winter, or early spring, birches bleed furiously.

Coming back to those hellebore leaves, I have a number of plants of some newer hybrid hellebores waiting for a milder day to be planted. These are some of the Helleborus x nigercors types and also Helleborus ericsmithii and so forth. I particularly like one called ‘Monte Cristo’ which has a bluish tinge to the foliage and pink leaf stalks and pink flushed flowers. ‘Merlin’ has particularly stunning dark green leaves that are attractively veined. Both looked amazing with the frost on them: they would make stunning curtains.

So what precautions should you take to protect plants from frost? The most vulnerable plants in my garden are the more tender subjects in pots. Where I can I move these up against the walls of the house under the eaves. This keeps off the winter wet and helps to protect against wind chill; often the most damaging blow for frozen plants.

Subjects such as cordylines and phormiums can be protected with horticultural fleece. If you are using this either use two or three layers of lightweight fleece or a layer or two of the heavier weight. Single layers of light fleece are not very effective. The fleece sleeve jackets are best for slim plants or those with long strappy leaves. Gather the foliage loosely together with a strip of fleece first and then slip the sleeve over the plant.

I must admit I only really use fleece to protect plants close to the house where they can’t be seen. For me the look of the garden in winter is all important so I tend to take a risk rather than detracting from the appearance of the picture. It’s a bit like wearing uncomfortable shoes really: sometimes you have to suffer for beauty! I suppose the beauty of frost for me is more of a friend than a foe?