Grapes in a cold climate – prune hard and keep under cover

 “The sweetest grapes hang highest” goes that famous old proverb. Except, of course, if you happen to garden in Ireland, in which case the sweetest grapes are almost certainly going to be those grown under cover of a conservatory, glasshouse or polytunnel. This is because, very much like its gastronomic soul-mate the olive tree, the grapevine loves the kind of long growing season, prolonged summer heat and bright sunlight rarely provided by an average Irish growing year.

So while the vines will crop reliably in many other European countries including parts of the UK, our damper, cooler climate makes it a gamble to grow them outdoors. There are exceptions to this rule. The most notable is the red wine grape variety now known as Rondo, an exceptionally hardy, disease-resistant, productive, early-ripening cultivar introduced into cultivation as a result of a Czech/German breeding programme.

Rondo aside, there are handful of other grape varieties that have also proven themselves capable of cropping outdoors in Ireland in a warm summer, when grown in a mild, sheltered garden and trained against a sunny wall or pergola, although none with quite its exceptional hardiness, productivity and disease-resistance. These include Madeleine Angevine, Solaris, Vanessa, Phoenix, Regent,Monarch and Findling.

However, for those of us who cannot provide such benign outdoor growing conditions, or indeed those who could, but would prefer to keep these favoured, sheltered spots for growing other choice plants, the solution is to grow your grapevine under cover. This provides the kind of summer heat and shelter (especially from rain) that grapevines enjoy, while allowing Irish gardeners the opportunity to experiment with some delicious dessert-grape varieties such as Muscat Hamburg, Lakemont, Flame, Chasselas Doré de Fontainebleau or Muscat of Alexandria. You will also have less of a problem fending off greedy birds and other garden wildlife that are otherwise only too happy to help themselves to the sweet, ripe fruit.

Whether you decide to grow your grapevine outdoors or under cover, late November-early December is a good time to plant one. Don’t be put off by a lack of space. Kept carefully watered, pruned and trained, grapevines will grow just fine in large tubs/containers. In fact, while the resulting crops won’t be as large as for plants growing in the ground, this method has several great advantages. Not only does the resulting root restriction curb the vine’s naturally exuberant growth but it also makes the time-consuming tasks of pruning, training, and thinning the bunches a whole lot easier, plus their compact size means that container-grown plants are suitable for even small glasshouses.

Bear in mind though that a grapevine’s root system needs a period of winter chilling, so you’ll need to move these pot-grown plants outside in winter before bringing them back under cover in spring to protect the leaves and blossom from damaging frosts.

Container-grown plants aside, the same requirement for winter chilling means that grape vines grown under cover should be planted with their root system just outside the structure. The vine can then be trained to grow through a suitable gap or under the frame of a glasshouse/polytunnel. As regards the ideal growing medium, the most important requirement is that it should be free-draining and fertile but not overly rich, as the latter can increase the likelihood of pests and disease.

In fact, the grapevine’s vulnerability to pests and diseases is probably the only drawback to growing it under cover, as glasshouses/polytunnels/ conservatories provide exactly the sort of sheltered conditions conducive to the spread of various mildews, mealy bug, scale insects and red spider mite. For that same reason, good garden hygiene – careful ventilation, pruning only in cold weather, the quick disposal of decaying plant matter, a diligent annual spring scrub-down of surfaces and supports – is a must.

Some organic growers also use biological methods of control (see koppert.com). Once your vine is in growth, a monthly liquid seaweed feed will help to keep plants healthy and well-fed. Again, for reasons of disease, don’t apply this directly on to the plant but on to the soil above its root system. To aid pollination of the flowers in spring, gently shake the stems.

To keep these sprawling, fast-growing plants productive and happy, you’ll need to provide a sturdy support system and follow a careful pruning and training routine (the best time for pruning is now). Commercial growers use what’s known as the Guyot system, but home gardeners growing grapevines against a wall or under cover generally use what is known as the rod and spur system.

Container-grown plants will also need to be pruned hard and trained as standards/cordons/“umbrellas” on to low supports (detailed instructions for these pruning techniques can be found on the website of the RHS (rhs.org.uk). All going well, you’ll be able to savour the taste of your very own grapes by early autumn, which is when all that hard work suddenly becomes very worthwhile. It’s not called the fruit of the gods for nothing.

This week in the garden: With winter really beginning to bite, it is time to keep an eye on any tender or half-hardy plants such as pelargoniums, salvias, aeoniums, ornamental bananas or echeverias that you may have recently moved under cover of an unheated glasshouse or polytunnel. On especially cold nights, it’s wise to give these overwintering plants extra protection in the shape of a layer or two of horticultural fleece. Only water lightly and very occasionally so that their root systems don’t sit for too long in cool, wet compost, and avoid sudden leaps in temperature/humidity by ventilating your glasshouse/polytunnel on sunny days.

Now in his 90th year, English rose breeder David Austin is famous for the hundred of supremely garden-worthy varieties, known worldwide as English roses, that he has introduced into cultivation, and which are prized for their scent, the beauty of their blooms, and their ability to repeat-flower. Some of the newest include Olivia Rose Austin (soft pink), Lady of the Lake (blush-pink), The Lark Ascending (apricot) and Tranquillity (white). Available from most good Irish garden centres, November is a good time to plant any of these roses (either as potted or bare root specimens) making sure to give them a very fertile, weed-free soil in full sun. See davidaustinroses.co.uk.

Dates For Your Diary: Friday, November 25th (8pm), Airfield Estate, Overend Way, Dundrum, Dublin 14: Exbury Gardens: Heaven with the Gate Open?, an RHSI lecture by its former head gardener John Anderson, the Irish-born plant hunter who earlier this year became head gardener of Windsor Great Park, see rhsi.ie. Saturday, November 26th, National Botanic Gardens, Glasnevin: members of the Irish Society of Botanical Artists whose work appears in the recently published Plandaí Oidhreachta (the beautifully illustrated book on heritage Irish produced by the Society of Botanical Artists and the Irish Garden Plant Society, as well as in the exhibition of the same name (also on show in the garden’s visitor centre until December 4th), will give demonstrations of their various painting techniques as well as talks in the gardens auditorium, see botanicgardens.ie and irishgardenplantsociety.com for details.