Grapevine

Light and exposure

The grapevine needs all the sun it can get. Reserve the warmest wall in the garden for it, the one that catches the midday and afternoon sun, due south in the northern hemisphere and due north in the southern one, against which it will be trained: the stone or brick gives back the day’s heat at night and gains the degrees a cool summer lacks. A well-exposed pergola or arbor also does the job and gives shade under the vine as a bonus.

Avoid damp bottoms of the garden and poorly ventilated corners. The grapevine wants direct light on the bunches and air circulating around the foliage. A spot sheltered from cold winds, backed against a building, brings together the best conditions in a cool climate. In a very hot one the requirement reverses: there it is midday shade that saves the berries from sunburn.

Watering

Once established, the grapevine roots deeply and copes well with drought. For the first two years, water regularly while the root system goes down, especially in a pot or against a wall that dries out the base quickly. After that, a generous watering during long dry summer spells is enough, at the base and never on the foliage.

Beware of excess water more than of shortage. Constantly waterlogged soil favors disease and dilutes the sugars in the grapes. At the end of the season, when the bunches change color, keep the vine on the dry side: water stress concentrates the sugar and clearly improves the taste.

Soil and repotting

The grapevine is not demanding about soil richness, it even prefers poor, stony, well-drained ground to rich soil that makes it run to leaves at the expense of fruit. Soil too rich in nitrogen gives an exuberant climber and little fruit. The key is drainage: it hates standing water around the roots.

At planting, work the soil deeply because the roots go far down. If your soil is heavy and clayey, improve drainage with gravel and sand, and plant on a small mound if needed. A dose of well-rotted compost is amply enough, no need to overdo the fertilizer.

Temperature and humidity

The grapevine stock is perfectly hardy in a temperate climate and spends winter outdoors without protection: it takes severe frosts once the wood is ripened, the dormant buds hardly suffering above -15 to -20 °C. So it is not winter cold that poses a problem, unlike many tender fruit trees; it only becomes decisive again in a harsh continental climate, where you switch to hybrid varieties.

The sensitive point is summer heat and its duration. The grapevine needs a long warm season to ripen, and a mild, short summer limits it. Late spring frosts can also scorch the tender young shoots at budbreak, for as long as the frost season is not over: against a warm wall, this risk drops clearly. At the opposite end, past 30 °C in the canopy the vine slows its photosynthesis and the sugars stop rising.

Pruning and upkeep

Winter pruning is the key to fruiting and it must be rigorous. The grapevine only fruits on the current year’s shoots arising from one-year-old wood, so that wood must be renewed every winter by pruning short. Adopt a Guyot or cordon training: keep a few spurs with two or three buds and a replacement cane, and remove everything else. Prune in full dormancy, before the sap rises, otherwise the vine bleeds heavily.

During the growing season, green pruning takes over and counts just as much. Trim back shoots that grow too long to concentrate energy on the bunches. Above all, remove leaves around the bunches from veraison on to expose them to sun and air: this is what ripens and dries them, and limits rot. Leaf removal is judged by climate, generous where sun is short, cautious and limited to the less exposed side where the berries risk sunburn. Also remove the laterals and the surplus bunches to keep only what the vine can bring to maturity in your climate.

Pests and diseases

In a damp climate, the grapevine has two major enemies, both fungal. Downy mildew (Plasmopara viticola) covers the top of the leaves with oily yellow spots and the underside with a white felting, and can wipe out the bunches in mild, wet weather. Powdery mildew (Erysiphe necator) forms a grey powdery felting on leaves and berries, which split and rot. A mild, humid summer is a dream ground for both diseases, a hot dry one calms them markedly.

Two strategies. The best, choose resistant varieties from the start, called hybrid or interspecific, which need little or no treatment, a real comfort in a rainy region. Otherwise, on a classic susceptible variety, you must treat preventively from spring, Bordeaux mixture against downy mildew and sulfur against powdery mildew, renewing after rain. In every case, air the vine through pruning and leaf removal, dry air is your best ally.

Propagation

The grapevine propagates very easily by cuttings, it is the simplest route. In winter, during pruning, take pieces of well-ripened one-year wood, twenty to thirty centimeters long with three or four buds. Keep them cool in sand until spring, then plant them in a pot or in the ground with a single bud sticking out. The take is generous.

Layering also works very well: peg a long flexible shoot down to the ground in spring, bury part of it leaving the tip out, it roots within the year and is separated the following winter. For varieties grafted onto a phylloxera-resistant rootstock, note that cuttings reproduce the variety but not the root protection: for a few vines in a garden the stake stays low, but where phylloxera is established an own-rooted plant eventually declines and a grafted plant from the trade is safer.

Month-by-month care calendar

Green Hub tips

• Choose an early, disease-resistant variety from the start, called hybrid or interspecific: in a short, damp climate, that is what changes everything.
• Train the grapevine against the warmest wall in the garden, the one that catches the afternoon sun: the heat given back at night by the masonry ripens a grape that would stay sour out in the garden.
• Do not be afraid to prune short in winter. The grapevine fruits on the current year’s wood arising from one-year wood, timid pruning gives lots of leaves and little grape.
• Remove leaves around the bunches from veraison on: sun and air ripen the berries and cut the ground from under downy mildew. In a very hot climate, go lighter so the berries do not burn.
• Always taste a berry before harvesting. A grape picked by eye, on its color, is often still sour: it is the sugar that decides.