Grapevine

Light and exposure

The grapevine needs all the sun it can get. Reserve the warmest wall in the garden for it, due south or south-west, against which it will be trained: the stone or brick gives back the day’s heat at night and gains the degrees our summers lack. 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 north winds, backed against a building, brings together the best conditions in our climate.

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, common in our regions, 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 Belgium and spends winter outdoors without protection, it takes severe frosts once the wood is ripened. So it is not winter cold that poses a problem in our climate, unlike many tender fruit trees.

The sensitive point is summer heat and its duration. The grapevine needs a long warm season to ripen, and our mild, short summers limit it. Late spring frosts, up to mid-May, can also scorch the tender young shoots at budbreak: against a warm wall, this risk drops clearly.

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 during dormancy, from December to February, before the sap rises, otherwise the vine bleeds heavily.

In summer, 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. Also remove the laterals and the surplus bunches to keep only what the vine can bring to maturity here.

Pests and diseases

In our 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. Our humid summers are a dream ground for both diseases.

Two strategies. The best, choose resistant varieties from the start, called hybrid or interspecific, which need little or no treatment, a real comfort here. 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 garden crop in Belgium, this has no practical consequence.

Month-by-month care calendar

Green Hub tips

• Choose an early, disease-resistant variety from the start, called hybrid or interspecific: in our short, damp climate, that is what changes everything.
• Train the grapevine against a south wall: 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 August on: sun and air ripen the berries and cut the ground from under downy mildew.
• Always taste a berry before harvesting. A Belgian grape picked by eye, on its color, is often still sour: it is the sugar that decides.