Thompson Seedless grape

Sun

Full sun, ideally at least 8 hours daily; choose a warm, sheltered position.

Water

Water deeply during establishment and dry spells, particularly from flowering through fruit swelling. Avoid waterlogged soil and frequent shallow watering.

Soil

Deep, well-drained loam is ideal; tolerates sandy or gravelly soils if watered appropriately. Avoid poorly drained ground.

Height

10-20 ft (3-6 m) on a support; longer if left unpruned

Spread

10-20 ft (3-6 m), controlled by training and pruning

Flowers

Late spring to early summer; tiny greenish flowers in branching clusters.

Foliage

Broad, lobed green leaves, often turning yellow in autumn.

Growth

Fast once established

Care needed

High

• Heat tolerant
• Wildlife
• Edible

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Hard

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   2 ft (0.6 m)

2. After 1 year

   3 ft (1.1 m)

3. After 2 years

   5 ft (1.5 m)

4. After 3 years

   6 ft (1.8 m)

   full size

About 3 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Toxic

Growth rate

Fast

• Install a sturdy wire trellis, pergola or arbor before planting, and tie young shoots loosely to it.
• Water deeply through the first two growing seasons; give established vines extra water during prolonged dry weather.
• Apply compost in spring and use fertilizer only where growth or a soil test indicates a need; excess nitrogen encourages leaves rather than fruit.
• Mulch the root zone, keeping mulch clear of the trunk.
• Remove flowers during establishment and thin heavy crops so the vine can ripen its remaining bunches.
• Use wildlife-safe netting or individual bunch bags as fruit ripens, checking regularly for trapped wildlife.

Pruning. Cane-prune while fully dormant, before spring sap flow: retain well-ripened one-year-old canes with roughly 10-15 buds each, plus short renewal spurs, and remove the old fruiting canes. In summer, thin crowded shoots and shorten excessive growth while retaining enough leaves to shade and feed the fruit.

Cut whole bunches in late summer or autumn when berries are sweet throughout the bunch, pale green to golden, and easily detached; grapes do not become sweeter after picking. Taste several berries rather than judging by colour alone. Expect the first substantial crop about 3-4 years after planting, sometimes later in cool conditions.

Winter

Cane-prune dormant vines and inspect the trellis, wires and ties.

Early spring

Plant dormant vines when the soil is workable; renew mulch and apply compost.

Late spring

Select and tie in strong shoots, remove surplus shoots, and watch for mildew.

Early summer

Thin excessive bunches after fruit set and water during dry spells.

Late summer

Protect ripening bunches from birds and wasps, and taste berries to assess ripeness.

Autumn

Finish harvesting and remove fallen diseased leaves and shrivelled fruit.

• Train over a sturdy pergola for summer shade and hanging fruit, with winter sunlight returning after leaf fall.
• Grow along horizontal wires against a sunny wall to capture warmth in cooler gardens.
• Use as a productive screen on a strong freestanding trellis beside a vegetable garden.
• Train over an arbor at the entrance to an orchard or edible garden.

Garden styles it suits: Mediterranean, Potager (kitchen garden), Edible landscape, Homestead, Modern courtyard and Farmhouse.

Plant it with: Lavender, Thyme, Rosemary and Yarrow.

Wildlife: Birds and mammals eat ripe grapes; wasps and other insects feed on damaged berries. The leafy canopy provides shelter for small garden animals.

• Powdery mildew: white powder on leaves and berries can spoil the crop. Thin shoots for airflow and, if needed, use a locally approved grape fungicide according to its label.
• Downy mildew and bunch rot: humid, wet weather encourages leaf damage and rotting fruit. Keep the canopy open, avoid overhead watering and remove infected material.
• Birds and wasps: ripening berries attract feeding damage. Use wildlife-safe netting or bunch bags and remove split or damaged fruit promptly.
• Poor ripening or few grapes: insufficient summer heat, shade, overcropping or pruning every cane back to short spurs can reduce production. Choose the warmest sunny site, cane-prune and reduce the crop load.

Grapes and raisins can cause life-threatening kidney injury in dogs; keep all fruit, dried fruit and harvest waste out of reach and seek urgent veterinary advice after ingestion. Comparable poisoning is not established in cats or horses, but do not offer them grapes or raisins. Ripe fruit and properly prepared leaves are edible for people.

• Niagara grape (Vitis 'Niagara')

  Also produces pale green grapes, but its berries normally contain seeds and have a pronounced musky aroma and slip skins.

• Concord grape (Vitis 'Concord')

  Has similar climbing growth and lobed leaves, but ripe berries are dark blue-purple, usually seeded, and have thick slip skins.

• Virginia creeper (Parthenocissus quinquefolia)

  Has leaves divided into five separate leaflets, rather than a grapevine's single lobed leaf, and small blue-black berries that are not edible.

The name commemorates William Thompson, who helped establish this grape in California; Vitis vinifera means wine-bearing vine.

Propagation. Take hardwood cuttings from healthy dormant one-year-old wood, or layer a low-growing cane. Cuttings preserve the cultivar, but in regions with grape phylloxera, buy certified vines grafted onto suitable resistant rootstocks.

Accepted botanical name

Vitis vinifera

In the US and Canada

Introduced in the lower 48 states, Pacific Basin and Puerto Rico.

Native range

Albania, Austria, Bulgaria, Corse, Cyprus, Czechoslovakia, France, Germany, Greece, Hungary, Iran and Iraq.

Measured

Soil pH 7 to 7.5. Average height 2000 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.