Blue Hubbard squash

Sun

Full sun, with at least 6-8 hours of direct sunlight daily; choose a warm, sheltered position in cool climates.

Water

Keep soil evenly moist, particularly during flowering and fruit swelling. Water deeply at soil level rather than frequently wetting the leaves.

Soil

Deep, fertile, well-drained soil enriched with compost or well-rotted manure; slightly acidic to neutral soil is ideal.

Height

1-2 ft (0.3-0.6 m), excluding any climbing growth

Spread

10-20 ft (3-6 m)

Flowers

Large yellow-orange flowers from summer into early autumn; separate male and female flowers grow on the same plant.

Foliage

Large, broad, roughly heart-shaped green leaves with coarse hairs, carried on long, trailing stems.

Growth

Fast in warm weather.

Care needed

Medium

• Pollinators
• Low allergen
• Edible

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

Difficulty

Moderate

Toughness

Fairly tough

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

1. Planting day

   0.5 ft (0.15 m)

2. After 1 year

   1.5 ft (0.45 m)

   full size

Full size in one season.

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

Cats and dogs

Safe

Growth rate

Fast

• Plant out only after frost danger has passed and soil has warmed to at least 60°F (16°C); harden off indoor-raised plants first.
• Allow roughly 6-8 ft (1.8-2.4 m) between plants and leave room for vines to run beyond their planting positions.
• Mix compost into the planting area, then feed according to soil fertility; avoid excessive nitrogen, which encourages leaves rather than fruit.
• Mulch once the soil is warm to conserve moisture and suppress weeds, keeping mulch away from the stem base.
• Place developing fruits on dry straw or boards to keep them off wet soil.
• If fruit repeatedly fails to set, transfer pollen from a freshly opened male flower to a female flower in the morning.

Pruning. Routine pruning is unnecessary; guide young vines into their allotted space without damaging them. In late summer, you can pinch out growing tips beyond established fruits to limit further spread, but retain healthy leaves to feed and shade the crop.

Pick mature fruits in autumn before frost, usually about 100-120 days from sowing, although cool weather can delay ripening; the rind should resist a thumbnail and the stalk should be hard and drying. Cut rather than pull, leaving several inches of stalk attached, and do not carry fruits by the stalk. Cure undamaged fruits in a warm, dry, airy place for about 10-14 days, then store somewhere cool, dry and frost-free.

Early spring

Prepare a sunny bed with compost and reserve enough space for long vines.

Mid to late spring

Sow indoors in individual pots about 3-4 weeks before your expected planting-out date.

Late spring to early summer

Harden off and plant after the last frost once soil is warm, or direct-sow in warm soil.

Summer

Water deeply, mulch warm soil and check flowers for bee visits and successful fruit set.

Late summer

Keep developing fruits off damp ground and check leaves for mildew and pest damage.

Autumn

Harvest mature fruits before frost, cure them and remove spent vines.

Winter

Inspect stored squash regularly and use any showing soft spots or deterioration promptly.

• Let vines run along the sunny edge of a large vegetable garden, away from paths and smaller crops.
• Use in a spacious potager for bold leaves, yellow flowers and conspicuous blue-grey fruits.
• Plant beside a compost-enriched growing area where vigorous seasonal ground cover is useful.
• Combine with upright edible crops in a broad kitchen-garden layout, keeping their root zones and foliage clear of the squash vines.

Garden styles it suits: Potager (kitchen garden), Farmhouse, Homestead, Edible landscape, Cottage garden and Family-friendly.

Plant it with: Sweetcorn, Sunflowers, Nasturtiums, Calendula, Borage and Dill.

Wildlife: Flowers provide pollen and nectar for bees, including specialist squash bees in parts of North America. Avoid insecticides on open flowers; bees are important for fruit set.

• Powdery mildew: white patches develop on leaves, especially later in the season; allow good airflow, avoid drought stress and remove badly affected leaves without stripping the plant.
• Squash bugs and cucumber beetles, especially in North America: inspect young plants and leaf undersides, remove insects and eggs, and use insect mesh before flowering, removing it when pollinators need access.
• Poor fruit set: cold weather, heat or limited pollination can cause tiny fruits to yellow and drop; maintain even moisture and hand-pollinate newly opened female flowers when necessary.
• Fruit rot: damp soil or damaged skins can cause decay; support fruits on dry material, improve drainage and harvest before frost damages the rind.

Normal cultivated Blue Hubbard squash is not known to be toxic to people, cats, dogs or horses. The hard rind, stalks and large raw pieces can cause choking or digestive problems if eaten. Exceptionally bitter squash may contain harmful cucurbitacins: do not eat it or feed it to animals, and discard the whole fruit because cooking does not remove these toxins.

• Queensland Blue squash (Cucurbita maxima 'Queensland Blue')

  Queensland Blue generally has a flattened, rounded shape with pronounced ribs; Blue Hubbard is usually elongated or teardrop-shaped, with tapered ends and a rougher rind.

• Buttercup squash (Cucurbita maxima 'Buttercup')

  Buttercup is usually smaller, dark green and squat, often with a distinct button at the blossom end; Blue Hubbard has a blue-grey rind and elongated, tapered shape.

The species name maxima is Latin for 'largest', referring to the large fruits produced by members of this species.

Propagation. Grow from seed, sown about 1 in (2.5 cm) deep in warm compost or soil. Sow indoor plants in individual pots and transplant while young to minimise root disturbance. Saved seed may not come true if bees have cross-pollinated the flowers with other Cucurbita maxima varieties nearby.

Accepted botanical name

Cucurbita maxima

In the US and Canada

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

Native range

Argentina Northeast, Argentina Northwest and Bolivia.

Measured

Average height 500 cm.

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