Vanda denisoniana

RHS Plant Profile
Denison's vanda

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A large-growing, evergreen, tropical epiphytic orchid species. As a typical example of monopodial orchid, the new growth emerges from the central tip of a long rhizome, covered in leaf-bearing, green sheaths. Strap-shaped, green or dark green leaves up to 30cm long, angle out from the main stem. As new leaves emerge from the tip, old leaves lower on stem gradually fall off. Large aerial root system hangs downwards at the base of the plant, attaching to any surface is it grows. New, thick roots grow directly from the main stem, and follow the ascending growing trend. Inflorescences, up to 15cm long emerge from axils of the leaf sheaths, in late winter and spring. Each flowering stem carries 4-6 waxy flowers, approx. 5cm in diameter. A distinctive feature of this species and its hybrids is its lip: with two large, white, fiddle-shaped side lobes. Flowers are usually bright yellow, but dark yellow-orange and pale varieties occur in nature and in cultivation.

Position

Full sun, Partial shade

Max Height

1-1.5 metres

Max Spread

0.5-1 metres

Size

Time to Maturity
5–10 years
Max Spread
0.5-1 metres
Max Height
1-1.5 metres

Growing Conditions

Moisture
Moist but well–drained
pH
Neutral

Position

Full sun Partial shade
Aspect
East–facing or South–facing or West–facing
Exposure
Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

  • H1A: under glass all year (>15C)
  • H1B: can be grown outside in the summer (10 - 15)
  • H1C: can be grown outside in the summer (5 - 10)
  • H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
  • H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
  • H4: hardy through most of the UK (-10 to -5)
  • H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
  • H6: hardy in all of UK and northern Europe (-20 to -15)
  • H7: hardy in the severest European continental climates (< -20)
H1A

Colour & Scent

Fragrance Flower
Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Orchidaceae
Native to GB/Ireland
No
Foliage
Evergreen
Habit
Columnar upright
Genus
A medium to large-sized, evergreen, tropical epiphytic orchid, valued for its large, bright-coloured, long-lasting flowers, often used by florists. As a typical example of a monopodial orchid, the new growth emerges from a central tip on a long, central rhizome, while older, lower leaves gradually drop off. Strap-shaped, green or dark-green leaves, up to 60 cm long angle out from the main stem. A characteristic feature of the plant is an impressive root system that hangs downwards at the base of the plant. New roots emerge from the central stem, following the ascending growing trend. Inflorescences emerge from axils of leaves and main stem, and carry up to 8 large, waxy, round-shaped flowers.
Name Status
Unresolved
Plant Range
Laos, Myanmar, Thailand, Vietnam

How to Grow

Cultivation

For successful cultivation and frequent flowering, plants require high light levels and long, light days. In summer, they would benefit from being in a warm and bright greenhouse or conservatory, but direct, mid-day sun should be avoided. Highly absorbent, sponge-like roots are the principal water-storage organs. Dark green or purplish tips of the roots may be observed as a sign of actively growing plant. They are heavy feeders and require regular application of orchid fertiliser between spring and autumn. High air humidity (70 -80%), good air circulation and regular misiting should be provided frequently when in active growth. In cooler climates with shorter days, plants may go dormant in winter. Misting may be reduced to avoid rots, but plants shouldn't be left dry for long periods. Ideal temperature range is 15°C in winter and up to 30°C during summer months. Plants can be grown in an open baskets, or in a coarse, bark-based epiphyte orchid mix.

Propagation

Propagation by seed is only possible in a controlled laboratory environment. Mature plants produce sideshoots (keiki) which may be removed and potted separately, when the new roots (preferably 3 or more) are at least 2cm long.

Suggested planting locations and garden types

  • Conservatory and greenhouse

Pruning

Remove spent flower stems at the base. Old, ''leggy'' plants with bare stems can be cut during their active growing season to reduce the size of the plant. Cut through the rhizome, below the new developed set of aerial roots. Lowering apical dominance by laying plant horizontally, or hanging upside down will support the growth of new roots.

Pests

May be susceptible to scale insect and mealybugs. Thrips can cause damage on flowers and developing flower buds.

Diseases

Generally disease-free. Poor air movement may cause bacterial of fungal rots. Good hygiene practice and sterilising cutting tools prevent the spread of virus diseases.