Gladiolus

Sun

Full sun; choose a sheltered position protected from strong winds.

Water

Keep the soil evenly moist during active growth, especially as flower spikes develop. Avoid waterlogged soil and keep dormant, stored corms dry.

Soil

Fertile, well-drained soil; improve heavy clay with organic matter and use raised beds where winter drainage is poor.

Height

2-5 ft (0.6-1.5 m), depending on cultivar

Spread

0.5-1 ft (0.15-0.3 m)

Flowers

Summer to early autumn; white, cream, yellow, orange, pink, red, purple and green, often with contrasting markings.

Foliage

Upright, narrow, sword-shaped green leaves that die back after the growing season.

Growth

Fast seasonal growth; spring-planted corms usually flower in about 10-14 weeks.

Care needed

Medium

• Pollinators
• Heat tolerant
• Low allergen

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

Difficulty

Moderate

Toughness

Needs looking after

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

1. Planting day

   0.5 ft (0.15 m)

2. After 1 year

   3 ft (1.1 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

Toxic

Growth rate

Fast

• Plant corms after the soil warms and frost danger has passed, about 4-6 in (10-15 cm) deep and 6 in (15 cm) apart.
• Water deeply during dry spells, keeping moisture steady while leaves and flower spikes develop.
• Mix compost into the bed before planting; use a balanced fertiliser during growth if the soil is poor.
• Insert stakes at planting time and tie tall flower spikes loosely as they lengthen.
• In cold areas, lift corms after foliage yellows and before the ground freezes; dry them, remove the old shrivelled corms, and store the new ones in a cool, dry, frost-free place.
• Where corms remain outdoors, mulch for winter protection and lift crowded clumps every few years.

Pruning. Remove spent flower spikes but leave the leaves until they yellow naturally. When cutting flowers for the house, leave at least four leaves on each plant to help replenish its corm.

Early spring

Check stored corms and discard any that are soft, mouldy or badly damaged.

Spring

Prepare a sunny, well-drained bed and plant once frost danger has passed.

Late spring

For a longer cutting season, make further plantings about two weeks apart, allowing enough growing time before autumn frost.

Summer

Water during dry weather, support flower spikes and check flowers and leaves for thrips.

Summer

Cut stems as the lowest flowers begin to open, or remove spent spikes after flowering.

Autumn

Let foliage yellow, then lift and dry corms where winters are too cold or wet for them to remain outdoors.

Winter

Keep stored corms dry, ventilated and frost-free; check occasionally for rot.

• Plant in a dedicated cutting bed for a succession of upright flower stems.
• Set small groups among dahlias and salvias to add vertical accents to summer borders.
• Use repeated groups of one colour for a more ordered, formal display.
• Grow shorter cultivars in deep containers with drainage holes, sheltered from wind.

Garden styles it suits: Cottage garden, Traditional, Formal, Potager (kitchen garden), Hot border and Romantic rose garden.

Plant it with: Dahlias, Salvias, Zinnias, Cosmos, Catmint and Ornamental grasses.

Wildlife: Open-flowered cultivars may attract bees, and hummingbirds may visit where they occur. Large, heavily ruffled hybrids are generally less useful to pollinators than simpler flowers.

• Gladiolus thrips cause silvery leaves, streaked petals and buds that fail to open. Remove affected flowers, clear plant debris and discard heavily infested corms; thrips can survive in storage.
• Fusarium corm rot causes yellowing, poor growth and brown, sunken corm lesions. Discard affected plants and corms, buy healthy stock and rotate the planting site.
• Waterlogged soil causes corms to rot. Improve drainage, use raised beds or containers, and never store damp corms.
• Tall spikes lean or snap in wind. Plant in a sheltered position and stake before the flowers become heavy.

Toxic to cats, dogs and horses if eaten, with the greatest concentration in the corms. Ingestion can cause drooling, vomiting or diarrhoea and abdominal pain; large amounts can cause more serious illness. People should not eat any part, especially the corms, which can cause gastrointestinal upset; sap may irritate sensitive skin.

• Crocosmia (Crocosmia × crocosmiiflora)

  Usually forms spreading clumps with arching, branched stems carrying smaller orange, red or yellow flowers; garden gladiolus usually has a stout, unbranched spike of larger flowers.

• Abyssinian gladiolus (Gladiolus murielae)

  Has fragrant, star-shaped white flowers with dark maroon centres on slender stems, rather than the broad, often ruffled flowers of garden hybrids.

• Byzantine gladiolus (Gladiolus communis subsp. byzantinus)

  Usually flowers earlier, with smaller magenta flowers on more slender spikes, and is generally hardier than large-flowered garden hybrids.

Gladiolus comes from the Latin for a small sword, referring to its leaves, while hortulanus means 'of gardens'.

Propagation. Separate the small cormlets from lifted corms during dormancy and grow them on separately; they usually need several growing seasons to reach flowering size. Seed-grown plants vary and will not reliably match a named cultivar.

Accepted botanical name

Gladiolus hortulanus

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