Hardy gladiolus
Gladiolus communis subsp. byzantinus ·
Slender spikes of vivid magenta flowers in late spring: a wild gladiolus that stays in the ground all year and comes back for decades.
- Size
- 2½ ft tall, 6 in wide
- Zones
- 6 to 10
- Light
- Full sun
- Flowers
- Late May to mid June
- Pets
- Toxic (mild)
- Job in a bed
- Accent
A bed built around hardy gladiolus
The planner designed this bed around hardy gladiolus when this page was made: a 12 × 6 ft (3.7 × 1.8 m) English border in zone 6, full sun. It chose the other plants from the 966 that suit those conditions, and says below why hardy gladiolus stands where it does.
The plants
- 1 Common thyme × 8, lavender
- 2 Heath aster 'Snow Flurry' × 4, white
- 3 Hyssop 'Blue Boa' × 5, purple
- 4 False sunflower 'Summer Nights' × 3, yellow
- 5 Inkberry 'Gem Box' × 1, dark green leaves
- 6 Wild geranium × 3, pink
- 7 Hardy gladiolus × 4, pink
- 8 Hyacinth × 12, blue
Why this plant
- Nothing here is unique to it. Its leaf, flower shape and colour are all on the plan already. Its case rests on where it stands and when it performs.
Why here
- In the middle. At 2½ ft it is the step between common thyme (10 in) in front and hyssop 'Blue Boa' (3 ft) behind: each is seen over the one before.
- 4 plants in 4 places. An accent is a punctuation mark: the repeat along the bed gives it rhythm.
Why now
- In flower for four weeks. From late May to mid June.
- Part of the bed's peak. With common thyme and wild geranium in late May: 3 kinds at once. No week has more.
- Leaves gone by midsummer. They die back and leave bare ground. A perennial that comes up late stands beside it, and grows over the gap.
Planned as an English border: 6 of the 6 groups (100%) are drifts, longer along the bed than they are deep. The flowers run from mid April to mid October: 28 weeks in all. Common thyme and heath aster 'Snow Flurry' finish the front edge.
The planner's own design check: 12 Excellent, 5 Good. It flags one thing to watch: Nothing on this plan is highly poisonous or an aggressive spreader.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where hardy gladiolus goes in a border
At 2½ ft it belongs in the middle of a bed. In the planner's ten height classes it is medium (24 in to 2½ ft).
Its job: accent. An upright plant used singly, like a punctuation mark, and repeated at intervals to give the bed rhythm.
Slimmer and more graceful than the florist's gladiolus, and it needs no staking or lifting. The magenta is superb with the grey of catmint and the blue of irises.
- A cottage-garden heirloom
- Vertical accents among late-spring perennials
- Naturalising in warm climates
What to plant with hardy gladiolus
Plants recorded as good partners for it, and what each pairing does:
- Bearded iris: in flower together for four weeks, from late May.
- Catmint 'Walker's Low': in flower together for four weeks, from late May; grows up in time to hide its dying leaves; a low mound at the foot of its spires.
- Peony: in flower together for three weeks, from late May; grows up in time to hide its dying leaves; a low mound at the foot of its spires.
Questions about hardy gladiolus
Does hardy gladiolus need sun or shade?
Hardy gladiolus grows in full sun (6 or more hours of direct sun a day).
It wants ordinary well-drained soil, of average fertility, and little watering once settled.
What zones does hardy gladiolus grow in?
USDA zones 6 to 10. It is hardy to zone 6, which means it survives winter nights down to about 0 °F (−18 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does hardy gladiolus flower in my zone?
In zone 5 it flowers late May to mid June. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.
| Zone 6 | Mid May to mid June |
|---|---|
| Zone 7 | Early May to early June |
| Zone 8 | Early May to early June |
| Zone 9 | Late April to late May |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should hardy gladiolus be planted?
5 in (12 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 6 in (15 cm), so a group knits into one patch.
It grows 2½ ft (75 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many hardy gladiolus plants do I need?
At 5 in apart, set out in staggered rows:
- 74 to fill 10 square feet (about 1 m²)
- 26 for a single row 10 ft (3 m) long
- 238 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as one at a time, repeated along the bed at intervals; a slender one reads better as a clump of three.
In the bed above, the planner used four in four groups.
Is hardy gladiolus poisonous to dogs and cats?
Yes: mild toxicity to dogs, cats and horses. Can cause drooling, vomiting and diarrhoea in pets if eaten. The corms are the most poisonous part.
Rated from NC State Extension and the ASPCA. Where references disagree, the more cautious rating is used.
Will hardy gladiolus spread?
It spreads sideways, by runners or roots; the risk of it taking over is moderate. Multiplies by offsets and seed and spreads through a bed over time. It is easy to lift where it is not wanted.
What can I plant to hide hardy gladiolus's leaves after it flowers?
A bulb's leaves have to be left to yellow for about six weeks after flowering, to feed next year's flowers. Plant it among perennials that come up late and spread wide, and they grow over the leaves as they fade:
- Catmint 'Walker's Low': 24 in tall and 2½ ft wide, a recorded partner, in flower mid May to mid September.
- Peony: 3 ft tall and 3 ft wide, a recorded partner, in flower late May to late June.
- Daylily: 2½ ft tall and 24 in wide, in flower late June to early August.
What does hardy gladiolus look like in winter?
Hardy gladiolus is underground: it dies back after flowering and waits as a bulb until spring. Mark where it is, so a fork does not find it first.
More Gladiolus
- Gladiolus Gladiolus x hortulanus
In these guides
Every fact on record
- Type
- Bulb
- Size
- 2½ ft (75 cm) tall, 6 in (15 cm) wide
- Plant
- 5 in (12 cm) apart
- Height class
- Medium (24 in to 2½ ft)
- Place in the bed
- Middle
- Flowers
- Late May to mid June; upright spires; pink
- Leaves
- Medium texture, summer-dormant; green
- Shape
- Upright, spreading
- Hardy in
- USDA zones 6 to 10
- Light
- Full sun
- Soil
- Average, well-drained
- Water
- Low
- Feeding
- None needed
Checked against NC State Extension and ASPCA poison lists. Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.