Bulb · Iridaceae
Garden Gladiolus
Gladiolus × hortulanus
Tuck the corms into spring soil and gladiolus rewards you with tall spires of color from late summer into fall.
Full sun
Every 5–7 days
41–86°F · 5–30°C
60–90 days
Overview
If you have never grown a flower from a corm, gladiolus is a gentle place to start. It sends up a tall stem lined with funnel-shaped blooms that open one by one from the bottom, and it grows from a corm, a plump underground stem that acts like a bulb and stores the plant's food. The sword-shaped leaves earned it the old name sword lily, and a tidy row of glads along a fence is a familiar summer sight you can absolutely pull off.
These are warm-season flowers you plant in spring, and they are wonderfully patient with beginners. Set the corms out once frost has passed and they open 8 to 12 weeks later, so you can plant a fresh handful every week or two and enjoy waves of color instead of one short burst. If you garden in zones 7 to 10 the corms can rest in the ground all winter, and if your winters are colder, simply lift them each fall and keep them dry until spring.
The nicest thing about glads is how little they ask: mostly just full sun and steady moisture. The one habit worth building is protecting the corm, which sulks and rots in soggy ground and can attract thrips if stored without a glance. Give the plants good drainage, a stake for the tallest spikes, and a small amount of attention, and they will hand you armfuls of flowers for the vase.
Care
The short version: settle the corms into full sun and rich, well-drained soil after the last frost, keep them evenly moist at roughly an inch of water a week, and lift the corms for winter wherever the ground freezes.
Light
Give your glads full sun, ideally six or more hours a day, and they will send up strong spikes that stand tall on their own. A touch of afternoon shade is fine, but in too little light the stems stretch, start to lean, and set fewer flowers.
Water
Keep the soil evenly moist as the plants grow and bloom, which comes to about an inch of water a week. That steady moisture fills out the flower spikes beautifully, and because the corm rots in waterlogged ground, good drainage matters every bit as much.
Soil
Plant into fertile, well-drained loam with plenty of organic matter mixed in, and avoid heavy clay that traps water around the corm. Aim for a pH of 6.5 to 7.0, close to neutral, and they will feel right at home.
Temperature
Glads are content across a wide range, roughly 41°F to 86°F (5°C to 30°C), once the season warms up. They are tender to frost, so the corms go in only after the last cold snap and come out before the ground freezes hard.
Humidity
Ordinary outdoor humidity suits them fine, and there is no target number to fuss over. What helps more is air moving through the planting, since still, damp air invites botrytis and corm rot.
Feeding
Glads are modest feeders that appreciate a soil test and a balanced fertilizer. Feed them once at planting and again as the flower spikes form, which supports both the blooms above and the corm building up below.
Pruning
Snip off the spent flower spikes once they finish so the plant does not pour energy into seed. Let the foliage stand until it yellows and dies back on its own, because those green leaves are quietly recharging the corm for next year.
Repotting
In cold zones, lift the corms each fall and replant them in spring rather than risk a freeze. Where they stay in the ground over winter, dig and divide the crowded clumps every few years so the flowers keep their full size.
Size & spacing
Spikes stand anywhere from 1 to 6 feet (30 to 180 cm) tall depending on the type, and the tallest appreciate a stake. Each plant spreads only 12 to 24 inches (30 to 60 cm), so you can set the corms fairly close together in a row or block.
When to plant
Gladiolus loves the warm season and has no patience for frost, so there is no need to rush. Plant the corms in spring once the soil has warmed, tuck in a fresh batch every week or two for a longer show, and the spikes will open from late summer into early fall.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Spring, after the last frost once soil has warmed; plant in succession 7-14 days apart for continuous bloom.
- Harvest: Late summer into early fall, about 8 to 12 weeks after planting.
Hardiness
USDA hardiness zones: 7–10
Temperature: down to -18°C
Troubleshooting
Take heart: most gladiolus trouble begins underground or travels in on the corm, which means it is easy to head off. Spot the early clues on the leaves and at the base and you can step in well before a planting is lost. Match what you see below, then act while it can still help.
Yellow leaves above corms that are rotting below
If plants wilt and the corms feel soft and turn brown inside, the likely cause is fusarium wilt or corm rot, which settle into ground that stays too wet. A run of cool, damp weather can also trigger botrytis or crown rot right at the base. An infected corm cannot be nursed back, so lift and bin the bad ones, sort out the drainage, and replant only firm, healthy corms in a fresh spot. You have not lost your knack, the soil simply held too much water.
Fix:
- Remove and destroy affected corms and plants
- Improve soil drainage
- Rotate planting location
- Plant only firm, healthy corms
Silvery streaking with buds that just will not open
Do not panic if you see this. It usually points to gladiolus thrips, tiny insects that scrape at the leaves and tuck themselves inside the flower bracts, and they often hitch a ride in on corms so the marks appear before you notice a single bug. You can turn things around by pulling the worst spikes, hanging a few sticky cards to keep an eye on numbers, and treating or setting aside any corms before they go into storage.
Fix:
- Remove and destroy heavily infested flower spikes
- Use yellow or blue sticky cards to monitor
- Apply an appropriate insecticide labeled for thrips if needed
- Treat or discard infested corms before storage
Toxicity
This is worth knowing without worry: gladiolus is poisonous to pets and grazing animals, and the buried corm is the most dangerous part of all. The leaves, flowers, and corms hold an irritant that brings on drooling, vomiting, and lethargy when eaten. A little care goes a long way, so keep animals out of the beds and put corms well out of reach as you plant and store them.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Mild
A cat that has chewed on the plant will often start to drool and be sick, then curl up quiet and worn out for a bit. Because the corm holds the strongest dose, a cat that digs one up gives you the most to keep an eye on.
Dogs Mild
A dog that has had a taste tends to drool a lot, feel queasy, and get loose stool within a few hours, and it usually passes. The one to watch for is a dog that finds and eats a stored corm, since that hits hardest.
Horses Mild
A horse nibbling the foliage may drool, go off its feed, and seem dull and slow for a while. The corms carry the most of the irritant, so it helps to keep them clear of beds and planting trenches.
Rabbits Toxic
The same irritant is hard on a rabbit's delicate gut, so a nibbling rabbit may drool and turn away from food. It is worth keeping the leaves, flowers, and corms somewhere a rabbit simply cannot reach.
Livestock Toxic
Cattle, goats, and sheep can scour and grow listless if they graze the foliage or root up a corm. A simple fence between stock and the planting, plus tidying away any lifted corms, keeps everyone safe.
Birds Toxic
A backyard bird that pecks the leaves or scratches up a corm risks drooling, being sick, and going lethargic. The kind thing is to treat every part of the plant as off limits to them.
People Caution
No part of the gladiolus belongs on a plate, and the corm especially can leave the mouth and stomach sore if it is swallowed. A little care keeps curious children away from corms while you plant and store them.
Keep corms and bulbs out of reach of pets, especially during planting and storage when corms are accessible.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Most garden glads are hybrids you buy by color rather than by name, but a couple of distinct species are lovely to know for their scent and their staying power.
Gladiolus murielae
If fragrance is your goal, this is the sweet-scented Abyssinian or peacock gladiolus, whose white blooms carry a deep purple throat.
Gladiolus × byzantinus
This dependable Byzantine heirloom rewards you with magenta flowers and returns on its own year after year, right down to about USDA zone 6.
How to propagate
One of the quiet joys of glads is how freely they multiply underground, so lifting the corms each fall simply hands you free plants for next year.
Bulbs & cormsEasy
Spring at planting; lift and separate in fall · One growing season
Here is the reassuring part: glads mostly copy themselves for you. Dig the corms in fall and set them back out the next spring, and you will find each parent has grown a fresh corm on top along with a little huddle of cormels at its base. Those big corms flower again in just one growing season, so this is about as forgiving as increasing a plant gets.
DivisionEasy
Fall when lifting corms · One growing season
As you lift the corms, gently twist the tiny cormels away from the base of the parent to begin new plants. The full-size corms bloom next season, and while the smallest cormels take a year or two to reach flowering size, there is nothing tricky about waiting them out.
SeedModerate
Spring · Two to three years
Starting glads from seed asks for patience and is really the path breeders take when chasing new colors. Sow in spring, then give it two to three years while each seedling slowly builds a corm big enough to flower, so there is no rush and no pressure.
Myths
Gladiolus flowers and leaves are safe for pets to nibble.
It is an easy thing to assume, but every part of this plant carries an irritant, and the ASPCA lists it as toxic to cats, dogs, and horses. Even a small nibble can leave an animal drooling, sick, and out of sorts, and the buried corm is the part that does the most harm. Keep pets away from the foliage and above all from the corms.