How to grow gladioli
Gladioli offer a brilliant array of flower colours. Some are hardy and overwinter happily in well-drained soils, others are best lifted each autumn and stored dry, or dried off in the pots where they grow. They can be planted informally in borders, in rows for producing cut flowers or used to create container displays.
- Gladioli are corms (bulb-like structures)
- Garden hybrids make good cut flowers
- Gladioli enjoy a fertile, well-draining soil or potting compost
- Some species and cultivars are hardy, others need frost protection in winter
- Plant most corms in spring
- Lift non-hardy gladioli in autumn and store dry over winter
- Propagate by growing on small corms from hybrids, and sow seeds of species
All you need to know
Choosing gladioliWhile many gladioli are easy to grow in the first summer, for a reliable display you will need to lift and store many of the popular garden hybrids somewhere frost free over winter. As a result, think about whether you want to do this each autumn, or whether you are just happy to see what comes up the next year. There are a few hardy types to try too which can more reliably left in the ground year after year.
- Garden hybrids which are not fully hardy (including summer flowering large or smaller flowered grandiflorus types, butterfly and primulinus hybrids, earlier flowering nanus types and acidanthera (Gladiolus mureliae)). On most soils and locations in the UK, lift these in late summer/early autumn and store somewhere dry and slighty warm. Note: On light, free-draining soils in warmer counties, you may be able to leave these gladioli in the ground and have them survive an average winter.
- Hardy types such as Gladiolus communis subsp. byzantinus. You will need a sunny location with a well draining soil, perhaps at the base of a wall. Will also naturalise in grass. They are left in the ground to come back year after year.
- Specialist species like Gladiolus cardinalis and Gladiolus carneus. These are often best grown in containers as this both shows off their delicate form and it will allow you to bring them into the protection of a greenhouse which is cold but frost-free.
Where to buy
Gladioli are available to buy as dry corms by mail order in spring bulb catalogues and from garden centres in spring. Less common species are sourced from specialist nurseries where you may also find plants in growth to purchase later in the season. You can also buy seed of species to raise yourself.
For stockist of harder-to-find species, search using the RHS Find a Plant.
Where to plant gladioli
Choose a sunny, open place, clear of competition and shade from surrounding plants. If you're growing tall hybrids, find a spot sheltered from wind to avoid the need for staking or installing a netting support to stop them blowing over.
How to plant gladioli
When planting each spring, dig well-rotted manure or garden compost into the soil to help retain moisture, improve drainage and add some nutrition. On poor soils, you can also add a general-purpose fertiliser, such as Growmore, when you plant.
If you are growing gladioli as cutting flowers in rows, say on an allotment, it's easiest to dig a straight trench and plant in several rows (rather than digging individual bulbs for each corm).
Plant corms at a depth of 3 corms stacked on top of each other (that's 10-15cm (4-6 inches) deep for large-flowered garden hybrids). You can plant a little deeper on light sandy soils to improve their stability in the wind. Either way, planting too shallowly can lead to the production of lots of small offspring corms rather than one, good-size corm for next year.
Space corms out at a similar distance to their depth. If you're planting in containers, you can plant closer.
Additional information for planting specific gladioli
Summer-flowering garden hybrids
The typical, traditional gladioli are planted from mid April through to May. If you plant in batches every couple of weeks they don't all flower at the same time, which also staggers the crop if they are grown as a cut flower. The growing tips only emerge after any danger of frosts is past; usually around the end of May/beginning of June
Early flowering garden gladioli (like nanus hybrids)
Plant into a sunny site in early spring (late March-mid April) for flowering in June or plant in autumn in a cold frame (as an early cut flower crop). You can also plant 5 corms into a 15cm (6in) pot, 6cm (2in) deep. Dig a hole in the ground and plunge the pot level into into the soil so the roots develop in the cooler weather. In early December bring the pots into frost-free conditions, such as a frost-free heated (cool) greehouse to flower.
Other garden gladioli
Plant acidanthera (Gladiolus mureliae) in pots or in the ground in April. Potted corms can also be planted in their pots just to fill gaps in summer borders. Plant Gladiolus communis subsp. byzantinus in early spring in a sunny, well-draining site.
Specialist species gladioli for growing in containers
Timing of planting may vary according to flowering time, so check for individual species. For example, early spring-flowering species need planting in autumn. Select a free-draining compost.
Feeding and watering
In the ground: Water garden plants regularly in dry weather and on free-draining soils. In addition to dressing of general purpose fertiliser, such as Growmore, at planting time, on poorer soils gladoli benefit from a liquid feed that's high in potassium (such as a tomato feed) to promote flowering when flowers spikes start to emerge - this is seen as the leaf sheath beginning to thicken and then the spike emerges.
In containers: Water keep the compost damp then, as the growth emerges, check daily to ensure the compost doesn't dry out. Liquid feed with a potassium rich fertiliser (such as a tomato feed) to promote flowering when flowers spikes start to emerge - this is seen as the leaf sheath beginning to thicken and then the spike emerges.
StakingYou don't have to stake, but it does ensure that the blooms don't flop over.
However, if you're growing gladioli for the show bench (competitions), you will usually need to stake individual flower spikes with canes. Do be careful you insert the cane far enough away so as not to damage the corm and its roots.
Alternatively, and usually where conditions are windy such as on an allotment site, the taller grandiflorus hybrids can be grown through a horizontal mesh such as pig wire fencing.
WeedingKeep the soil surface free from weeds by regular hoeing, but take care not to damage new shoots.
If you're growing for cut flowers, try to cut the flower spikes while leaving behind as much foliage as possible. This is not always possible, but the remaining leaves will support the development of next year's corm.
Cut flowers: cutting and conditioning
Cut flowers: growing and selection
Lifting, sorting and storing
Spring-flowering types in the ground
Foliage of the spring-flowering types fades around six weeks after flowering, after which they can be lifted and stored.
Summer-flowering garden hybrids in the ground
The foliage of these will stay green into autumn. For the garden gladioli that need frost-free conditions, lift before the foliage fades, usually around six weeks after flowering. Cut off the leaves (which will still be green) just above the corm leaving a stub of a few centimetres (one or two inches). Detach any of the cormlets (small corms) and dry off the corms in a warm, airy place for a few weeks. After this time, you should be able to twist off and discard the old corm that is shrivelled beneath the main, new plump one that is kept. Rub away any dirt and store undamaged corms in trays in a cool frost-free place indoors over winter, checking occasionally and discarding any rotten ones.
On a well-draining soil in warmer regions, you can try to avoid the need for annual lifting by growing half hardy cultivars in a south-facing border, with the protection of a wall behind. Add a mulch of bracken or bark chip in winter to provide some insulation. However it is risky so if in doubt, lift for winter.
For pot grown species, reduce watering after flowering as foliage starts to brown off. Keep dry during the dormant season.
DividingOver the years gladiolu left in the ground successfully and container-grown gladioli can get congested, so periodically lift and divide in autumn, replanting larger corms at a wider spacing.
Most people buy corms from the garden centre or by mail order in spring as they are easy and reasonably priced to buy. However, if you want to have a go, you can try the following propagation methods.
Plants also reproduce from cormlets (small corms) which grow around the central corm. These can be stored if necessary and transplanted into a nursery bed in spring 5cm (2 inches) deep. In the case of specialist species pot up in containers and grow on. Corm-raised stock should reach flowering size in 1-2 years.
Gladioli species can be grown from seed. You'll find perennial plantings can self-seed. Sow specialist species in spring in a cool greenhouse. Corms should reach flowering size in 2-3 years.