over 200 species of Gladioli, mostly growing in southern and tropical Africa,
and also in Madagascar, the Middle East and Europe. Most of the Gladioli grown
in UK gardens come originally from southern African plants, and are available in a wide
variety of hybrids and varieties.
from southern Africa generally fall into two groups:
Original species of Gladioli can show much variety in flower colour. This can make them
tricky to identify and plants grown from seed can flower in a range of quite
- Winter growing,
producing flowers in spring and early summer – the corms of these plants
need to dry out in summer after flowering, and start to grow again in
autumn. Bulbs are generally planted in autumn. The seeds of these
plants germinate better in cooler temperatures (eg 15°C) and are generally
sown in the autumn. Many of these plants are half hardy and need
protecting against hard frosts, but not all. Some, such as the Whistling Jack, have naturalised in warmer parts of the UK, such as Cornwall.
- Summer growing,
producing flowers in late summer/autumn – the plants die down in the
winter, and the corms are lifted in autumn or can be left in the soil over winter in warmer parts
of the UK. Bulbs are generally planted in the spring. The seeds of these
plants germinate across a wide temperature range (15-25°C) and can be sown
at most times of year, most commonly in the spring.
- By division: Mature plants have cormlets that can be separated from the mature
corms and grown on in pots until big enough to plant in the final position.
Separate corms when the plant is dormant.
- By seed: Gladioli are easy to raise from seed. They are best sown in free
draining seed compost at a depth of 3mm and kept at 10-15°C for winter growing
species and 15-25°C for summer growing species. They seem to be tolerant of
wide variations in germination temperature. Germination typically takes 4-6 weeks. Seedlings
need to be potted on and then grown through a second season before planting in
the final position or into pots. Flowering should start in the second or third
prefer sun and light well drained soil. Some species prefer moister conditions.
The plants respond well to regular feeding when growing and flowering.