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How to grow gladioli for a delightfully flamboyant cutting garden

Continuing her series on growing bulbs, Clare Foster explains how best to harness the gloriously flamboyant attributes of gladioli in a cutting garden or border all summer long

By House & Garden | September 12, 2021 | Gardens

Continuing her series on growing bulbs, Clare Foster explains how best to harness the gloriously flamboyant attributes of gladioli in a cutting garden or border all summer long

Immortalised as ‘gladdies’ by Barry Humphries’ comic creation Dame Edna Everage, gladioli are the undisputed divas of the plant world. The towering grandiflorus hybrids come in a rainbow of gaudy colours that can look faintly ridiculous in a tasteful English border, but they are, by the same token, rather fabulous planted with dahlias in a deliberately flamboyant cutting garden.

In addition to these highly bred supermodels, however, you can find a handful of more delicate species gladioli that sit comfortably in a garden border, as well as ranges of smaller hybrids in the Nanus group, and the new Glamourglad group, which have been bred in the Netherlands. Most bloom towards the end of the summer, but some flower from late May onwards. You can also extend the flowering time for successional colour by planting bulbs (or corms, as they are sometimes known) at two-week intervals in spring.

For the cutting garden, take your pick from the array of colours available in the Grandiflorus group, from pale cream and butter yellow to deepest, darkest purple and everything in between. Some are bi-coloured; others have picotee edges or blotched throats. Most grow to about 1.2 metres, with a sturdy flower spike that starts opening from the bottom upwards. In the vase, they last for well over a week and, when the bottom florets start to look tired, you can just pull them off, leaving the top ones still fresh. Pick out the colours that are going to work best in your flower arrangements – from the colour-saturated ‘Velvet Eyes’ (magenta purple with a crimson flush) to the richly sensuous ‘Chocolate’ (deep red suffused with chocolatey maroon). Vibrant ‘Green Star’ can look amazing in a vase with magenta and purple varieties, or with the simple ‘White Goddess’.

For a mixed border, there are several species you can try that combine well with other herbaceous perennials. I have been growing the beautiful Gladiolus papilio ‘Ruby’ for six or seven years now.

A single plant that I brought back from Forde Abbey Nursery in Somerset has now increased to a dozen or more plants, which I am spreading round my garden. Some years, I dig them up in autumn with the dahlias, to be replanted the following spring, but I have also left them in the ground under a mulch and they are hardy enough to survive the winter in my garden in the south of England. Growing to about 80cm, ‘Ruby’ is delicate and willowy, with beautiful dark crimson, hooded flowers that appear in late summer. I also have G. papilio, which has smaller flowers in a curious mixture of bruised purple and greeny-yellow. It is an understated plant that can get lost if it is planted alongside too ebullient a neighbour. Try it with late-summer salvias or among a froth of Erigeron karvinskianus.

Another species that will look lovely in a border – as well as planted en masse in a large pot – is G. murielae, an elegant beauty with fragrant white flowers, each with a star-shaped burgundy throat. Only one or two blooms appear at a time on the stem, so the effect is less ostentatious than others.

Among the earlier gladioli is G. tristis, which can appear from May. It grows to about 90cm, producing a graceful flower spike with scented, delicate greeny-white blooms and narrow leaves.

G. x colvillii ‘The Bride’ has G. tristis as one of its parents and has larger, showier flowers, while G. x colvillii ‘Irish Gold’ has distinctive yellow blooms with a hint of lime green. G. communis subsp. byzantinus (90cm) also flowers earlier in the summer, appearing at the beginning of June. I have seen this naturalised on a hillside in Morocco – a stunning sight, with swathes of its magenta-pink flowers cascading down the slope. It can grow in a meadow situation in the UK, too, or team it with Geranium ‘Rozanne’ and Euphorbia palustris in a border.

The dwarf Nanus hybrids also flower in early summer, growing on average 40-50cm tall. These are among the hardiest of the gladioli, with sturdy flower spikes that can be woven in with soft herbaceous plants in a border, or displayed incontainers. Pot-luck mixes are available, or choose a cultivar such as ‘Charm’, with pure lipstick-pink blooms, or ‘Halley’, which has white flowers with butter-yellow throats. More recent introductions include the members of the Glamourglad group, which grow to about 60cm. The dazzling bi-coloured blooms of cultivars such as ‘Flevo Cool’ or ‘Flevo Laguna’ might be too much for some gardeners, but they work brilliantly as cut flowers.

How to cultivate gladioli

All these gladioli are half-hardy, but can survive milder winters in the south of England if they are given some protection. In a border, they will do best in free-draining soil in a sunny spot, mulched with a thick layer of compost in winter. In a pot, use a loam-based compost mixed with potting grit. For the late-summer varieties, plant the bulbs in spring, either in pots under cover in early spring to be planted out later on, or directly into the ground when the weather is warmer in late spring. For a succession of flowers, plant them every couple of weeks during May and early June.

The early-flowering gladioli, such as G. x colvillii, G. communis subsp. byzantinus and G. tristis, can be planted in autumn, but plant them outdoors only if you live in an area with mild winter weather. If you have a greenhouse, start them off in pots – with no more than five bulbs to a 15cm pot – and plant them out when the weather warms up in spring.

Original article appeared on House & Garden UK | Author Clare Foster