Growing Gladiolus in South Africa

We are so very glad to see you! Some of you may remember the late, great Dame Edna Everage (Barry Humphries, following in the footsteps of our own Pieter-Dirk Uys and Tannie Evita). Dame Edna famously brought a touch of local botanical charm to the world stage, using a long spray of purple gladioli —her ‘heat-seeking gladdies’—as a ‘possum picker’ to select contestants on her show. On that theatrical note, here is a gladdie growing guide, filled with all the glowing details you need to know about Growing Gladiolus in South Africa.

August babies can proudly claim the Gladiolus as their birth flower! Part of the Iridaceae family, this beauty is a classic summer garden powerhouse, symbolising strength and remembrance. Known fondly as the ‘sword lily’—though it’s not a lily at all—this plant’s leaf shape and vibrant blooms certainly know how to make a statement!

Gladioli have been cultivated in Europe for over 250 years, but their lineage is proudly South African. Seven historical species originate in the summer rainfall regions of southern Africa, spanning from the Eastern Cape above East London to southern KwaZulu-Natal and as far as the Lesotho border. In fact, all but ten of the species are native to sub-Saharan Africa!

Today, over 10,000 varieties of Gladiolus dazzle gardens worldwide, thanks to hybrids of our wild, veld-born beauty. 

When to plant  Gladiolus  bulbs in South Africa?

On the whole, Gladiolus are a summer-flowering variety, so planting out in late spring through summer is best. However, there are some that come from the winter-rainfall areas, which should be planted in autumn. If planted in parts of the country that experience dry winters, they will need to be given enough water to get them going.

What are the best conditions for  Gladiolus  to grow in?

As a proud member of the Geophyte plant group, this cormous bulb is a real garden champion, going from bulb to bloom in about 90 days. The local lovely rewards your patience with clusters of large, trumpet-shaped flowers that blossom in a range of colours—basically the whole rainbow except true blue. The flowers open progressively from the bottom up, giving you about two weeks of fabulous blooms.

Growing gladioli is a breeze: just give them well-draining soil enriched with organic matter (like compost), especially if your soil leans on the clay side—they would rather settle in sandy loam. Find a sunny spot with a bit of wind protection, keep the water coming during their growth, and you are good to go. Gladioli definitely prefer the open ground to a pot, and with their impressive height (often over 1 to 1.5 meters), it is best to plant them towards the back of your garden beds or borders for a dramatic backdrop. Some of the taller varieties may need a bit of support, so check the packet for height details and have a stake ready for the real high-flyers!

How to plant and care for Gladiolus? 

Loosen your soil to a depth of about 30cm. Next, you will need to space out your corms about 15cm apart and cover them with about 3cm of soil, preferably deeper in sandier soils, to ensure the stems don’t topple over. Then, don’t forget to mulch with a layer of compost. Water every three to four days for 10 minutes, unless there’s been rainfall.

A few weeks before they are due to flower, give them a feed of organic fertiliser which is high in potassium (the ‘K’ number, so look for a slow-release 3:1:5) or Hadeco Bulb Food every couple of weeks. Just make note to fertilise them again once their flowers have died back, before the bulb goes into dormancy, so that the next season’s crop of flowers can be produced. 

Where do gladioli grow best?

Gladiolus dalenii thrives in both full sun and semi-shade.G. geardii prefers to keep cool in semi-shade, while other species love basking in full sun and are more than happy to soak it up all day long.

Cutting glads for the vase

Of course, many people grow loads of glads not only to have colour in the garden through summer, but also for the vase to bring the gorgeousness inside. So in the case of cutting, you need to pick them when the lowest bud on the flower stalk is open, with the one above showing a little bit of colour. If you want to get them open quickly, nip out the tip. Refrain from cutting the stem when the buds are tightly closed, as they may not open.

Do I soak gladiolus bulbs before planting?

Soaking before planting is entirely unnecessary. Glads are perfectly content for you to skip the fuss and just get them straight into the ground.

Do gladiolus bulbs multiply?

Gladioli do multiply! The mother bulbs produce cormlets, which can be harvested and replanted in spring or early summer.

After-flowering Care 

In South Africa, there’s usually no need to lift bulbs once they go dormant, unless you’re dealing with heavy clay soil that won’t drain or temperatures that regularly drop below freezing.

A quick note of caution: parts of the gladiolus flower and leaves are toxic, so keep them off the menu! Some species may also cause skin irritation or allergic reactions, so grab those gardening gloves when cutting blooms for the vase.

While glads may be your favourite, they are sunbirds too, thanks to the abundant nectar they produce. These feathered friends are the primary pollinators for many gladiolus species, so if you’re an avid birdwatcher, glads are a great choice!

Here’s to a season of gardening with gladness!