Last Updated on October 28, 2022 by Plant Mom Care
Gladiolus, indigenous to South Africa and Europe, belongs to the Iridaceae family and contains about 300 species. These fast-growing plants grow as high as 2 – 5 feet and are popular with gardeners.
They grow from bulbs called corms and bloom in summer. The root systems of these annuals are small, enabling gardeners to plant several corms in a single container or almost 50 corms in a 2 x 4-foot space.
The funnel-shaped, orchid-like flowers open from the bottom to the top of 3-foot-long flower spikes. Their colors have been developed by hybridizers to create colorful blooms in red, pink, orange, yellow, green, purple, and white. The only color not found in their palette is true blue.
Several modern cultivars have frilled or ruffled petals that add to their appeal. The flowers attract pollinators – which makes them ideal companion plants in vegetable gardens to increase vegetable yields.
The corms can be planted starting in spring until early summer, with flowering starting after roughly 90 days and the flowering season lasts for two weeks. Planting corms every week will prolong the flowering period until autumn in the garden. Stop planting around 12 weeks before frost is predicted. When planting, place the corms (hairy side down) about 6 inches deep to provide support for emerging shoots.
Wait for night temperatures to reach around 60°F before planting the corms – planting them in lower temperatures will make the corm rot and die.
Gladiolus Light Requirements
They grow best under full sun, but will still bloom under partial shade.
After planting, water them thoroughly. Then water them weekly, keeping the soil consistently moist through their growing season. Watch the plants in dry weather – increase the watering frequency if they show signs of wilting.
They prefer low to moderate humidity levels.
They grow better in day temperatures between 50 – 77°F with night temperatures not above 60°F. They can tolerate temperatures up to 100°F if humidity levels are high and they are watered appropriately.
They can tolerate various types of soil provided that it drains well. The best soil is loose sandy loam.
Repotting is seldom necessary for these plants since they naturally die down after flowering – you simply empty the pot after the foliage dies and collect the corms for repotting in spring.
Choose a tall pot as they can grow tall although their root dimensions are small. Tall pots enable you to insert deep stakes to support the plants. Plants in short pots will still grow but will be too shallow to insert stakes.
Make sure the pot has lots of drainage holes because the corms will rot if the soil stays too damp. Add a layer of rough gravel first to help the soil drain better. Using a terracotta or clay pot will also help evaporate excess water from the soil.
Half-fill the pot with well-draining soil and place the corms (root side down) on the soil – there should be at least 3 – 6 inches of space from the top of the corm and the lip of the pot. Cover the corms with soil just a little below the pot’s lip and water thoroughly until water runs out. Move the pot to a sunny location and water once weekly when new growth emerges.
Plants grown from bigger corms produce more flowers and thicker stalks.
They grow better in fertile, well-draining soil – add compost to improve fertility if the soil is poor. Start planting the corms in spring, when the soil has warmed up to at least 60°F.
Prepare the garden bed by loosening the soil about 12 – 15 inches deep. Add compost and mix it well. Make a 4-inch deep hole and place the corm inside with the hairy side facing down. Add soil and press down firmly.
Spacing between corms should be about 6 – 8 inches. If you’re growing gladioli for cut flowers, then plant corms in rows to make it easier to access the flowers. Water them thoroughly after planting.
Feed new shoots with a balanced fertilizer or add a layer of compost. Keep the stalks from falling over by supporting them with stakes. Deadheading flowers isn’t necessary – the idea that deadheading will lead to more flowers isn’t true.
Simply remove dead flowers to improve the overall appearance. After the plant has finished flowering, cut down the flower spike but leave the rest of the plant to continue growing and replenishing the corm until the foliage naturally dries up.
Cut back the dead foliage and dig up and store the corms for planting in spring. These plants can become perennialism in zones 8 or higher but usually, gardeners plant them as annuals.
Cut off the flower spike when the lowest flowers are open and place it in a vase.
The buds on top will open as usual as the lower opened flowers fade. Change the water every day. Corms frequently have little “cormels” attached to them. You can try planting them but it will take years before they’re big enough to flower properly.
Gladiolus Common Problems
The biggest pest threat to these plants is thrips. These minute insects attack flower buds and foliage. They are difficult to see so look for signs of damage such as small white patches, silvery streaks on the foliage, brown leaf tips, and buds that won’t open. They can be treated and eliminated with insecticidal soap.
These plants, particularly those commercially cultivated for the floral industry, are also threatened by viruses like the cucumber mosaic and bean yellow mosaic viruses. Symptoms include pale-yellow mottling on the foliage, reduced corm production, and short life spans of the plants.
There is no treatment or cure – infected plants have to be removed and destroyed to prevent these viruses from spreading.
Does gladiolus return every year?
They can return every year although the corms might have to be dug up and stored over winter and replanted in spring.
What time of year should gladiolus be planted?
Start planting when the soil temperature is above 60°F in spring. The flowering season can be prolonged if you plant corms every 2 weeks from spring till July – this staggers the flowering season until early autumn.
How many times will gladiolus bloom?
They only bloom once every year, for around 1 – 3 weeks. The flowering season can be prolonged by planting corms 2 weeks apart till early summer for a longer display.
How many flowers can one gladiolus bulb produce?
Each flower spike can produce up to 20 flowers however, the plant might produce 2 or 3 more flower spikes if the corm is larger than 1 inch.