Inexpensive and easy-to-grow, gladiolus bulbs bloom in lovely colours and provide outstanding cut flowers for summer bouquets. Here’s how to add them to your garden.
1. Pick the right area
- Because of their lanky physique, glads can be awkward in the landscape.
- For the best effect, grow them in groups at the back of the border or station the tall spires, against a fence or building. Let the structure act as a backdrop while blocking wind and helping to support the plants.
- Cut gladiolus when the first flowers at the bottom of the spike are open. The others will quickly unfurl in the vase.
2. Plant them in spurts
- Gladiolus bloom about 10 weeks after planting. By planting the corms every two weeks from early spring through midsummer, you’ll enjoy a succession of blossoms all season.
- Choose a sunny, well-drained spot and mix an all-purpose, granular fertilizer into the soil as you dig.
- Use about one level soup spoonful of 10-10-10 fertilizer per corm.
- Plant the corms 10 to 15 centimetres (four to six inches) deep and 10 centimetres (four inches) apart.
- The small nubbin of new growth indicates the top of the corm and should point up.
3. Keep them together
- Gladiolus grow tall and slender, so plant them in groups of five or more.
- Stake with bamboo canes and some soft garden twine to inconspicuously “corset” the group.
- Water only if the soil becomes very dry, as gladiolus hate wet soil and can develop root rot.
- Provide plants with a second helping of balanced fertilizer when flower spikes appear.
- In midsummer, watch for signs of thrips. These nearly invisible, sap-sucking insects make silvery streaks in leaves and distort flowers.
- Control thrips with a commercial insecticide labelled for this use, as directed.
4. Make their new home welcoming
- In areas where gladiolus are not hardy, dig the corms when the leaves begin to yellow in late summer. Trim the leaves to 2.5 centimetres (one inch) from the corm. Brush away loose soil.
- Store corms in a paper bag of peat moss in a cool, dry, dark place. And unheated room or a garage that remains above freezing is ideal.
- Many gardeners in warmer climates dig and store the corms to keep plants from growing small, weedy offspring called cormlets.
- Cormlets reach flowering size in about three years. Because the mature corms are inexpensive, there’s little reason to nurture cormlets.
5. Find the right species for your area
- The common summer-flowering gladiolus are hybrids that are usually tender.
- In the mildest parts of British Columbia, they may survive outdoors if protected with a 10 centimetre (four inch) mulch in late fall.
- There are other types that withstand more cold. G. communis ssp. byzantinu, for example, is hardy to Zone 5 and grows 0.6 to one metre (two to three feet).
- Plant gladiolus in groups of five or more for a care-free display of colour from late summer onwards.
Topping out at 1.2 metres, with bold, colourful spikes of funnel-shaped flowers atop leaf blades, gladiolus are like exclamation points for the garden. With the right care and attention, these plants can make your garden’s colours pop.