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Tender bulbs make for summer delights

Photo by Nick Windsor via Unsplash

For vibrant cut flowers this season, plant summer bulbs like dahlias, gladiolus, and lilies. These summer-blooming tropical bulbs are called ‘tender bulbs’ because they can be killed by our cold temperatures if left outdoors during the winter, or if they’re planted too early in the spring. They do need well-drained soils, but consistent watering. 


Dahlias are planted from a tuberous root. Plant outside in full sun after the last frost date for optimal flowering. The taller varieties of dahlias should be planted 6-7" deep and shorter varieties to 2-3" deep. Space about 12-18" apart, depending upon variety. Look on the package for specific directions. 

Taller varieties need to be staked for support. Extension State Master Gardener Specialist, Candice Hart, loves growing dahlias for their unique colors and shapes. She says despite their relatively low maintenance nature, consistent watering is key for blooming, as she has lost blooms due to lack of watering during dry periods. Flowers are ready to harvest when they are fully open. 


Gladiolus are planted from an energy-storage structure called a corm. Corms can be planted outside two weeks before the last frost date (about May 14 in central Illinois) and every two weeks until the beginning of July for a staggered supply of these beauties. Plant corms 2- 6" deep, depending on the size. Corms may be spaced only 2 to 3" apart for flower production, but 6" apart if planted within the landscape. To ensure tall, straight flower spikes, staking is necessary. Gladiolus are harvested when the first few florets at the bottom are open. 


Lilies are the only true bulbs on the list. They are perennial flowers that will return year after year and require minimal care. Bulbs can be planted in the ground in fall or early spring, or some cut flower growers prefer to grow their lilies in crates. 

There are two hybrid lilies preferred for growing cut flowers: OT Hybrid is a cross between Asiatic lilies and Trumpet lilies, combining beauty with heat tolerance. LA Hybrid lilies are a cross between Easter lilies and Asiatic lilies with large flower heads and slight fragrance. Plant bulbs 4 to 8" deep and 8" apart. Harvest when the flowers are just starting to show color. Because lilies are perennial, do not harvest all the foliage. 

Candice uses bamboo and string for staking, and prefers the ease of a granular slow-release fertilizer on her cut flower beds. She suggests cutting flowers in late afternoon or evening when lots of food has been stored up, or in the morning when the stems are full of water. She cuts stems longer than needed and removes all foliage that will be in water. Finally, she allows warm water uptake for 1-2 hours.