Gladiolus Bulbs (Corms) - "Espresso" Darkest Red Gladiolus (10 Bulbs), Perennial Compact Height for Borders and Containers Great for Cutting. Gladiolus is a perennial favored for its beautiful, showy flowers. Its flowers grow on tall spikes and are often found in cutting gardens or in the back along the border (because they are tall). Gladioli have many different colored flowers, and grow between 2 to 6 feet in height. It's good for cut flowers. Planting Plant gladiolus bulbs in the spring once danger of frost has passed and the soil has warmed. Ready your garden by using a garden fork or tiller and loosen the soil to about 12 to 15 inches deep. After loosening the soil, mix in a 2 to 4inch layer of compost. Plant your bulbs 4 to 8 inches deep with the pointed end facing up. Space the corms 3 to 6 inches apart. Water the corms thoroughly. Gladioli like well-drained, light soil and full sun. It takes about 90 days from the time gladioli are planted to root, grow, bloom, and store enough energy for the next season.