10 GLADIOLI MIXED GARDENING BULB CORM BEAUTIFUL SPRING SUMMER FLOWER PERENNIAL Plant gladioli corms about 10-15cm deep and about 10-15cm apart, in fertile/well drained soil in spring. Planting can be done in succession from early March onwards to the end of May at fortnightly intervals. This ensures a continuity of flowers throughout the summer months. When planting in a heavy soil, place some sand underneath each corm to help with drainage.