Gladiolus is a corm-grown flower known for tall spikes of funnel-shaped blooms in a wide range of colors. It is valued as a cut flower because the spikes open from the bottom up and last well in a vase. Conventional advice puts Zone 6b as too cold to overwinter corms in the ground — but several years of leaving them in a sunny, well-drained spot in the Hudson Valley suggest otherwise. Whether that reflects a warming climate pushing the valley out of true 6b or simply good drainage and microclimate is an open question, but the corms have come back reliably.
Plant corms after the soil has warmed and frost danger has passed. Stagger plantings every two weeks for a longer bloom window. Stake tall varieties to prevent the spikes from toppling. In fall, you can either lift, cure, and store them dry and frost-free over winter — or leave them in a well-drained sunny spot and see what returns.
Fusarium wilt
Sudden wilting, brown streaks in stems, yellowing leaves. Affects sweet basil varieties most.
No cure. Remove and destroy plants. Do not replant in the same spot for 3+ years. Choose resistant varieties.
Botrytis (grey mould)
Grey fuzzy mould on petals and stems, worst in cool wet conditions.
Remove affected parts immediately. Improve air circulation. Avoid overhead watering. Apply copper fungicide if severe.
Mosaic virus
Yellowing, mottled, or distorted leaves. No cure — spread by aphids.
Remove and destroy infected plants. Control aphid populations to prevent spread. Do not propagate from infected tubers.
Gladiolus Thrips
Silvery or whitish streaking on leaves, brown flecking, and flowers that fail to open or appear deformed and discolored. Severe infestations leave corms with rough brown patches.
Remove and destroy affected blooms. Inspect corms before storage and discard damaged ones. Store corms cool and dust with an appropriate insecticide. Spray plants with insecticidal soap or spinosad during active growth if thrips appear.