Gladiolas corms


I purchased a box of gladiola corns (?) and planted them
them in early June in full sun in a large container, just as I had done in previous years. This is a 3b climactic zone.
The soil is a “4 in 1” mixture (a blend of top soil, compost, peat, and I’m not sure what else but it could be
sand?). My question is: why aren’t these gladiolas blooming? Thank you.



Hello, thank you for contacting the Toronto Master Gardeners.

I am sorry to hear that that your Gladiolas failed to bloom.  Gladiolas grow from corms, these corms store all of the plants energy and ability to thrive and flower, so to understand why your Glads did not flower we must look at the corms.

  • You mentioned that these were new corms.  Did you notice that they were smaller than those that you have planted previously?  Small or inferior corms may not have enough energy stored to produce flowers.  If you feel that this is the case, don’t discard them, instead feed them with a balanced fertilizer, lift in the fall and overwinter carefully.  In the spring continue fertilizing and you probably will have some amazing blooms next summer.
  • You also mentioned that you are gardening in zone 3. Could you have had a hard frost after planting out?  Freezing temperatures or soggy soil can cause the corms to rot or even partially rot, thus surviving but failing to flower.
  • Gladiolus are also very susceptible to thrips.  These little pests will inhibit the buds from forming or cause them to fall off.  If you see signs of thrips (tiny black spots on the underside of leaves) you can try treating with insecticidal soap.

Here is a link to an article in “Gardening know how” with some more information on gladiolas and how to overwinter them.