How to Grow Gladiolus Bulbs Inside

Remove corms from the garden for the best indoor gladiolus displays. Your corms are adapted to the seasonal cycles of light, unlike newly purchased corms that may be from another region. Dig the plants up in fall and set them in a dry area. Once the foliage is dry, cut it off. Place the corms in sphagnum moss inside a paper bag.

Allow the corms to rest between four and 10 weeks from the time you dig them up until replanting. Store them indoors where temperatures are between 38 and 58 degrees Fahrenheit.

Plant the corms six to eight weeks before you want to see blooms. Use a pot with wide drainage holes that is just 1 or 2 inches wider than the corms.

Fill the pot with equal parts peat moss, potting soil and perlite for drainage. Place the corms 3 to 5 inches deep in the soil mixture with the pointed end up, and then fill around them with soil. Water the pot until it is evenly moist.

Place the pot in a room with medium light, where the temperature is 55 to 60 F. Gradually increase the light and heat over the next three weeks until the pot is in an area with full sunlight at 70 F. The tops of the corms should be visible by this time.

Rotate the pot so the corm grows straight. Fertilize every two weeks with a water-soluble fertilizer applied at the rate recommended. Keep the corm evenly moist but not soggy.

Cut spent flower stems back to the base of the plant. When all blooms have faded, move the pot outdoors so the foliage can finish collecting solar energy for the next season's growth. Pull the corms from the pot in fall and repeat the process.