From the ArcaMax Publishing, Gardening Newsletter:
http://www.arcamax.com/news/gardening/s-156754-152389
Question: My gladioli bulbs sprouted and produced flowers, but now the
flowers are passing and I don't know what to do. Should cut back the
flower stalks? Will the plant bloom again?
Answer: Glads are spectacular when planted en mass. Each bulb or corm
produces only one flower stalk, but each stalk produces several
flowers which open in progression. Once the blooms are spent, the
entire flower stalk should be cut down; it will not produce new
flowers. Leave the foliage alone and it will wither and die down at
the end of the season. After the foliage dies, you can dig your corms
and store them. Gladiolus corms will produce flowers about 100 days
after planting. You can prolong the blooming period by planting corms
at 1-2 week intervals over a period of 4-6 weeks.