Gladiolus flowers are grown from corms that are not winter-hardy in most northern parts of the country. Glads produce flowers ranging in color from white to pink and yellow to bright orange. If your gladiolus is not blooming, it may be because of one or more reasons that you will need to correct to encourage future blooms.
Encourage growth and flowering by planting only healthy gladiolus corms. A healthy corm has a fat shape with a high center. Corms that are flat and thin are not good for producing flowers. If the corm is thicker, you will have quality flowers. Corms that are smaller than 1 inch in diameter may not flower the first year. These small corms will develop into larger corms the following growing season if they're planted.
Gladiolus plants need at least 1 inch of water per week. During dry spells, you will need to water the plant and soil to keep the plant healthy so it will flower. Plants that remain in dry soil for long periods without any water will wilt and not produce any blooms.
Well-balanced fertilizers such as 8-8-8 — nitrogen-phosphates-potassium — will encourage foliage and flowering. Follow the manufacturer's directions for the type of fertilizer you choose to use. Gladiolus plants need fertilizer when you prepare the bed, at midseason and again when you see flower spikes appear.
Location affects flowering. Gladiolus plants need full sunlight to encourage flowering. Plants in a sunny location will have sturdier stalks and flowers. The flowers will be larger and brighter. Corms planted in shade may be smaller and may not flower.
In areas such as Illinois and Wisconsin where winters are extremely cold, corms should be removed from the ground approximately six weeks after the plant has flowered and just after the leaves start to turn yellow. Place corms in a room with warm temperatures and good air circulation until the outer part of the corm is dry. Next, set the corms in a location where winter temperatures are between 35 and 45 degrees Fahrenheit.