- One of the main reasons for a gladiola's failure to blossom is due to poor-quality corms. Corms are the enlarged bulb structure that produces the sprouting stems of the plant. Damage can occur during, digging, division, storage and packaging. Look for corms that have a diameter of at least 3/4 inch and a round, full shape. Avoid small, flat corms that may produce substandard plants and blossoms.
- While fertilizer plays a major role in the appearance of blossoms on many types of flowering plants, too much nitrogen can restrict bud formation, resulting in a plant that produces lush foliage but no flowers. Excess nitrogen in the soil usually occurs from an overspray of nearby lawn fertilizers. Avoid this by planting your gladioli away from lawn areas or waiting until after the plants stop blooming for the season to apply your grass fertilizer.
- Gladioli prefer loamy, well-drained soils. Poor drainage can result in fungal conditions and poor bud formation. Although areas around foundations provide sturdy backdrops for gladioli, these locations can experience standing water. Planting gladioli in raised beds can help prevent this problem. Amend the soil with organic matter when planting these flowers near a foundation or porch. Augmenting heavy soils, such as those that have a high concentration of clay, can help encourage proper drainage around the underground corms. Organic matter such as manure and peat moss will help loosen the soil and encourage flowering.
- A lack of sunlight can deter both foliage growth and blossom formation. Gladioli grow best in bright sunlight, but will tolerate a few hours of filtered light, especially during the heat of summer. Trim away the lower branches of overhanging trees to supply a larger dose of sunlight to the gladiola plants.