Gladiolus has a narrow stem with blade-like leaves and tall, spectacular flower spikes producing 3-5 inch blooms. Though these exquisite flowers may seem daunting, they are quite easy to grow. Simply plant in the spring, and enjoy beautiful blooms in late summer.
Gladioli grow and bloom best in full sun, but they will also thrive in partial shade. Well-drained, loose, fertilized soil is recommended. Gladiolus plants do not fare well among weeds. It is essential to keep gladioli well-watered, providing them with at least 1 inch of water per week.
These colorful and elegant flowers grow well in a variety of climates, but care varies from warmer to cooler regions. With a bit of extra effort, any gardener can enjoy their beloved gladiolus for years to come.
All About Gladiolus
Gladioli are a subset of the iris family, boasting over 255 separate species which vary in color, texture, and size. The blooms are most diverse in South Africa, where the flowers originated. Now, gladioli are grown in many parts of the world including Europe and North America.
The hybridization of gladioli originated in England during the Georgian period as an experiment, bred by the nurseryman James Colville of Chelsea in 1823. Colville’s original hybrid is still cultivated today. It has deep pink flowers with a cream stripe on each of the bottom three petals. Gladiolus hybrids became popular in America nearly a century later, resulting in the establishment of the American Gladiolus Society in Boston in 1910.
Gladioli are perennials, grown from corms. Corms are similar to bulbs, but rather than having leaves or leaf bases, they instead have rounded, swollen stem bases. Most gladiolus corms are hearty enough to be replanted for many years. In warmer climates, corms may remain in the ground where they are dormant during cooler winter months. The blooms and corms of gladiolus are not safe for pets to consume, so it is best to keep pets away from garden beds where they grow and sheds or other storage areas where they may be kept during cooler months.
How to Grow Gladiolus
Though they may appear intimidating with their delicate blooms and tall, elegant stalks, gladioli are not finicky flowers. They are adaptable to grow in a variety of different gardens including container gardens, vegetable gardens, and flower beds.
Gladioli prefer full sun, but they may also grow in partial shade. However, avid gardeners note that the blooms from shaded plants do not bloom as vividly or grow as hardy. Soil should be airy, like sandy loam or loosened clay. Well-prepared soil with good drainage is a must, but so is a good fertilizer, such as 13-13-13 or organic cottonseed meal. Fertilizer should be spread at a rate of 0.3-0.4 lbs every 10 square feet.
It is recommended to plant gladiolus in groups of 10 to 15 corms which both produce a more stunning visual effect and add support to the other stalks around them to prevent drooping. They should be planted 6-10 inches apart from one another and 2-6 inches deep. Larger corms should be planted deeper than smaller ones. Taller varieties of gladiolus may need to be staked, caged, or otherwise supported. Planting near tall, bushy plants is a good way to support gladioli without using artificial supports. Mulching up to 3 inches thick is also recommended to preserve soil moisture and keep weeds at bay.
Watering is essential to a healthy gladiolus. At least 1 inch of water per week is recommended, but this may increase during drought months or if the flowers are grown in raised beds. Pruning and trimming are not necessary for gladiolus.
Gladiolus Year-Round Care
Gladioli are surprisingly hardy, and they can last through the seasons with a bit of extra work. In USDA hardiness zones 7 and 8, gladiolus corms can be left in the ground through the cold seasons and will return the following year. The stalks will need to be cut back and can be composted, then a thick layer of mulch will need to be laid to keep the bulbs insulated until the weather warms. But in cooler climates, corms need to be removed from the ground when the weather cools, typically just after the first frost. In each season, gladioli require care to keep them alive, healthy, and thriving.
Gladiolus corms should be planted in late spring, once the danger of frost has passed. At this time, it is vital to prepare the soil. Make sure it is loose, well-fertilized, and warm enough to plant. It is recommended to wait until the soil has warmed to at least 55°F or 13°C before planting. Local frost dates can be found in a farmer’s almanac or on www.almanac.com. Otherwise, novice gardeners can contact a local garden club for more information about frost dates and ideal planting times.
Make sure when planting to allow 6-8 inches between corms. Place the corm in the hole about 4 inches deep. It is also important to remember to plant them with the pointed end facing up. Cover the corms with loose, well-fertilized soil and press them firmly into place. If the gladioli are being planted for cut flowers, it is best to plant in rows to allow easy access for cuts. It is recommended to water the gladioli thoroughly immediately after planting.
Between the last frost date and into early summer, gladiolus may be planted in groups of 10-15 corms every 10 days. This method of planting will create ongoing blooms throughout early fall.
Gladiolus will typically bloom between 2-3 months of planting, depending on the varietal, with most coming to full bloom in late summer.
Once gladiolus stalks reach 2-3 inches, it is important to weed and mulch the area to ensure proper growth and moisture retention.
Summertime is when the gladiolus comes to full bloom. Remove the faded or dead flowers to guarantee continuous blooms. If the gladiolus is not being used for cut flower displays, which should be cut when the flower is nearly fully bloomed and at an angle near the bottom of the stem, then they should be cut down once all the flowers on a stalk are gone. When the flowers do go, cut the stalk about 2 to 3 inches above the soil. It is important not to remove the gladiolus at this time. Leaving the plant in one piece, unharmed, allows it to mature and grow the corms that can be used for the following season.
Depending on location, drought conditions may occur during the summer months. Atypically dry weather will mean that more water will be needed to keep gladiolus alive and healthy. Be sure to water slowly, directly into the soil, between the hours of twilight and early evening. Also, make sure mulch is present, remaining in place, and generally around 3 inches thick to keep the soil cool and damp.
In USDA hardiness zones 6 and colder, it is recommended that gladiolus corms are trimmed, carefully dug up, and stored indoors in a dry, temperate place throughout the fall and winter months. Mid-autumn is the best time to divide and dry for later transplantation. Any time after the first frost, once the greens start to fade, the energy from the plant concentrates into the corm. This is the ideal time to remove the corm from the ground to be kept for the following season.
After the gladiolus leaves begin to yellow, crackle, and brown, it is time to prune the foliage to the ground and carefully dig up the corms. Corms should be allowed to dry in a warm, shaded, and well-ventilated location for around 20 days. It is recommended that they are not exposed to direct sunlight at this time. Once the corms are dry, remove the old, dry soil from them. Then remove and discard the old bottom corm and any foliage that may still be present.
At this time, baby corms may be attached to the new corm. This is normal. Keep any new corms about ½ inch diameter or larger, and discard any smaller offshoots. These larger, new corms can be kept to grow as separate plants the following spring, although it may take 2 to 3 years of growing and saving the corms’ offshoots before they eventually become a fully formed and flowering gladiolus.
In USDA zones 7 and warmer, corms may be kept in the ground until the following season. If an uncommon cold streak with temperatures of 28°F or lower happens, it is recommended to tarp the area tightly to prevent freezing. Always check the almanac before the winter season if directly in zone 7, as winters can vary from year to year.
In cooler climates, corms must be stored indoors over the winter months. Storage is quite simple. The corms should be kept in mesh bags in a well-ventilated, dark room with temperatures between 35°F and 50°F. It may also be a good idea to dust the corms with an organic anti-fungal powder at this time. They should be checked occasionally for moisture which may cause the corms to rot.
Varieties of Gladiolus
There are over 250 known varieties of gladiolus. Gladioli grow in a vast variety of colors including lavender, burgundy, rose, white, yellow, and pink. They are also one of the few flowers that bloom in a brightly colored green. Because of their vast colors and varieties, gladioli are a florist’s dream. Their tall stalks boast multiple, orchid-like blooms, and they last beautifully in a vase when properly cut.
Some varieties come in a single color while other varieties are multicolored and even have intricate patterns. Priscilla gladioli fade from yellow in their center, to soft pink with lavender edges. Abyssinian Sword Lilies are star-shaped flowers, white, and have star-shaped deep purple centers. While another variety is simply known as Impressive is mostly white and boasts three plum-colored diamond shapes on its three bottom petals.
Gladioli also vary in size and shape. The Mozart varietal has delicate, graceful, lemon-colored flowers while Zizanie gladioli have extra large, curled over petals and an eye-popping red and white cane pattern. The Live Oak varietal has sharp edges on its petals that give its orange blooms a modern, tropical look. Some varieties of gladiolus even have humorous names like Bananarama which are bright, creamy yellow with soft, rippled petals.
Avoiding Pests and Diseases
Before planting gladiolus, be careful to check out the corms. If they feel soft or crumbly, they are no good and should be thrown out. Always begin with healthy corms to help prevent common diseases. Common diseases in gladiolus vary from viruses to fungus, and bacteria to bugs.
Bean yellow mosaic virus is commonly found on gladioli. If yellow patches or streaks appear on the leaves, treatment should be applied immediately. Common treatments for bean yellow mosaic virus and cucumber mosaic virus include using insecticidal soap or neem oil to control the population of the aphids that spread the virus.
Corm rot is caused by fungal growth during winter storage. Corms may become soft and covered with bluish-green fungal growths. Drying corms thoroughly during the beginning stages of the storage process can help prevent corm rot.
Scab occurs in gladioli when the soil is not healthy or well-drained. Symptoms of scab infections include the appearance of tiny, reddish-brown, dots on the bases of the leaves.
Thrips are small insects that can attack the corm while in storage. They are a common problem with gladioli. Treating the corm during winter storage and assuring that storage temperatures range between 35-50°F can help prevent this issue. Soaking the corm in hot water for a few minutes or treating it with a diluted solution of Lysol can also help prevent this problem.
Fun Facts about Gladiolus
Gladioli have also been called “sword lilies” for the blade-like shape of their leaves. “Gladius” is the Latin word for “sword,” giving the flower its name.
While they come in a variety of different colors, a blue gladiolus has never been found.
Not all gladiolus varieties have a fragrance.
Both Vincent Van Gogh and Claude Monet created beautiful paintings of gladiolus during their lives.
The gladiolus is the birth flower of August. It is also a symbol of both remembrance and infatuation making it an ideal flower for memorials and for Valentine’s Day.
The gladiolus is an elegant and stately flower that may seem difficult for a novice gardener. But with a bit of care, even a new gardener can get the hang of growing them.
Have you planted your Gladiolus plants already? Arent’ they beautiful flowers?
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