Gladiolus are popular garden flowers known for their tall, striking flower spikes. Propagating these vibrant plants is a rewarding method to multiply your collection and ensure continuous blooms.
Understanding Gladiolus Propagation Methods
Gladiolus propagation primarily involves two structures: corms and cormels. A corm is a swollen, underground stem base that stores food, serving as the main reproductive unit for a mature gladiolus plant. Each growing season, a new corm forms on top of the old one, which then shrivels and dies. Cormels are small, miniature corms that develop around the base of the main corm, providing a natural means for the plant to produce numerous new, smaller plants.
While gladiolus can also be propagated from seeds, this method is less common for home gardeners. Seed propagation results in genetic variations, meaning offspring may not resemble the parent plant, and it takes significantly longer to reach flowering size, often two to three years. Using corms and cormels offers a more reliable and quicker path to established plants and blooms, making them the preferred methods for most garden enthusiasts.
Propagating Gladiolus from Corms
Propagating gladiolus from their main corms begins with careful post-flowering management and proper winter storage. After gladiolus have finished blooming in the fall and foliage begins to yellow or after the first light frost, dig up the corms. Use a garden fork or spade, inserting it far enough away to avoid damage, and gently lift the entire plant from the soil. Shake off loose soil, but avoid washing the corms, and discard any that appear damaged or diseased.
Next, cut the stalk down to about 1 to 2 inches above the corm. The corms then require a curing period to dry and harden their outer layers, which helps prevent rot during storage. Spread the corms in a single layer on a screen or in a shallow tray in a warm, dry, and well-ventilated area, away from direct sunlight. This curing process takes two to three weeks at 80 to 85°F (27 to 29°C) to ensure proper drying and disease control.
Once cured, the old, shriveled mother corm at the base of the new corm should be removed and discarded. You can also gently remove any loose outer husks, but keep the protective wrapper intact. For protection against fungal issues, dusting the corms with an all-purpose garden fungicide or “bulb dust” can be beneficial. Store the prepared corms in breathable containers like mesh bags, paper bags, or old nylon stockings, ensuring good air circulation.
The ideal storage conditions for gladiolus corms are in a cool, dry, and frost-free location with temperatures between 35° to 45°F (2° to 7°C). An unheated basement, cool garage, or even the vegetable bin of a refrigerator can be suitable storage spots. Check the corms periodically throughout the winter, removing any that show signs of mold, rot, or shriveling. In the spring, once the danger of frost has passed and the soil temperature reaches at least 55°F (13°C), the corms are ready for replanting. Plant large corms 4 to 6 inches deep with the pointed end facing upwards, spacing them 6 to 8 inches apart.
Propagating Gladiolus from Cormels
Propagating gladiolus from cormels provides an effective way to generate many new plants, though it requires more patience. During the autumn digging process, after separating the new corms, collect these smaller cormels. They often have a hard, protective outer shell.
Before planting, cormels benefit from a preparation step to encourage germination. Soaking them in lukewarm water for 24 to 48 hours can help soften their tough outer coating, improving water absorption and promoting quicker sprouting. Do not soak them for excessively long periods, as this can lead to rot.
Once prepared, cormels can be planted in the spring, typically after the last frost. Plant them shallower than mature corms, about 2 inches deep, and space them 2 to 3 inches apart in a dedicated nursery bed. Cormels usually take one to two seasons of growth to develop into flowering-sized corms, with some taking two to three years before producing blooms. This extended growth period differentiates them from directly planting mature corms, which typically flower in the same season.
Caring for Propagated Gladiolus
Proper care ensures robust growth and abundant blooms for gladiolus. All gladiolus, whether from corms or cormels, thrive in locations that receive full sunlight for at least six hours daily. The soil should be well-drained and rich in organic matter; gladiolus do not tolerate soggy conditions, which can lead to corm rot. Incorporating compost or aged manure into the soil prior to planting can improve both drainage and fertility.
Consistent watering is important, especially during dry periods and as flower spikes begin to develop. Aim to provide about 1 inch of water per week, ensuring the soil is thoroughly moistened to a depth of 6 to 8 inches. Avoid frequent, shallow watering, which encourages surface roots. Mulching around the plants with a 2- to 4-inch layer of organic material helps retain soil moisture and suppress weeds.
A balanced granular fertilizer can be applied once the plants are about 6 to 8 inches tall. Follow product instructions for application rates. Taller varieties may require staking to support their heavy flower spikes and prevent them from bending or breaking, particularly in windy conditions. Insert stakes at planting time to avoid damaging the corms later. Regularly inspecting plants for common pests like aphids or thrips and addressing them promptly will help maintain plant health.