Prized for their majestic flower spikes, Gladiolus (Sword-Lilies) are popular summer-flowering bulbs. Whether used in borders, containers or as cut flowers, they always provide a spectacular effect with their rich and cheerful colors and their breathtaking vertical lines. And they are so easy to grow! With very little work needed, they will burst into bloom and add bright notes of summer color to the garden, in your pots or inside your home. However, some basic rules need to be followed to enjoy beautiful and impressive flowers all summer long.
1. Choose The Right Corms
- Choose corms that are large, firm, and plump.
- The size of the corms is highly correlated to the height of the spike and the number of florets per spike. The larger the corm, the bigger the plant and more spectacular the flowers.
- Moreover, large corms will typically bloom about 10-15 days ahead of medium‐sized corms. Smaller sizes usually require 3-4 weeks longer than the larger sizes.
- Flower bulbs are measured in centimeters around the broadest circumference of the bulb. The optimum size for Large and Medium Flowered Gladioli corms is 12-14 cm. Small Flowered Gladioli corms have an optimum size of 8+ cm.
2. Select The Right Site
- Best flowering occurs in full sun in humusy, medium moisture, well-drained soils.
- Gladioli adapt to a wide range of soils except clay.
- Provide consistent moisture during the growing season and do not allow the soil to dry out. Lack of water may cause shorter spikes, smaller florets, and smaller corms for next season. After flowering, you may reduce watering.
- Click here to see all Gladiolus varieties
3. Planting Your Sword-Lilies
- Gladiolus corms can be planted from spring through early summer. They may be started indoors as early as a month before the average last frost date (for earlier blooms) or planted directly in the ground after the danger of frost has passed.
- Plant large corms 4-6 in. deep (10-15 cm), medium-sized corms 3-4 in. deep (7-10 cm) and small corms 2-3 in. deep (5-7 cm).
- Corms may be spaced 5 in. apart (12 cm). Sword-Lilies are often planted too far apart from one another, in which case they do not show their best. Planting them close together will also enable them to hold each other and reduce the need for staking.
- Set the gladiola corm with the sprout facing up. Cover the corm with soil and water as needed. Mulch to keep down weeds and conserve soil moisture.
- Plant in groups of 7 minimum for best visual impact.
- Sword-Lilies bloom for 2 weeks or so. To extend their colorful show, you may plant them every two weeks from the last frost date until early summer. It typically takes 10-12 weeks from planting to flowering, depending on weather conditions and variety. The last planting should be no later than early July to give the corms enough time to develop and mature before frost.
- Click here to see all Gladiolus Garden Ideas
4. Cutting Flower Spikes
- To enjoy the best your sword-lily flowers, pick them when the first florets are beginning to open. The remaining florets will open in time.
- Cut the spikes in the early morning or evening for optimum freshness - make sure at least four leaves are left on the plant to allow corm development.
- Place the flowers in warm water to keep the florets from wilting. Leave them in a cool, dark place for several hours before composing your bouquet. This will help the flowers harden off and last longer.
- Change the water daily, and give stems a fresh cut to extend their life.
5. Fall Care
- Most sword-lilies are winter hardy in zones 8-11, so in these warm climates the corms can be left right in the ground. If you live in a colder area and you want to save your corms for next spring, you may dig them up before the first frost and store them over winter before replanting them next spring. Not sure about your growing zone? Check here.
- Corms are usually ready for digging about 6 weeks after they have bloomed. Their leaves should be yellowing and dying back.
- Dig your corms when the soil is dry. Wash off soil and cut the tops off just above the corms. Place them in a light, warm, well-ventilated place for 2-3 weeks to cure (to get rid of excess moisture).
- After corms are cured, separate the new corm from the old dried corm. These two parts should snap apart easily by hand and leave a clean scar on the new corm. Remove the loose husks, leaving the wrapper husks intact. The small cormels can be saved and planted the following year, but it will take 2-3 years to produce a blooming-size corm from them.
- Before putting the corms into storage, dust them with an insecticide for thrip control. Place the corms in trays, paper bags, mesh onion bags, or even nylon stockings for winter storage.
- Store them in a dry, cool, frost-free place where the temperature remains between 35-40 °F (1-4°C).