Crocosmia, also known as montbretia, is a popular summer-blooming bulb with showy spikes of orange, red, or yellow flowers. However, this vigorous plant has an aggressive spreading habit that can quickly get out of control in the garden. If left unchecked, crocosmia will creep stealthily via underground corms and stolons, colonizing large areas and crowding out other plants.
If you know how crocosmia grows and how persistent it is, you can stop it in its tracks before it takes over your whole garden. Here are the best ways to get rid of crocosmia that is taking over your flower beds.
Monitor and Remove Unwanted Growth
Keep a close eye on crocosmia plants that are already there, especially those that are near the edges. Remove any new shoots that appear in places where you don’t want plants to grow. Getting rid of small clumps is much easier than getting rid of big, established patches.
Check the area around mature clumps and pull out all the weeds to get rid of sneaky stolons. I’ve seen sprouts grow roots up to 20 feet away from the main plant. Watch out for rogue growth and get rid of it before it takes hold.
Cut Back Foliage After Blooming
Cutting off the plant’s dead leaves in the fall keeps its corms from storing energy for next year’s growth. This won’t kill the corms, but it will make them weaker and slow their growth.
Use hand pruners or hedge shears to cut all the yellowing leaves and stems back to ground level. Don’t leave any greenery sticking up for the plant to continue feeding on.
Dig and Divide Overgrown Clumps
Every 3-5 years dig up large clumps in early spring and divide them into individual corms or smaller groups. Replant 18+ inches apart to restrict spread via underground stolons. Discard excess corms or give them away.
Use a garden fork to lift out the entire clump carefully. Gently tease apart or cut the chain of connected corms. Dividing congested clumps reduces their vigor and controls rapid multiplication
Grow in Containers
For extremely spreading varieties like ‘Lucifer’ or ‘George Davison’, grow them in containers rather than planting in the garden. A pot’s restricted space prevents the corms and stolons from running wild.
Plant a few corms per pot in quality potting mix. Situate in full sun with drainage. One container per variety is plenty, as crocosmia will quickly fill its allotted space.
Use Physical Barriers
Installing physical barriers can block those roaming stolons. Try sinking vertical root barrier strips or plastic edging around clumps. Or plant in a sunken pot with just the foliage poking out.
For mass plantings, lay thick black plastic sheeting under the soil surface. Just be sure to leave access to dig up and divide the clumps occasionally.
Choose Less Invasive Varieties
Some crocosmia spread more aggressively than others. To enjoy the flowers without the spread, try these better-behaved cultivars:
- ‘Solfatare’ – compact plants with sulfur-yellow blooms
- ‘Severn Sunrise’ – glowing apricot flowers on short stems
- ‘Star of the East’ – low-growing with orangey-red blooms
Remove Wayward Growth Ruthlessly
Don’t hesitate to rip out invading crocosmia, corms and all, from prized garden areas. Keep removing regrowth for a season or two until it eventually dies out. Stay vigilant to prevent it from creeping back.
With constant monitoring, dividing overgrown clumps, using barriers, and taking quick action on unwanted growth, you can control energetic crocosmia. Enjoy their fiery floral display without this beautiful bulb taking over your garden.
Tips to Stop Crocosmia Spread
- Monitor edges of clumps and remove new growth
- Cut back spent foliage after blooming
- Dig and divide congested clumps every few years
- Grow extremely spreading varieties in containers
- Use physical barriers like plastic edging or root barrier
- Choose less invasive crocosmia cultivars
- Ruthlessly remove unwanted plants, including all corms
Common Problems with Crocosmia
While a beautiful bloomer, crocosmia is prone to certain problems. Watch for:
- Root or corm rot – Caused by wet soil. Ensure good drainage.
- Powdery mildew – Promote air circulation, water at soil level.
- Rust – Improve air flow, remove debris, use preventive fungicides.
- Aphids – Attract beneficial insects, hose off with water, use insecticidal soap.
- Snails/slugs – Handpick, use traps and baits, copper barriers.
Catch problems early before they impair plant health and allow crocosmia to spread unrestrained. Proper site selection, maintenance, and pest control keeps your plants, and garden, healthy.
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Crocosmia is a genus of perennial plants in the Iris family, native to Africa. They are often grown for their showy, brightly coloured flowers that bloom in the summer. Crocosmia plants are easy to grow and care for, making them a popular choice for gardens and landscaping projects.
Crocosmia plants typically range in height from 1 to 4 feet and produce sword-shaped leaves and tall, arching stems. The flowers are borne in clusters at the top of the stems and are often bright orange or red in colour, although some species have yellow or pink flowers. Crocosmia plants are also known for their attractive seed pods, which add interest to the garden even after the flowers have faded.
Crocosmia plants prefer full sun to partial shade and well-draining soil. They are typically planted in the spring or fall and should be watered regularly until established. Crocosmia plants don’t need much care and don’t need to be pruned much. However, cutting off the spent flowers can help the plant produce more flowers. They are also resistant to most pests and diseases.
Crocosmia plants are mostly grown for their pretty looks and are often used in beds, borders, and container gardens. They are also popular as cut flowers and are widely used in floral arrangements and bouquets. Additionally, some species of Crocosmia have medicinal properties and have been used to treat a variety of ailments in traditional African medicine.
Crocosmia is a colourful and easy-to-grow plant that provides a burst of colour in the summer garden. With their brightly coloured flowers and attractive seed pods, they are a popular choice for gardeners and florists alike.
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Five Mistakes to Avoid Planting and Growing Crocosmia Bulbs – Montbretia
FAQ
How do you control crocosmia?
Every three to five years, in early spring, dig up the dormant corms, separate them into single corms, and plant them back in smaller groups. Crocosmias also tend to spread, though some do it more easily than others. Over time, they can make big, dense swathes. To control them, dig up and remove unwanted corms.
Is crocosmia an invasive plant?
Once cultivated as an ornamental, it has since become invasive on the west coast, spreading in disturbed sites as well as wet grasslands, open woodlands, pastures, gardens, wastelands, and along roadsides.
What is the problem with crocosmia?
Dislikes. Growth may be stunted in very dry soil. They won’t flower well in deep shade.
Do crocosmia bulbs multiply?
Crocosmia corms multiply readily, so clumps will become congested and flower less vigorously over time. The best time to divide and replant congested clumps is in spring.
How does Crocosmia spread?
Crocosmia spreads primarily through its corms, which are underground storage structures that resemble bulbs. The corms grow and divide over time, forming new corms that can produce new shoots and flowers. In the wild, crocosmia can also spread through the seed that it produces.
How to keep Crocosmia from taking over your garden?
By pulling up some of the plants, you’ll give the others room to flourish. You can also spread a thick layer of mulch around the base of the plants to help inhibit their growth. With a little bit of effort, you can easily keep crocosmia from taking over your garden.
How do you keep Crocosmia from flopping?
There are a few ways to prevent crocosmia from flopping: Staking: Using stakes or other supports to prop up the stems of the crocosmia can help to keep the plants upright. Insert stakes into the ground near the base of the plants, and then tie the stems to the stakes with twine or gardening wire.
Should I remove Crocosmia If I live in an invasive area?
However, if you live in an area where crocosmia is considered invasive, you should consider removing the plant. In general, it’s important to know how non-native plants might affect local ecosystems and take the right steps to control them.
Is Crocosmia a spreader?
Crocosmia is not a very aggressive spreader, but if not controlled it can colonize an area and form large clumps that can crowd out other plants. Therefore, it is important to be aware of the plant’s behavior and spread rate in your area. Crocosmia can grow back if the corms are not removed when the plant is dug up.
How do I prevent Crocosmia diseases?
The best way of preventing crocosmia diseases is to purchase healthy bulbs from a reputable greenhouse or garden center. Inspect bulbs carefully and never purchase bulbs with cuts or bruises. Handle the bulbs carefully. Be sure to plant crocosmia in well-drained soil, as most diseases of crocosmia are a result of excess moisture.