Home Gardening Center Tip Sheet: Cannas, Coleus, and CaladiumBy Sonia Uyterhoeven
|·· Annuals & Perennials ··|
A Tapestry of Tropical Plants
Cannas, coleus, and caladiums provide a tapestry of magnificent colors and textures. With their bold leaves and distinctive colors, they were popular in Victorian gardens and traditional bedding schemes--and still are today in contemporary garden design.
Coleus (now with the genus Solenostemon) are an old-fashioned plant that now comes in a whole range of outrageous colors and patterns, from chartreuse to pale pink and fiery orange to deep purple-black. The shape and texture of the foliage is even more varied, ranging from huge to tiny leaves with all sorts of scalloped edging, ruffles, and frills. You may have to pay a little more for these newer cultivars. But once you know how, it’s easy to propagate your own and make enough plants for your garden and to share with friends.
To propagate simply take a cutting from your plant; cut below a leaf node (where the leaves attach), and pull off the lower leaves. Remember to cut off the growing tip if a flower is starting to form. Place in potting soil and keep moist. Coleus is a tender perennial and will be killed by the first frost. Take cuttings in the early fall to over-winter as houseplants. Keep these plants in a bright area throughout the winter and feed once a month. In March take another batch of cuttings to place outside in your garden. Cuttings can also be rooted in damp sand, damp vermiculite, or even in a glass of water.
Once outside, coleus is one of the easiest, no-fuss plants in your garden. Coleus will thrive in sun, partial shade, and full shade. Some varieties do better in certain situations than others, but overall they are very adaptable. If you are moving coleus from sun to shade or vice versa, the trick is a gradual transition. Coleus thrives in average garden soil. They like moist, well-drained conditions. If a plant dries out and wilts, water immediately to revive.
Coleus benefit from a good shearing when they are small plants (around 6 inches tall). This pruning--cutting the branches back to just above a leaf node--induces the plant to produce more shoots and creates a full, well-branched specimen. Once grown, coleus can be constantly pruned to create a compact, formal look or left to grow into an informal flowering plant. The flowers are fairly insignificant light purple spires. If left to go to seed, the plant will complete its life cycle and die.
Coleus will grow into large, voluptuous plants from 12 inches to 3 feet tall, depending on the variety. They take up very little root space and work exceptionally well in containers to create colorful displays. Mix and match coleus with other plants; their bright or subtle colors make great combinations, picking up and playing off other colors in a display. They also make wonderful bedding plants. Several varieties can be planted in large masses to create a tapestry of color and texture.
Cannas (the genus Canna) are grown primarily for their bold, tropical leaves. They are a wonderful addition to containers or flower borders. The golden rule for growing cannas successfully is plenty of sun and good moisture.
Plant your cannas outside when any chance of frost is past (late May in New York City-area). Cannas grow on rhizomes (an underground stem that produces shoots and roots). Plant the rhizome 4 to 6 inches deep with the growing points (the eyes) facing upward. If you buy cannas in a pot, plant the level of the pot even with the soil. Cannas are heavy feeders and thrive in rich organic matter. Amend your soil with plenty of compost and add a balanced slow-release fertilizer.
Cannas are fairly maintenance free during the summer. You can fertilize them mid-summer to give them a boost. Add supplemental water during dry spells to keep the plants healthy. Flowers will start in late July and continue until frost. Once all the flower buds are finished, dead-head flower spikes down to the next set of buds. At times it can be difficult to locate the next set of buds because they are tucked inside a sheath that wraps around the flower stalk. Make sure not to cut off the sheath, as this is where the next set of flower buds is developing.
In the fall, wait until after the first frost before you remove your plants. The frost will kill the foliage and give the plant the signal that it is time to go dormant. Cut the dead foliage down to 4 to 6 inches. Remove the rhizome from the ground. Inspect the rhizome and take off any dead or decaying parts. Cleaning off all remaining soil will help to complete a proper inspection of the rhizome.
Place the rhizomes in a cardboard box or a plastic bulb crate that is lined with newspaper and filled with damp (just slightly moist) peat moss or a mix of peat and old compost. It is important that the rhizomes are not too dry and not too moist. If they dry out, they will shrivel and die; and if they are kept too moist, they will rot.
Store them in a cool garage that does not get above 50–55°F or go below freezing. In the spring, give the rhizomes a little water to help develop the rhizome and new buds. Remember when storing rhizomes: Cold + Wet = Dead, and when growing cannas: Sun + Moisture = Healthy.
Some nice cannas to try in your garden are: ‘Australia’ (with its dark burgundy foliage); ‘Tropicana’ (with its exotic green/red/gold and purple variegated foliage); ‘Stuttgart’ (whose white/green variegated foliage performs best in part shade).
Caladiums or angel wings (the genus Caladium) have large, arrowhead shaped leaves in a startling array of color and patterns. The leaf size ranges from 6 to 14 inches, and the foliage grows from 12 to 24 inches tall and wide. A great accent plant for containers, they perform best in shade or part shade, but many of the newer hybrids have thicker foliage and can handle some sun if given plenty of water.
Caladiums need warmth, ample moisture, and frequent feeding to thrive. Make sure the outside temperature is around 70°F during the day and in the 60s at night before you plant them outside. Plant the tubers 2 to 3 inches deep with the knobby side facing upwards. If you can’t discern top from bottom plant it on its side. You can plant them deeper but they will take longer to emerge.
Deadhead the flowers to ensure good foliage. Fertilize every few weeks with a foliar feed to keep the foliage nice and lush through the summer. You can over-winter the tubers by storing them in peat moss or in net or old onion bags at 50-60°F. Pot up in February to get a head start but make sure you provide bottom heat (around 75°F).
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