Alternanthera is a large genus incorporating 200 species of bushy annuals and perennials that are grown mainly for their attractive colorful leaves. The foliage is smooth or toothed, and is the main feature of the plant, while flowers are less noticeable. These plants are easily grown from cuttings or seed, but the colors resulting from seed-propagated plants is unpredictable.
Ripe seeds are removed from within the flowers of alternanthera plants for early spring propagation. Alternanthera dentata 'Purple Knight' and Alternanthera ficoidea 'Red Threads' both germinate in moderately cool temperatures, about 55 to 64 degrees Fahrenheit. Keep in mind that plants grown from seed may exhibit unexpected foliage colors that may be different from their parent. Well-drained soil in full sun or part shade are ideal conditions.
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Late summer or spring are the best time to take cuttings, or clones, of alternanthera plants. A sharp blade ensures a clean cut of the short stem cuttings. They are placed in moist soil until well-rooted. Sections 1 to 2 inches in length will root readily. Young cuttings and plants should be protected over their first winter. When they are well established, they can be transplanted into containers or placed in the garden bed. Alternatively, propagate by division in late summer or spring.
It is best to plant young and fully developed specimens outdoors when frost is past. Soil should be moist and well-draining, and the location should receive plenty of warmth and full sun or part shade. Prune to maintain a desired size, particularly if you are growing it as a bordering crop. If possible, bring plants indoors to protect them in the winter. For greenhouse growing, provide full light exposure and plenty of water during the growing season but cut down on watering in the winter.
The variety of Alternanthera species makes this a versatile genus, offering compact, ground cover, trailing, bushing and other growth habits. Plant in full sun for the showiest and most colorful foliage displays. The ruby foliage of Purple Knights makes it ideal as a colorful potted, edging or ground cover specimen. Alternanthera ficoidea 'Versicolor' is a creeping type and exhibits multi-colored, slender leaves and is often used as edging. The burgundy colors of the mounding Alternanthera ficoidea 'Red Threads' plant make it stand out in the garden, where it can be planted in groups.