Culture tips for ‘Alternanthera ‘Purple Knight’ By Scott Rusch

Alternanthera ‘Purple Knight’ comes from a genusof about 200 species of bushy annuals and perennials. This variety is astriking, dark purple-leafed accent plant with a vigorous, upright andspreading habit that arches over the edge of containers. It has exceptionalheat tolerance and even thrives in conditions such as subtropical summers.Although the foliage is darkest in full sun, Purple Knight performs well infull sun to partial shade.

Its colorful, oppositely arranged leaves are generallylinear to oval, often with toothed margins, and vary in size. Purple Knightwill flower under short days; the flowers are small and are formed in terminaland axillary spikes. Plants adapt easily and are best used as annuals in summer bedding, in an edging or as a backdrop in the landscape. They are excellent massed in hanging baskets and combine well with just about any plant.

Alternanthera Purple Knight is one of five foliage items newfor summer 2002 that were traditionally only available as cuttings, but can beordered as seeds or plugs. Seed will be available in August.


Seeds should be covered lightly with a coarse vermiculite.Germinate Purple Knight seeds at a temperature of 72-76° F and maintain 95percent relative humidity until cotyledons emerge. For more uniformgermination, provide light in the germ chamber or germinate on the bench; lightincreases germination uniformity. Keep soil moisture high until radicleemergence, then reduce moisture levels after the radicle penetrates the medium.

Do not allow the seedlings to wilt. Growth regulators arenot needed to produce top-quality Purple Knight plugs. While growing the plugs,temperatures should be in the range of 65-72° F. Plugs can be held at62-65° F.

Growing On

Purple Knight is a very easy and quick crop to grow at 8-9weeks from sow to finish. Growers should use a well-drained, soilless mediumwith a pH of 5.5-6.3 and a medium initial nutrient charge (EC 0.75 mmhos/cmwith a 1:2 extraction).

This variety is a moderate feeder; fertilize plants weeklywith 200 ppm nitrogen in a complete fertilizer. Growth regulators are generallynot needed; however, if necessary, a Bonzi spray at about 30-45 ppm iseffective in controlling height and spread.


When finishing Purple Knight plugs, allow 4-5 weeks fromtransplant to finish in a 4-inch container from a 392-plug tray. Using largerplug sizes will reduce crop time. Night temperatures should be kept at62-65° F; increase day temperatures slightly to 65-75° F.

Purple Knight can tolerate drier conditions onceestablished, but to avoid damage to leaf tissue, irrigate plants before theyare severely wilted.

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Scott Rusch

Scott Rusch is a sales specialist for PanAmerican Seed, West Chicago, Ill. He may be reached by phone at (630) 588-3464 or E-mail [email protected]

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