Knock-Out Roses

Adam's Needle (Yucca filmantosa)

Leafy Information

by Joann Vieira, Horticulture Director

2012 Cary Award Winners

Two wonderful groups of plants have been awarded the Cary Award designation for 2012—the ‘Knock Out’ Series of Roses, and Adam’s Needles (Yucca filamentosa and its cultivars). Both extend the season, are pest & disease resistant, are hardy, and are readily found in nurseries and garden centers. For more information on these winners, visit the Cary Award website.

Knock Out Roses

This group of hardy, long blooming and disease resistant roses has made rose growing a more practical endeavor for busy home gardeners. Prior to the introduction of the first Knock Out rose, easy, disease resistant roses were hard to find. Many of the roses commonly available required extensive maintenance for meager rewards of bloom.

Mr. William Radler, the father of the Knock Out family of roses, began growing roses as a child. As his passion grew, so did the time invested in spraying, pruning and mulching. This motivated him to begin breeding roses for hardiness and disease resistance. In 1988 he bred the first Knock Out rose, introduced in 2000—the year that it was recognized as the All-America Rose Selection. Mr. Radler continued to refine the breeding & selecting process, hoping to develop additional colors and fragrances. The family of Knock Out roses now includes 7 distinct selections: the original red-pink single (Rosa ‘Radrazz’); Double Knock Out (Rosa ‘Radtko’) which is pink; Pink Knock Out (Rosa ‘Radcon’)- a paler single pink; Rainbow Knock Out (Rosa ‘Radcor’) which bears coral petals with a yellow center; Blushing Knock Out (Rosa ‘Radyod’) with pale pink flowers that fade as the petals age; and Sunny Knock Out (Rosa ‘Radsunny’) which is a light clear yellow which fades to cream. Garden shoppers will most likely find these roses in nurseries under the trademarked ‘Knock Out’ names.

Left untamed, these undemanding shrubs will grow 3-4' tall, but can easily be maintained smaller with a spring haircut. Blooming will occur off and on (mostly on) all summer until hard frost forces this cheerful plant to call it quits. The hedge of Knock Out Roses that surrounds the elliptical lawn adjacent to the Winter Garden at Tower Hill began blooming in early June, rested a moment, and continued to flower until early November. Even in this wet growing season, no sprays for black spot were required, nor any sign of powdery mildew. Planted in full sun, in a good organic garden soil, all of the Knock Outs should perform similarly.

Adam’s Needle

Adam's Needle (Yucca filamentosa) is a hardy evergreen sub-shrub which was a popular landscape plant during the Victorian era, and in cultivation since the mid 1600s. In addition to being a highly regarded ornamental, it was also known for its ethno-botanical uses (fiber, medicine, soap, food, fish-stunning, etc.). It’s also a great passalong- plant, shared from neighbor to neighbor. At some point, it fell from favor until variegated leaf forms began to appear and drew notice. Now, 3 or 4 variegated cultivars can be easily found and add a bright note to gardens year-round. The brightest selection is ‘ColorGuard’ with a brilliant yellow center to the 18” sword-like leaves which are tinged with pink and rose during the winter months. The cultivar ‘Gold Sword’ is similar – punctuated with streaks of gold and green at the center of the leaves, while ‘Gold Edge’ is, as you would expect, rimmed with creamy yellow. No matter the hue present in these cultivars, all have wiry threads at the margins of the leaves, hence the specific epithet ‘filamentosa’. Though the Yuccas perform best in full sun in well-drained soils, they are tolerant of a few hours (4) of shade, and rich soils. In the best situations they will reward gardeners not only with beautiful foliage (deep green in the species) but also dramatic 7’ spikes of large creamy white bells in June and July. Yuccas are native to the Southeast U.S. where they grow in Louisiana and as far north as Virginia.