The ‘Benton Olive’ iris is a highly regarded cultivar, captivating gardeners with its distinct beauty and unique appeal. It offers a sophisticated touch to any garden space, making it a desirable addition.
Understanding ‘Benton Olive’ Iris
‘Benton Olive’ is a Tall Bearded Iris, known for its stately presence and elaborate blooms. Hybridized by Morris in 1949, this cultivar features a unique color palette: olive-gray and pale blue standards, with olive-tan falls often flushed with blue-purple and veined with brown. Its large, fragrant flowers emerge on erect stems, typically reaching about 36 inches (91 cm) in height. It blooms from late spring into summer.
Ideal Growing Conditions
For robust growth and abundant flowering, ‘Benton Olive’ irises require full sun, meaning at least six hours of direct sunlight daily. While they can tolerate some afternoon shade in extremely hot climates, insufficient sun leads to poor or absent blooms.
Well-draining soil is crucial, as these plants are susceptible to rot in overly moist conditions. A slightly acidic to neutral soil pH, ideally around 6.5 to 6.8, is preferred. Incorporating compost or other organic matter can improve drainage in heavy clay soils, but sandy or gravelly soils are naturally excellent. ‘Benton Olive’ irises are hardy in USDA Zones 3-9.
Planting and Establishment
The best time to plant ‘Benton Olive’ iris rhizomes is late summer to early fall, ideally between July and September, or at least six weeks before the first hard frost. This timing allows rhizomes to establish a strong root system before winter. Before planting, loosen the soil to a depth of 10-15 inches and incorporate compost to enhance drainage and fertility.
When planting, create a small soil mound in the center of the hole, spreading the roots down its sides. Plant the rhizome so its top is at or just slightly below the soil surface, often with a portion exposed to the sun. Planting too deeply can inhibit flowering and lead to rot. Space rhizomes 12 to 24 inches apart for good air circulation and to prevent overcrowding. After planting, water thoroughly to settle the soil.
Ongoing Care and Maintenance
Fertilize ‘Benton Olive’ irises in early spring, about one month before bloom season, and again after blooms fade in late summer or early fall. Use a low-nitrogen fertilizer (e.g., 5-10-10 or 6-10-10), as high nitrogen encourages leafy growth at the expense of flowers and can promote rot. Apply fertilizer around the plants, ensuring it does not directly contact the rhizomes, then water well.
Deadhead spent blooms by cutting flower stalks back to an inch or two above the rhizome to prevent seed formation and redirect energy into the plant. Regular weeding reduces competition for nutrients and maintains good air circulation around the rhizomes.
Dividing iris rhizomes every three to five years is essential for long-term plant health and prolific flowering. This process, ideally done six to eight weeks after flowering, prevents overcrowding and revitalizes the plant. Dig up the clump, separate healthy young rhizomes, discard older woody sections, and replant the divisions with trimmed foliage.
Troubleshooting Common Issues
Iris borers are a common pest; their larvae tunnel through leaves and into rhizomes, often leading to bacterial soft rot. Signs include ragged, water-soaked leaves, dark streaks, and mushy rhizomes. Prevent borers by removing old iris leaves and debris in fall to eliminate overwintering eggs, and inspecting leaves in spring for early tunneling signs. Discard infested rhizomes; minor infections can be treated by removing diseased tissue and allowing the area to dry.
Bacterial soft rot, often associated with borer damage or poor drainage, causes rhizomes to become soft and odorous. Improving drainage and ensuring proper planting depth helps prevent this issue. If soft rot occurs, remove infected parts, sterilize tools, and allow the remaining rhizome to dry in the sun.
Poor blooming can result from too much shade, overcrowding, incorrect planting depth, or excessive nitrogen fertilizer. Addressing these environmental and cultural factors often resolves blooming issues.