Iris plants are celebrated for their diverse forms and vibrant blooms. Among these, certain varieties, referred to here as “Irispolar” types, stand out for their unique characteristics. These Irises are particularly valued for their cool-toned colors, such as brilliant whites, icy blues, and deep purples. They also exhibit notable resilience to cold temperatures, making them a favored choice for gardeners seeking both elegance and hardiness.
Understanding “Irispolar” Varieties
Many Iris varieties fit the “Irispolar” description due to their cool color palettes and inherent hardiness. For instance, Bearded Irises, known for their ruffled petals and “beards,” often feature cultivars with cool hues like ‘Earl of Essex’ (white and purple) or ‘Ice Pinnacle’ (white and lavender). These can thrive across a broad range of climates, typically hardy in USDA Zones 3 to 10. Siberian Irises are another example, recognized for their slender, grass-like foliage and often blue-violet flowers, with cultivars such as ‘Caesar’s Brother’ (deep purple) or ‘Snow Queen’ (pure white). Siberian Irises are exceptionally cold-hardy, performing well in USDA Zones 2 to 9.
Planting and Site Selection
Planting “Irispolar” varieties requires careful attention to location and soil preparation. Most Irises, including Bearded and Siberian types, need full sun (at least six hours daily) for abundant blooming. Soil should be well-draining, with a slightly acidic to neutral pH, ideally around 6.8. Heavy or waterlogged soil can cause rhizome rot, so improve drainage with compost or other organic material.
For Bearded Irises, plant rhizomes at or just below the soil surface, with the top visible or slightly exposed. Siberian Irises can be planted deeper, about one to two inches below ground. Space Bearded Iris rhizomes 12 to 24 inches apart, and Siberian Irises two to three feet apart, to allow for proper air circulation and growth. After placing the rhizome on a small soil mound and spreading its roots, backfill and tamp the soil firmly.
Ongoing Care and Maintenance
Consistent care helps “Irispolar” varieties thrive and produce their characteristic blooms. Water thoroughly after planting to settle the soil, then once or twice a week for the first few weeks, keeping soil moist but not saturated. Established plants are somewhat drought-tolerant but benefit from regular watering during dry periods. Fertilize in early spring when new growth emerges and again after blooming. Use a low-nitrogen, balanced fertilizer (e.g., 5-10-10 or 10-10-10), applying it around the plant and avoiding direct contact with rhizomes to prevent burn or rot.
Deadhead spent blooms by cutting the flower stalk down to the foliage; this redirects energy to rhizomes rather than seed production, encouraging healthier plants. Remove weeds and debris to help prevent common pests like iris borers and diseases such as leaf spot and rot.
Winterizing and Cold Protection
Prepare “Irispolar” varieties for colder months, especially in regions with harsh winters. In fall, once foliage yellows or after the first frost, cut back leaves. Trim Bearded Iris foliage to about 4 to 6 inches, often shaping it into a fan. Siberian Irises can be cut back closer to the ground. Removing spent bloom stalks and dead foliage helps prevent the overwintering of pests and diseases.
After the ground freezes, apply a layer of light mulch (e.g., evergreen boughs, straw, coarse sand, or arborist chips) to insulate rhizomes and prevent heaving from freeze-thaw cycles. Avoid heavy mulches that trap moisture around rhizomes, as this can lead to rot. Remove winter protection promptly in early spring as new foliage sprouts. While many “Irispolar” varieties are naturally cold-hardy, these measures provide additional assurance for successful overwintering.