Irises thrive their best with regular, thoughtful care

Irises put on quite a show this spring, but now what? With more than 300 species varying in flower form, color, cultural needs and blooming times, keeping track of the care each needs can be overwhelming.

Rhizomatous irises tend to be heartier than bulbous varieties and do better in this climate. With more than a century of breeding providing a vast number of beautiful hybrids to choose from, bearded irises are the most widely grown, although some beardless types, such as the Japanese and Siberian irises, are becoming more popular.

Bearded irises have swordlike leaves that overlap, forming flat fans. Variegated varieties have the added bonus of being showy even when not in bloom.

Irises should be watered regularly from the time growth first starts until about six weeks after blooms fade, as the buds for next year’s flowers and increase in rhizomes form after the plants have bloomed. Leaves should be cut back to a few inches above ground level one month after the blooms have died back.

Division is usually necessary every three to four years as the rhizome clumps become overcrowded and bloom size and number diminishes. Divide and replant after the flower heads are removed.

Keep the large rhizomes bearing healthy leaves and discard old and leafless ones. Break or separate rhizomes with a sharp knife and trim the leaves and roots to about six inches.

Let the cut ends heal for up to a day before planting. Amend the soil with organic matter prior to planting.

Rhizomes should not be buried. They need to be set with tops barely beneath the soil.

Bearded irises will grow in almost any soil. However, they require good drainage and a lot of sun.

To avoid rhizome rot in clay soil, plant in raised beds or ridges. If planting on a slope, be sure to set the growing end of the rhizome facing uphill.

Water regularly until frost hits. Mulch new plantings in the fall to prevent heaving from alternate freezing and thawing.

Beardless irises, such as the Siberian and Japanese types, require different care. Rhizomes of this group have more fibrous roots than the bearded types (which have fleshy roots) and require more moisture.

Plants need to be divided when clumps develop hollow centers. When dividing, it is important to dig and replant quickly, keeping roots moist until planted.

This should be done in early spring or late summer. Rhizomes should be planted approximately 2 inches deep in full sun.

In really hot areas, plant in partial shade. Water frequently throughout the growing period and continue for several weeks after plants have bloomed.

This week in the garden

• Keep snipping off those faded blossoms of annual and perennial flowers. Pinching back stems will keep plants compact and healthy. If you haven’t done so already, pinch back chrysanthemums to increase bushiness and flowering later in the season.

• Deadhead rhododendrons after they finish blooming. Carefully break off the spent flower head just above the point where the new leaf buds are coming out. Fertilize the plants.

• Watch for pests such as mites on geraniums, fuchsias and other susceptible plants. Protect these plants with frequent water sprays. Slugs and weevils are also very active, so treat accordingly.

• Fertilize roses after the first bloom. Use 10-5-5 or 6-10-4 granular formulations according to the label directions for roses, or you may use liquid fertilizer on the foliage every two or three weeks.

• Keep weeding! Weeds compete with plants for nutrients and water and are flourishing with all the rain we’ve had.

• Be sure to water the lawn according to temperature and soil moisture, not the calendar. Water deeply when the top one to two inches are dry. It will require more than a 20-minute sprinkle to properly saturate the soil to a depth of five or six inches.

• Water in the early morning when temperatures are low to minimize evaporation. In addition to their regular watering schedule, it helps to deep-water trees and shrubs a couple of times during the hot weather by letting a hose run slowly enough for the water to soak into the ground beneath the plant.

• If you are still buying annuals, be sure to pick the smaller but bushy plants. Plants that are outgrowing their cellpacks or are blooming profusely will actually take longer to overcome transplant shock and start to grow.