Growing irises - planting & caring for irises - garden design (2023)

Sons:

Varieties suitable for zones 3-9

Height/spread:

Irises come in many different sizes, some are as little as six inches long and others can grow up to four feet.

• Dwarf varieties 6 to 12 inches tall and wide
• Dutch varieties 1-1/2 to 2 feet tall and 6 to 12 inches wide
• Large bearded varieties range from 2 to 4 feet tall and 1-1/2 to 2 feet wide

Exposure:

Irises need full sun for at least half the day. Some cultivars tolerate partial shade such as Siberian irises and Pacific Coast natives (Iris innominate, Iris tenax, Iris macrosiphonAndIris douglasiana). Many irises will grow in total shade, but they most likely won't bloom.

heyday:

Most irises bloom in spring or summer. Dwarf varieties tend to flower earlier in spring, medium-sized varieties flower later in spring, and larger bearded varieties flower in late spring and summer. Re-blooming strains will bloom once in summer and again in fall.

Color:

There is an extremely wide variety of colors, ranging from white to almost black; although most commonly in shades of lavender, purple, white, and yellow.

Toxicity:

Irises are known to be poisonous to pets, with the bulb being the most poisonous part. See moreCommon poisonous plants for dogs and cats.

There are 2 main groups of irises: rhizomatous and bulbous. The bulbous irises flower in late spring, while the rhizomatous irises flower in summer.

Rhizomatous irises:

Grown from rhizomes (a type of bulb) and can be further divided into 3 categories:

• Bearded:Irises are the most commonly grown and get their name from the distinctive "beard" of white or colored hairs in the middle of each fall (outer surrounding petals). Many cultivars produce multiple flowers per stem and come in a variety of colors.
• Bartlos:Beardless irises include the Siberian, Japanese, Pacific, and Louisiana types, and all have smooth traps. Known for being very adaptable, Siberian irises are a good choice for low-maintenance mixed beds. Japanese and Louisiana strains do better in moist to wet soils, while Pacific Coast strains do best in milder climates with winter rains and drier summers.
• Hood:Crested irises thrive in full sun or partial shade in moist, humus-rich soil.

bulbous irises:

This group includes the Dutch hybrids and the smaller netted or dwarf irises. They all shed their leaves after flowering and go into a dormant phase over the summer. Dutch hybrids tend to flower earlier than the tall bearded rhizome-like varieties and are the well-known variety used in spring bouquets by florists. Reticulated irises are good for growing in groups, but should be divided every two to three years to avoid overcrowding. They are also good forSteingärtenand bustle in pots.

When to plant:

The best time to plant iris rhizomes or bulbs is late summer to early fall to give them ample time to take root before the growing season ends. In hotter climates, they can be planted in September or October.

Where to plant:

Choose a sunny location for your irises where they will not be exposed to standing water. Raised beds are ideal for growing irises as they provide the good drainage needed.

How to plant:

Prepare planting beds up to two weeks in advance by loosening the soil to a depth of 10-12 inches to establish good drainage. Organic material can also be mixed in at this time. Iris rhizomes should be planted where they are easily visible on the soil surface, or thinly covered in warmer climates. They can be over-fertilized with a low-nitrogen fertilizer (avoid high-nitrogen as it can cause rot). Make 2 rows in the bottom with a small ridge in between. Lay the rhizome on the comb, spreading the roots to both sides. Steve Schreiner of Schreiner's Iris Gardens in Oregon says, "There are two reasons irises don't flower: planted too deep or not enough sun." B. Dutch irises should be planted to a depth of 5 inches, with the pointed end up and the roots down, and a spacing of 6 bulbs per square foot.

Boden:

Most irises prefer average to fertile, neutral to slightly acidic, well-drained soil. However, Japanese irises prefer lime-free soil.

For more information on planting bulbs, seeOnions 101: Planting and storing onions

Maintenance:

Cut back the flower stalks after flowering but leave the foliage intact so it can continue to collect and store nutrients and energy that will be stored for the following season. Cut off the leaves at ground level after they turn yellow in fall; This reduces the possibility of overwintering diseases or pests.

Dividing Iris Rhizomes:

Rhizomatous species need to be divided every 3-5 years, typically just after flowering. A reduction in flowering or rhizomes being pushed out of the soil can be signs it's time to dig them up and divide them. If this is a dividing year, don't cut back the foliage - so you know where it is. Carefully dig up the rhizomes and divide them by pulling them apart with your hands. However, some may need to be cut with a knife. Healthy rhizomes are about ¾ to 1 inch in diameter, with good root structure and one to two leaf compartments. Older or unhealthy (soft, rotten, or hollow) rhizomes should be discarded. Wash the roots with water and inspect for diseases or pests, especially iris borers. Trim the leaves to 4 to 6 inches and replant as above, with the rhizome on a ridge and the roots fanned out. Water newly planted irises well.

Modifications & Fertilizer:

Apply a low-nitrogen fertilizer a month before flowering. Mulch should not be used on rhizomes or near the leaves as this can cause rot. For post-flowering varieties, apply a light fertilizer fertilization after the first bloom and water regularly during dry periods of summer for an enhanced fall second bloom.

Irrigation:

Irises generally have low water requirements once established, but can use a little more water if they are unusually dry just before flowering. Louisiana, Siberian, and Japanese irises need more water than the bearded species.

propagation:

Although irises can be grown from seed, they can take a few years to flower. Most often they are propagated by dividing the bulbs or rhizomes in late summer or early fall.

Diseases and pests:

Irises can be severely damaged by iris borersThripseif not controlled.white fliesSlugs, snails, aphids and nematodes can also be a nuisance. Deer rarely harm irises, but will occasionally bite off the flowers of crested species, although they usually spit them out and leave them behind. Irises can also be affected by bacterial leaf rot, root rot, leaf spot, rust and viruses.

Others:

Any part of the iris can cause severe discomfort if ingested. Gloves should be worn when handling iris plants, rhizomes or bulbs as the sap can cause skin irritation.

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