The Iris genus is a large and diverse one filled with a multitude of Iris varieties. Irises are generally divided into two groups–bearded and non-bearded.
No matter the variety, growing Irises is straightforward and rewards you with beautiful spring blooms.
Types of Irises
There are over 300 species of Irises with thousands of cultivars of Irises, making them a staple in many gardens. The following are some of the more popular varieties to enhance your landscaping endeavors.
This is the most popular variety of Iris named for the fuzzy, beard-like growth that the flower produces. There are several colors available to suit your preference. These Irises prefer full sun and are hardy in USDA zones 3a to 10b. This type of Iris reaches a height of between two and three feet tall.
Dwarf Bearded Iris:
A shorter version of the Bearded Iris, this variety works well as a border flower or as an addition to a rock garden. These miniature versions multiply quickly and are a great choice to fill in bald patches in the garden. These Irises reach a height of between eight and 15 inches tall. The plant prefers full sun but will tolerate partial shade. Grow these Irises in USDA zones 3a to 10b.
Dwarf Crested Iris:
These simple Irises work well in natural, woodland gardens as they grow well in partial shade. These Irises bloom from March to May and reach six inches tall. These dwarf Irises prefer slightly acidic soil and will tolerate full sun if they must. Plant these little beauties to attract pollinators such as hummingbirds and bees.
This beardless variety is a hybrid cross with a light fragrance. This Iris grows from bulbs and blooms in spring. The Dutch variety grows three to four inches tall and makes excellent cut flowers. Plant this type in full sun in USDA zones 5 to 9.
Another beardless type of Iris with many advantages. Unlike some Iris varieties, the leaves on this type stay attractive, and look much like an ornamental grass, long after the blooms die off. Also, this breed is more cold hardy than other varieties and will grow in USDA zones 3 and up. Naturally more resistant to insects and rot, the only downside to Iris type is the flowers are not as showy as other varieties. Still, these plants are low maintenance, reach a height of four feet tall, and grow well in either full or partial sun.
Planting Irises: When to Plant
The ideal time for planting Irises is late summer to early fall to allow the roots time to establish before the cold sets in. For bearded Iris varieties, closer to fall is recommended as this type tends to go dormant in the mid-summer heat. Should you purchase or inherit Irises before late summer, feel free to plant them sooner, as long as the risk of frost has passed. It is better to have the Irises in the ground than sitting in a pot.
Choosing Where to Plant Irises
In most cases, Irises prefer full sun exposure for optimal growth and blooming. Provide at least six to eight hours per day of sun. Most bearded Irises need space to spread and prefer a flower bed on their own. Companion plants are welcome as long as the Irises aren’t crowded or shaded by their companions.
Ensure the soil for your Irises is well-draining, fertile, and slightly acidic. Amend heavy soils before planting to ensure proper drainage and nutrient levels. To prepare the soil, use a shovel or garden fork to loosen the top 12 to 15 inches of soil. Lay a 2 to 3-inch thick layer of compost or manure over the site and work it into the soil.
How to Plant Your Irises
Rhizomes are planted horizontally with the roots underground and the tops of the rhizomes left exposed. If planting Siberian Iris rhizomes soak the rhizomes overnight before planting. Begin by digging a hole approximately 10 inches wide and 4 inches deep. Make a ridge with the soil that runs the diameter of the hole and lay the rhizome on top of the ridge. Spread the roots out and down into the hole on both sides of the ridge. Backfill to cover the roots, leaving the top ½ inch of the rhizomes exposed.
Plant each rhizome one to two feet apart with the ideal grouping being no more than three rhizomes to allow for spreading. Water the soil thoroughly to saturate the ground. Do not mulch the area as this encourages rot.
To plant Iris bulbs, dig a trench 3 to 4 inches deep in the pattern you wish your Irises to grow in. Place the bulbs, pointed end upward, 3 inches apart to avoid crowding the mature plants too early. Cover the bulbs up and water them in until the soil is consistently moist but not soggy.
Companion planting is the practice of planting different, but complementary, plants close to each other for the mutual benefit of each plant type. Benefits can include plants that repel insects, plants that do not compete for the same soil nutrients, or plants that help each other grow larger or produce more product. From an aesthetic aspect, companion planting can prolong the visual appeal of an area by grouping plants with differing bloom times together.
Same Blooming Time
Columbines begin blooming in the spring but continue to produce new flowers well into the summer if expired blooms are deadheaded regularly. The plant’s foliage, which begins green, turns a deep red as the growing season progresses, adding contrast to the Irises’ green leaves. Columbine is also known to attract hummingbirds.
Another springtime bloomer, the bright yellow of these flowers pop against the deeper color of purple or red Irises. Daffodils look best when planted in groupings of at least 10 bulbs, typically in a circular pattern.
These miniature carnation-like flowers make excellent border plants to place in front of your Irises. Common colors for Dianthus are pink, red, and white with the blooms giving off a cinnamon-like fragrance. Flowers will first appear in May and will continue to bloom until fall.
Salvia: Salvia features long spikes of several small flowers in either purple, blue, or pink. These flowers are big pollinator attractors and the foliage remains attractive, even in high temperatures.
Shasta Daisies: Daisies are low maintenance and are great at filling in bare spots in the garden. Depending on the variety, these flowers will grow between 3 inches to 3 feet tall. The Shasta Daisy prefers the same soil type as the Iris so shares the space easily. Daisies make long-lasting cut flowers, with regular harvesting encouraging new blooming. Flowers begin appearing in early summer.
Delphiniums: Delphiniums are tall plants with showy blooms on long stems, reaching between 2 to 6 feet tall. Delphinium blooms are most often blue but can be pink. Lavender, red, or yellow. This plant prefers the same sunny locations as Irises as well as the same soil moisture level. You’ll extend the bloom time by fertilizing your Delphiniums once in the early spring, before new growth, and again during active blooming. With proper feeding and watering your Delphiniums will continue to bloom once the Irises finish and well into early fall.
Care After Iris Planting
Irises don’t have high water requirements, preferring lighter, regular waterings from early spring to the first half of summer. An average of one inch of water per week will often suffice. From late summer to early fall, watering once every second week is usually enough.
Use a 10-10-10 fertilizer to feed your Irises twice during the growing season. The first feeding occurs in early spring with a followup feeding once the plants have finished blooming. Follow your fertilizer’s directions for quantities.
Deadhead expired blooms as they die off. This practice won’t extend the plant’s blooming season but keeps the plants looking tidy. In mid to late fall cut all the foliage back to just above the soil. This practice allows the rhizomes to store energy needed to overwinter successfully.
Overwintering Iris Plants
The most important step to overwintering your Irises is cutting back to foliage to avoid rotting leaves, which may spread to the rhizomes. You can choose to harvest the plant’s seed pods in late summer if you wish to plant more Irises next year. Once harvested, store the pods in a cool, dark place.
The Iris is a common plant in gardens for good reason. These hardy plants produce beautiful flowers early in the growing season. The fragrant flowers attract pollinators to your garden and get along well with a multitude of other garden plants.
Yes, Irises are considered toxic and should be kept away from pets and small children.
The Iris means faith, hope, courage, and wisdom.
Uses of the Iris include using its essential oil in aromatherapy as well as the orris root being used to color and flavor some types of gin.
On average, cut Irises will last between five and seven days.
Irises, especially the bearded variety, spread quickly and can become overcrowded. It is recommended to divide your Irises every three to four years to elevate the crowding.