Elegant and vibrant, Blue iris (Iris spuria) is a perennial iris known for its tall stature and stunning blooms, making it a captivating addition to any garden.
I. Appearance and Characteristics
Iris spuria, or blue flag, blue iris, is a species of the genus Iris, part of the subgenus Limniris and the series Spuriae. It is a rhizomatous perennial plant, from Europe, Asia and Africa.
The Latin specific epithet spuria refers to ‘spurious’ meaning false. Linnaeus thought that the plants were hybrids rather than a true species.
It is written as 假鸢尾 in Chinese script and known as Jia Yuan Wei in Pinyin Chinese.
In Czech, it is called Iris Iris žlutofialový.
It is pronounced as ‘EYE-ris SPUR-ee-uh’.
Due to the wide distribution of the species, it has many different common names, including ‘spurious iris’, ‘false iris’, ‘bastard iris’, ‘blue iris’ (in England), ‘butterfly iris’ (also in England), ‘meadow marsh iris’, ‘iris steppe’, ‘iris des steppes’ (in France), ‘Steppen-Schwertlilie’ (in Germany), and ‘dansk iris’ (in Sweden). and ‘salt iris’ (also in Sweden).
Another is ‘seashore iris’, but this probably applies to Iris spuria subsp. maritima. Also ‘salt iris’, and ‘salt marsh iris’, but this applies to Iris halophila (formerly a subspecies).
It was first described in 1753 by Linnaeus, who described it in the first volume of Species Plantarum as being a German species.
On 4 November 1876, John Gilbert Baker described the iris in The Gardeners’ Chronicle on page 583. An illustration of the iris was published in 1981 in Grey-Wilson and Mathew, Bulbs plate 28. It was then published in 1982 by P.J. Redoute in ‘Liles and related flowers’ (183).
It has several subspecies; Iris spuria subsp. demetrii (Achv. & Mirzoeva) B.Mathew, Iris spuria subsp. demetrii (Achv. & Mirzoeva) B.Mathew, Iris spuria subsp. maritima (Dykes) P.Fourn. and Iris spuria subsp. musulmanica (Fomin) Takht. It used to have 3 other subspecies, which have now be re-classified as separate species; Iris spuria subsp. halophila (now Iris halophila), Iris spuria ssp. sogdiana (now Iris halophila var. sogdiana and Iris spuria subsp. notha (now Iris notha).
It has been grown and cultivated in Britain since 1573. It naturalised in south Lincolnshire in 1836. Another colony was growing in Dorset, but in 1972 it was deliberately vandalised and damaged fatally.
It was originally found on 10 July 1955 growing in Limhamm, Skane in Sweden. It was later published in Botanical Notices in 1958.
Blue iris was verified by the United States Department of Agriculture Agricultural Research Service on 20 April 1998, then updated on 1 December 2004. As of March 2015, Iris spuria is a ‘tentatively accepted name’ by the RHS.
It has a thin, slender rhizome that is about 2 cm in diameter, fibrous and has a creeping habit. Under the rhizome are wiry roots.
The creeping habit creates compact clumps of plants. They can reach over 90 cm (35 in) wide.
It has erect, slender, sword-shaped, acuminate (ending in a point), glaucous green to blue green basal leaves. They can grow up to between 25–90 cm (10–35 in) long and 5–12 mm wide. They are normally nearly as long as the flowering stem. After the plant has flowered and set seed, the leaves die in the late summer.
It has a strong, erect, round stem that can reach up to between 50–80 cm (20–31 in) long.
The stem has 1 or 2 lateral, upright branches, or pedicels, which are about 2 cm long.
The stem also has keeled, lanceolate, green, spathes (leaves of the flower bud) (or bracts). These are 40–80 cm (16–31 in) long, and have a membranous tip. The upper cauline (on stem) leaves are shorter than internodes.
The stems (and branches) hold 1–4 terminal (top of stem) flowers, in summer, between May and July. They flower after Iris germanica and are similar in form to Iris x hollandica.
It has large, lightly scented, flowers that are up to 6–12 cm (2–5 in) in diameter, and they come in shades of lilac, mauve-blue, violet-blue, purple-blue, violet, or blue.
It has 2 pairs of petals, 3 large sepals (outer petals), known as the ‘falls’ and 3 inner, smaller petals (or tepals, known as the ‘standards’. The falls are broadly ovate, elliptic, or orbicular with a long claw (section leading to the stem). The fall is 4.5–6 cm (2–2 in) long, and 2.5 cm wide. They have purple or violet veining, and a central yellow or white stripe or signal area.
The standards are short, lanceolate or oblanceolate, erect wavy, and 3–6 cm (1–2 in) long and 8–20 mm wide.
It has a 7–10 mm long perianth tube, the ovary has a long tapering beak, which can be up to 40mm long.
It has a narrow, violet style, 2.5 cm long violet-lilac stigmas, 1.27 cm long anthers, which equal the filament length.
After the iris has flowered, it produces an oblong-ovate, hexagonal (2.5–4 cm long)) seed capsule in September. It has a long beak-like appendage on the top, and 6 visible, longitudinal groves. Inside the capsule are light brown, angular seeds, with a loose membranous testa (surface).
Like many other irises, most parts of the plant are poisonous (rhizome and leaves), and can cause stomach pains and vomiting if mistakenly ingested. Handling the plant may cause skin irritation or an allergic reaction.
II. How to Grow and Care
Sunlight and Soil
Iris spuria needs full sun, at least six hours a day, for the best flowering. Partial shade is tolerated, especially in areas with extremely high summer temperatures. However, both flowering performance and disease resistance may be altered. The soil should be humus-rich, neutral to slightly alkaline, and well-drained. Heavy clay soils may need amending with compost or other organic matter to improve drainage.
Watering
Water the plants well after planting and maintain moisture in the soil for the first few weeks while the plant is establishing. Once established, Iris spuria is quite drought-tolerant, but it will appreciate regular watering during dry periods. While consistent moisture should be provided during the growing season, wet soils must be avoided to avoid rot issues. Less moisture is needed after blooming since most Spuria irises are summer dormant (Do not water your spuria irises when dormant as this will cause rot).
Fertilizing
They are very heavy feeders, so make sure you fertilize them regularly prior to bloom. Apply a balanced slow-release fertilizer in early spring, just before new growth begins. Avoid heavy applications of nitrogen, which can lead to lush foliage at the expense of blooms.
Mulching
A layer of mulch around the plants can help to conserve moisture and suppress weeds. Be careful not to mound the mulch up against the plants, as this can cause rot.
Planting Instructions
The best time to plant Iris spuria is in mid to late summer. The rhizomes (a type of bulb) should be planted about 2 inches (5 cm) deep and 24-36 inches (60-90 cm) apart. Space them far enough apart to grow in the same location for years as spuria irises resent being transplanted. They usually do not bloom the first year after planting. The second year should produce several bloom stalks.
Pruning
Deadhead spent flowers and removed any dying foliage in fall. Old flower stems can be cut down after blooming is over, not only for neatness but to allow air to reach the rhizomes.
Propagation
Blue iris can be propagated by division. Every 3-4 years, you may need to divide the plants if they become crowded or if flowering decreases. The best time to do this is shortly after flowering, in late summer or early fall.
Pests and Diseases
Iris spuria is generally quite disease-resistant, but keep an eye out for slugs, snails, thrips, gray mold, mustard seed fungus, or crown rot.
III. Uses and Benefits
Incorporating Iris Spuria into your garden design can add height, color, and structure to your space. Here are some ideas on how to use these striking plants:
- Borders and Beds: Iris Spuria’s height and vibrant blooms make them perfect for the back or middle of flower beds and borders. They add vertical interest and a burst of color that contrasts beautifully with lower-growing plants. Consider using them as a backdrop for shorter plants with complementary or contrasting colors.
- Pond and Stream Edges: These Irises thrive in moist soil, making them perfect for planting around the edges of ponds or streams. They provide a striking focal point and add structure to these areas.
- Mixed with Grasses: Iris Spuria can look stunning when interplanted with ornamental grasses. The grasses add texture and movement, while the Iris Spuria adds height and vibrant pops of color.
- Mass Planting: For a truly dramatic effect, consider mass planting Iris Spuria. A large grouping of these tall, colorful flowers can be a breathtaking sight.
- Containers: For those with smaller gardens or just a patio, Iris Spuria can also grow successfully in deep containers. This allows you to enjoy their beautiful blooms even if you’re limited in space.
Remember to account for their height and their need for full sun when deciding where to place them in your garden design. The beauty of Iris Spuria, combined with its versatility, makes it an excellent choice for many garden layouts.
IV. Companion Plants
Iris spuria can be successfully grown alongside various other perennials, many of which can complement the distinctive features of the Iris. Here are some suggestions for companion plants:
- Salvia (Salvia spp.): These plants are beloved for their vibrant flowers and sage-like scent. They can create a delightful contrast to the tall, elegant form of Iris spuria.
- Nepeta (Catmint): With its lavender-blue flowers and grey-green, aromatic foliage, Nepeta provides a lovely contrast to the tall, upright form and vibrant blooms of Iris spuria. Both plants prefer full sun and well-drained soil.
- Euphorbia seguieriana: The chartreuse flowers of this Euphorbia species can create a striking contrast with the typically blue or purple flowers of Iris spuria. Both plants are drought-tolerant and prefer sunny locations.
- Stipa gigantea (Giant Feather Grass): The tall, arching stems and golden oat-like flowers of Stipa gigantea provide a lovely backdrop for the bold flowers of Iris spuria. Both plants enjoy full sun and well-drained soil.
- Iris ensata (Japanese Iris): Pairing Iris spuria with another species of iris can create a display of varied colors, heights, and bloom times. Both species enjoy similar growing conditions of full sun to partial shade and moist, well-drained soil.
As with any garden design, it’s important to consider the specific needs of each plant in terms of light, soil, and moisture to ensure they’ll thrive together.
