Tripetala irises comprise an extremely small collection of iris species, and one species called I. setosa is widely cultivated. This iris group derives its name from the fact that a quick look at the flowers gives the impression that they have just three petals. This is mainly because the standards of these irises are really minute, sometimes condensed to the size of bristles. Compared to the style arms of the flower, these standards are very small.
- I. setosa
- This Tripetala iris species is found growing in the wild in several places having cold and wet climatic conditions in the northern hemisphere – ranging from the eastern regions of Asia across Japan to Alaska as well as the eastern coast of Canada. Hence, it is very natural that this iris species is found in various different forms. The plants usually grow just up to a height of 6 inches (15 cm) in some places, while it may reach a height of 3 feet (90 cm) in other places. I. setosa is generally found growing in peaty bogs, damp meadows, and light woodlands as well as along the shorelines. This iris can be grown quite easily in gardens. As far as its appearance is concerned, I. setosa bears some resemblance to Siberian irises. However, different from the Siberian irises, I. setosa have a tendency to live for a very brief period.
I. setosa plants have a preference for damp, acidic soils. It can grow comfortably in full sunlight as well as partial shade. The flowering spikes of this iris are branched and each bears six or even more flowers in the beginning of summer. The color of the flowers varies from blue to purple. The falls are very broad giving the flowers a liberal scattering look. The taller forms of I. setosa look very elegant when they are grown beside water. I. setosa is also a wonderful border plant, especially when their foliage combines with paler hued grasses of the same height. On the other hand, the smaller forms of this iris species are ideal for growing in rock gardens.
The foliage of I. setosa also has red stains at its base. The rhizomes of this iris are plum and often enveloped with fiber resulting from the remnants of the dead leaves. This covering possibly serves as insulation for the rhizomes in their cold original habitat.
This iris species has several named cultivars including “Kosho-en” bearing white blooms and “Kirigamine” whose blooms have a velvety blue-purple hue.
- I. tridentata (syn I. tripetala)
- This Tripetala iris species has a preference for growing conditions that are also liked by I. setosa. It is a perfect iris species for growing in containers with water, provided the rhizome remains above the level of water.
- I. prismatica
- This is considered to be a lonely Tripetala iris species. In fact, it is a unique Tripetala iris that is not grown very commonly. I. prismatica has its origin in North America and is found growing in the wild in marshy lands and moist woodlands the length of the Atlantic coast extending from Nova Scotia to Carolina. The plants grow up to a height of 2 feet (60 cm) and have thin, sinewy stems. This iris usually grows in clumps and produces slender glaucous leaves. I. prismatica has a preference for light shade and damp soils. The blooms of this iris species are elegant and come in a pale violet hue. I. prismatica “Alba” is the white form of this iris species.
- I. unguicularis (syn. I. stylosa)
- The original home of this Tripetala iris species is in the stony regions in Greece, Crete, Algeria, Asia Minor and Syria.
These plants begin to flower sporadically in the fall and the flowering season continues all through the winter till the onset of spring, provided the growing conditions are favourable. The flowers of I. unguicularis practically do not have any stems – they emerge from the perianth tube, which roughly grows up to 8 inches (20 cm) in height. In order to display the entire beauty of the flowers, it is suggested that you trim the leaves just at the onset of winter in order to enable the flowers to open without being damaged. This is important because the foliage of the plant grows up to a height of 24 inches (60 cm) – almost thrice the height of the perianth tube that bears the blooms.
The flowers of I. unguicularis are found in almost all shades of blue – ranging from light blue to deep sky-blue, while there are some that come in a mauve-violet hue. Many other forms of I. unguicularis are found in other colors. For instance, I. unguicularis “Alba” produces white flowers and “Starkers Pink” bears soft pink-hued blooms. The blooming season of I. unguicularis begins much later than the other species belonging to this iris series. Moreover, the flowers of this iris species are relatively smaller, while the leaves are finer. However, the falls and standards of I. unguicularis are broader compared to those of other Tripetala irises.
This iris species has a preference for soils that have proper drainage and providing them with lime dressing from time to time is beneficial for the plants. I. unguicularis plants require full sunlight, but can tolerate cold and are frost resistant. Plants of this Tripetala iris species need to be planted outdoors in spring and watered often till they are properly established. In effect, I. unguicularis plants require sufficient water all through the year, excluding the summer months when the plants like to bathe in the sun.
Plants of this iris species do not require any extra care and you don’t even require dividing them on a regular basis to maintain their normal flowering. However, if you choose to divide the I. unguicularis clumps, you should ensure that the divisions are very small, as the plants will re-establish themselves somewhat reluctantly when the divisions are extremely small. Even if you allow the plants to be on their own mechanisms, they will re-seed without problems. It is interesting to note that even if the parent I. unguicularis plants have been infected by a virus, their seedlings will not be contaminated. This is one iris species which really deserves to be treasured, not just because its blooms are aromatic, but also owing to its habit to bloom early in the season.
- I. lazica
- This Tripetala iris species bears resemblance to another species of the same series – I. unguicularis. However, unlike the latter species, I. lazica is more comfortable in more clammy and damper places and possesses the aptitude to endure cooler temperatures. I. lazica has its origin in Georgia and the north-eastern regions of Turkey. In the wild, this iris species is found growing on shaded sandy banks, usually under a bracken or scrub. These plants produce fairly dull flowers that come in a dark purple-blue hue and have large, erect standards, while the falls are pendent. Different from I. unguicularis, the flowers of this iris species do not have any aroma. When grown in places having mild climatic conditions, I. lazica blooms during winter. On the other hand, the plants flower in early spring in places where the winters are cold and harsh.
Aril and Arilbred Irises
Bearded Irises / Culture / Species
Evansia or Crested Irises
Louisiana or Hexagona Irises
Miniature Dwarf Bearded Irises
Novelty Bearded Irises
Pacific Coast or California Irises
Reticulata or Dwarf Bulbous Irises
Scorpio or Juno Irises