Plant of the Week – Iris unguicularis

The first plant profile of 2014 is about the winter iris. I chose this plant because there are a few scattered around the Dry Garden area of Ashridge which is where I have been working this week. It gives such a bright injection of colour at a usually grey time of year, I hope you enjoy the read! 🙂

iris unguicularis

Genus: Iris

Species: unguicularis

Family: Iridaceae

Common name: Winter iris.

Translation: From Greek iris meaning “a rainbow” relating to the many colours of the flowers. The unguicularis is Greek again, meaning “narrow-clawed” in reference to the lower end of the petals.

Type of plant: Herbaceous perennial.

Origin: The Mediterranean, specifically Algeria – it used to be known as the Algerian iris.

Technical details

The ideal growing conditions for Iris unguicularis are in full sun, in an exposed or sheltered position, with well-drained soil.

Soil: Iris unguicularis thrives in most soil types and pHs, including: alkaline or neutral: and clay, loam, sand and chalk.

Resilience: Hardy.

Propagation: Propagation is easiest by division, from midsummer to early autumn.

Cultivation: Iris unguicularis is a herbaceous rhizomatous perennial, a popular plant for winter colour. It flowers in late winter to early spring, ideally suited at the base of a sunny wall. It favours alkaline soils, so lime rubble can be a useful autumn top dressing with bone meal and potassium to enhance flowering.

Pest and disease problems: Iris unguicularis can have problems with slugs and snails, and may be subject to bacterial soft rot, grey moulds and viruses.


Interesting Facts 

1. Geophyte is the collective term for the type of plant structure that stores water and nutrients in an underground part of the plant – this refers to bulbs, corms, tubers and rhizomes.


Bulbs have lots of layers, just like an onion. If you cut them open you can see they are made up of scales which are modified leaves that store food. Tulips, daffodils, hyacinths and snowdrops are prime examples of bulbs.

Corms look similar to bulbs, however if you cut them open you would see they don’t have scales. They are modified stem tissue that store food, prime examples are crocosmia, gladiolus, freesias and crocuses.


Tubers are very different to bulbs and corms, you know one already – the potato! There are also tuberous roots which are just enlarged, modified roots that store food. Dahlias, day lilies and sweet potatoes are prime examples.

Rhizomes are stems which grow sideways instead of upwards, running along the surface of the soil or just below it. Irises, gingers and cannas are prime examples of rhizomes. rhizome

2. Iris unguicularis was originally introduced into Britain from Algeria in the nineteenth century by the bulb collector and botanist Dean Herbert (1778 – 1847). It is also found naturally in Turkey, Syria, Lebanon and Israel.

3. Iris unguicularis thrives in Mediterranean-like conditions. Hot and sunny summers produce more winter flowers – a dull summer leaves it with less.

4. Iris unguicularis is mid-blue, there are three main varieties which are most popular:

‘Mary Barnard’ is a deeper violet-blue and the flowers are flatter and more substantial. This plant was collected by Mary Barnard in Algeria in 1937 but not registered under her name until 1962.

‘Walter Butt’ is a silver-lavender colour with larger flowers and a floppier habit.

‘Alba’ is a beautiful white form, it may also be listed as ‘Bowles’s White’. It has a strong golden yellow stripe in the middle of the petals.

5. Iris unguicularis is sometimes referred to as Iris stylosa, however the former should be used as this is the older botanical name.

6. Iris unguicularis has a clump-forming habit, meaning it can be readily divided. However it doesn’t respond well to being transplanted, it is best left once planted.

7. Iris unguicularis was used in ancient times by the Egyptians, who would grind together salt, small doses of dried iris, mint and pepper, to make a substance for cleaning the teeth. Recent research has shown that the iris really does have beneficial properties and a preparation made from iris is effective in combating gum disease.

8. Iris unguicularis has a mild toxicity level, causing a nasty but not serious digestive upset if the geophyte is ingested.

9. In Greek mythology Iris is the Goddess of the rainbow and messenger of the Gods. The Greeks planted irises on women’s graves in hope that the Goddess Iris would guide their souls to their final resting places.

10. The iris is the national flower of France, commonly known as fleur-de-lis.


Plant Names Simplified (Johnson & Smith)

RHS A-Z Encyclopedia of Garden Plants

Collins Guide to Bulbs (Patrick M. Synge) (if you want greater detail on the difference between bulbs, corms, tubers and rhizomes!)



  1. avian101

    As always, very interesting post Becky! Pretty flower too! 🙂


    • Thank you HJ, glad you enjoyed the read! 😀 x


  2. You can really learn a lot on this blog. Thanks.



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