librarian2003 (librarian2003) wrote in weagardening, @ 2009-05-13 11:10:00 |
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Week 4 - Plant of the Week - Pacific Coast Irises
Our plant of the week for this week isn't strictly a bulb, but is mainly available from bulb merchants, and so isn't so much of a cheat.
GARDENING FOR PLEASURE
Plant of the Week
Pacific Coast Irises
The Pacific Coast, or Californian, iris are members of the beardless group, and comprise a number of iris species, mainly I. innominata, I. douglasiana, I. tenax and I. munzii, all of which are endemic to the west coast of North America. Botanists classify the wild beardless irises into several "series". Those growing along the Pacific Coast are members of the series Californicae. Their nearest relatives may be among the Siberian irises (series Sibiricae) ranging today between Japan, China, the Himalayas, central Europe and France.
Ancestors of today's Pacific Coast irises probably reached the New World across the Bering Strait at various times during the Ice Ages when lowered sea levels left a broad land bridge between the two continents. Under favourable conditions, they extended their ranges eastward to the Atlantic shores and south at least into northern Mexico.
The isolation during glacial periods must have lasted long enough for irises from different areas to look and act differently, but not enough for them to become mutually infertile. When the ice retreated and their ranges once again overlapped, many were still able to cross and form hybrids. This seems to be the condition for all the PCI species; they can even produce hybrids with some of the Siberian irises, although such hybrids are almost always infertile.
The 11 species of Pacific Coast iris cross with each other in nature, as well as in the garden. Iris breeders have been able to exploit this trait to create hybrids that combine the most desirable features of species and individual plants:
- branching stalks that carry several flowers
- broader petals and a wide colour range
- longer blooming season
- evergreen, straplike foliage
- clumping habit
Nearly one thousand PCI varieties have been named, introduced and registered during the past few decades. Colours are extremely variable, including reds, yellows, browns, grey, blues, purples, pinks and cream. The falls and standards are sometimes different colours, or are streaked and veined in a darker shade. Individual plants bloom for three or four weeks.
Hybrids can range from 6in to 18in in height.
It would be difficult to grow most of the species in the UK, but hybrids bred from inter-species crossing are usually quite easy in British gardens. Pacific Coast iris have a poor survival rate when they're shipped as bare root divisions, so buy as potted, growing plants.
Fortunately they're very easy to start from seed, and almost every seedling is attractive. Sow the seeds as early in autumn as possible, in a peaty soil mix that is one-third sand, perlite or sharp grit to improve drainage. Cover with about 1 cm of mix. Keep in a cold frame or greenhouse, or a sheltered spot outside for the winter, and keep the soil evenly moist. Germination is high, and under the right conditions, some plants can be expected to bloom in 18 months.
The seeds will germinate in spring and resemble blades of grass at first. Prick out into individual pots when about 4 inches high, and keep in a frame or greenhouse for the first winter. Pacific Coast iris transplant well as seedlings, and will bloom their second or third spring. Established plants are drought and frost tolerant.
PCIs resent being divided yearly; it is best to let them grow undisturbed for a few years. Mature plants hate being moved, and this should only be done in September or October, when they are forming new roots, and disturbance is minimal. Otherwise, they are very accommodating.
In choosing a site for Pacific Coast iris, the most important factor to bear in mind is good drainage. They will flower best in full sun, although they will tolerate light shade. They’re usually considered to need acid soil, but opinions are now changing, since the hybrids seem to do well in a relatively neutral garden soil.
PCIs eventually form broad clumps and are eye catching when in full bloom. They combine well with low growing ornamental grasses, heuchera and pulmonaria, and with annuals like clarkia and Californian poppy.
Jo Hanslip
May 2009
Sources:
http://www.pacificcoastiris.org/
http://www.britishirissociety.org.uk/in
Suppliers
Broadleigh Bulbs
http://www.broadleigh-bulbs-autumn.co.u
Pottertons Nursery
http://www.pottertons.co.uk
Seeds
http://www.thompson-morgan.com
Images are at Photobucket:
Pacific Coast Hybrids
There are a number of pages of images, so keep scrolling back.
Delicious enough to eat! And I think these are one of the Next Big Things.
Jo