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Series Californicae (Diels) Lawrence

related links… Botanical Classification

Series Californicae (Diels) Lawrence. A group of plants within the Section Limniris from the Pacific Northwest states of the USA, with three cornered or cylindrical capsules having three ribs and tough leaves. Horticulturally The American Iris Society has a class that is the same as the botanical series and is abreviated CA. These plants are also referred to as PCN's or Pacific Coast Natives but there are several species that occur on the Pacific Coast that are not part of the botanical series.

See below:



Dykes in The Genus Iris, 1913;---------------------III. The Californian Group.------------------

In California itself and in the neighbouring States along the Pacific coast, there are to be found two sets of Irises, one with comparatively large rhizomes clothed in the broad tough remnants of the leaves of former seasons and the other with very slender wiry rhizomes and leaves that turn a warm red-brown as they die off, instead of the yellow-brown to which the leaves of other Irises fade.

The former of these groups, of which I. longipetala is representative, is in many ways not unlike the Asiatic I. ensata. Its three members will be found described and separated at p. 89. The eight species that form the Californian group, as here defined, resemble each other in their general habit of growth and whole appearance, though they differ in their structural details. All have very slender rhizomes, not much thicker than a quill, and the root fibres are comparatively few in number. The leaves are tough and rather thick and are noticeable among a collection of Irises for the red-brown colour to which they fade as they die. Unless the winter is exceptionally severe, the leaves of most of the species persist until the young growths appear in spring, I. tenax and I. Hartwegii being perhaps the most conspicuous exceptions, though even in the case of these two species the leaves do not die away completely at any time. A peculiarity, in which all the species apparently agree, is to be found in the pink colouration at the base of the shoots. In no other group of Irises is this colour so vivid or so persistent.

As garden plants, these Californian Irises are most valuable, owing to their almost evergreen foliage and to the delicacy and extraordinary range of colour to be found in the flowers. It may be said indeed that no two specimens of any of them are exactly alike in their colouring and they are also valuable in having a flowering period that continues over a longer period than that of most other species of Iris.

In spite of this, they are still comparatively rare as garden plants, owing largely to two causes. In the first place, they will not grow in a soil that is strongly impregnated with lime, and in the second, the paucity of their root fibres makes transplantation somewhat uncertain (cf. Fig. 4, p. 39, showing a rhizome of I. bracteata ).

It should therefore only be attempted during the months from April till July, when growth is active and before the main root thongs have thrown out their lateral fibres. The nurseryman's habit of sending out all herbaceous plants in the autumn is fatal to these Californian Irises, and we can imagine that this is one reason why they are not more widely grown. Fortunately, when once these Irises are established, they readily set seeds, which germinate freely. It should be noted, however, that the seeds do not germinate until March or April, in accordance with the almost invariable rule among Irises that the majority of the seeds germinate when the active growth from the rootstock begins. It is therefore essential that the soil in which these seeds are sown should be kept fairly moist at a time when dry east winds and the growing strength of the sun combine to parch the surface soil in England. My experience has been that, when, owing apparently to drought, the seedlings do not appear in spring, they are apt to appear with the setting in of the autumn rains. In this latter case, they should remain in the pots throughout the winter and, if very small, will benefit by the protection of a cold frame, where frosts will be less likely to uproot them.

It is unwise to plant out seedlings of any Californian Irises until they have made at least four leaves and are fairly sturdy. They must usually therefore remain in the seed pans until June or July. Between that time and the winter, however, they grow rapidly and there should be no danger of losing any from the effects of frost. If, for any reason, the seedlings cannot be planted out by August at the latest, they are probably better left in the pans, though I have succeeded with some that were planted nearly two months later and merely covered with a light during the winter. All the species seem to delight in a light warm soil, well enriched with humus in the form of thoroughly decayed leaf soil. The plants then grow rapidly into large clumps, which flower most profusely. I. tenax, especially, is capable of producing so many flower spikes that the foliage is entirely hidden beneath the mass of flowers.

Moisture is needed when growth is rapid in March and April, but in the late summer a thorough roasting in the sun, far from being detrimental to the plants, seems to ensure a more abundant display of flowers in the following season.
Of many of the species of this group, there are undoubtedly some fairly well marked local forms, such as the I. Watsoniana Purdy, a variety of I. Douglasiana with short stiff fan-shaped tufts of leaves and dark flowers or I. amabz'lis Eastwood, which also I have so far failed to distinguish specifically from I. Douglasiana. The extraordinary variations in colour and growth that occur among the plants in cultivation have led me to take the view that, if we were to describe one or two of these forms under specific or even varietal names, we should have to describe an indefinite number, all equally different and yet all agreeing essentially in their structural details. The species that form this group may be separated as follows:-

Stems branched….........1

Stems unbranched…..........2

Tube linear, at least ½ in. long; spathes green…............Iris Douglasiana
Tube funnel-shaped, very short; spathes scarious…............Iris tenuis

2 ,
Perianth tube short, funnel-shaped….......3
Perianth tube at least I in. long, linear….......4

Stem clothed in short, bract-like leaves ; spathes broad….........I. bracteata
Stem bearing only 1-2 narrow leaves and spathes with narrow, often distant valves….........I. tenax
(N.B. I. Hartwegii (see p. 40) is probably only a local form or, at most, a subspecies of I. tenax.)

Style branches longer than the crests….....5
Style branches equal to the crests…......I. tenuissima

Stem clothed in short, inflated bracts…...........................I. Purdyi
Stem bearing only 1-2 narrow, linear leaves…...............I. macrosiphon
Diels in Engl. & Prantl, Nat. Pflanzenfam. Aufl. (1930)
Noted as CA in AIS registrations.
G.H.M. Lawrence in 'A reclassification of the genus Iris' in Gentes Herbarium 8:346 (1953), New York.


It includes the following species:
Iris bracteata Watson
Iris chrysophylla Howell.
Iris douglasiana Herbert
  • var. douglasiana R. C. Foster
  • var. oregonensis R. C. Foster

Iris fernaldii Foster
Iris hartwegii Baker
  • subsp. hartwegii (Parish) Lenz.
  • subsp. australis (Parish) Lenz.
  • subsp. columbiana Lenz.
  • subsp. pinetorum (Eastwood) Lenz

Iris innominata Leach
Iris macrosiphon Torrey
  • var macrosiphon Eastwood.
  • var elata Eastwood.

Iris munzii R. C. Foster
Iris purdyi Eastwood
Iris tenax Douglas
  • subsp. tenax Lenz.
  • subsp. klamathensis Lenz.

Iris tenuissima Dykes
  • subsp. tenuissima (R. C. Foster) Lenz.
  • subsp. purdyiformis (R. C. Foster) Lenz.

Iris thompsoni R. C Foster


-- Main.RPries - 2009-11-06
Topic revision: r9 - 25 Nov 2016, BobPries
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