Sir Michael Foster on Tectorum (1883) Gardeners' Chronicle
This is part 2. in a six part article on "Hybridization" for other parts click on number part 1
; part 3
; part 4
; part 5
; part 6
2. Iris tectorum
. — I have compared the above I. Milesii
with I. tectorum, which is to my mind one of the handsomest of Irises, and of which, since it does not seem very largely grown, I may, perhaps, say a word or two. As an outdoor plant I do not find it very happy, but as a pot plant it is very useful, and the plan I adopt with it is as follow-, :— I grow the plants on in pots rapidly in summer, exposing them freely in the open, but never letting them lack water. In autumn, when growth has slackened, I gradually dry them oft", at first in the open, subsequently under glass, eventually drying them quite up, almost as if they were bulbous plants. They are kept dry on the greenhouse shelf until the time when, in midwinter or later, they begin to push. I then clean them, top-dress them without changing the pots, soak them, and let them grow, giving water very cautiously at first, but more freely afterwards ; and they seem to me to flower all the better for being somewhat pot-bound.
Planted in the open they do not, I imagine, get an adequate ripening of the rhizome in autumn ; hence in spring they give plenty of young growth, but comparatively few flowers. Moreover, they start into growth somewhat early in spring and are apt to be injured by east winds and spring frosts. This year, for instance, a whole bed of most luxuriant growth was cut down to the ground by that terrible east wind at Easter. When it is remembered that, as the name implies, this Iris grows in China, on the roofs of houses, it will be seen that some form of "drying off" is likely to prove the proper means of culture.
Now that I am speaking of Iris tectorum, I may say that for some three or for years past I have been trying very hard to hybridise it. Though I have so far failed, I have obtained some results which are not without interest. Last year I had I. tectorum and I. fimbriata in bloom at the same time. I crossed repeatedly in both directions but did not get a single pod to swell. This result has increased the suspicion which I have had for some time, that the two species, in spile of certain striking resemblances, are by no means closely allied to each other ; that in fact the likenesses are superficial and the differences deep. I have crossed I. tectorum with several beardless forms (sibirica, longipetala, &c. ) but never got a pod to swell ; on the other hand flowers crossed with bearded Irises (several belonging to the pumila group, germanica, and iherica) have given me thoroughly well swollen pods, but with imperfect seeds, such as I have never yet been able to germinate. Still I do not despair of eventually getting a cross with some form either of the Pogoniris or Onocyclus group, though I do not think I ever shall with any of the Apogons. Is it possible that the conditions provided by the possession of a thick fleshy rhizome are of more importance in determining the relations of pollen to ovule than the form of the flower ?
I have found by experiment that I. tectorum, in spite of the careful and elaborate structure of the flower, with all its arrangements for insect visits, fertilises itself very readily, and seeds most freely. On the other hand X. fimbriata with me refuses to fertilise itself, and indeed I have as yet failed to get seed from fimbriata even when I crossed one flower with another. Lastly, I have raised a great many seedlings of tectorum, but have as yet seen no variation save perhaps in the size of the flower or intensity of colour. ---Sir Michael Foster
continued here as part 3
To see original article in Biodiversity Heritage Library click here "Notes on Irises", The Gardeners' Chronicle August 25, p. 231-232
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