All about dwarf bearded irises

Press, 4 March 1988, Page 16

All about dwarf bearded irises

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Derrick Rooney

Dwarf bearded irises, I wrote last week while discussing irises for the rock garden, really deserve a separate article about their origins and their cultivation. So here it I is. i I First, their cultivation. I Dead easy: full sun, gritty soil, good drainage. Regularly clear away any dead leaves.

Spray them once in winter with lime sulphur arid several times in spring with dithane (sold under the trade name “maneb”) to control leaf spot and rust, the two diseases likely to trouble them.

(Add one of the plantderived non-toxic (to mammals) aphicides (pyrethrum or derris) to the spray in spring if necessary. Spray again with the fungicide after warin, humid spells in summer. ( Split up the clumps every second or third year, about three weeks after flowering, and replant the younger outside rhizomes. Discard the old rhizomes from the middle of each clump. ) Plant firmly with no more than half an inch of soil on top of the rhizome. Feed in early autumn '(about now) with a highpotash, high-phosphate [fertiliser, and again in (spring with the same fertiliser, plus additional nitrogen. Dust the ground around them lightly once a year with dolomite. That’s it.) As for their origins, these colourful springflowering garden plants are derived from a complex cocktail of wild species, mostly of Southern and Eastern European origin.

The names attached to i these European species i are numerous, and in- ) elude many which are I now regarded as syno- ■ nyms. Others which differ in only minor detail have

been merged, so that in recent years European botanists have greatly reduced the number of recognised species. , Some well-established names have disappeared in the process, the bestknown one probably being Iris chamaeiris, the major parent of the small garden irises. ) This name is now considered to be no more than a later, arid thus invalid, synonym of ; the widespread Iris lutescens, which in spite of its name, meaning “yellow,” may have purple, j white i or blue flowers. The (constantly yellow organ is the beard. ; ) j 'lris lutescens is widely distributed throughout South-Eastern Europe and Western Asia, and! the name now embraces many regional forms which differ in details too minor to warrant species rank. The yellow-flowered Iris italica, which I have grown in the rock garden, fits here. Apart from the yellow beard the characters by

which I. lutescens may be identified include the unbranched stem, which is more than 3cm long and many; have one or two flowers. The standards (the; erect upper petals) and the falls (lower petals) need not be the same colour. I. pumila, which is of more northerly (distribution, is somewhat similar but has a shorter l flower stem (less than one centimetre) and short, curved leaves. I have, just received seed of the latter species, collected in Austria. Horticulturally, this little iris lent its name to a hybrid group often sold for growing in rock gardens. The “pumila hybrids,” as they are known, are’also called “miniature dward beardeds,” or “MDBs.” Those displaying a greater influence from the taller I. lutescens are known as "standard dwarf beardeds,” or "SDBs.” Of course, these are not the only genes in the mix. Other contributors include Iris attica, the smallest of the bearded irises (and now regarded las a Greek subspecies of I. pumila), and the eastern Mediterranean I. suaveolens, perhaps better known in gardens as I. mellita. A selection of this, often grown in rock gardens, has red-rimmed leaves and smoky purple flowers. It goes under the horticultural name “Rubro-mar-ginata.” I grow also a Greek form (with pretty yellow flowers.) I Very popular overseas (one North American nursery grows 30 different clones) but seldom seen in New Zealand is Iris aphyllal This is a plant of Central Europe but extends east into the Soviet Union. As might be expected of a plant widely distributed in a number of countries it has numerous aynonyms —- “The World of Iridaceae” lists 28. Five

geographical varieties and three subspecies are recognised. ; Iris aphylla has* blue or purple flowers on stems which characteristically branch below the (middle. The form grown in New Zealand . — and ,1 have seen only the one) — has purple flowers, I grows about 25cm tall, i and is fairly late to break into growth in the spring. I understand it tri be of Greek origin. j Other species i in the SDB mix include I. reichenbachii, j which resembles I. lutescens but has sharply; keeled bracts on the flower bud and toothed lobes on the style-arms, which. project over the falls. Like the 'taller I. imbricata and the smaller I. suaveolens, Reichenbach’s Iris has standards markedly big'•ger than the falls, which are tucked back against the stem. j ( I. subbiflora also (resembles I I. lutescens but grows in winter and has leafy flower; stems. I. variegata is one of (the parents of a gapden classic, “Gracchus/' which dates back to the 1880 s and was one ofjittie first iris hybrids registered. It is still grown by enthusiasts. Ito ( A taller plant) I. vd,riegata has yellojv flowers with brown vetoing (and netting on the falls. It has lent its name to a whole class of hybrids. (

Modern dwarf bearded irises are so ) interbred that bits and pieces of all these species are likely to surface in them — alongside elements (from )sev-

eral I have not mentioned. They all hybridise read L ily, and getting the species true to name is not easy. The societies which run seed exchanges occasionally offer seed of known wild origin, and this is probably the best way to get them. Bearded iris “species” are occasionally! soldi in garden centres but the names are usually suspect. Most ' gardeners aren’t bothered about this and would prefer to grow the hybrids,) which are less troublesome and probably more free flowering. But it is arinoying to anyone trying to put together a collection of "original” plants, i ! The problem is not peculiar to irises. The retail plant trade seems)to regard) itself as exempt from the usual standards of accuracy of label!ing. ( I |

In some cases the mistakes can be traced back to the (wholesale growers, but most garden centres nevertheless just do not seem Ito want to know about I the (mistakes i on their labels.: I’m | not talking about

just names, but also about the labels which deliberately give misleading information, for example by understating the ultimate size of a tree.

I have in my garden a specimen of Eucalyptus viminalis, the “manna gum.” Planted in 1975, it is now, 13 years later, well over 20 metres tall, with a trunk diameter of more than 60cm. I distinctly recall that when I bought it, from one of a well-known chain of garden centres, the attached label estimated its ultimate height to be 12ft (4 metres). It had reached that height within two years. I don’t know why the gardening public don’t make more fuss about that sort of misleading labelling. A retailer of any other commodity who tried it on would very quickly be sent down the road.

When you buy a Volvo car you expect to get a Volvo, not a Volkswagen. When you buy a refrigerator you expect to get a refrigerator, not a washing machine. So it should be with plants.