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A Northumberland Alpine Gardener's Diary

This entry: 03 August 2009 by John Richards

Gentiana in the Dolomites. Entry 123.

Primula rot

I find this is by far the most dangerous time of year for the less easy Asiatic primulas, particularly those multicrowned plants that are more than a year old. Just a few hours of warm weather and dry air (and warm means only 20C or over), even out of the direct sun, and there is a danger that leaves lose turgor. In many cases, turgor once lost will never be regained. At this point it is vital that the limp leaves are removed, NOT by pulling (you may easily remove the rosette or even the whole plant) but by cutting off at the base with a small pair of fine scissors (by far the most important tool at this time of year). If the limp leaves are not removed promptly, rot rapidly sets into the crown and the plant is lost.

I am delighted to say that I managed to save a little seed of Primula sonchifolia this year (only enough for me says he rapidly!), as seed failed last year and I have no young plants coming on. Consequently, I only now have six two-year olds. These all showed signs of stress after one dry warmish day on Friday. I rapidly cut off all the limp leaves and sprayed in the cool of the day, and all the survivors look much healthier again.

Often associated with these limp leaves is root degeneration. Roots wither and die back almost to the crown. These symptoms are similar to those caused by vine weevil, but often if the plant is unpotted and examined carefully, no larvae are found. As long as a few roots remain, this condition need not be fatal. I repot into fresh compost and put the repotted plants back into the shadiest, coolest, most humid spot available for a couple of weeks.

As I say, these symptoms usually affect older plants. One solution is to make sure you always have young plants coming on, as single rosettes are always easier to manage than multirosetted monsters! Nevertheless, much can be achieved by spraying plants nightly in the evening cool. Don't overwater! That will just lead to more rot; just a gentle spray to cool the leaves by the latent heat of evaporation, and to reduce evapotranspiration is all that is needed.

The Paraquilegia chop

In perhaps the most detailed recipe ever published on how to grow a difficult plant well, Mike and Christine Brown wrote an article on the cultivation of that most delectable of all Himalayan alpines, Paraquilegia anemonoides in the Alpine Gardener, September 2005 (p. 272). This is a species I had failed with on several occasions, but to be fair I had never seriously tried to grow it under glass before. Shortly after I had purchased a seedling, Mike generously gave me a few seeds in the autumn of 2007.

I have followed Mike's recipe in nearly all regards. Seedlings were potted on regularly when young, using a well-drained, loam-based compost with a good addition of dolomitic lime. They are plunged in slighly damp sand in the winter, when dormant, but have twice-daily watering from a drip when in growth, and are grown in partial shade under glass. They are also given an occasional liquid feed when in full growth. There are only two regards in which I had ignored Mike's advice, so far. I had not yet watered with 'fizzy' (carbonated) water, although Mike says only to do this is the plants look stressed, and I had not attempted the 'June cutback'.

As will be seen from the accompanying photo, the plants look so well, that the idea of cutting the leaves back to the crown in the middle of the growth season was heartbreaking. However, another very successful grower of paraquilegia, Ian Kidman, who lives only 12 miles from here, also tells me that he does this, but later, in late July (the Browns live 180 miless south of here in Cheshire).

In the end I have decided to conduct an experiment, although with only three large plants to play with, this cannot be replicated. In the end I have chopped only one. Watch this space!

The Paraquilegia chop

Just occasionally, a plant comes into full flower at quite the wrong time of year, and this has been true of Primula villosa. I was lucky enough to be given two young plants at the Hexham Show this spring and they have grown superbly into great multiirosetted clumps while in the cooler alpine house.

Recently, I interpolated myself onto the discussion part of this website, to point out that the attractive Primula shown at one of the summer shows as P. nanobella was in fact the much larger P. florida, equally attractive but a good deal easier to grow, at least to flowering! In this the exhibitor was largely blameless, as several recent sendings of supposed P. nanobella in Jurasek and Holubec lists (which are, I should add, unlike those of another Czech collector, usually very accurate), have proved to be P. florida. I should also add that I am sure that the late autumn collection of seed from dead and dormant material is fraught with many hazards.

At the time, I posted a picture of P. nanobella taken in the wild. This time, one of Jurasek's sendings was true to name, and the seedlings, potted on whole and kept very cool, are doing well so far. I thought you might like to see them. They are in a 10 cm diameter plastic pot so you can see that they are not very large!

Here are two campanulas flowering now, both planted out in the alpine house. I had never grown the Cretan endemic Campanula hierapetrae before. This is a dwarf relative of the Cycladean C. heterophylla from the Afendis Kavousi (Sitia) range where it is said to be rare. We hope to go there in a couple of months and will try to find it.

I have figured the Italian C. isophylla before. It is soundly perennial in the alpine house here.

There are some plants that I used to find easy 30 years ago, and which have undoubtedly become more difficult, possibly symptomatic of climate change. Celmisia argentea and C. sessiliflora are two good examples, as is Phyllodoce caerulea, and indeed most cassiopes. Another is the smallest of all rowans, the miniscule Sorbus poteriifolia. I have failed with this recently, both in a woodland bed and in a shady trough. Finally, grown in a pot in a shady plunge, I have achieved some measure of success. I find it is necessary to protect from frost as the flower buds and leaves develop in May. I doubt if these few berries will last until the first autumn Show, a pity as the autumn colour can be good.

Outside, Dierama pendulum is at its best.

I am following this with a new hybrid lily. We boughts bulbs at the Harrogate Show in the spring, very cheaply (I think £1.50 each). I think its lovely, but sadly I have lost its name.

Dolomite Gentians
My next instalment from our Dolomites holiday last month follows. I am starting with our emblem, G. acaulis, a good garden plant, found in acidic localities in the wild, often growing amongst alpenrose, Rhododendron ferrugineum. It is diagnosed by sepals (and bracts) which in the words of our editor in his excellent 'The Alpine Flowers of Britain and Europe' are 'widest above the base'. The second, beautiful pale form was photographed on the Vial del Pan.

Dolomite Gentians

However, on the Dolomite limestone, by far the commoner plant is the less mat-forming G. clusii. This has 'sepal teeth, triangular, widest at the base'. Quite so!

This is not (only!) a trivial academic distinction as in my experience the two species behave quite differently in the garden. Both are good garden plants, but G. acaulis makes wide-spreading mats, best in a heavy soil, while G. clusii prefers a light, scree mix in a raised bed or trough and forms tight tuffets.

I would ask you to examine the cover photo of our most recent edition of the 'Alpine Gardener' and draw your own conclusion as to the identity of the plant illustrated there. Remember, as the caption says, G. acaulis is the Society's emblem!

The commonest gentian in most of the Dolomites, is the Spring Gentian, Gentiana verna, which grows as a native plant not 30 miles from where I live in northern England. I was amazed to discover in the latest edition of 'The Rock Garden' (123:10) that it also grew in northern Scotland. I was about to send of another rocket when I had the sense to check 'The New Atlas of the British Flora' where I discovered that some miscreant has introduced it to Assynt!

More cushion-forming, with a tighter habit of growth and rather bluish leaves is G. brachyphylla, usually limited to sites above 2350 m. Being a plant of acidic ground, the type subspecies is rather local in the Dolomites, being replaced on calcareous sites by its subspecies favratii (formerly G. orbicularis). Here it is above the Pordoi Pass.

Very much a chasmophyte, confined to boulders and cliffs, is the tiny tufted G. terglouensis, with very narrow leaves. This is mostly a high level plant too, but comes down to below 2000 m below the Gardena Pass, where it occurs associated with late snow-lie against north-facing cliffs..

Finally in the G. verna group is G. bavarica. This always grows in sopping wet sites, often in sphagnum moss, where it creeps around with yellowish rounded leaves all down the stem. It is assuredly, not a garden plant!

Finally, the attractive annual G. nivalis. A great Scottish rarity, in the Alps this is often found in rather mundane sites, as here where it grows on waste land next to a hotel on the Campolungo Pass!

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