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A Northumberland Alpine Gardener's Diary

This entry: 23 August 2009 by John Richards

Ericaceae in the Dolomites. Entry 125.

Bulb repot

Over the last week I have been working my way through my modest bulb collection, repotting and sorting. Nearly all the bulbs I grow in pots live on the hotter, sunnier side of my larger (16 x 8'), hotter, glasshouse which has no automatic watering. They are plunged to a depth of up to 18 cm in sand, meaning that the smaller pots are plunged to the rim, but a few of the larger ones stand somewhat proud. I have to say, and this is crucial to what follows, that I don't really differentiate between them in terms of growing conditions. They all get more or less the same treatment.

Over the last two seasons, I have been rather disappointed by the flowering of some of the subjects for which I have the greatest affection; the winter-flowering Narcissus romieuxii group for instance, Galanthus peshmenii, Sternbergias and most of the autumn crocus from Greece. Rightly or wrongly, I have assigned the cause of this poor performance to insufficient summer baking. 2007 and 2008 were both very poor summers of course, and although water had been largely withheld from pots from the time of foliage die-down (roughly mid-May) until the  summer re-pot, I had watered the plunge a few times. Also, I had initiated the re-pot in the last week of July, and now believe that was too early.

Consequently, this year the pots were left undisturbed until August 20th. For a  full three months, no water had been applied whatever to the bench, and it has been a hotter summer. On unearthing the bulbs, the effects have been interesting. It does seem that most of my targets have benefitted from the extra baking. Nearly all the autumn crocuses look better for this treatment, with a good increase of plump, flowering-size bulbs (but not C. laevigatus 'Fontanayei' which has hated it). The African narcissus and sternbergias have also done well. The effect on S. greuteriana has been spectacular with a three-fold increase, all apparently flowering size.

However there has been a considerable down-side and I have lost more subjects than ever before. These included Biarum bovei, Cyclamen libanoticum, Polyxena corymbosa, Allium falcifolium, Narcissus cordubensis and (not surprisingly) several Erythroniums and spring flowering crocus. Several others, even 'easy' narcissus such as 'Hawera' and 'Solveig's Song' have been planted outside before they dwindle to nothing. The lesson is obvious; some bulbs love baking and others don't. I suppose I should now separate these onto different benches.........

A raised bed

Sheila and I spend about a day a week volunteering at the University of Newcastle Botanic Garden, 'Moorbank' which is situated on the Town Moor, only about a kilometre from the heart of the city. When employed, I was for a time Director of the garden, but never had enough time to give to it, so it is very rewarding to be able to help coax the 1.5 hectare site back to its flourishing best. We have been able to persuade about 20 people to join us in this theraputic task, and it is not unusual for those attending at any one session to reach double figures.

All this has meant that we have been able to initiate a number of new projects. Few of these have much relevance to alpine gardening. However, last year the succulent collections under glass received a much-needed make-over (also undertaken by another group of volunteers incidentally). This freed-up a considerable amount of stone, for the original plantings had been surrounded by over-liberally constructed raised beds, made from the lovely honey-coloured, level-bedded sandstone originating from the Ladycross Quarry, situated about six miles south of where we live in Hexham.

For some years, old potting soil had been dumped into a large pile, and the combination of the two resources stimulated us to build a new raised bed. This runs along the side of the glasshouse range, in full light, some degree of shelter, and doubtless with some ameliorating effect in winter from the adjoining heated glass. The site is drive-way, hard and level. The bed is of a considerable size, about 20 m long.

It was mostly built by one of the volunteers, Chris Peacock, although some sections were later rebuilt, and was filled as he built with well-rotted compost and rotted turf in the lower half, topped with the old potting soil, and top-dressed with 'alpine grit', the only element that cost any money. We were very careful to compress the infill as it was built, and then to make the surface very convex at the outset, so the settling effect has been minimal.

A raised bed

The bed was finished about a year ago. Since then I have been planting it, very largely with seedlings I have raised, and cuttings from established plants here. So far about 250 plants have been introduced (as well as many bulbs).

I have to say that this project has been a revelation to me. The conditions we have created are well-drained, light, sunny, breezy, open and with a relatively high pH, very different from my shady, humid, sheltered garden at home with its heavy, acidic, humus-rich soil. Many alpines that I struggle with here, dianthus for instance, have thrived. There have been virtually no losses at all, and the rate at which many young plants have grown has been remarkable. As a consequence, I am saving many of the more interesting subjects I have raised over the last couple of years for Moorbank, rather than see them dying a claggy death here.

Here are a few subjects grown there that are performing now. I raised Platycodon grandiflorum 'Apoyama' white form from AGS seed, and it has done exactly what it said on the tin. Recently I found a pink form of the same thing in a local garden centre, unlabelled (for £1.50!). Of course, the original, which I grow here is blue, and typically much taller ('Apoyama' is the dwarf).

There is a very healthy-looking Daphne blagayana to the left of the previous picture, grown from cuttings from my own plant. This dislikes the acid conditions here in Hexham.

I have been pleased with Wahlenbergia cuspidata, grown from seed I collected near the Sani Pass hotel in the Drakensberg. This was not hardy in Hexham, but has overwintered twice in Newcastle, covering itself with a shower of huge blue flowers for some months. It is now reaching the end of a long season.

Perhaps the outstanding subject at present is another hardy South African, Nemesia caerulea. This, or hybrids of it, has suddenly hit the garden cenres in a big way, the latest craze for bedding and hanging baskets. But the plants shown here were grown from wild-collected seed, and what a superb, hardy, late-flowering subject with a long flowering period!

Yet one more South African, purchased from an AGS stand l;ast autumn and not turning a hair during the last, moderately severe winter. This is I think Eucomis pole-evansii 'Purpurea', and what an interesting plant is this.

Lets move on to a few 'real' alpines, not in flower, but establishing well (both these androsaces overwintered in this position without being covered). Both A. brachystegia and A. tangalushanensis are as yet very scarce in cultivation, but on this evidence they definitely show promise.

Finally, for the time being, young plants of Gentiana purdomii.

Zinc troughs

Alongside the raised bed we have two zinc 'troughs'. These were originally used to store rainwater within the glasshouses, but the automatic watering system has long since made them redundant, and they were due to be thrown out. We drilled drainage holes in them and  filled them with an alpine compost. Originally they were planted mostly with spring bulbs and these have done superbly and have been figured on these pages before. Sadly, one of the troughs has become overrun with Cymbalaria hepaticifolia and will have to be empted and replanted, but the other also now has a number of healthy alpines.

Zinc troughs

The little delosperma on the right is D. lavisiae, another plant I brought seed of back from the Drakensberg.

Here to finish with is an 'autumnal' bulb (but really best in late July!), that we now must call Acis autumnalis. This has really thrived in the zinc troughs.

Dolomite Ericaceae

Continuing my series of vignettes from the Selva Dolomites, here are a few (lime-loving for the most part!) Ericaceae.

The classic Dolomite Rhododendron is Rh. hirsutum with eye-lashed leaf edges and lacking a rusty leaf underside. It is not often showy, but can be at its best as a small plant on limestone boulders. It seems to be rarely grown in gardens.

Dolomite Ericaceae

The 'alpenrose', Rh. ferrugineum is also common in the Dolomites, but usually grows in a layer of 'duff' under trees or in scrub. It has rusty-backed leaves.

On the 2200 m Passo di Pennes, west of the Adigo, we found a small group of white Rh. ferrugineum, a form I had never seen before. We brought a few small cuttings back, but they have not thrived.

One of the most sought-after of all Dolomite plants is Rhodothamnus chamaecistus. This lovely thing is rarely grown. I have never grown it, but my experience with the (at least very closely related) Turkish Rh. sessiliflorus suggests that it hates disturbance of any kind. The best recipe is probably to introduce quite young seedlings to a permanent position and then leave them severely alone. This has worked for me in a polystyrene trough.

Rhodothamnus is very scarce in the Selva region. There is a bit right at the top end of the Vallelunga, and at least one boulder in the valley floor has two plants. However it is abundant further east, and the nearest site to Selva where it can be found commonly is the Falzarego Pass, especially below the 'loop' road at the summit. This is a high site (2300 m) but it is a very early-flowering plant, best in May at lower levels.

My companion remarked how very like the American Kalmiopsis leachiana Rhodothamnus is. Why are they not put in the same genus? Is this a bit of American hubris?!

Finally, a couple of smaller subjects. Arctostaphylos uva-ursi, the bearberry is a lovely thing and a good garden plant, not grown often enough. It is very tolerant of lime. Following this is a photograph taken towards the upper end of the Vallelunga. I have striuggled to name this, and have finally come to the conclusion that it must be a strange, leggy, shrubby version of Vaccinium uliginosum.

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