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Where were all those April showers?

April 24, 2019
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After a dire March; cold, wet and windy, April has been (mostly) a joy, although until today (24th) we have had not a drop of rain – so much for April showers! It has also been unseasonably warm (again, after an even more surprising mini-heatwave at the end of February), with day temperatures in the low 20s °C for a week and with night temperatures not falling below 10°C.

All this alternation of hot and cold, wet and dry, has resulted in stop/start growth of an unusually exaggerated nature. Many plants, notably early rhododendrons and magnolias, lasted well in the cool weather but have been hurried to their conclusion in the warm spell of the last 10 days. Many alpines, too, including a wide range of primula species, saxifrages and pulsatillas, flowered early and lasted well until the weather became unseasonably warm.

Peonies are mostly 2-3 weeks ahead of normal and several, including the divine P. ostii, with its great silky petals tinged with pink on opening fading to pure white, are now finishing their short-lived but oh-so memorable display. The plant shown is now 3m across and 1.5m high and is about 15 years old from seed. The latter is set sparingly if left to nature but the assistance of a rabbit’s foot, or more mundanely an artist’s paintbrush, should ensure a better result. The seeds, like those of most peonies, are large and oily and do not store well. It’s best to sow them as soon as they are ripe but be prepared to wait two years before the first signs of germination are seen, the first season as with many peonies having been taken up with establishing a root system.

While we’re on peonies…

Just a few flowers of some of the herbaceous peonies. All species raised from seed but not necessarily exactly what they claim to be in every case!

A few celmisias

As the days lengthen and warmth increases, celmisias that have been slightly ‘off-colour’ through the winter start to brighten up and the silvers in particular take on a glow that will last throughout the season and well into the autumn. Personally, I would not care too much if none of my New Zealand daisies ever flowered, it is for the fine foliage that I chiefly grow them. Also, they love our cool, moist, seaside climate and are mostly very long lived and trouble free. In order of occurrence here are C. haastii, C. spedenii and the intriguing flower buds (fully 20mm across) of C. semicordata.

Mertensia maritima

While we are on plants which have better foliage than flowers, I would recommend the so-called Oyster leaf  (Mertensia maritima), an interesting member of the forget-me-not family. It has a boreo-arctic distribution in Europe, Asia and N. America, where it often occurs on coastal shingle and stabilising sand, including locally along the coasts of Scotland, Northern Ireland and Cumbria. The leaves are fragrant when crushed but whether of oysters is open to dispute; it is certainly used as a culinary herb in some parts of Scandinavia. As its habitat suggests, it requires a perfectly drained site, preferably in full sun. The flowers are disappointing but the winter rosettes are a particularly bright glaucous silvery blue. Seeds are set freely and are easily raised, I have not tried vegetative propagation.

Late Kabschia saxifrages

Most of my Kabschia saxifrages had finished flowering by the end of March but two from the ‘Allendale’ stable (‘Bonny’ and ‘Hobbit’) were best in early April this year. The former is a good clear yellow but as yet fairly sparsely flowered here. ‘Hobbit’ is just the opposite, now a 25cm wide cushion that has been covered in flowers for three weeks.

Sebaea thomasii

This vibrant yellow-flowered Gentiana verna lookalike comes from the Drakensberg mountains of Lesotho where it typically grows in damp turf on rocky hillsides. It seems to be quite easy to grow in the open ground, in our case in a semi-shaded damp crevice bed, although it is usually seen in pots at shows where a big plant always catches the judges eyes.

The form shown is the larger flowered variant. Even more dwarf and somewhat more free-flowering is the form ‘Bychan’ from Aberconwy Nursery. It is not difficult to raise from cuttings of new growth taken soon after flowering ends in May/June. I presume it is OK from seed, although so far I have not collected any from my single plant.

Arum creticum

This is a plant whose flowering I always anticipate with pleasure as winter gives way to spring. Having seen it growing in abundance in sub-montane rough pastures in its Cretan homeland, it has a special place in my affections. It is easy to grow either from tubers, which may be bought dormant in winter, or from seed, which generally germinates freely. The plant shown is c.12 years old and every year it slowly increases and puts forth more of its showy blooms. It is growing in a fairly rich soil with moderately fast drainage in a position in full sun.

Corokia cotoneaster  ‘Little Prince’

Corokia is a genus in the Argophyllaceae family comprising about ten species native to New Zealand, Australia and Rapa Iti. Corokia species are shrubs or small trees with zigzagging (divaricating) branches, hence their common name (not uniquely) of wire netting bushes. All are hardy and several species and cultivars are widely grown in NZ, sometimes as hedging plants, but few are seen in Europe or N. America.

C. cotoneaster ‘Little Prince’ is, as the name suggests, dwarf (0.5 m high after 10 years) and of late has covered itself in its tiny yellow flowers which show up quite well against the bronzy foliage. It can get a bit out of hand if not clipped now and then. Apparently in NZ it produces copious red berries but it has never fruited here, maybe because I have only one plant and it is a dioecious species? Cuttings taken in June/July root quite easily and make good plants in c.2-3 years.

Exochorda giraldii  ‘The Bride’

This splendid shrub never fails to provide a bright focal point in the garden from early March until the end of April. It may need quite determined pruning to keep it to an allotted space but does not resent even quite drastic attention with the secateurs. Propagation form semi-hardwood cuttings is easy.

Some mid-season dwarf rhododendrons

To finish with a blast of colour, here are a few of the best of our mid-season rhododendrons. They’re easy to grow in any freely drained acid soil and so rewarding. If they are getting too big, trim them back after flowering. If you want replacements, cuttings taken in June/July will generally root pretty well in 50:50 peat:sand (I’m afraid nothing seems to be as good as peat in rooting dwarf ericaceae) in a shaded propagator, and should flower in 2-3 years.

Image of John Good John Good

John Good is a retired research forest ecologist with a lifelong interest in all aspects of the observation and cultivation of plants, alpines and woodlanders being of particular appeal. He has lived in North Wales for more than 40 years and he and his wife, Pam, have lived in their current hillside home and garden overlooking the sea for 27. He is an Emeritus Professor of Environmental Forestry at Bangor University and maintains a strong interest in all matters related to land use in general and the balance between agriculture and forestry in particular.

He has been a member of the AGS for more than 50 years and a judge at our shows for half of these, as well as being a member (now friend) of the RHS’ Joint Rock Garden Plant Committee. He has travelled and lectured widely on alpines and written many articles and several books on the subject, the latter leading to his having served as AGS Director of Publications and Assistant Editor of our journal. He has also always been heavily involved in his local North Wales Group.