The great thrill of rock gardening is the challenge of the new; and while this applies to other types of gardening, in growing alpines there is a greater variety of novelty. It stirs the competitive urge for sure, but in the way of a child learning about the world. It is the expression and application of intellect to know more about the plants individually and the garden as a whole.
One of the great things the Czech collectors have done is to open up the sourcing of wild collected material. No regard is paid to your status or your social connections--with the Czech's it is strictly a commercial transaction and anyone can buy. At present we can buy from a great number of reputable collectors from many different countries. Not to be overlooked is the huge reservoir that lies within many established rock gardens on this continent and elsewhere. They become repositories for past collections, and by lucky circumstance these plants may be re-discovered and come into culture again. With the understanding that most people who practice alpine gardening aspire to grow the plants well and learn more about them, I wish to make some comments on but a small selection of notable plants.
That plants have different requirements, I hardly need to say. But looks can be deceiving, true cultural secrets only being uncovered through careful investigation. At first glance, Daphne velenovskyi is so miniature and scarce that it is reasonable to assume it is difficult. Not so at all! The real obstacle is that its propagation (vegetatively or by seeds) is less successful. We have plants in the garden dating from 1992 that are now ~30cm across. It really wants no more than a sunny exposure amongst rocks in gravelly soil - almost total neglect. D. velenovskyi will also tolerate partial shade. Young plants transplant easily and bloom immediately. It grows in the Pirin Mts. of Bulgaria at higher elevations (to 2400 m) on hot, rocky slopes with grasses and scattered Pinus mugo. Extremes of temperature occur daily, and the flowers are resistant to several degrees of frost.
The Dryas octopetala clones were found growing in huge troughs at Barrie Porteous' garden in Muskoka, Ontario. The labels were long gone (buried?) but they were Halda collections. Walking around a corner I was stunned to see these mats of dwarf, dark green leaves engulfing the troughs and, upon looking closer, saw there were 2 different forms; another case of the value of old gardens as repositories. The troughs sat in rather deep semi-shade, though I have since grown these two Dryas in full sun. They are very adaptable and not fussy, simply liking a good gravelly soil (limestone preferably). Barrie's troughs were shaded and moist enough that sphagnum moss was growing in the mats. Great for the Dryas as the stems would root into the moss.
I thought Anemone obtusiloba might grow very well in those troughs also. In nature it grows in moist, rich soils. It has a huge geographical distribution so it is reasonably accommodating. A bit of shade helps as does a drink from the hose. A small herbaceous plant of rich, damp soils, it has a wide distribution from Afghanistan to West China. There are both yellow and blue flowered forms; the blue petalled selection we grow was raised from seed from Jim Archibald. It has grown well for us in partial shade with attention to its moisture needs. In spring the blue buttercups are freely produced over a period of 4 weeks. If adequately fed and watered, it will continue to bloom longer, less a summer dormancy, to resume blooming in September. It also responds well to container culture and is suitable for a damp trough or as show specimen.
Two new trough candidates from the North American West are Antennaria aromatica and A. rosea v. confinus. A. aromatica, of which the white, woolly mats are indeed scented, hails from the high level of flats (2740m 3050m) in the Beartooth Mountains in Wyoming where there is a short, quick summer with abundant snowmelt moisture and a gradual drying. By contrast, A. rosea v. confinus grows at ~2500m in the San Bernardino Mountains of California. Even at this elevation there will be more summer heat to deal with. The mats of both are found on north-facing slopes with some shade, an adaptation to consider when planting in a rock garden that is subject to intense heat.
We offer a large number of Saxifraga, including kabschia selections, all grown in tufa, as this provides the best substrate for the plants to grow on. The blocks do well in soil in the garden. The secret for success is to find the right combination of exposure (north-facing slopes with afternoon shade are favoured), adequate moisture (summer drought will stress them) and keeping the soil cool with some air movement and stone mulching. Light feeding with dilute liquid feed and either Spanish River Carbonatite or Greensand is beneficial. While they are not as hungry as some Primula or Gentians, they do need a steady source of nutrients. Watering, if needed in periods of drought, should be done in the early morning to allow the leaves and crown to dry.
The new Czech seed colletions from China have provided a sudden increase in the number of excellent Androsace spp. available, excellent both for variety and growability. I mentioned this to Halda and he agreed that the Chinese species are 'hardier' than those from the Himalaya. Again, appearance can veil true cultural requirements. Many of the high altitude species that are quite tiny and hairy are very tolerant of rain and soil moisture. The hairiness may be more an adaptation to cold. I have found that the new small species are very good candidates for the rock garden, in scree conditions generally, but with a bit of compost added and attention to water needs. A windy, open site is still desired.
Potentillas tend to be overlooked, perhaps due to the predominance of yellow flowers. A new species, P. porphyrantha from the Caucasus, has vivid pink flowers (red in bud) on low mounds of white, tomentose leaves. Entirely easy to please, you can really plant it anywhere and it will thrive. Another neglected species is Potentilla uniflora from the Rockies. The tiny dentate leaves are accented with silver, a perfect foil for the flowers held barely above on short stems. It too, is very easy to please.
Yet another treasure from the archives of the Porteous garden is a micro-form of Globularia repens 'nana' that is about half the size or less of the usual selection of this useful and lovely carpeter. Like its larger siblings, G. repens 'nana' provides the tapestry that will blend together and soften elements of the rock garden.
I am always watching the seed lists for Scutellaria spp. This year we have sufficient numbers of S. orientalis ssp. pinnatifida. The flowers of bright yellow are outrageously bold , held at length on decumbent stems. It will tolerate a wide variety of conditions; basically plant it and forget about it until it draws your attention in June with those saucy flowers. A bonus is that those wonderful flowers will continue on into September.
So, there is always a story to go with the plant, and finding those details will help you decide how to best prepare the planting space. One great thing nowadays is that research has been made easier by the likes of Google; but books, catalogues and seed lists are still very useful. The look and feel of real paper still can't be beat.
(2009 Catalogue Introduction)