Summer Flowering Bog Plants
Having just described a selection of the earlier flowering bog garden plants, I perhaps ought to mention that a number of these will provide colour well into the summer too. Plants do not recognise the line I have drawn separating spring flowering kinds from summer blooming varieties and thus some will encroach upon the season of the other, particularly in years where weather conditions are unusual. So, broadly speaking, it can be taken that those I have selected for the spring garden will be over by the time the true aquatics start making a show. Therefore, their placement in the bog garden is not quite so critical as those I will now describe. For these flower in unison with marginal plants and waterlilies and need careful positioning if they are not to spoil the overall picture.
Just as aquatic irises can be used to great effect around the margins of the pool, their moisture-loving counterparts can be exploited in the bog garden. I have already mentioned the lovely purple-flowered Iris kaempferi when discussing its confusion with the truly aquatic . However, I only wrote a couple of words about this, when a couple of pages would be insufficient to extol the virtues of this beautiful plant and its myriad varieties.
For ordinary garden decoration a good mixed strain is difficult to beat. Cultivars with fancy Japanese names have been imported in considerable numbers in recent years and these are of uniform colour and habit. However, beware of the ‘Higo’ strain. An amazing selection of brightly-coloured sorts with huge clematis-likewhich look like exotic tropical butterflies at rest on slender sword-like foliage.
These are really magnificent irises, but totally unsuited to general garden use. Their flower heads are so large that the wind snaps them off and heavy rain does little to aid their beauty. ‘Higo’ irises were developed by the Japanese for the florist and for exhibiting. They were not intended to withstand the rough and tumble of the garden, being grown almost exclusively in pots and afforded considerable protection from the elements.
Iris sibirica and its cultivars thrive in most situations, not resenting an alkaline in the same way as do Iris kaempferi, and being more tolerant of the moisture level of their growing medium. Indeed, Iris sibirica can be grown reasonably successfully under ordinary border conditions and will survive equally well when temporarily immersed in water.
Typical Iris sibirica has narrow grassy foliage and finely sculptured sky-blue flowers which appear during June and the early part of July. These are not over-bearing like some of the modern Iris kaempferi hybrids and conform readily to any planting scheme. Its cultivars are rather more boisterous, but retain their dignity and form neat clumps no more than 60-70cm high. I like ‘Blue Moon’, ‘Snow Queen’ and the purple-flowered ‘Caesar’. ‘Mrs Saunders’ has dark blue flowers with white reticulations, while ‘Emperor’ is of the deepest violet-blue. ‘Perry’s Pigmy’ is deep blue or violet and being less than half the size of the others is an invaluable plant for the smaller water garden.
The delightful little Chinese Iris bulleyana can also be recommended when space is at a premium. Scarcely more than 40cm high, it produces tufts of grassy foliage sprinkled with delicate, rich blue blossoms. These put one in mind of Iris setosa, except that this adaptable species is slightly dwarfer with bold, broad, sword-like leaves. Innumerable forms of Iris setosa have crept into cultivation from time to time. Of these the compact variety nano is an absolute gem. Growing no more than 15cm high this has stout fans of leaves and full size flowers of the same incomparable blue.
Iris ochroleuca is one of the more vigorous bog garden species with handsome glaucous foliage and contrasting flowers of white and gold. It grows more than a metre high, and although not really a plant for the smaller garden, where it can be accommodated it provides excellent background material. The equally robust Iris aurea is sometimes put to the same use. While its deep yellow blooms are just as striking, its foliage is more sombre and lacks the stiff architectural form displayed by that of Iris ochroleuca.
As noted earlier when discussing aquatic irises, they always benefit visually from an association with a scrambling or creeping subject. And what better to use than Lysimachia nummularia (creeping jenny). A plant of many parts, this more or less evergreen carpeter smothers the soil with pleasant rounded leaves, which in the cultivar ‘Aurea’ are rich glowing yellow. Throughout June and July the sprawling tangle of stems are host to innumerable bright yellow flowers the shape and size of a common buttercup.
Being a not uncommon native, some people regard Lysimachia nummularia with suspicion. This is unfortunate, for it is one of the most adaptable plants for bog garden and poolside planting. Not only does it provide ground cover between taller growing plants, but can be used successfully to mask the edge of the pool where it meets the surrounding ground. It has no qualms about entering the water either, for here it will produce roots quite freely from its leaf joints. If some of this semi-aquatic growth is removed and planted in the bottom of the pool it will grow and serve as a submerged oxygenating plant, although it will not flower. But do not try to submerge ordinary growth as this will almost certainly perish. It seems to need a period of adaptation before becoming a stable submerged plant.
A number of other lysimachia species are recommended for the bog garden from time to time. However, these are coarse clump-forming plants 60cm or more high and better suited to stream or riverside planting. If one desires the upright spire-like growth so characteristic of those species, then it is better to select a cultivar or two from the range offered by Lythrum salicaria (purple loosestrife).
This is not to say that Lythrum salicaria itself is of little value, for its stiff bushy clumps of foliage support deep rose-purple blossoms which put on quite a show from July until September. It is just that I think the cultivars are better for the modern garden. They are more compact, generally shorter, and embrace a colour range that passes from purple through rose-red to pink. I would choose the lovely soft pink ‘Robert’, or delicate rose ‘Lady Sackville’ and it would be difficult to deny a place to ‘The Beacon’ with its well-proportioned spikes of rich rosy-red.
Astilbes are equally valuable, particularly some of the compact modern cultivars. These fit in with any design as they grow little more than 75cm high and are only available in friendly pastel shades. Their feathery plumes of flowers and attractive divided leaves associate with most other plants, which means that they can be planted freely without becoming obtrusive and offending the eye.
‘White Gloria’ with its contrasting dark green foliage is my favourite, although the aptly named ‘Peach Blossom’ runs it a close second. The bright crimson ‘Fanal, ‘Red Sentinel’, and lilac-pink ‘Cattleya’ also rate highly with me. As do the tiny pink-flowered cultivars of Astilbe crispa — ‘Perkeo’ and
These have congested tufts of dark green crinkled foliage and only grow 15cm high. But the real king of the miniatures is Astilbe chinensis ‘Pumila’. Slightly taller than the Astilbe crispa cultivars, this produces prostrate tufts of dark green leaves and beautifully proportioned spires of purplish-rose flowers.
Aruncus sylvester is a majestic relative of the astilbe, forming immense clumps of luxuriant foliage and towering plumes of creamy-white flowers a couple of metres high. It is often grown in the bog garden where its huge mounds of foliage dwarf and smother less vigorous neighbours. In such a situation it is totally out of keeping. I like to see it planted in solitary splendour at the edge of the pool where it can be reflected in the cool glassy stillness of the water. If surrounded on the landward side by a verdant lawn, it presents a picture of unparalleled beauty, the greens of grass and foliage complementing one another perfectly.
Before leaving astilbe and aruncus, I ought to mention their forgotten relatives the filipendulas. The well-loved Filipendula ulmaria (meadow sweet) is a frequent inhabitant of stream sides and ditches throughout Great Britain. Even if sweetly scented and quite charming, it does not really deserve a place in the bog garden. Especially when the double form flore-plena and golden-leafed ‘Aurea’ can be grown. There are many other species worthy of consideration if you have a large garden, for most of them grow to more than a metre high and half as much through. Only the dainty F.hexapetala (dropwort) in its double form is worth considering, for this has delicate fern-like foliage and crowded heads of cool icy-white blossoms. These are only in evidence during June and July, but the splendid filigree foliage persists for much of the year and is a constant delight.
The leaves of the perennial lobelias can also make a significant contribution. Particularly the rich beetroot-coloured ones of Lobelia fulgens. Unlike the familiar bedding lobelias, the hardy perennial species grow in upright spiky clumps varying in height from 60cm – 1m. They are not all blue flowered either, the blossoms of both Lobelia fulgens and the green-leafed Lobelia cardinalis being vivid red.
Lobelia vedrariensis is the tallest kind and has violet blooms and bright green leaves suffused with maroon, while the shade-loving Lobelia syphilitica has rather ordinary green foliage and bright blue flowers. Although flourishing well in moist conditions, they will not survive the winter insoil. In fact with Lobelia cardinalis and Lobelia fulgens it is a wise precaution to over-winter a clump or two in a cold frame, for their emerging foliage is prone to damage by severe weather and particularly vulnerable to attacks from slugs and snails.
Some of the mimulus would appreciate similar protection for the winter months, especially the downy-leafed species like the bright red Mimulus cardinalis and lilac-pink Mimulus lewisii. Even the cultivars of the bright yellow Mimulus luteus and reddish-copper Mimulus cupreus benefit from having a rosette or two of over-wintering foliage moved to a safe haven in case of severe winter weather.
Most mimulus grow between 25-60cm high, the modern cultivars like ‘Bonfire’, ‘Scarlet Emperor’ and ‘Yellow Velvet’ tending to occupy the lower end of the scale. They are all extremely showy, producing brightly coloured, antirrhinum-like flowers from the end of May until July and often again during late summer. Apart from growing well in moist conditions, a number will also spread and colonise the marginal shelves in several centimetres of water. Forms derived directly from Mimulus luteus are particularly prone to doing this. Varieties like the golden ‘Hose-In-Hose’ in which one flower appears to be inside the other, and the incomparable large yellow-flowered ‘A.T. Johnson’ with its profusely spotted petals.
For the sink garden or rock pool there is a superb dwarf variety called ‘Whitecroft Scarlet’. This is a remarkable plant, scarcely more than 8cm high, with mats of tiny carpeting foliage and unusual hooded blossoms of brilliant scarlet. Certainly the best dwarf plant for the bog garden, and although not reliably perennial is easily raised from seed and will flower the first year.
Before I leave the flowering bog garden plants, I must write a word or two about another unreliable perennial; Zantedeschia aethiopica (white arum lily).
Why nurseries and gardeners persist with this plant outdoors I will never know, for to survive the winter in this country it must be grown in at least 30cm of water. From such cold inhospitable depths it takes a long time to surface and consequently flowers very late or not at all. The only method of growing it well is to have it in a pot which is plunged in the bog garden when all danger of frost has passed. The pot and plant can then be removed to the safety of the greenhouse for the winter months. Alternatively the hardy variety ‘Crowborough’ can be tried, but this is smaller and less imposing than the true florist’s arum.