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Happy when it’s wet

21 June 2021
featured image plants for wet july
Astilbes are ferny-leaved plants with plumes of flowers that love moisture

Do you have a bog garden, a damp garden area or a streamside in need of planting? Read on for inspiration.

Words Veronica Armstrong

Bog primulas
An awful name for such lovely flowers, the many species and hybrids that go by this common name boast tiered whorls of flowers, all the way up their stems, held above a basal rosette of leaves. The colourful flowers range from cream through to yellow, orange, red, pink and purple. They love moisture so grow well in damp areas and alongside streams. They self-sow freely, but clumps can also be divided after flowering. They look best planted in drifts, where they can make a splash of colour. A good partner for irises, which combine to create a naturalistic effect.

There are many species of Iris, named so after the Greek goddess of the rainbow. They like different growing conditions and several like moist conditions, so they’re ideal for pond or streamside plantings. The water-loving irises originated from species in Europe, Asia and North America, and cultivars include Japanese, Louisiana and Siberian irises.

Iris ensata, the Japanese iris, is a semi-aquatic or bog plant that does well in damp soil alongside a pond or stream, where it may naturalise. It also likes slightly acidic soil and plenty of sun. The leaves are upright and sword-shaped, and a variegated form (I. ensata ‘Variegata’) is also an option. In spring, rich blue, purple, mauve or white flowers appear.

I. ensata is similar to I. laevigata, another Japanese native, and will grow with its rhizome crown under water. They may be fed with a general-purpose aquatic fertiliser to give a flowering boost.

Louisiana irises are hardy, vigorous and quite tall-growing. They will grow in a garden bed as well as in and alongside water. They bloom from mid to late spring then go summer dormant and start actively growing again in autumn. The flowers come in a wider range of colours, from white through to yellow, red, pink and purple. In late summer the rhizomes can be dug up, and those with green tips can be replanted and will form the new season’s growing shoots.

I. sibirica, the Siberian iris, is very similar. This clump-forming perennial likes full sun or partial shade and consistently moist soils. It blooms in velvety lilac, purple and blue through to yellow, white and raspberry, from late spring, which is earlier than the Japanese irises.

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Iris ensata ‘Gypsy Princess’ ticks the boxes for those looking for a hardy bog garden plant.

Filipendula ulmaria is another ideal plant for damp soil or boggy areas. This herbaceous perennial has ferny leaves and produces sprays of small white or soft-pink flowers, which have a strong, sweet smell. The leaves are scented too. This plant spreads by seeds and also via creeping underground rhizomes. The ferny leaves are a good foliage contrast to that of the sword-like iris leaves, if you plant them together.

Another ferny-leaved plant, astilbes flower in early summer, producing many fluffy spires in a range of colours from white through pink and purple to red. They grow in shade or light sun and flower best where they get some morning or dappled sun for a few hours. There are about 25 species and many cultivars of Astilbe, varying in heights from about 20cm to more than 1m tall. Astilbes will clump up and can be divided every few years. Just make sure you keep them consistently moist!

Chinese meadow rue
For something really delicate and pretty, one cannot go past Chinese meadow rue (Thalictrum delavayi). This beautiful perennial has lacy green foliage and airy clusters of pendulous lilac flowers with creamy stamens. It likes dappled shade and rich, moist but well-drained soil. The very pretty white form, T. delavayi ‘Album’, has a cloud-like effect when its flowers pop up above its ferny foliage.

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Thalictrum delaveyi, the Chinese meadow rue, has airy clusters of pretty lilac or white flowers.

The quintessential foliage plant for damp areas and stream or pondside plantings has to be Gunnera. This herbaceous, clump-forming perennial is best known for its giant leaves that can grow up to two metres in diameter – positively umbrella-sized! The leaves and stems are covered in spikes. They produce large cone-shaped brownish pannicles of tiny reddish flowers, followed by berry-like fruits, similar to cycad cones. These ancient plants are considered to be about 150 million years old, so it’s easy to see why they are also called ‘dinosaur food’! However, they may become a weedy pest in some areas, with the ability to overshadow natives, which is why Gunnera tinctoria is on the New Zealand Plant Pest Accord, meaning it is an unwanted organism that cannot be sold, distributed or propagated.

Another striking foliage plant for pond margins or stream edges is Rodgersia, of which there are several species. With textured, palmate bronzy leaves, they have airy plumes of cream or pink star-shaped flowers that develop into reddish seed heads in autumn. They like a sheltered spot and team well with ferns and astilbes.

Ligularias are sculptural plants that deserve a place in the moist and shady garden, although some can take more sun. Ligularia reniformis has big, glossy, almost circular leaves that give it its common name – the tractor seat plant. In summer it has yellow, daisy-like flowers, but this plant is usually grown for its leaves. It likes moist but well-drained soil and will quickly wilt if it dries out. Trim back the old leaves and keep an eye out for snails, which love the leaves too. L. ‘Britt Marie Crawford’ (syn. Farfugium ‘Britt Marie Crawford’) has chocolatey brown leaves and reddish undersides and produces orange-yellow flower clusters.

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Ligularia reniformis, the tractor seat plant, has large heart-shaped leaves and yellow flowers.

No pond or streamside with shade should be without some ferns, one of the most ancient groups of plant families. There are literally hundreds of species of ferns, including some of our native species. Most ferns require moist but well-drained soil, enriched with humus.
For height, try the silver fern or punga, Cyathea dealbata. This fern has the typical shuttlecock shape and the leaves turn silvery on their undersides as they age. Other choices are shield ferns, such as Polystichum vestitum (the prickly shield fern, pūniu), which has long, dark-green, prickly fronds.
Asplenium bulbiferum, the hen and chicken fern, is a good choice. Known as pikopiko, it has the added bonus of producing baby fernlets along the edges of mature fronds.

Blechnum novae-zelandiae (the palm leaf fern or kiokio) has fronds that start out pink in colour, changing to green as they age. The smooth shield fern Parapolystichum glabellum (syn. Lastreopsis glabella) has lacy green foliage and is low-growing, as is the creeping shield fern, P. microsorum subsp. pentagulare (Lastreopsis microsora subsp. pentangularis). The latter makes a good ground cover, provided it is given shade and moisture.

Great for waterside plantings, try papyrus grass (Cyperus papyrus), an aquatic perennial sedge with long leafless stalks topped with fluffy green, powder-puff flower heads. Our native Carex secta is a popular tussock-forming sedge. It has bright green leaves, ageing to a clump with a trunk-like mound of roots and old stems, topped with the leaves.

For larger areas, cultivars of harakeke (Phormium tenax) are suitable as they are adaptable and will happily grow alongside streams. The stiff, upright sword-like leaves can grow to a few metres tall with even taller flowering spikes. The reddish flowers have nectar beloved of our native birds, such as tūī and bellbirds. Although harakeke prefers damp conditions, it is very tough and can survive periods of dryness too.

Tree types
A number of trees like damp areas too, but one would need a large garden to grow them.

Think of weeping willows (Salix babylonica), with their delicate foliage spilling over ponds and streams, such as those along Christchurch’s Avon River. Large trees, they need plenty of room!

Another large tree, up to 20m tall, is the beautiful pin oak, Quercus palustris. This tree grows well in damp acidic soils and has the added bonus of scarlet autumnal foliage.

The swamp cypress (Taxodium distichum) is adapted to wet areas by having aerial roots, which may help them stabilise in muddy waters. This conifer has feathery green foliage that turns a russet red-gold in autumn before the leaves drop – an unusual feature in conifers.

Growing plants alongside water, especially still water, has the added bonus of beautiful reflections, and any of these planting ideas should beautifully enhance a waterside area.

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