Alpine and Rock Garden team blog

A 20-tonne heap of organic ‘stuff’ has appeared under the black walnut, Juglans nigra, in the Woodland Garden. The size of this pile of composted bracken could seem intimidating, but to us lucky ones who have to spread it on the beds, it’s an annual task that pays big dividends. 

Bracken mulch to be spread over the woodland garden beds

Why mulch?

In nature, autumn delivers a deep mulch of leaves to the woody and herbaceous plants growing on the forest floor. The fallen leaves insulate the ground and gradually decompose. Soil organisms work them into the ground where they deliver micro-nutrients and act as fantastic soil conditioners. It’s a perfect circle.

But here at Kew, we have to pick up the fallen leaves – to protect our turf and keep the paths accessible (and to prevent homicidal impulses from the Rock Garden team, who rightly object to the arrival of leaves on their beautifully kept beds).

So to make up for robbing the Woodland Garden of its leaves, in mid-November we mulch! Kew produces a ‘soft mulch’ using composted plant material from on site mixed with horse manure, but this has quite a high pH and high nitrogen levels, neither of which are suitable for the majority of woodlanders.

Why bracken mulch?

Bracken mulch (Pteridium aquilinum, composted for two years) is low in nitrogen and has a neutral-to-acid pH. It is a good soil conditioner too, increasing the soil’s ability to hold water and nutrients (Kew has a very free-draining soil, so we have to work hard to keep it in good health).

How and when

We mulch in November when the soil still has some warmth from the past season and before the spring-flowering bulbs start to emerge. We cut back the herbaceous plants, and weed and remove the majority of the leaves on the bed so that we can see exactly where to put the mulch.

Using wooden boardwalks to drive our loaded barrows onto the beds, we spread the bracken mulch in a layer 6-8 cm thick. We take care not to smother rosettes – like Meconopsis and Primula species, and we leave a good bare circle around the base of smaller shrubs (it is easy to over-mulch woody plants, effectively choking them).

Job satisfaction

It’s rewarding work, because the beds look beautiful with their rich, red-brown duvet... at least for a few hours, before the oaks chuck down another layer of crispy golden leaves. These we collect and put aside to make leaf mould (but that’s a story for a future blog).

And even now, plants are stirring under ground. The Trillium buds are just visible, gathering pace for spring which, despite the evidence to the contrary, is just around the corner.

- Katie - 

While many plants are still just emerging, a range of early flowers is taking advantage of the light and moisture before the leaves clothe the trees and shade the woodland floor for the rest of the summer.

For a few weeks now, the borders in the Woodland Garden, around the Temple of Aeolus, have been carpeted with blue Chionodoxa but these have now mostly faded, only to be replaced by an equally brilliant blue covering of Scilla bithynica. This small bulb, from Bulgaria and north west Turkey, forms a shimmering haze of blue through which taller plants emerge. 

Kew's Woodland Garden in March

A stand of the crown imperial, Fritillaria imperialis, displays clusters of downward facing cups of orange at the top of metre tall, leafy stems. This impressive bulb comes from Asia, with a range stretching from Turkey to the foothills of the western Himalaya. It grows naturally in summer dry meadows and steppe but does well in the Woodland Garden because, when in full leaf, the trees draw excess moisture out of the soil, so the bulbs are never in waterlogged ground. 

The impressive crown imperial, Fritillaria imperialis  

Two of my favourite woodland plants are among the many others appearing just now: Erythronium, the dog's tooth violets, and Epimedium or barren wort. 

Erythronium - the Dog's Tooth Violets

A few species of Erythronium are found in Europe and Asia but most come from North America. They grow best in humus-rich soil and dappled shade. Their elegant flowers, with petals that arch back when fully open, come in colours ranging from white and yellow to pink and lilac purple. They are in the lily family and closely related to tulips. The common name comes from the shape of the bulb, which is like a canine tooth. 

Left: Erythronium hendersonii from Oregon and California,

Right: Erythronium oregonum from British Columbia to southern Oregon 

The beautiful yellow flowers of Erythronium tuolumnense, named after Tuolumne County in California, the only place where it grows wild. 

Epimedium - the Barren Worts

Epimediums also have a broad range in the wild, extending from southern Europe and North Africa to Japan, with their centre of diversity in China. They grow from a mat of thin rhizomes and some species, like the Caucasian Epimedium pinnatum, form dense ground cover. Garden hybrids have been created, including a cross between E. pinnatum and the East Asian E. grandiflorum. It is called Epimedium x versicolor and various cultivars exist with flowers in subtle colours, from soft pink to pale yellow. 

Left: Epimedium pinnatum subspecies pinnatum, from the Caucasus,

Right: the hybrid Epimedium x versicolor 'Versicolor''

The ghostly Epimedium x versicolor 'Sulphureum'

Soon these early woodlanders will finish flowering and give way to the summer shade lovers that are only now just poking through the ground, such as ferns, hostas and lilies, so make the most of these delicate ephemerals while they last. 

- Richard -

The Davies Alpine House at Kew has suddenly burst into spring. The last few warm days have brought a lot of bulbs into flower, after having been sitting there anticipating the impending warmer weather.

Plants from South Africa

A lot of plants from South Africa have been putting on a show, notably Gladiolus gracilis with its amazing graceful, pale blue trumpets, looking every inch a summer visitor. Sitting in the sand plunge bed to protect it from cold and fluctuating temperatures we have Daubenia aurea var. cocccinea, which in the wild would be beetle pollinated. It has very sturdy tepals (similar to a petal) which will not be easily broken by an attack of hungry bugs. This plant is found in the Roggeveld Mountains of South Africa and the flowers can be yellow or bright red. 

Left, Gladiolus gracilis, and right, Daubenya aurea var. coccinea

Synnotia variegata, a South African Iris relative, is also flowering well, and has amazing, unreal flowers, which are zygomorphic, meaning symmetrical in one plane only. The flower narrows into a long tube and they must be pollinated by something with a very long tongue, either a bee or a moth. At the base of the flower are hairs that almost feel like real animal hair. 

Synnotia variegata

Plants from Chile

From Chile we have two very unusual flowers: one green and one almost black. Miersia chilensis has very small flowers, all green but for the purple stamens. The general appearance of the plant is of a mass of green, with each flower immaculately sculpted to look like a small insect, and probably attracts insects to aid pollination. The blackish flowers are of Gethyum atropurpureum, and look almost bat-like, with long, brownish black petals. This plant has a very unusual smell, and can fill an entire glass house with its unpleasant odour, but it is probably very attractive to prospective pollinators, as it sets lots of seeds every year. 

Left, the strange, fly-like flowers of Miersia chilensis,

and right, the dark flowers of Gethyum atropurpureum

Plants from Central Asia and Europe

 Lots of very attractive corydalis from central Asia are flowering now. Corydalis popovii is a particularly good example of a tuberous, semi-desert species which comes from Tadjikistan. 

The Central Asian Corydalis popovii

Also from Central Asia, one of the first tulips to flower is Tulipa orthopoda. Its buds have amazing purple-blue outer markings and open when the sun comes out to reveal a lovely white, starry flower with a bright yellow centre. A stunner. A bit nearer to home we have Narcissus assoanus from Spain, which has been flowering for weeks now, making the house look bright even on a dull day.

Variations on classic spring bulbs:

Tulipa orthopoda on the left and Narcissus assoanus on the right 

- Kit -

The main flowering seasons for cyclamen are autumn and spring. The summer gap is filled with Cyclamen purpurascens and the rare C. colchicum and the winter is mainly left to Cyclamen coum.  Some spring cyclamens can flower very early, including the closely related C. alpinum and a visit to the Davies Alpine House will reveal a few more species, flowering in the more protective environment under the glass.

But out in the open, Cyclamen coum is now flowering on the Rock Garden at Kew. Although we haven't yet had much freezing weather this winter, this plant is very resistant to frosts, which seem to have no effect on the flowers or leaves.
 

Frosted flowers of Cyclamen coum on the Rock Garden

The leaves of Cyclamen coum are rounded to heart-shaped and often have attractive silvery markings. The small flowers have short, wide petals that vary in colour from deep magenta to pale pink or white. C. coum has a wide range in the wild. It can be found from Bulgaria, across northern Turkey to the Caucasus Mountains and from south-east Turkey to northern Israel. Over this range there is some variation in leaf shape and patterning, and flower colour.
 

Cyclamen coum covering a woodland floor in Georgia, near Tbilisi

 In the wild C. coum grows in woodland, where it can create vast swathes of pink flowers. It can also be found on rocky ledges or on the sides of gorges, in gullies and along field margins.
 

Clinging to a rocky gorge wall in south-west Georgia

It can sometimes be seen growing naturally with snowdrops, a combination that also looks great in the garden.
 

Cyclamen coum and the snowdrop Galanthus woronowii in the wild

Cyclamen coum is easily grown in the garden, in sun or partial shade. The soil should be well-drained but not too dry in summer, when it is dormant. In the wild it often grows in areas where the annual rainfall is very high, such as north-east Turkey and western Georgia. It will seed around itself to form large colonies over time, making a beautiful sight in the winter months. 

- Richard -

The daffodils flowering in the Davies Alpine House now are normally among the first species of Narcissus to appear at this time of year but they have been out for over two weeks already and some, like the paperwhite, have been blooming since early November. The paperwhite, N. papyraceus, comes from the Mediterranean region and produces masses of small white, scented flowers, with up to 20 on a single plant. In countries such as Spain, where it can be quite common in the south, the flowers are picked for Christmas.

The paperwhite, Narcissus papyraceus

Another species flowering now, Narcissus romieuxii, is one of the hoop petticoat daffodils. Their common name comes from the wide, flared corona. In some daffodils the corona forms the prominent trumpet at the center of the flower and in others it can be very short like a shallow cup, as in the pheasant's eye, N. poeticus.

Narcissus romieuxii comes from North Africa and the flowers are usually a shade of yellow, some being deep yellow and others pale. It also comes in pure, glistening white. Originating from North Africa and flowering so early means this species is best kept under glass but another hoop petticoat, N. bulbocodium, does well in the garden and can be naturalised in grass, seeding around to eventually create large colonies that flower in mid spring. This group of species also includes the pretty N. cantabricus.

Left, a yellow Narcissus romieuxii, and right, the white form

More highlights

Other plants to see now include the first of the 'juno' irises. These bulbous irises mostly come from Western and Central Asia and really get going in January and February but there is one species from the Mediterranean region that flowers in December, Iris planifolia. Like some of the daffodils, this iris has been out for a couple of weeks. It is normally blue-flowered but the white form is looking particularly good at the moment.

The white form of Iris planifolia

Late November and December is normally the time to see the giant Madeiran squill, Scilla madeirensis, in the Alpine House but this year it has already been and gone. There is a closely related species flowering now though, with similarly impressive, though slightly smaller flower spikes. Scilla latifolia is from Macaronesia - the islands in the North Atlantic off the African coast that include the Canary Islands and Madeira. Unlike S. madeirensis, the flower stems are not straight but bend over and then turn up at the ends to hold the spike of purple-violet flowers upright.

Scilla latifolia

The species of Massonia normally flower in December. The genus is named after Francis Masson, Kew's first plant collector, who was dispatched to South Africa by Joseph Banks in the late 18th century. With two wide leaves, several centimetres across, lying flat on the ground and a tuft of sweetly scented flowers emerging from between them, Massonia pustulata is one of the more unusual looking plants on display at this time of year. The flowers have insignificant petals but prominent stamens holding the small yellow anthers. It comes from the Cape Region of South Africa, where the climate is mediterranean, so it is dormant during the dry summer months.

Massonia pustulata

So plenty to see now, and before you know it the snowdrops will be out and spring will be here!

- Richard -