ICY COVERING OF CRYSTALS TURNS THE COUNTRYSIDE WHITE ON A CLEAR NIGHT
Onclear, still winter nights, a delicate covering of crystals turns the countryside white. The phenomenon is hoar frost. Leaves, flowers and stems are covered with delicate patterns. Spiders’ webs are outlined with a fragile coating. Fine feathers and needles turn grass silver and give trees a ghostly frame.
The name hoar comes from the old English word, hor or har, for white or grey. These frosts form on cold, cloudless nights, with little or no wind. The conditions must be right for crystals to form directly from water vapour present in the air. This process is called sublimation and happens when air changes to a solid without passing through a liquid stage. A true hoar frost is formed solely by sublimation, and is neither frozen dew nor droplets of water. In practice, the frost is often a combination of frozen dew and sublimation.
On these nights, the ground, and the air just above it, steadily cool as they rapidly lose heat to the atmosphere by radiation. Eventually the dew point is reached – this is the temperature at which water vapour in air condenses into liquid water. Both the air temperature and the dew point need to be below the freezing point of water for hoar frost to form.
When the radiation persists, and the temperature continues to drop, the air becomes supersaturated with moisture. The excess moisture is deposited in the form of needle-like crystals that bind themselves onto surfaces.
A crystal world
If there is a lot of moisture available during the long winter night, hoar frost is formed in a thick layer. This can resemble a covering of snow. The pure white is caused by the reflection and refraction of light as it interacts en masse with the frost’s crystalline structure.
An area of high-pressure during the winter will provide the quiet conditions suitable for the formation of a hoar frost. An old weather rhyme says ‘clear moon, frost soon’. When it occurs on successive nights, and does not melt during the day, an ever thicker coating of crystals are formed. This can be 1in (2.5cm) or more long. Conversely a cloudy sky or windy conditions inhibits radiation, preventing a frost.
It is possible for a lawn to be coated with hoar frost while trees and shrubs are frost-free. This happens when the ground temperature is several degrees colder than the air higher up, which remains above freezing point.
Places that are particularly susceptible to a frost are known as frost hollows. As air chills its density increases. On a clear night, slopes in undulating country lose heat by radiation cooling the air above them. The cold air runs downhill like water into hollows and valleys. It is known as a katabatic flow, from the Greek word katabatikos, meaning downhill. If it is trapped by embankments across the valley or by natural spurs jutting outwards, a lake of cold air can form. The valley floor is coated with a thick hoar frost whereas higher up may be frost free. During March 2012 there was only one air frost at a weather station in east Surrey situated above a downland valley. A weather station close by on the floor of the valley recorded 16 air frosts.
Hoar frost in the garden
Gardeners can inadvertently create frost pockets by building a solid fence across a slope. The type and texture of soil is also a factor in contributing to the likelihood and severity of a frost. Sandy soils lose heat more rapidly and reach the frost point more readily than a clay soil. Moist soils will not cool as briskly or lose as much heat.
Hoar frost can be harmful to more delicate plants, shrubs and trees. Water freezes within the plant’s cellular structure, breaking down the walls. A vulnerable time is just after dawn when the air is often at its coldest. Rays from the rising sun are cast onto foliage, causing a rapid defrosting. This ruptures the sides of the plant’s cells when the sap expands. By putting fleece covers over plants, frost is prevented from forming on the plants themselves and averts that sudden thawing. Plants inside a glass cold frame get some protection from a coating of hoar frost. The covering raises the temperature inside by several degrees, giving some protection from radiation.
The longer the duration of the frost, the more a plant suffers. It is the buds and flowers that are most tender. One plant that is susceptible is Magnolia soulangiana. A mild winter induces the tree to flower early, then a spring frost scorches it.
In an average year, many places will have twice as many grass or ground frosts than air frosts. Air temperatures measured at 4ft (1.2m) can often be up to 40C higher than those on the lawn, flower bed or vegetable patch. A thick hoar frost can blacken potatoes while the blossom high on an apple tree may be untouched, remaining just above freezing.
The effects of nature’s frozen tracery are unpredictable, but its beauty remains one of the wonders of the winter.
Words: Ian Currie Photography: Alamy
VIVID BERRIES AND LEAVES OF SPINDLE TREE PROVIDE FOOD FOR BIRDS AND VISUAL TREAT
With the approach of winter, spindle trees start to set the garden ablaze with the colour of their fruit and foliage. These shrubs, botanically known as euonymus, shake off their previously plain appearance, as the leaves burn red and purple. It is, however, the bright, jewel-like fruits that gleam in misty hedgerows. In spinning cascades of pink and orange, they create droplets of pure, bright colour amid the drab branches of other deciduous shrubs. These fruits persist like hot embers long after the foliage has fallen.
A feast for birds
The fat seed capsules are divided into four plump symmetrical lobes like miniature lanterns. These split to reveal glossy orange, rounded fruits that descend from their covers and spin in the breeze. As they ripen and become more prominent, the colourful seeds provide a valuable food source. Persisting well into winter, birds feast off them through the coldest months.
The birds are attracted by the orange fleshy seed coat, with its high-calorie nutrition. Inside the coat the true seeds remain intact after being eaten. Because of this, they are able to make their way through the birds’ digestive tracts to be deposited far away from the parent plant. This is an exquisitely balanced natural relationship. It supports native birds, helping them to survive through winter, while the spindle tree is able to propagate itself throughout the countryside.
The native Euonymus europaeus is such a veritable larder for birds that it will often be aggressively defended by robins making it part of their territory. For this reason,
it is known as ‘robins’ bread’ in some areas of the country.
The fruit is poisonous to humans, as are all parts of the plant. The toxic berries, however, have been put to good use. One traditional remedy for head lice involved applying the crushed berries to the scalp. Referencing the plant’s poisonous nature, the name ‘euonymus’ may originate from Euonyme. In Greek mythology she was the mother of vengeance-wreaking goddesses, the Furies.
The bright fruits are often initially seen dangling below a mantle of colourful leaves. Before it falls, the spindle tree’s foliage has one of the most impressive transformations in the British landscape. It turns from an unobtrusive dark green to a bright pinkish red with splashes of purple and hints of orange.
‘Red Cascade’, a cultivar of Euonymus europaeus, has the brightest and perhaps best colour for this time of year of any plant. A spreading shrub, it reaches 10ft (3m) across and 8ft (2.5m) high. The scalloped leaves gradually turn deep red, starting at the midrib and spreading to the leaf edges. Before the metamorphosis is complete, the leaves take on hues of pink, orange and purple. ‘Red Cascade’ bears plentiful fruit, the branches bowing under the weight.
A lesser-known characteristic of spindle trees is just as fascinating. A close look into the criss-crossing mass of leafless winter branches and the ‘winged’ outline of the straight stems becomes apparent. The branches develop four wings of corky bark, which if cut through have a cross-shaped silhouette. This feature is most prominent on Euonymus alatus, known as the winged spindle. Originating in Asia, it grows to 10ft (3m) in height, gradually spreading to a similar width. With age the bark of the main stems may become fissured, adding to the unusual and sculptural winter outline of this plant.
A limestone lover
The native European spindle, Euonymus europaeus, thrives on alkaline soils and is common on the chalk downs of southern England and on limestone hills and vales. Preferring full sun and freely draining soils, it is tolerant of winds and hard frosts. While it can be found in the shrubby lower canopy of ash, beech or yew woodland, the leaves will be at their most colourful in an open, sunny position. The one situation it will not tolerate is boggy, waterlogged ground. In its natural habitat a spindle tree may live for over 100 years.
Once a very common hedgerow plant, a campaign of grubbing out in the 1970s has left it a rarity in the wild. The spindle tree was thought to harbour crop diseases and pests, especially black bean aphid, which is a major pest of vegetable crops. There was little evidence that euonymus was a truly significant threat to farming.
Now the native plant is spreading in gardens, where it is an easy-to-grow, highly ornamental shrub.
Where to grow in the garden
Ideally, spindle trees are grown where there is an unobstructed view of them in winter. The centre of an island bed is a good location, where its summer foliage offers a useful green foil for tall flowering herbaceous perennials. A winter border with bright-stemmed winter dogwoods Cornus alba, Cornus sericea and Cornus sanguinea is another good site.
There are over 170 species of euonymus around the world but just a handful make suitable garden plants. Euonymus europaeus prefers alkaline soils, but will also grow well in neutral or slightly acidic ground as long as the soil is free-draining.
It is one of the easiest shrubs to maintain, growing in full sun, part shade, sheltered or exposed situations. It is a tough plant that can be used to provide a windbreak, particularly when grown with other wind-tolerant trees such as hawthorn and dog roses. With its abundant food, it is an excellent choice for a wildlife or nature garden.
‘Red Cascade’ is one of the best cultivars of E. europaeus for the garden. Its colour and fruit has earned it an Award of Garden Merit from the Royal Horticultural Society.
Euonymus planipes is another good spindle tree for the garden. Displaying some of the most dramatic winter colour, it grows to 10ft (3m) high. With pinnate leaves reminiscent of an ash tree, it has a vase-like shape that spreads upwards and outwards from a narrow base.
Euonymus alatus ‘Compactus’ is an ideal shrub for less spacious gardens, reaching only 3½ft (1m) in height. With the same distinctive winged wood as the larger E. alatus, it makes an attractive, smaller sculptural winter plant.
Spindle trees need little work. They form a naturally balanced and well branching framework. Little pruning is required, removing only dead, diseased or crossing and rubbing branches, or branches that are growing in an awkward place. Any pruning is done in late winter or early spring before weeding around the base. The tree will then benefit from a mulch of well-rotted garden compost.
The spindle tree is a fascinating plant, valued for its unique aesthetic qualities, wildlife-friendly properties and its many practical uses. It deserves a home in British gardens where the bright fruits and colouring leaves welcome the changing of the seasons and feed hungry birds.
Words: Melissa Mabbit Photography: Alamy
FLOWER-FILLED HAVEN FULL OF COLOUR AND FRAGRANCE
All summer long, a garden nestling in the valley of the River Pang in Berkshire resonates to the sound of bees. From a small wildflower meadow at the front of the house to a formal walled garden at the rear, the plot is filled with nectar- and pollen-rich blooms. Since starting to keep honeybees eight years ago, owner Fran Wakefield has filled her quarter-acre plot with plants that provide these essential foods for her two hives.
“Nearly everything I plant now is with bees in mind,” she says. “It’s wonderful to see them in the air at this time of year. They are always so busy and even when you can’t see them, you can hear them. They make a lovely noise.”
Making a bee-friendly plot
Tithe Barn and its garden are in Tidmarsh, an ancient village surrounded by low-lying flower-filled meadows. The soil is rich loam with chalk from the river. The 18th century barn sits almost in the centre of the 28½sq yd (24sq m) plot. When Fran moved here more than 30 years ago, the garden was bounded by leylandii and saw very little sun. The sloping plot was mainly lawn with an old acacia tree in the centre and a few containers to provide colour. Then eight years ago, the neighbouring manor house was pulled down and redeveloped. As a result of the work, Fran lost hedges and the acacia tree, although she gained a new wall to match her existing two 10ft (3m) high red brick walls.
“The changes let the sunshine in,” she says. “I thought, I need to make the most of this.” She decided to strip the garden out and start anew. At the same time, she wanted to keep bees, something she used to do. She got two hives, which are each home to between 45,000 to 60,000 bees in the summer.
“I wanted to create a classical walled garden to complement the 1760s brick and flint barn,” she says. “There is a formal framework of low hedges, straight paths and box-edges borders filled with flowers in soft pastel shades.”
This scheme provides the backdrop for her bee-orientated planting in the rear garden, where one of the hives is located. The other sits in a small wildflower garden at the front of the barn. It all combines to create a haven for both Fran and her bees.
Abundance of flowers
The wildflower meadow replaced an area of lawn to the left of the drive and courtyard area. “It’s a favourite bee haunt,” says Fran. The hive here is surrounded by corn poppies, white field chamomile and purple toadflax. Rich in pollen and nectar, these are magnets for the bees.
From the front of the barn, a path leads down the side, past a small patio with pots of hostas, to a gate into the walled garden.
In summer, this is a riot of colour with roses, peonies, clematis, delphiniums and other herbaceous perennials in full bloom. Flowers tumble over antique terracotta pots, fill the beds, line paths or climb arches and walls. This abundance of flowering plants is ideal for Fran’s honeybees, as it is easy for them to work their way across the borders. They do not have to fly far from their hives in the garden to find sufficient pollen and nectar. Each colony needs to collect 66lbs (30kg) of pollen and 264lbs (120kg) of nectar simply to survive. To provide a store of honey, they need to gather more than this.
“The bees have plenty of choice for their foraging,” says Fran. “They like single, simple flowers such as geraniums that give them easy access to their pollen or nectar.
“I avoid hybrids or double flowering plants, as the bees struggle with these. However, if there is something I want that the bees don’t like, such as a rose or peony, I still plant it. There is enough in the garden for the bees to feed on.”
To the right of the gate is a border of lavender ‘Hidcote’. Every single stem on this plant has multiple flowers, so the bees can work it easily, moving from one to the next with little expense of energy. Lavender also has the ability to release its nectar gradually, to keep the bees coming back.
To the left, a climbing rose, ‘Goldfinch’, covers the walls of the nearest corner. This restrained rambling rose is ideal for a small space. Its button-like, fruit-scented blooms are covered with golden anthers, loved by the pollen-gathering bees. The petals fall onto the square brick courtyard below. Here, square Victorian seed pans are filled with succulents and thyme. These tiny, low-growing plants are ideal for the bees, flowering even when a lack of water affects other plants.
“They all shrug off drought, and are virtually maintenance free,” says Fran. “The only thing I do is add crocks and pea gravel to the bottom of the pot to ensure good drainage because waterlogging will kill the succulents.”
Fran’s second beehive sits in a quiet and sheltered spot between two herbaceous beds along the east wall. Creamy white rose ‘Alberic Barbier’ standards and allium ‘Globemaster’ are planted here. The bees swarm to the alliums’ starry clusters of violet-purple flowers. Flourishing alongside them are valerian, hardy geraniums, catmint and delphiniums. All are popular with the bees, particularly the open-cupped geraniums, which allow easy access to their nectar to the short-tongued honeybees. The open flowers of delphiniums are visited for their pollen, rather than nectar. Valerian and catmint both have clusters of small flowers that are easy for the bees to work. Flowering through the summer into autumn, they provide a long-lasting food source.
Behind the beds, espaliered apple and pear trees, their varieties now forgotten, grow along the east wall. Planted as part of the redesign, they burst into a mass of blossom in spring. On warm days, they are covered in bees seeking nectar and in turn helping to pollinate the trees.
A place to drink
A path leads past these herbaceous beds, to a corner where an arbour is tucked away beneath trees. This is an area of dry shade where pachysandra, ivy, and periwinkles grow. Flowering from March, pachysandra and periwinkles provide food for bees early in the season when other flowers have yet to bloom. The late-flowering ivy is an important source of nectar later in the year when the bees build up their store of food to see the colony through the winter.
A shady stumpery spills over with ferns and hostas, one of Fran’s favourite plants.
“I’m passionate about hostas, growing 20 different varieties. The leaves are like an embroidery. The bees do go to the spike-shaped blooms, but they prefer flowers they can work and work, such as the verbena,” she says.
Access to water is essential for the honeybees. As well as drinking it, they carry water back to the hive where it is used to regulate the temperature. They also use it to break down nectar from plants such as oil seed rape, which crystallises in the hive. The rape grows in the countryside beyond the garden, and Fran often watches her bees travel out to work it. Under the arbour is a rescued animal feeder perched on brick pillars. Planted with waterlilies, it is an important place for the bees.
A path continues along the back wall, where a border is planted with more hostas and frothy yellow alchemilla. This is another plant whose myriad tiny flowers are covered with foraging bees. The foxgloves planted here are another of Fran’s favourites.
The south and west boundary walls support clematis ‘Montana’ and climbing roses. Covered with big, open flowers, clematis are ideal for bees. Climbing rose ‘Perennial Blue’, is a mass of bluish purple blooms each July. Its open flowers are good for the bees who can get into them easily and take pollen.
A central pathway connects the back wall with the barn’s terrace. It widens in the middle of the walled garden to create a square that encloses a still, round pool. “I love watching the honeybees sit on the edge of the pool to drink, before flying off in search of more nectar,” she says.
Fran puts as much energy into her garden as the bees that work the flowers. She is rewarded not only by the beautiful plants but also the honey from her bees. “The garden gives me a deep connection with nature. This comes from the fact that the flowers I grow are to attract insects, not only for their beauty,” she says. “I’m giving nature’s cycle a helping hand.”
Words and Photography: Nicola Stocken
The feature about Fran's bee garden originally appeared in the July / August 2015 issue of LandScape.
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