Gardening in January – 1. Frost and Snow
The Ultimate Guide for January
Gardening in January, the middle of winter, may still seem a distant dream – rather like the summer holidays.
But this is the turning point of the year when you can increasingly start to enjoy gardening again.
Much cold weather lies ahead, but often the first spring bulbs are poking through the ground, the buds on many shrubs and trees are beginning to swell, and the days are starting to grow longer – albeit almost imperceptibly.
Gardening in January is all about preparing and making sure that your plants survive frost and other weather conditions that may occur during this month. If you want to jump to the tasks and don’t care about how plants survive frost and snow, follow me to the second part of the guide: Garden Work in January.
Gardening in Winter
The garden can be a beautiful place in winter: small, dainty, often fragrant flowers stud bare branches, and variegated evergreens gleam in the watery sunshine. In summer, such subtleties would be lost, overwhelmed by massed foliage and bigger, brighter blossoms.
Witch-hazels are among the most enchanting and colorful of winter-flowering shrubs. They tolerate shade well and look stunning against a dark background. The spidery, fragrant flowers are usually yellow, although there are varieties with reddish or orange flowers.
Viburnum Tinus is evergreen and reliably produces clusters of pinkish-white flowers from November through to spring. For sunshine-yellow flowers, look to Mahonia lomariifolia and the hybrid M. x media ‘Charity’. The large flower heads and bold, somewhat spiny, evergreen foliage, often tinged with red, make them eye-catching.
Use walls wisely
Walls offer protection and shelter to shrubs such as the silk-tassel bush, Garrya elliptica, with its long pendant catkins of silvery grey and glossy evergreen foliage. Winter jasmine, Jasminium nudiflorum, has lax green stems that are smothered with yellow flowers in winter. It will need tying in but can also be supported by other plants such as pyracanthus.
Pyracanthus also have beauty at this time of year, with evergreen foliage and persistent red, orange, or even yellow berries. This paragon among wall shrubs tolerates hard pruning and can be trained close to house walls. Japanese quinces (Chaenomeles) are also ideal for growing near walls. They lose their leaves in winter but will usually flower in February or even January in mild areas.
There are some climbers which you can plant to brighten winter days. The most reliable are the tough ivies, which carry berries in winter. Look for ones with variegated foliage—a few take on richer tints in winter. Clematis cirrhosa is evergreen and produces clusters of dainty, pale yellow flowers. Position it on a south or south-west facing wall.
The Christmas rose (Helleborus niger) survives frost and produces stunning white flowers in winter depths.
On the Ground
Cotoneaster dammeri provides pleasant green ground cover. Later in the year, it will be smothered with bee-attracting flowers followed by berries. For something brighter, try variegated euonymus such as Euonymus fortunei ‘Emerald ‘n’ Gold’ or the winter-flowering heather, Erica carnea, and its many varieties. Unlike most heathers, Erica carnea tolerates alkaline soil. Smothered in bloom from November to May, types come with white flowers and all shades of pink. There are others with handsome bronze-tinted or golden foliage that will further enrich the winter garden.
Bulbs are apparent candidates for winter color, and snowdrops are the earliest to flower. Snowdrops are one of the most welcome sights this month though they may not flower until later in severe winters or cold. They continue blooming until early spring.
It is the clear vibrant color of its flowers that makes this crocus such a winner. A native of Turkey and western China, Crocus ancyrensis has striking, deep orange-yellow, rounded, half an inch to one and a quarter inch flowers, that are produced in profusion in January and February, with five blooms growing from a single corm. The tiny flowers have a great impact at the front of a herbaceous or mixed border. As with other crocuses, this one may be planted in a pot and brought indoors just as the flower buds begin to show. It should be grown in full sun, in gritty, poor to moderately fertile, well-drained soil.
Propagation: Sow seed as soon as ripe in containers in a cold frame. Leave seedlings for two years before planting out. Remove the cormlets during the dormant season.
It just wouldn’t be spring without crocuses. These brave little plants come from Europe, North Africa, the Middle East, Central Asia, and western China. Because of their popularity, there is now a bewildering number of varieties. Appearing in January, ‘De Jager’ is one of the best of the early flowerers. Its striking blooms are a rich purple-violet on the inside, honey brown on the outside, with pronounced violet stripes. The flower stalks grow to four inches, and shiny, dark green leaves appear as the flowers begin to fade. It should be grown in full sun, in poor to moderately fertile, gritty, well-drained soil.
Propagation: Collect seed as soon as ripe and sow immediately in containers in a cold frame. Leave seedlings for two years before planting out. Remove cormlets during the dormant season.
Sieberi crocuses are not the most robust members of the family but are well worth the effort, with their vigorous growth and scented flowers that appear in late winter and early spring. ‘Bowies’ White’ is a particularly beautiful cultivar, with its pure white flower and deep golden throat. It will grow to two or three inches and will flower over a long period. The foliage is grass-like. Planted in a raised bed or trough it can be seen to its best advantage. It should be planted three inches deep, in gritty soil, that is well-drained but not too fertile in full sun.
Propagation: Collect seed as soon as ripe and sow immediately in containers in a cold frame. Leave seedlings two years before planting out. Remove cormlets during the dormant season.
If you are interested in crocus flowers, we have a guide with 7 Types of Crocus Flowers With Great Colors.
Gardening in January would not be complete without mentioning the hellebores. The earliest to bloom is the white Christmas rose, Helleborus niger.
Bergenias come from the meadows, rocky moorlands, and moist woodlands of central and eastern Asia, but are now much-loved denizens of our gardens, valued for their glossy architectural leaves and white, pink or red flowers. ‘Ballawley’ is an asset to a winter garden, as its mid-green, twelve-inch leaves turn a wonderful rich bronze purple. In spring, crimson bell-shaped flowers appear on striking red stems. Bergenias do not fare well in extremes of heat and drought but tolerate cold, exposed conditions, and poor soil. In fact, poor soil enhances their winter color.
Propagation: Divide deteriorating dumps or root rhizome sections every three to five years in autumn or spring. Young rhizome sections with one or more leaf rosettes may be rooted in autumn.
In the wild, Helleborus niger comes in a variety of shades from creamy white to dark pink but, in cultivation, we associate it with white flowers. This variety has been available for some years now, with particularly large (two to four-inch), beautiful, bowl-shaped, shining white flowers with green eyes. The flowers appear from early winter to early spring on sturdy purple flecked stems above its dark green and leathery lobed leaves. Helleborus niger and its ‘Potter’s Wheel’ variety can be unpredictable in growth, so give them ideal conditions. They like heavy, neutral to alkaline soil in dappled shade sheltered from cold winds. It is best to incorporate organic matter when planting and to mulch every autumn.
Propagation: Divide after flowering in early spring.
This vinca is quite invaluable as a ground cover plant for the shady areas under shrubs or trees, or at the back of a border in front of a yew hedge. Being evergreen, it helps to furnish the garden throughout the year, and its narrow, lance-shaped, glossy leaves, up to three inches long, look good all through the winter. As spring begins to make its appearance, upright shoots carry single, star-like, whitish, or pale blue, one-and-a-half-inch flowers, which greatly add to its charm. Vincas have a reputation for being invasive, but Vinca difformis is less so than other members of the family. It may be grown in any soil that is not too dry, either in sun or partial shade but it will flower better when it is in full sun.
Propagation: Divide from autumn to spring.
Daphnes are renowned for their beauty and their scent, so plant them where you can savor both to the full. Daphne bholua is an upright semi-evergreen that grows to about ten feet tall with a five-foot spread when mature. Leathery, dark green leaves are carried on stout branches and, from mid to late winter, its flowers appear as terminal dusters. The half-inch cylindrical tubes flare out into four lobes, deep reddish mauve in the bud, but becoming white with a mauve reverse on opening. A moisture-retentive, neutral, or slightly acidic or alkaline soil that drains well is best. Daphne bholua ‘Gurkha’ is a hardy deciduous form.
Propagation: Sow seed in a cold frame when ripe. Insert softened cuttings in early to mid-summer and semi-ripe cuttings in mid to late summer.
Originally from the Himalayas and China, this erect prickly shrub has chalky white young shoots that are very conspicuous in winter. In fact, the stems are green but carry a waxy, white bloom that gives them their frosted appearance. It is at its most impressive in winter but is also attractive in summer when its saucer-shaped white flowers appear, followed by spherical yellow fruits. A vigorous grower, but achieving no more than about ten by ten foot, Rubus biflorus should be grown in well-drained, moderately fertile soil in full sun. Prune it back in early spring to two or three buds above the base or permanent framework.
Propagation: Root greenwood cuttings in summer and hardwood cuttings in early winter.
There is nothing more cheering on a cold and dark day than the flowers of this winter flowering deciduous viburnum. Heavily scented, tubular, dark pink flowers age to become white flushed with pink. Borne in dense clusters up to three inches across over a long period, from late autumn to spring, the flowers are remarkably frost resistant. When the four-inch ovate leaves appear later in spring, they are bronze but change to a dark green as they mature. ‘Dawn’ will reach ten feet, with a six-foot spread, within a few years. It may be grown in sun or partial shade in any moderately fertile, moist but well-drained soil.
Propagation: Sow seed in a cold frame or a seedbed in autumn. Take greenwood cuttings in summer.
Myrtles are excellent for growing in exposed coastal or mild districts and Myrtus lechleriana is a fine Chilean species that can reach 20 foot by twelve in these conditions. One of its charms is the cinnamon-colored outer bark that peels off in patches to reveal the beautiful creamy surface beneath. Its flowers are delicately scented, creamy blooms that appear in late summer to early autumn. The oval leaves are pointed, coppery brown when young, going dark green with age. It is best to shelter myrtle from cold, drying winds and to grow it in moderately fertile, moist but well-drained, soil in full sun.
Propagation: Sow seed in a cold frame in autumn. Root semi-ripe cuttings with bottom heat in late summer.
This deciduous Far Eastern magnolia is considered by many to be one of the most beautiful trees in the world. It can take up to fifteen years to flower, but, when it does, the effect is so spectacular that the wait seems worthwhile. The blooms, resembling enormous goblets, are rose-pink outside, paler within, and maybe up to twelve inches across. It flowers from late winter to early spring, before the ten-inch, mid-green leaves appear. This lovely tree appreciates moist, humus-rich, neutral, or acidic, soils. It becomes conical shaped as it matures, finally reaching about 50 feet with a 30-foot spread.
Propagation: Root greenwood cuttings in early summer and semi-ripe cuttings in late summer.
It may be the hardiest of all the mimosa species but it is still only suitable for growing outside in milder areas and, even there, it needs a sheltered position. But with these conditions, it will reward you with masses of sweetly scented, small, yellow flower balls, in eight-inch terminal racemes, from winter to spring. As it is an evergreen, the flowers are set off by its attractive foliage – fern-like, hairy, five-inch leaves, made up of up to 80 linear, glaucous leaflets. It can grow to 100 feet, with a 30-foot spread, and likes full sun, in neutral or acidic, moderately fertile soil.
Propagation: Sow seed in spring, at not less than 64”F, after soaking in warm water. Root semi-ripe cuttings in summer.
Weather in January
The coldest nights of the year often occur during January, with the worst affected areas being inland, well away from the coast.
The western coastal regions can be surprisingly mild in some years, and gardens in inner cities are usually a degree or two warmer than those in more exposed country areas. There are often wide temperature variations between different parts of the country.
Although sheltered areas in the south and west may still not have received very severe and damaging frosts, Scotland and other northern regions will almost certainly have been affected.
Snow is almost sure to be a problem for short periods this month, except in milder areas such as the Isle of Man, the extreme south-west of England, and the coastal regions of southern Ireland.
Light falls of snow cause little damage and require no action, but heavy falls can break or damage branches on shrubs and trees, and you should knockoff the snow off the branches before damage occurs.
Heavy snow can also damage fruit cages if the top nets have been left on, so it is a good idea to remove and store the nets if you have not already done so.
How do Plants Survive Frost and Snow?
Hardy plants are the mainstay of the garden.
We plant them, tend them in spring and summer and then forget about them until the following year, sure that they will make it through our chilly winters of sharp frosts and snowfalls.
But have you ever wondered how plants survive such conditions?
Many shrubs and trees that withstand low temperatures lose their leaves or, in the case of several herbaceous perennials, their top growth dies down in winter.
This is a sensible strategy because photosynthesis – a plant’s primary way of generating energy – can’t occur in freezing conditions.
Plants become dormant during these months, reducing their internal functions to a minimum to save energy.
Frost generally poses a more significant threat to plants than snow, especially if it comes at an unexpected time – a frost in late April or May or early autumn can do untold damage.
This is because plants acquire hardiness gradually as temperatures fall in autumn and then lose hardiness in spring when warm conditions return.
Unseasonal weather takes the plant by surprise and can mean that the young foliage of a tough plant such as ivy can be blackened by a late frost in May, despite it having retained healthy green leaves in sub-zero temperatures throughout winter.
How do Plants Survive Freezing Temperatures?
A plant’s ability to remain unfrozen at temperatures below 0°C (32°F) is known as ‘supercooling,’ and the hardiest of plants, such as the black spruce from Alaska, can survive an incredible -40°C (-40°F) without suffering any ill effects.
Plants have several ways to survive frost. When the cooler weather arrives in autumn, hardy plants increase the far unsaturated content in their cells. This has a lower freezing point than water and keeps the cells functioning at 0°C (32°F).
As temperatures drop to just below freezing, ice crystals begin to form in less hardy plants between the cells and the water-conducting tubes in the stems and leaves. When the temperature falls at night and rises during the day, the continual expansion and contraction of ice between the cells can rupture them, causing sudden wilting and discoloration.
Besides, as ice crystals grow, they draw water from inside the cells, dehydrating them and creating a concentration of sugars and salts. As a result, the sugars and salts begin to crystallize and prevent the cells from functioning correctly. Ice formation can be rapid in tender plants, and experiments on peach trees show that it spreads to the whole plant within 20 minutes once the ice starts to form.
Dehydration of the cells during a freeze followed by a rapid thaw can be fatal for a plant, as water suddenly re-enters the cells, causing them to burst. This is the reason why camellias should never be planted facing east towards the early morning sun: after a frosty night, its heat can damage their flowers and buds.
Plants survive frost with additional methods. At -2 to -4°C (28 to 24°F), sugars and salts in their cells act as antifreeze – just as salt on roads prevents ice forming – lowering the freezing point of sap by a few degrees to keep the plant functioning.
When temperatures plummet still further, more defense systems are required.
Scientists have discovered that some, such as winter cabbages, produce proteins that restrict water movement out of the cells, preventing dehydration. Antifreeze proteins in other species lower the temperature at which water freezes or limit ice crystals’ growth between the cells. Recent research has identified a protein that allows cells to continue to function even when severely dehydrated.
From the mighty oak to summer-flowering phlox, hardy plants have evolved winter survival techniques so sophisticated that scientists are still trying to understand precisely how they work.
How do Plants survive Snow?
Snow can be less harmful to plants than heavy frost because it acts as an insulating blanket – preventing soil temperatures from falling below 0°C (32°F).
However, heavy snow causes physical damage, breaking off branches and exposing shrubs and trees’ inner parts to disease and cold.
For this reason, it is advisable to trim hedges into an ‘A’ shape to help them shed a heavy load.
Ground-hugging alpines, such as saxifrage, can easily bear the weight of the snow above them. They also use heat radiating from the surrounding soil and rocks to survive severe winter temperatures.
A cloche protects fragile plants from being flattened by snow and also creates a warm pocket of air.
Roots and bulbs tend to be less resistant to the cold and frost than stems and leaves, but this is because many don’t need to be.
Soil temperatures remain higher than the air temperature in winter and offer protection for plants whose upper parts die down.
Hardy bulbs, tubers, and roots systems act as storage organs for food and water and keep the plant alive during the colder months.
The food inside them also acts as an antifreeze, protecting them from the harmful effects of frost.