Garden Conditions: Too Dry
Availability of water – too little, too much, or just enough is the most important influence on plants. Miserable , direct exposure to sun or wind, deep shade or excessive competition are just as hard on plants as drought, and. Particularly in the case of poor soil, these factors can often be more difficult to identify. When combined with dryness, therefore, they need some care to overcome. There are two basic approaches to lessening the impact of too little water: use simple techniques to alleviate the effects of dryness; and choose plants that are adapted to a dry environment. Identifying a drought problem is the first step towards dealing with it. This section highlights key dry spots in the garden and suggests ways to deal with them. To find out whether you are likely to have a drought problem read on.
Is your garden too dry?
Your plant choices should take local climate into account. Weather is governed mainly by the prevailing wind and the amount of cloud and rain. Where prevailing winds blow off the sea, cloud will be common and rainfall high. As the air travels across the countryside dropping rain as it goes, it becomes less moisture-laden, so the last land it crosses receives the least rain. Mountains and hills produce a similar effect to land by the sea. The slopes that lace the prevailing wind have a higher rainfall than those over the other side. Wet or dry weather can also be very local. On the side of the country away from the prevailing wind or on high ground that is sheltered from it. There is relatively low rainfall.
Wind will help dry a site, so windswept sites can be short of water. Wind dries exposed wet but also leaches water from the leaves of the vegetation.
Gardens badly subject to frosts will feel the effects throughout the year. The last spring frost and the first serious autumn one controls the timing of everything you and your plants can do: they truncate the- growing season. On the positive side a dry site may be less vulnerable to frost damage; the plants themselves contain less water so their tissue is more frost-damage-resistant.
The shape of the surrounding land helps to mould the garden environment. Plants on slopes lacing the sun will feel its full strength. In these conditions you can create a garden for the sun-lovers from the Mediterranean, the southern states of America, the Australasian subtropics and southern Africa. Despite the dry conditions that these countries experience, not everything is like a cactus. In the autumn, Nerine bowdenii opensthat are sparkling and crisp. Amaryllis bella-donna is even more dramatic and dew-drop fresh. The fleshy, low leaves of mesembryanthemums are succulent beneath their scintillating many-coloured carpels of flowers. Ground sloping away from the sun will be a lot less hot and dry in summer. It will also be very slow to warm up after the winter and will receive scant benefit from the winter sun which, if it reaches it at all, will do so at a very low angle. Here, with less contrast between the seasons and less stressful heat on the plants, flowering periods can be prolonged and of a subtler beauty.
Geranium pratense (meadow cranesbill), will flourish in such a site, relishing any sunshine and coping with much dryness, whereas they would flag under an unmitigated baking. The pure blue species is extremely garden-worthy and there are some wonderful forms: G. pratense ‘Mrs Kendall Clark’ has large saucer-shaped silvery blue blooms; G. pratense ‘Plenum Caeruleum’ has double flowers like miniature blue; G. pratense ‘Plenum Violaceum’ is another double but this time in violet-maroon. In fact the geranium genus is full of plants that are easy to grow, persistent, attractive in foliage, generous of bloom and very well able to look after themselves.
Cold air flows downward, just like water, to collect in pockets and pools below. Where barriers impede air flow, frost pockets may form on slopes -your fabulous yew hedge is better with a gap for ‘frost’. Frost pockets restrict the choice of plants; the earliest flowers, particularly, should be bone-hardy ones such as snowdrops and winter aconites.
Does your garden stand high or low? Height gives a shorter season: knock 1°C off your mean temperature for every rise of 600m above sea level (2°F for every 2,000ft). Drying winds are more likely on higher ground. Alpine plants cope by keeping close to the soil. Ground-hugging Dryas octopetala (mountain avens), mound-forming Armieria (thrift) species and miniature rosettes of saxifrages demonstrate distinct adaptation for high mountains. Luckily, most mountain-top plants are also happy in low altitude gardens.
Shallow soil over poor subsoil or underlying rock will afford little water storage. The soil will be less ‘alive’. There are wide-spreading shallow-rooters and deep-delving tap-rooted alpines, which drill their way through difficult layers into the debris below, and these may cope. Deep soil will nurture almost every plant, although smaller ones could be overwhelmed by more rumbustious neighbours.
Heavy clay cracks as it dries, exposing delicate roots and allowing the air to suck up the last traces of water. However, when properly managed, clay is a Tat’ soil in which a good range of plants can grow strongly. Many of the more suitable plants are large and dramatic versions of familiar favourites, like Inula magnified with huge rich orangey-yellow daisy flowers.
Sandy soil usuallyvery rapidly and has no long-term water reserves. With little organic matter of its own. It has an unlimited appetite for added compost and manure. There are plants that enjoy such sites: I.intoniuni vulgare (sea lavender) and related species, together with Eiyngium maritimum (sea ) flourish in sand.
Soft dark loam is for the fortunate few and must be treated with reverence. If it is shallow, add to it whatever and whenever you can. It will repay your offerings with healthy plants. Some specials that ought to be considered are listed in the margin.
Some gardeners produce or inherit man-made dry areas. Walls and hedges in particular are likely places for over-dry soil.
Walls often shelter the ground immediately around them from rain; soil at their feet can be very dry indeed. Some walls are made of materials that can suck up soil water and then allow it to evaporate. Walls also reflect the sun’s heat and cause even more dryness. However, slightly tender climbers, such as carpenterias will survive more happily against a sun-facing wall than elsewhere and Geranium ‘Kashmir White’ and G. ‘Kashmir Purple’ bask at ground level.
Hedges and trees have root systems that thirst for water and. Spreading out from their base, they can dry a considerable area. Privet hedges produce an extraordinary mass of greedy roots, leylandii hedges are almost as bad.
How plants cope with dryness
Every variation in plant structure, form and colour has evolved for a reason. The shape of the whole plant, the shape of parts such as leaves, the make-up and surfaces of the parts, the type of root system, and the periods during which the plant grows all influence performance.
In dry places plants have to maximize water use, minimize water wastage and find other ways to survive droughts. They have to deal with a lack of water to the roots a well as with dry air around stems, leaves and flowers. The greater the air movement, the greater the water loss.