Where Does your Garden Grow?

This is an excerpt from the Book called “Planting Design Essentials   by Jill Anderson and Pamela Johnson . Continue reading to learn more about Where Does your Garden Grow?, thanks to the author.

Analyzing your local area, knowing your soil, evaluating the light, assessing moisture levels, providing shelter from exposure 

Is your climate warm, cold, wet or dry? What kind of soil joes your garden have?  Which plants grow well in the local area?  All these questions need answers before you can begin to choose the right plants for your garden. 

Plants grow all over the world and have adapted over millions of years to tears to grow in their native conditions.  Even if we only used plats which are native to the garden’s local geography, we’d still have to understand its unique conditions before knowing whether a plant will happily grow there or not.  So when putting together a planting scheme with plants which may wel come from another continent it is vital to understand their growing preferences and whether they are suitable for the garden you wish to grow them in. 

All garden soil can be improved, but you cannot change its basic character.  If the base rock beneath the soil is chalk you can’t grow acid-loving plants other than in containers with ericaceous soil.  If the ground is sandy and free draining those plants which like damp conditions will struggle unless there is a source of water nearby.  Soil can vary from town to town and even from one street to another, and the climate can change depending on which side of the hill you live.  Being familiar with and understanding the local climate, geology and growing conditions is vital when choosing plants for a garden, as is knowledge of where a plant originally came from and the conditions it has adapted to. 

Analyzing Your Local Area 

Climate and Weather Conditions 

If you have been gardening in a particular area for many years you will be more familiar with the local climate than if you’ve just moved from another part of the country.  If you are new to an area you can find out how it’s affected by the seasonal weather by enquiring at local garden centres, plant nurseries or gardening groups.  Allotment holders are also a great source of valuable information, and all gardeners enjoy talking about the weather.  Looking at plants growing locally will give many clues as to what the climate is like. 

If  Plants such as hibiscus as hibiscus and tender pal, trees are thriving, then the winters are probably mild and dry.  Some gardeners hwever are unlucky and live in a frost pocket; this happens when cold air gets trapped in a dip and the land doesn’t warm up as quickly as the surrounding area, and as a result plants which are unharmed elsewhere may be frosted and damaged in a frost pocket.  Cities and large towns can be a few degrees warmer that the surrounding country side due to the heat generated by the buildings and retained by bricks and concrete, resulting in a micro-climate that can significantly affect the types of plants that will grow.  However, a roof garden in city can be affected by strong wind that will damage the plants and dry them out. 

Climate and Weather Conditions
Climate and Weather Conditions


Hilltop gardens will be windier, colder and dryer than further down the hill, whereas at the bottom a garden will be more sheltered and the soil will probably be damp, giving quite different growing conditions.  There may also be less topsoil on higher growund, as over the years it will wash down to the valley floor where it can be plentiful.  Flat open country will usually be wind swept; a good indication can be trees that have grown bent over due to being pushed by the wind.  You often see this on the coast where constant winds shape the trees and hedges.  Coastal gardens will also have salt-laden wind, which can damage plants that are not adapted to this environment. 

Local Flora 

Hundreds of years ago many areas of the UK were covered in forests and woodland, and in some areaswe still enjoy the legacy of this in spring when the bluebell woods are in full bloom.  Even in city gardens the native bluebells still persist, which indicates how well adapted they are to our soil and climate.  Simply by watching which native plants, sometimes  called weeds, choose to grow in our gardens tells us a great deal about the legacy left in the ground and the type of conditions we’ve inherited.  Ground elder, nettles and comfrey all tell us that that the soil is rich and moisture retentive, whereas a self-seedeed verbascum 

Indicates dryer poorer conditions.  If you have an area in your garen where nothing will grow except the weeds, they are giving you a clue as to what the conditions are and which cultivated plants will also be happy there. 

Knowing Your Soil 

Understanding soil is fundamental to understanding how plants grow.  Getting to know the soil in your garden is an essential starting point, as many problems with plants can be traced back to the earth they are growing in.  Soil is not a static, dead material; it is dynamic and alive and can vary from one part of the country to the next or even from street to street, garden to garden.  It will change according to the seasons and the weather and Is vulnerable to pollution and physical damage. 

Geology and Ancient History 

 For most of us the geology under our feet is not something we generally consider in great detail, but the soil we stand on is just the top layer of a complex geological profile made up of base rock, subsoil and topsoil.  Topsoil is the layer we refer we dig in, plant in and work with.  Beneath the topsoil is a layer called subsoil, which may be encountered when digging deep holes for planting large specimens or during construciton work.  Other than tree and large shrub roots very little grows in subsoil, as there is no air or food.  Care must be taken not to contaminate topsoil with subsoilpreferably leave it undistrubed if possible. 

Under the subsoil layer is the parent rock; this will determine the type of soil in your garden.  Sandstone will produce sandy soil; chalk will prodice chalky soil and so on.  This happens in combination with the ancient geological history of a region such as forests, rivers, glaciers, plate tectonics and changing coastlines. Knowing just a little geology and ancient history of your region can help you understand a great deal about the very valuable layer of topsoil in your garden.

Knowing Your Soil
Knowing Your Soil

What is soil? 

Soil is a mixture of minite particles of rock and partially decomposed plants and animals called humus.  The types of rock the soil is composed of will define it as being clay, chalk, silt, sandy or peaty.  However, healthy soil will also have air, water, food and a micro-cosm of organisms including plants and animals.  These organisms play a vital role in maintaining a healthy soil, which is the key to growing healthy plants.  The basic mineral particles in soil are usually clay, silt  and sand (clay particles are the smallest and sand the largest).  Your soil properties are dependant on the combination of these three different minerals. 

Acidity and Alkalinity (PH Levels) 

The acidity or alkalinity of your soil is dependant on the presence or absence of calcium, which is washed out of the soil by rain.  If the base rock is alkaline, such as chalk or limestone, them this will leach back into the soil, which will therefore always be alkaline. 

If you try to grow acid-loving plants in an alkaline soil they will at best look sickly with yellowing leaves for a while and then ultimately die.  These acid-loving plants, having adapted to alkaline-free soil, are called ericaceous.  Equally there are many plats-especially vegetables-which require calcium to thrive, and it is easier to increase the calcium content of soil (by adding lime) than it is to remove the calcium.  Acidic soil can have lime added to it regularly when required, but alkaline soil cannot be made acidic. 

Even replacing all the topsoil will not work, as the calcium will be coming from the base rock, so it is much better to work with what you have and grow acid-loving plants in containers with ericaceous compost.  Tap water often contains calcium, which can significantly affect acid-loving platns so collected rain should be used to water plants such as rhododendrons and azaleas. 

So how do you know what type of soil you have?  A lot can be learned from simple observation-for instance, what plants grow nearby, eithey in wild conditions if you’re in a rural area, or in the neighbour’s gardens? 

Rhododendrons, camellias and azaleas growing in an area indicate that the soil is acid.  Houses built from local materials such as flint and limestone occur in areas with alkaline soils. 

But the use of a soil testing kit is a sure way of establishing the levels in your own garden.  The PH scale is a method of conveying how acid or alkaline a soil is; it ranges from 1to14, with 7 being neutral.  Below this the soil is acidic, whereas from 7to14 it will be alkaline.  Most plants prefer a soil that is 6.5 on the scale (nearly neutral), and it is unusual to find soils outside the range of 4-8. 

Evaluating The Light 

Which Direction does your Garden Face? 

A good way to tell the direction your garden faces without a compass is to remember the sun always rises in the east and sets in the west, so if the sun is on your left in the early morning you will be facing south.  You need to know this in order to understand which parts of the garden will get the sun as it moves through the day.  A wall facing due south will be sunny and sheltered for most of the day; if it faces west it will get the warm late afternoon sun, but be shaded in the morning sun and can take a while to warm up; while north facing walls will get very little sun through the day and will be shaded and cool.  The direction of the wind will also affect the temperature, depending on whether it is blowing from a warm or cold land or sea. 

In winter the days are shorter with less daylight, and the sun does not get as high in the sky.  In the height of summer the sun will be overhead at midday and the days will be longer.  This can make it difficult to judge correctly how sunny a garden gets in the middle of winter when the sun may not reach parts of the garden at all.  Equally, a garden with lots of deciduous trees may seem lighter in winter without the tree canopy and quite shady in summer due to the leaes blocking out the sun. 


Full sun or Semi Shade? 

 Of course, daylight is relevant to any aspect of garden design and particularly a planting scheme, but evaluating it is not always so straightforwad.  Fully understanding the light leavels in all areas of your garden is essential to choosing the right plants.  There are various terms used when referring to gardens and Plants such as ‘full sun or ‘semi shade’.  What do these terms really mean?  How much light does ‘full sun’ equate to?  What denotes deep shade and what is the relevance when choosing plants? 

Full sun means just that:  daylight all day long, not just for a few hours in the morning or afternoon.  Imagine a field with nothing but grass in it.  The centre of the field receives full sun or daylight throughout the day.  If the field has trees on its boundaries the areas where the trees cast a shadow do not receive full sun, but are in ‘part shade’.  The shorter the days and the lower the sun gets in the sky the field will be in part shade. 

In a garden, particularly a small garden, full sun can be difficult to achieve, and even in a large garden there are usually trees, shrubs or structures creating shade.  The problem with growing sun-loving plants in anything less than full sun is they will not perform so well.  They will become ‘leggy’ as they grow towards the light, with long weak stems which are more likely to fall over or require staking.  They will probably produce fewer flowers and be more prone to pests and disease. 

Plants which have adapted to semi shade, for example those living on the edge of woodland, will cope well with just a few hours of dappled sunlight during the day.  Deep shade means no sunlight at all, but again there are plentry of plants which have adapted to these conditions even if they are not the most showy or colourful.  A boring healthy plant will always look better than a sickly ‘crowd pleaser’. 

Assessing Moisture Levels 

How wet or dry a garden is can also be quite difficult to evaluate, because it is’t so obvious by just looking at the soil.  An open sunny part of the garden will probably be dryer than in a shady corner, but even digging down a few centimetres doesn’t give us the full picture.  The amount of moisture the ground can hold depends on the type of soil in the garden.  Heavy clay will hold more and sandy soil will hold less. 

The height of the water table in your area could also have a big impact on moisture levels.  All ground has a water table, which can be many metres down or just a few centimetres below the surface, and in most cases this changes seasonally through the year, depending on the amount of rainfall.  After a few months of no rain the water table can go down significantly, or a long period of heavy rain can bring the water table up close to the surface.  Digging a hole is one way to look for the water table in your garden, but your local council or planning office should also have this information. 

If you live in an area with a very high water table this will dramatically affect the moisture content of your soil and will determine which plants you can grow. 

Plants which like very dry conditions will not thrive if their roots are wet for long periods; however, thirsty plants like hydrangea and willow will love it.  Ground with a high water table for most of the year can be difficult to drain as the water has nowhere to be drained off to; in this case building raised planting beds is the only solution for any drought tolerant plants you wish to grow. 

Existing plants, walls and buildings will also affect the moisture levels in a garden.  The ground under trees, large shrubs and hedges tends to be dry because the plants are taking up the moisture.  The ground at the bottom of a wall can be dry because it is sheltered from the rain.  These places are also usually shady, giving rise to the term ‘dry shade’, which is most gardeners’ least favourite conditions. 

If there are no physical signs on the ground of the moisture content in the soil, looking at which plants grow locally will give you clues.  Willows, rhododendron, hydrangea and large-leaved perennials are a good indication that water is present and pine, buddleia, gorse and thyme would indicate very dry soil. 

Providing Shelter from Exposure 

Gardens hate strong winds.  More than drought, rain or frost, wind can do more damage to plants by drying out leaves, battering them down to the ground and breaking branches and stems.  Fragile roots can be damaged by plants being rocked in the ground, particularly trees and shrubs.  Some of the hardest types of country to create a garden in are open wind-swept plains or coastal regions with howling gales.  These are extreme conditions, but nearly all gardens are susceptible to damage from strong winds. Sometimes this is due to air turbulence, which can be created when wind hits soild barriers such as walls and fences.  In towns and cities wind tunnels are common between buildings. 

Growing plants that have adapted to these conditions is sometimes the only solution, but there are many ways to protect against damage.  Shelter breaks that use tough hedging or trees, such as rows of tall poplars, are a common site in open farmland.  Use open trellis work or deciduous hedges instead of solid fencing and walls.  VuInerable plants can be protected in winter by wrapping them in horticultural fleece or even pruned stems, branches and leaves.  Staking can prevent rocking, and regularly tying in climbing plants and wall shrubs will help, in addition to the use of plant supports.  Grow plants with smaller leaves that will not get torn in the wind-think of pictures of bananas and palms after  a hurricane. 

All the practical information you can gather about the climate and weather in your area will help you understand the growing conditions in your garden.  This will also help you to know what you can grow and, possibly more importantly, what you can’t grow. 

With a garden plan and study or site analysis, you can now look at the style you would like the planting to have.

Where Does your Garden Grow?