You’ll often hear the term ‘frost pockets’ used by gardeners. Frost pockets are low-lying areas such as valleys and hollows where cold air (which is heavier than warm air) flows downhill, accumulates and causes frost. So if you live in a valley or hollow you should take extra care against frost.
Climate change: Almost all scientists now agree that the earth’s climate is changing. The effects of global warming are much debated and contentious, but there is widespread expert opinion agreeing that there will continue to be a general rise in temperature, with a resulting frequency of flooding and droughts, as well as other extreme weather conditions all over the world.
Global warming will deliver a mixed bag to us gardeners as milder winters will allow a greater number of tender species, such as citrus fruits, to be grown outdoors in temperate zones, as well as increased yields of many vegetables, fruit and flowers due to increasing levels of CO2, which plants absorb in photosynthesis. Problems will include an increase in pests and diseases as well as increased maintenance to cover the longer growing season, and certainly many species of plants will suffer or face extinction. As gardeners we are all in a position to make a positive difference to our environment simply by planting and caring for plants appropriate to our environment. Recycling organic matter, improving the soil and planting for wildlife are just a few of the ways we can start to redress the balance and help to heal a planet that is under stress.
Plants you can expect to see more of include olive (Olea europaea), ginger lilies (Hedychium), banana (Musa basjoo), Canary Island date palm (Phoenix canariensis) and century plant (Agave americana).
At present, this Agave americana might not survive an average temperate winter. However, with milder winters due to climate change, such plants will become more commonly seen. In the right conditions, and over 30 years, these plants can grow up to 2m (6ft) high.
Wind
When it is severe or continuous, wind can cause much physical damage to plants. The best way to protect your garden from wind is to create windbreaks. These are simply plantings of trees or hedging that will reduce the speed of the wind by taking the brunt of the wind themselves, thus ‘breaking’ the wind. Natural windbreaks are generally more successful than man-made ones. So, if you have an area of garden that is particularly exposed to the wind, you should consider planting a screen of trees or shrubs that themselves are wind resistant. Ask advice from your local garden centre as to which plants these would be for your area.
Hedges are the perfect barrier for providing shelter from wind within a garden.
Rainfall
Rainfall is an essential aspect of climate that provides the water for your plants to grow. In areas of low rainfall, irrigation schemes can be very effective, but even they still depend on rain falling at some time. Most of our gardens still receive the water that they need through regular rainfall. Unfortunately, rain does not fall at predictable intervals and in consistent quantities, so your plants need to be able to cope with this variability in rainfall. This can sometimes present two main problems:
Waterlogging of the soil, occurs with consistent heavy rain where drainage is poor.
Drought conditions, where rain is sparse over long periods and the soil has dried up and the ground has gone hard.
In both cases, action can be taken to improve matters. Drainage of waterlogged soil can be improved by the addition of coarse grit. Cultivation of the soil will further improve matters (see here). If the problem is persistent, a more complex solution has to be found, such as installing underground drains. This is an area where professional help should be sought.
In dry soil conditions, the addition of organic matter will assist water retention, but generally a regular watering regime has to be undertaken to ensure that the soil is kept moist. If you have free-draining soil and persistently dry conditions, then you should choose plants that suit the conditions. Grasses and many plants from the Mediterranean region are suitable for dry conditions. There is always an answer for whatever the situation.
Plants for wet positions
Betula nigra (river birch)
Caltha palustris (giant marsh marigold)
Gunnera manicata
Ligularia ‘Gregynog Gold’
Lysichiton americanus (yellow skunk cabbage)
Matteuccia struthiopteris (ostrich fern)
Persicaria amplexicaulis (bistort)
Rheum palmatum ‘Atrosanguineum’ (Chinese rhubarb)
Rodgersia aesculifolia
Trollius europaeus (common European globeflower)
Humidity
Humidity is the amount of water vapour in the atmosphere. It is also affected by the moisture content of the soil. At one extreme, high humidity can encourage the growth of mould and fungal diseases, while a low humidity can increase the rate at which plants dry out and wilt. Low humidity can be improved in a garden by introducing water features and soaking all hard areas and soil, occasionally hosing down with water. Gardeners often refer to this as ‘damping down’. The opposite extreme to low humidity occurs mainly in rainforests, where plants adapt to these very particular conditions. Careful selection of moisture-loving plants is therefore important.
It is unlikely that you will have a perfect balance of all of these elements of climate in your garden, but a basic understanding of your local conditions will help enormously. Knowing that you can take some steps to work with the climate and not against it will help to improve your gardening results.
Euphorbia myrsinites naturally grows in exposed rocky places, and so is ideal for planting in a drystone wall.
Astilbes are moisture-loving plants and are best grown in partial shade.
Getting to grips with the stuff that you grow things in can save you a lot of wasted time and money. A plant adapted for boggy conditions will thrive in a heavy, clay soil with poor drainage. Planted in a well-drained, sandy soil, lavender will thrive just as it does in its native Mediterranean soil. Of course, you can contrive soil conditions by planting in containers or raised beds, but as it’s usually not possible to change your type of soil, it is essential that you understand what you have.
You don’t need a degree in chemistry to gain an understanding of the many different types of soil. Although you could spend many years learning about and specializing in soil types, the structure of the soil, the balance of nutrients in the soil and the constituent make-up of the soil, it just isn’t necessary when you start out in your gardening endeavours. Instead, a simple appreciation of soil types and their respective strengths and weaknesses will do to get you started.