This is a water based solution which has a pH below 7. Most acid soil lie in the range of 7 to 5 though some peat soils may be lower.
In simple terms this is how acid or alkaline something is – only a water based solution can have a pH. A pH of 7 is neutral, below 7 is acidic and above 7 is alkaline. The only way to know the pH of a soil is to measure it, either by adding it to a solution which changes colour according to the pH or using a pH meter. Both have there draw backs, with the solution it can be hard to check the colour as the soil discolours the liquid while on the other hand pH meters; if they are to be reliable they are expensive and need constant recalibration with a buffer solution. I’m very dubious about how reliable the ph meters for the domestic market are and I would say for your own garden the kits of indicator solutions are probably better.
Don’t get too hung up on the absolute accuracy of individual test as the pH of soil is vary variable and you may well find slightly different readings in different parts of your garden The advent of pH metes has lead to people publishing the recommended for plants down to a tenth. I don’t really see this has any practical value.
When plants are grown in a soil which is to alkaline for them they suffer from iron deficiency as a result of the effect the pH has on the nutrients which are available to plants growing in it. Sequestered iron is iron in a form which is not affected by the pH and so it remains available to the plants. It is really only a short term measure so it has to be regularly reapplied to the plants.
The pH confusion
People get terribly worried about lime near Rhododendrons, to the extent that some people insist that you should never water ericaceous plants with hard water. The problem is the whole soil pH thing courses all sorts of confusion. So let’s ignore all that’s been said before and start from the very beginning. First off soil contains water but of course its not pure water it contains allsorts of dissolved minerals the plants need to grow. These are called plant nutrients and their presence is not enough; they must be in a form which makes them available for the plants to take up. The soil water will also have a pH; all water based solutions have one. How it is calculated isn’t important for our purposes but it effect is.
The sugar analogy
For a minute let us imagine we are dissolving sugar in water, we can carry on adding more and more sugar until no mater how long we stir the water no more sugar will dissolve. Now imagine we start to heat the sugar and water gently on a stove, the sugar will all now dissolve and we can dissolve still more. Now imagine the temperature of the water is the pH and the sugar is one of the plant nutrients. As the pH is altered the amount of the nutrient that is available in the soil water also changes. To further complicate things, as if it was needed, the availability of different nutrients changes differently as the pH changes.
The result of all this is that in alkaline conditions there is a lot less Iron, Manganese, Zinc, Copper and cobalt available for plants to take up than there is in acidic soil conditions. Just adding these nutrients to the soil is not going to help as the same process that had made them unavailable in the first place is going to act on the additional nutrients making them unavailable; if a pint pot is full pouring more water in it still leaves a pint of water.
Manipulating the pH
This leaves two options: change the pH or provide the missing nutrients some other way. Changing the pH of a soil is not that easy as the complex system that makes up soils tends to resist the change moving the pH back to the original level when to try to change it. Moving a soil towards an alkaline pH is the easier than towards an acid pH one. One is to add an acidic compost to the soil but the only readily available one is peat and that is becoming increasingly problematic because of the environmental concerns surrounding it. A second means of making the soil more acidic is to add a chemical to it. Three chemicals are generally recommended: sulphur, aluminium sulphate and ferrous sulphate. The other option is to provide an alternative source of the missing nutrients for the plants and this can be achieved by using sequestered iron which provides the missing iron in a form that remains available even if the pH would make it unavailable.
After all of this you may have noticed lime has not been mentioned since the first sentence. Lime is in practice mainly calcium carbonate with some other chemicals mixed in according to the source. The calcium is a plant nutrient but its carbonate has the effect of make the soil water more alkaline and it is this change to the soil water, not the lime, which has the effect on the ericaceous plants.
This is a catch all term for plants which need acidic soil to grow in.
When faced with an area of waterlogged garden the solution put forward is always to put a drain in, as if digging a trench and putting in a length of perforated pipe will magically make the problem go away. If only life was so easy. If you are going to drain a piece of ground you need to address two questions, one you may not be able to answer, the second your are going to have to.
The first question is what is coursing the poor drainage, this can have answers and sometimes the reason is never actually found. It is still important to try and understand the circumstances behind the problem if an effective means of tackling it is to be found. Possible courses are:
- A buried layer stopping or slowing water percolating down to the water table
- High water table
- A depression blocking the natural drainage
- A vertical structure blocking the natural drainage down a slope
The second is where you are going to drain the water to. This is the thing people always over look; they will happily stand looking at the problem debating the cause while never considering what they are going to do with the water once they have got it into a land drain. The bottom line is if you are going to drain an area you have to have somewhere to drain the water too. The problem is if the water isn’t draining away it may be because there is nowhere for it to drain to.
Before going any further down the drainage route the question needs to be asked; “is drainage the best solution?”
- Drainage is expensive and a big upheaval
- Persistently wet ground opens the opportunity to grow a range of different plants
- Drainage isn’t always practical
If you are going to drain an area of garden you have to consider the practicalities, you are going to have to dig a trench – lots of trenches possibly –, bring in gravel and dispose of a lot of now unwanted subsoil. You also have to find somewhere to drain the unwanted water too, clean up all the mud (you are digging out very wet soil) and make good the area so that it once again looks like a garden and not the morning after the battle of the Somme!
Alternatively you could except the situation and fill the area with suitable plants. It is always far easier to plant with the prevailing conditions than try to fight them. Once you have accepted that this area is water logged and you are going to have to live with this it opens up whole new palette of plants to work with. Have a good look at the area and live with it for a while, at least a year, and seen how much sun it gets and when, is it wet all summer or just in winter, is there standing water in the area and how long for, all year, all winter or just when the weather is very wet. How big is the area affected and how does the area change over the course of the year. This way you can build up a mental map of the area so you appreciate which areas are going to be water logged just during winter, which all year round, which are going to be a bit wetter than ideal and which are going to be covered with standing water most of the year. These different areas provide you with the conditions needed to grow plants which would otherwise be very difficult otherwise. If you are prepared to spend a little time and patience you can turn what at first appeared a problem in to a real asset to you and your garden.
Finally not everywhere is going to be appropriate for this treatment and if the waterlogged area is your main area of garden then you are probably going to have to find a means of draining it; but for a small part of a garden, or even a large part of a very small garden, you may well be better seeing the possibilities of your garden and using them.
What soil is should at first sight be pretty self evident but to a soil scientist, yes there is such a person (they study soil), soil is a very complex thing. The problem is we all tend to overlook soil; it’s that muddy stuff in the garden. It is though a complex and delicate ecosystem in its own right. The main parts are:
- Soil water
- Organic mater
- Soil flora
- Soil fauna
- Mineral components
- Soil air
In the coming posts I’ll walk you through the problems associated with starting a new garden. I grant only a small number of people are at anyone time in this position but it will illustrate how a garden develops, provides a logical starting point and even if you are not actually starting a new garden there should still be things of interest to you.
OK so you moved into your new house, the place is full of empty cardboard boxes and packaging, making the place look like an upmarket ruff sleeper’s convention, you found the kettle and your child’s favourite cuddly toy; stare out of the window and see the garden. You will in all likelihood be faced with one of three scenarios.
A bare patch of mud with a fence around it.
A bare patch of grass with a fence around it.
An existing garden.
If it the second or third option you can, for the time being, just cut the grass and worry what to do later, it isn’t going to come to any harm and there will be lots of more urgent things you need to right now like get some sleep and recover from the move!
If you look out on an area of mud and/or weeds you may have to do something soon rather than later as that mud will end up getting everywhere and the weeds, even if not present now, will soon be growing vigorously.
You may have noticed I haven’t mentioned fences yet as in all possibility the garden will already be fenced off so I will come back to that later if you don’t mind. As they say ‘Roman wasn’t built in a day’.
The first thing we need to decide is if there is a weed the problem. If there’s none or just some weed seedling which have just come through we can ignore them but if the weeds are big enough to hold the soil together you are going to tackle them before we can do anything else. A lot, no.., A GREAT DEAL has been written and said about the use of chemicals in the garden and I’m not going to dive in what is a very opaque and opinionated debate at this point. The bottom line is that to clear a garden sized weed problem in a reasonable time is going to mean using a weed killer.