Key Takeaways
- There are five main types of problem soil types – compacted, waterlogged, tired, poisoned or ‘no topsoil’. Some can be improved – others just need to be removed and replaced.
- When clients ask how they can improve garden soil quickly, I always tell them the best soil improvements take time and come from gradual amendments – there isn’t any quick fix.
- Finding out what your soil type is before amending saves time, wasted effort and money. A simple jam jar test is always the place to start from.
- Find out your soil’s pH, too. A quick and cheap litmus test tells you what will grow well and what won’t.
- If you plan ahead and aren’t too fussed on the outcome, just adding well-rotted organic matter a few months ahead improves almost every soil problem.
As a professional landscaper and an avid gardener, I always maintain that the soil is the most important part of any successful garden. Yet, many do not understand it properly or look after it well enough. In this article, I cover the five types of problem soils you will find in your garden and how to improve them.
Problem Soils
There are five types of problem soils that I have encountered as a professional landscaper. Not all soils are straightforward to improve, but here is how I approach each one.
1. Compacted Soil
Compaction happens when air and water cannot move through the soil. True compacted soil is caused by heavy machinery and often customers tell me they have compacted soil when actually it is not. Compacted soil crusts over after rain and drains poorly so that no plants will grow in it. I recommend digging as deep as you can to loosen it, let air in, and help water drain. Add lots of compost with sharp sand or horticultural grit to keep it loose.
2. Waterlogged Soil
Waterlogging occurs most often in heavy clay soils and I often see it close to a blocked gutter, an overflowing drain or at the bottom of a hill; the first thing you need to do is identify the source of the problem. Symptoms of waterlogged soil include yellowing and/or browning of plant leaves, plants appearing as if they are wilting, and a sour rotting smell. If your garden stays wet and soggy I always advise laying drainage pipes or a French Drain to carry water away to a ditch, drain or pond.
3. Tired, Exhausted Soil
Old gardens in city centres or new housing estates built on heavily compacted fill often have dry, dusty soil with no nutrients. Add plenty of organic matter and mulch to bring it back to life. Mulch is a fantastic gardening hack; it’s cheap, easy and readily available as just about any organic matter can be used as mulch.
4. Poisoned Soil
Poisoned soil is ground contaminated with oil, petrol or weedkiller, and the sign is plants that simply will not grow in it. I see this a lot on housing estates. Often the only solution is to dig it out and replace it with new top soil. I’ve had to do this on many jobs over my time, so it’s worth testing if you in any doubt. Also, if you do change your soil, check your local council for advice on safe disposal. Alternatively, loosen the soil and let toxins break down naturally – you can test it with cress seeds (which are cheap, fast-growing and sensitive to toxins) before planting.
5. No Topsoil
Remove the soil where you want to grow vegetables or a thriving border, and improve it where you want low maintenance planting and a gravel mulch. What tips the decision is your budget, your plans for the garden and the size of the area. Adding new good quality topsoil on top is the middle route. You will need to either dig up the good soil buried underneath and improve it over time or replace the bad soil.
On a new-build plot that usually means a multipurpose soil like our landscaping topsoil, laid at 100mm for turf and 150mm in beds, once the compaction underneath has been broken up. If you can’t do either, you’ll have to work with what you’ve got. The key is to be as gentle with the structure as possible and of course keep adding organic matter of any type to gradually increase nutrients and encourage living creatures.
Where a site lacks workable topsoil, importing soil for the whole area gets expensive fast. Raised beds are cheaper: you fill only the boxes, buying soil for the area you actually plant. Building a raised bed from pallets is the cheap way in, though the timber only lasts three or four years in contact with soil.
Improve or Remove Your Problem Soil?
Deciding whether to remove these materials or add new, good quality topsoil on top can be influenced by many factors including your resources, your goals for the garden and how much space you are trying to re-invigorate. As a golden rule, if you are looking for a thriving garden or looking to grow vegetables, it is best to dig it out and start again. However, if you are just looking for a low maintenance garden with a few hardy plants and some gravel mulch, for example, then digging in some compost or good topsoil around your plantings might be enough to do the trick. The planting itself is in planting into gravel.
Soil Testing and pH
Two tests tell you most of what you need: a finger test for texture and a litmus test for pH. Texture decides drainage and workability, pH decides what will grow. You can do a quick finger test (roll a sample of soil between your thumb and forefinger; sandy feels gritty, clay sticky/smooth, silt silky, loam balanced) or simple jam jar sedimentation test. See our articles for more on what makes good topsoil or how to test your soil with a simple jar experiment.
Testing Soil pH
Soils can be acidic or alkaline, measured on a scale called pH. At pH 7, soil is neutral. Above that is alkaline, below is acidic. Most plants prefer pH 6.5, which is slightly acidic.
Some plants only grow in certain pH levels. For example, rhododendrons, heathers & camellias need acidic soil and will not grow well in alkaline soil. Vegetables like cabbages and other brassicas need alkaline soil to grow well. pH also affects pests and diseases. For instance, brassicas are less likely to get clubroot disease if the soil is alkaline. Measuring your soils pH helps you predict nutrient availability for different plants and grass. This can be achieved with a simple litmus paper test.
Typical pH Ranges by Use
Different garden projects prefer different acidity levels. The ranges below are practical targets for common plantings and turfing projects.
| Use | Typical pH range |
|---|---|
| General ornamentals and turf | 6.0 to 7.0 |
| Raised beds for vegetables | 6.0 to 7.5 |
| Blueberry and ericaceous shrubs | 4.5 to 5.5 |
| Roses and many fruit trees | 6.0 to 6.8 |
How to Improve Soil pH to Suit Your Plants
The pH of a soil does not remain constant. The very action of rain and natural cycles within the soil slowly make it more acidic.
Sometimes you need to add lime or chalk to make it less acidic. Hydrated lime (calcium hydroxide) is the most common garden lime although chalk (calcium carbonate) works too. I always add lime in autumn because it works slowly and may not be fully effective until the next spring. Because liming is difficult to reverse, use small amounts and check the results before adding more. I always wear rubber gloves, a mask & sunglasses when using lime.
Lime & Manure Don’t Mix. I never use lime & farmyard manure at the same time. They react together and release too much ammonia which burns plant roots and wastes both materials.
If you want to grow rhododendrons, camellias or blueberries, test your pH first. Sulphur is the material that actually lowers soil pH, but it works slowly, and on chalky ground the soil undoes it. Where your soil is alkaline, I grow acid-lovers in pots or raised beds filled with ericaceous compost, because the garden soil can’t reach the roots there.
How to Improve Garden Soil Using Compost, Soil Conditioners & Grit
Three materials do the improving: compost and other organic matter for structure and fertility, grit or sharp sand for drainage, and fresh topsoil where there is nothing left worth improving.
Compost and Organic Matter
In the industry, we have a saying: add some organic matter and you’ll fix almost any soil problem – and in my experience this is nearly always true. Almost any soil is improved by adding some compost. Organic matter takes many forms and does many useful jobs. It helps dry soil hold water better and keep nutrients in place. It loosens up heavy clay soil and breaks up compacted ground. Best of all it brings in earthworms and beneficial life, which is brilliant for any garden. To add it, you can use any or all of the following:
- Garden compost
- Well-rotted horse manure
- Chicken manure
- Mushroom compost
- Green compost
- Wood chip
- Bark fines
- Leaf mould
- Seaweed
- Brewers’ waste
Applying Compost
Spread a 2-5 cm layer across the surface and work it into the top 15-20 cm of soil. Reapply annually as part of an ongoing soil improvement plan. That’s compost doing its own job, feeding soil that is already there. Where the ground has to be built up you want soil instead, and I set the two against each other in topsoil versus compost.
Horse & chicken manure must be well rotted before use or they will damage plant roots. Mushroom compost is also useful but can be alkaline so avoid it for ericaceous (acid-loving) plants. Those I top-dress with ericaceous compost instead, in pots, raised beds or borders where the soil is already acid. It won’t make an alkaline border acidic, but unlike mushroom compost it won’t push the pH up either.
When to Avoid Adding Compost
There is one situation where you should not add organic matter and that is when your soil is peaty and waterlogged. Doing it can encourage a build-up of methane and other toxic substances. If your soil is peaty and stays wet (a clue that indicates you have that problem is a sulphurous smell coming from the soil), compost won’t help. Instead, you need to install proper drainage & add sand, grit or LECA. This stops water sitting in the soil for too long. Then add your compost!
Sand and Grit Soil Conditioners
When you need to improve drainage, coarse sand, gravel and 2 to 4mm grit are the materials, dug into the soil over the winter months. I use a 2 to 4mm horticultural grit for this.
Coarse grit or sharp sand does help break up heavy clay and improves the drainage. However, it must be incorporated properly using a combination of grit and compost. I avoid relying on sand or grit alone as you’ll likely to end up with brick-like soil and no improvement in drainage. For clay soils, mix 4-6 cm of grit with a good amount of compost into the top 15-20 cm to loosen the profile.
Can Garden Soil Quality Be Improved Quickly?
There aren’t really any quick fixes to improving your topsoil fast – it’s a gradual process that needs time for nature and wildlife to work its magic If the topsoil quality is already good and just needs a boost, you might be able to add compost and see improvement in a few months but for poor quality and problem soils I always tell customers the fastest way to fix garden soil is replace it with or add to it a good quality topsoil from a reputable supplier. .
Next Steps
Now you understand that healthy soil is fundamental to successful gardens and know the best way to improve or remove problem soil types. Whether you’re levelling a lawn, building raised beds, or framing a gravel garden, the right garden soil – paired wisely with the right amendments – can deliver brilliant results.
If you would rather talk your soil through with a person, ring Outdoor Aggregates on 0330 043 7585. The office is open 7am to 7pm, seven days a week.
Have you ever worked a difficult soil round into shape? What were you dealing with, and how long did it take to see a change? Tell us in the comments.
FAQs
How can I fix garden soil quality quickly?
Garden soil quality cannot be fixed quickly because good soil is built gradually rather than in one go. When there is no time to wait months for results, buy quality topsoil from a reputable supplier and work with that instead. True topsoil forms over several years as living organisms colonise it and build it up and nothing in a bag shortcuts that.
What is the best way to improve garden soil over winter?
The best way to improve garden soil over winter is a modest layer of well-rotted manure spread on the surface in autumn and left for the frost and the worms to work in. Use well-rotted horse manure for this and do nothing else to it. No-dig gardens are entirely possible, but turn the soil once at the start where it is very poor or compacted.
Can I build a vegetable garden on top of weedkiller?
A vegetable garden can go on top of weedkiller once the weedkiller has broken down, and how long that takes depends on which one was used. Glyphosate (Roundup) is gone within days, though it’s still preferable to wait weeks or months before sowing anything edible. The long-lasting herbicides, aminopyralid, clopyralid and picloram, can hold on for up to 3 years and there it is best to start again with fresh soil.
How do I make my soil not so dry?
Dry soil holds its water once it is covered with a mulch and given a proper soak each week. Bare soil loses moisture to evaporation and crusts over, and a mulch stops both. Mulch is one of the best hacks in gardening because it is cheap and easy to come by: fresh cut grass works, so does leaf mould.
Is there a solution for excessive water that the soil in my garden doesn’t process?
Excessive water needs somewhere to go before the soil can be improved, so the fix starts with finding what is causing the flooding. A ditch or a pond at the lowest part of the garden will catch the surplus, and a French drain will carry it away. Sometimes clearing the gutters and drains is the whole answer. Once the water is moving, compost and soil conditioners improve the structure so the ground holds less of it.
How do i make good soil out of bad soil?
Bad soil turns into good soil by having organic matter added to it, year after year, until the structure changes. There is no immediate version of this. What you get over time is compost worked through the profile, better structure and nutrients, and earthworms, which are worth their weight in gold in any garden.