Soil – Simple testing – the dry test

To test your soil for structure: the dry test

  • dig a small area and remove any plant material.
  • Turn it over and water it lightly tonight.
  • Tomorrow about midday, dig down until it feels moist.
  • Remove a fist full and squeeze it together in your hand.It should stay in a clump, not ooze out between your fingers (too much clay), wring out dirty water and feel spongey (too much humus) or feel dry and fall apart (too much grit).
  • hand ful of soil

    The soil should stay together

    If the soil is not right, add humus (potting mix or compost), clay to bind it or grit (as washed sand) to improve drainage.

    This doesn’t mean your soil has all the best nutrients, it means you have a great growing medium. We’ll look at nutrients next.

The best soil ?

Different soil structures favour different plants but here’s a rough overview.

bunch of raw carrots

Home grown carrots

Root crops like carrots, swedes, turnips and beets all require sandy “open” soils. They have adapted to sending long tap roots down to find water. These tap roots store water and nutrients and fatten up into the vegetables we see in the shop. Carrots grown in a heavy loam (lots of humus) will have lots of leaves and little or no root. Often the excess moisture will create areas of rot in the carrot.

An assortment of home grown leafy vegetables

An assortment of home grown leafy vegetables

Leaf crops like lettuce, chard, cabbages brocolli etc, require a high loam soil. They need the soil to hold moisture because their large amount of leaves will create a lot of evaporation of water.


Fruit crops require soil structures in between. Generally speaking, the taller the crop, the more clay content. The soil has to be firm to support the top of the plant swaying. Vines on the oither hand (beans, peas, etc) require more water than a bush, son prefer a soil higher in humus.

Flowers vary depending on the variety and trace elements. The most common exception is roses which are deep rooting and will thrive in a clay soil where other plants would become waterlogged. Because the roots go deep, they are also more drought tolerant than many other flowering plants.


Soil – creating the best growing medium

There are three basic components in soil. At this point we are looking at soil structure rather than the various nutrients needed for the different types of plants. This is a very simple version for the average gardener, not a geological exercise :

  • Humus – this is basically plant material, mostly plant fibre. It retains water in the soil. Too much and you have peat, that never dries out. The humus in the soils has the added benefit of slowly decomposing and releasing trace elements into your soil. As a general rule, you need to add this to your soil every three years.
  • Grit – this is usually in the form of sand and fine gravel. This allows aeration and drainage of water through the soil. Too much grit and the soils will be dry and barren. Water passes through it before the roots can take it up. On dry days the plants will rapidly wilt and die. Grit, being stone, decomposes very slowly to release trace elements. Just a tip – if making your own soil, make sure the sand is washed – sea sand contains enough salt to kill most plants.
  • Clay – clay binds the lot together and has the ability to expand with water to counteract the drainage action of the grit.

So without getting all technical and bogged down with soil chemistry, these are your three main components that we need to balance to create a good growing medium. In the next installment, we’ll look at a simple test to see what we  need to get this mix perfect.


We have set up our paths and retaining walls, the next step is to create your gardens. Whether it’s a vege garden, seed bed or established shrubs and trees, the major factor in their survival is the soil itself. Get the soil right now and you will reap the rewards for many years to come, so it’s worth the effort.

You can simply dig over the exposed ground, throw some seeds or seedling plants in and hope for the best but you’ll be disappointed.  If you are lucky you’ll get half the possible results. If you spend some time setting your gardens up properly, you’ll reap the rewards for decades to come.

There are two main points to consider, regardless where you live: the soil and drainage, which includes watering as well as run off. The two are closely interrelated.


Gardens perform best when raised. Using a border will reduce weed invasion, especially if you have layering grasses in your lawns, like buffalo, couch or kikuyu grass. Raising garden beds means you can control the moisture content in the soil better because you can drain off excess water. Few plants survive if their roots are swamped for prolonged periods. It reverses the flow of nutrients and promotes destructive strains of fungi and bacteria. The other extreme is true too; where we need to retain the moisture in the soil. Plants need a moist environment for nutrient exchange at their roots.

Ideally we need a soil that will allow water to filter through it, yet hold water so the plants can use it. It sounds like an impossible conflict but it can be done. Firstly raising the soil level will give us somewhere to drain the excess water off to. Secondly by creating the right kind of soil we can end up with the ideal growing medium that allows excess water to drain away but retains enough for plants to flourish.We’ll look at creating the ideal soil later.

Water is a precious resource, so if we have to water our garden, we need to do it a little as possible and make every drop count. We do this by contouring the soil to form a shallow pan in the centre of the garden bed, before we begin planting. Water will pool here, and filter through the soil, keeping it available longer for the plants to utilise. This technique works well whether you are in an arid area or you have a heavy rainfall.

Diagram -crosssection of contoured garden bed

Contourinjg the soil improves watering efficiency.

Permanent garden borders

Layering lawn grasses send runners underground that sprout up to form the lawn. These runners can easily pass under borders for gardens.  They will generally not travel more than a metre under ground without sending sprouts upwards to get find light, so they are usually contained by a path. Fortunately these runners will not usually go below 150 mm (approx. 6 inches) in normal circumstances. However invasion is a problem when it comes to garden borders. These are too narrow and usually too shallow to prevent the runners invading your garden,

If you are contemplating a lawn that will include layering type grasses, it is worth adding permanent garden borders at the start.

When I put my vegetable beds in the back lawn, I cut strips off some corrugated roofing iron that were 200mm deep and buried these like a wall in a 300mm trench. The last 100mm  was filled with a little concrete to create a flat bed, then I laid a low brick wall (only three courses high) on this concrete bed, for the garden border. It’s been 5 years now and only grasses to appear in the vegetable garden are seed type grasses.

Permanent weed barrier

Permanent weed barrier


Lawn – think ahead.

Without getting too scientific, from a gardener’s point of view, there are basically two types of lawn grasses:

Layering grasses – these grasses spread by sending runners out in all directions. These runners will drop roots down and send shoots upwards, seeking light. Because the runners are underground, they are more resistant to heat, making these grasses more hardy. As the shoots form leaves, they shade the runners below. The leaves that die off form an insulating mat beneath the the green shoots and after a year or two, you have a spongy mat of green grass. These include the couch grasses like kikuyu and buffalo.

Kikuyu shoots invading a wall

Planted close to a building the shoots will climb within walls to appear as high as the roof!

Unfortunately these grasses can also be very invasive and should not be planted close to any building. Think ahead because once established, some layering grasses are difficult to get rid of later. It’s best to include a mowing strip or a path between the lawn and any building to prevent the grass invading the walls or even the roof. Layering grasses take longer to cover an area but tend to be more drought tolerant.

Seeding grasses – these reproduce by seed and are the quickest to establish a lawn, however they usually have a drought cycle, where they quickly flower and drop seeds and die when the weather gets hot, leaving the soil bare and fully exposed to the sun. At the next rain the seeds will germinate and create a new lawn. Regular mowing will prevent the seed heads and flowers forming, prolonging their life cycle.

The ideal lawn is a mixture of both types of grasses, chosen for your climate and the amount of wear the lawn will receive.

Lawn – creating a lawn that lasts

I have a useless tiny front yard because I situated the house closer to the road, to give me a larger rear yard. Here where I live in Melbourne’s Western Suburbs, we have a climate that can be quite extreme. Summer days frequently exceed 35ºC (95ºF) and winters see a frost, even occasional snow. Add the extra complication of water rationing and it can be a tricky task to keep a lawn alive here, throughout the year.

The local hardware was selling all these great looking turfs but I noticed, in our first summer, few people had green lawns because of the heat and water rationing. Not only did their lawns die back but the exposed soil turned to dust, which tramped through the house. Our area was mainly grain farms and has that read earth that stains carpets. Some people gave up and used fake grass but to me fake is fake and not an option!

We had two Huskies that I used to walk daily and on these walks, I started to pay attention to people’s lawns and the grasses that survived the summer heat in the parks. The survivors, I saw, weren’t the grasses being sold in the local hardware. They were from the couch grass family – grasses that spread by underground layering, rather than by seeding.

I’m not not going to go into detail which grasses I used, because your area will have a different requirement to mine. Rather , use the method I did, to create a lawn that can handle your climate. Now I have other shrubs and bushes to reduce the wind, my yard has a different micro-climate to what it had when I started and that is reflected in my lawn today.

You need to go walkabout like I did, in your own area and see what your survivors are. Both in the heat of summer and the coldest part of winter. Once you have found the survivors, identify them and learn how they propagate or spread. It might be by seed, root or by plugs. It will be a mix of grasses; some that thrive in the heat and others that thrive in the cool.

When you have decided on your mix, work a small section of lawn, say about a square metre (or square yard). Get the soil perfect in this spot because this is going to be your outpost in the desert. It is this area that will be sectioned, dug up in a few months and replanted, to create other square metre outposts that will tame your desert into an all weather lawn, perfectly adapted to your climate. It will consist of a variety of grasses, some for the cold and others for the heat but will endure long after the expensive turf carpet laid lawns are scorched to nothing.

Concrete – calculating the amount to buy

This can be quite scary to the novice but it’s really quite simple. Here in Australia and New Zealand, we use the metric system (and when you compare the two methods, you’ll see why!) It’s much easier to calculate in cubic metres. In the USA, you’ll use the imperial Cubic Yards system to order concrete. I’ve simplified it to calculate the volume required based of the area in square feet, with a different value for each common depth or thickness of concrete used.

Usually the supplier will assume you want standard paving concrete. If you want a different mix, you’ll need to make that known before they give you a price because the different ratio of cement to sand to stone, will effect the price of the concrete.

Common thicknesses
Footpaths : 3 -4 inches
Driveways : 6 – 8 inches ( 0.15 – 0.2 m)
Side walks, barn and granny floors : 5 – 6 inches (0.125 – 0.15 m)
Porches, Home garage floors : 4 – 5 inches (0.1 – 0.125 m)
Farm building floors, Home basement floors : 4 inches (0.1 m)

Calculating the Volume of concrete
You’ll hear the concrete suppliers talk in terms of Yards or Metres of concrete. They are referring to cubic yards or cubic metres.

In imperial (Cubic Yards)
A cubic yard is smaller than a cubic metre (1 cu yard = 0.7646 cu metres)
In other words a 3inch deep area that is 36 feet by 36 feet will use 1 cubic yard of concrete.

Concrete Volume per sq.ft of Slab
Depth        Volume (cu yds per sq.ft.)
3 inches                                 0.009 cu yds per square foot
4 inches                                 0.012  cu yds per square foot
6 inches                                 0.019  cu yds per square foot
8 inches                                 0.024 cu yds per square foot
10 inches                              0.031  cu yds per square foot
Thus if my path is 3 feet wide by 10 feet long, that’s 30 square feet (sq ft)
At 3 inches deep I will need 30 x .009 cubic yards or 0.27 cubic yards of concrete.

In metric (Cubic metres)
Metrics are far easier, measure the depth (D), width (W) and length (L) in metres (so the depth of 100mm becomes 0.1metres). Put your measurements into this formula:

D x W x L = Volume of concrete to order in cubic metres

So if my path is 100mm deep, a metre wide and 10 metres long:
0.1 x 1.0 x 10 = 1 cubic metre

Keep in mind the concrete supplier will have a minimum order, usually around 0.6 cu metres.
Disposing of left over concrete

It’s not easy being 100% accurate with concrete and it pays to go over rather than under when ordering, so it’s common to get some concrete left over. How do you get rid of it?
It’s not really biodegradable and you can’t just throw it out on the lawn.

The solution is simple. Lay a a sheet of plastic on the ground and pour the excess concrete on it, preferably spread it thinly if possible. Allow it to set over night and tomorrow break it up and put it into the rubbish bin.

If you have more concreting to do later, pound it up and use it for the crushed rock base on the next job.

If you have kids or feel excessively creative yourself, why not cast it in a square mould and create a paving tile. Later the kids can tile it with colourful broken bits of china and make a mosaic paving slab.

Retaining walls and garden beds

We have our paths laid now. Let’s move on to the next step in landscaping our block – the gardens and retaining walls.

Raised beds make a great show and are not as backbreaking to tend and there’s a range of materials to create the retaining walls to hold back the soil. You can spend a fortune on interlocking concrete block (that will suck out the moisture from the soil, like blotting paper). You can buy railway sleepers (which are usually pine slabs treated with toxic chemicals like arsenic, these days) and spend the weekend with a chainsaw to create low beds but the cheapest and most permanent would have to be brickwork.

Don’t go and buy new bricks. If you look around, you’ll find someone wanting to get rid of some. For a garden wall, you don’t need whole ones either, so check out the local dump.

The secret to brick laying is to have a good base or footing. Start by laying the bricks either along the edge of the path, making sure there’s enough gap left to push a wheel barrow comfortably. If the path looks too narrow, lay some boxing beside the path and pour a concrete footing using the “Heavy Paving mix” of 1 of cement, 2.5 of sand and 3 of stone. This should be poured to a depth of 70mm (3 ins.) and be one and a half widths of the bricks you will use, wide. If your wall is more than 3 bricks high, put a strip of reinforcing mesh in there too. For a wall over 1 metre high you’ll need to make the base 100mm (4 ins.) deep.

Do not lay bricks directly onto the ground, always use a foundation. It helps prevent the finished wall from cracking with soil expansion and contraction.

Laying the second row of bricks next to a string line.

Use a stringline to get them straight or you’ll regret it later.

Also the resulting wall is almost waterproof, enough to act like a dam, stopping excess water draining away from waterlogged soil after a heavy downpour, so we need to add some drain holes at the base of out retaining wall. This is easily done by adding strips of 1cm wide wood between every third or fourth brick when you cement them in place. A couple of days later, when the mortar is set, using another piece of wood, simply punch these back into the wall and into the soil behind to leave a narrow drainage slit in the brickwork.

You’ll probably think “it’s only a garden wall, so near enough is good enough” but don’t be tempted to lay the bricks in a line, by eye. You’ll spend the next years cursing the kinks in the wall and wishing you had used a string to guide you. It pays now to set up a stake at at each end and run a string line down as a guide. Even walls made of all broken bricks look really cool when they are perfectly straight.

>The mortar mix is 1part cement, 1 part hydrated lime and 6 parts sand. Lay a bed of mortar onto your foundation first, just enough for three bricks at a time and lay your brick on this. Tap it down with light taps of a hammer. Check itl touches the string line, without deflecting it and scrape of the mortar that squeezes out between the brick and foundation.

When laying the next brick, add a wad of mortar to the end. It will want to fall off, so using the trowel, angle off all the edges and the wad will stay there. Now lay this one next to the first and tap down so they are the same height. Continue laying the first layer (or course). Don’t be in too much hurry to add the second row until the first one has firmed up.

Adding mortar to the end of a brick

The mortar will want to slip off the end of the brick unless you slope off the ends.

Don’t get hung up on doing a perfect job with the mortar joints. After a couple of hours you can scrape off any dags of mortar before they fully cure and become sharp protrusions.

Bricks are porous so before you put your soil in, add a layer of plastic with some drainage holes if you are in a dry climate. It will save a lot of watering.

Next instalment, I’ll show you a few tricks to use when you add the soil, that will give you a fantastic fertile garden.

Concrete mixes for different jobs

I had a comment from a reader who has a problem with a pond. They concreted a hole in the ground to create a garden pond. The concrete is not cracked anywhere but it won’t hold water. When they fill it the water level slowly drops and the surrounding ground seems moist.

The reason the pond is not holding water is probably due to the type of concrete used. Paving concrete is porous and acts almost like blotting paper. Concrete can be waterproof – they make ferro-cement boats out of it. You often see concrete water tanks on rural properties, for storing water. There are different recipes for concrete, depending on the requirements. There are additives you can add to concrete to make it waterproof and also the mix ratio of sand to cement to gravel is different. Here’s some commonly used cement, sand and gravel mixes:

For light paving (footpaths, mowing strips etc.)

Where there is no heavy vehicle traffic use 1of cement, 3 of sand to 6 of gravel. Lay 70mm (3 ins) thick on a gravel base. This mix is porous and can be trowelled off to a plaster like finish. It has a working life of 2 hours if the temperature is below 35 degrees Celsius and will set in 48 hrs and reach full strength in about a week. Add jointing strips to accommodate ground movement every 5 to 6 metres.

For heavy paving (Driveways)

To take the added strain of vehicles we cut the sand back a bit and add reinforcing mesh. The mix is 1 of cement, 2.5 of sand and 3 of stone. This should be poured to a depth of 100mm (4 ins.) with reinforcing mesh over a gravel base. You have a maximum working time of 2 hours. It will set in 48 hours, enough to walk on but don’t put a vehicle on it for at least a fortnight until it has cured. This is also the mix used for foundations and floors in multi storey buildings.

A heavy traffic driveway with a pit and trap ready to pour

A heavy traffic driveway with a pit and trap ready to pour

For ponds and basement walls and water tanks (waterproof)

This mix will hold water like a pond or tank or prevent water leaking into a basement. Use 1 of cement, 2.5 of sand and 3.5 of gravel. Note that fish ponds should be filled once the concrete is set and the water left to stand for a week, then emptied out and replaced. Leave the replacement water to age for a few days before introducing any fish. It’s best to add aquatic plants first, leave these a week to settle in and soften the water, then add your fish. For water tanks you can add some sodium silicate (a.k.a. egg preserver) as an added waterproofing agent. There are several proprietary concrete additives that will give you their own ratios.

Super strength for columns and suspended floors

This is the type of mix used for casting columns and spans and is used in conjunction with reinforcing bar and mesh. Use 1 of cement, 1 of sand and 2 of gravel.

Working with ratios

So, if I want to lay a path that will not have vehicles driving over it, I can make my own concrete by mixing one shovel full of cement, 3 shovels full of and and 6 shovels full of gravel, to make light paving concrete.

If I want to make a pond I would mix my concrete by adding 1 shovel full of cement to 2.5 shovels full of sand and 3.5 shovels full of gravel.