The chemical brothers…understanding acidity and alkalinity (pH)

Anyhow if you’re still with me, I’m hoping you’ll soon have a better understanding of pH in your soil and maybe even think  about regularly testing your own soil one day.

Back in 1909 in Denmark at the Carlsberg Laboratory the focus (believe it or not) wasn’t on beer.  A chemist called Peder Sorensen had discovered the importance of ‘potential hydrogen’ and thus pH was born.  I’m assuming he kept his findings in his awkwardly named Peder file.

I like to think Peder relaxed after his great discovery and had a quiet beer.

Mr Sorensen produced a logarithmic scale which starts at 0.0 and goes to 14.0.  Zero is the most acidic, while 14.0 is the most alkaline.  All importantly 7.0 is neutral and pretty much where we aim for with soil for our veggie patch.  Unlike a temperature or volume scale like most of us are used to, each step up or down on this scale is actually a ten fold increase.  To illustrate the power of this let’s say your soil pH is 6.0.  It means it’s 10 times more acidic than a pH of 7.0 but 100 times more acidic than a pH of 8.0!  So the take home message is your pH chart doesn’t work like the volume on an amplifier – small numerical changes are actually BIG!

In your soil, the pH has a huge influence on the availability of nutrients to your precious vegetables.  It seems crazy, but can keep pouring on phosphorus, but if you’re soil is too acidic, you’re plants can’t access it.  You can see by looking at the below chart that a sweet spot is between 6.5 and 7.5.

Testing your soil’s pH.

There are a couple of kits available in nurseries and hardware suppliers that cost less than $30 and will last for years.  In the kit you’ll find a colour card, a small bottle of liquid and some powder.  Take a sample of your soil and put it on a small plate.  Add the liquid to make a paste, then dust over with the powder.  Almost immediately you’ll see the soil turn a colour that you can match on the colour wheel to discover your soil’s pH.  As I’m doing a lot of pH testing for clients, my own garden and testing the Backyard Harvest bio-compost product, I’ve invested in a professional lab model which can be calibrated for ongoing accuracy.  This was several hundred dollars, so it may pay to see if cheaper hand held models are available.

How to change your soil’s pH.

Generally soils in productive gardens will need to be made more alkaline, however there is an exception in the case of blueberries and if you’re growing ornamentals then hydrangeas and azaleas also prefer acidic soil.

To raise soil pH (make more alkaline) we need to add calcium in the form of dolomite (calcium magnesium carbonate).

To lower soil pH (make more acidic) use elemental sulphur.  This stuff forms with the water in the soil and produces sulphuric acid which lowers the pH.

Having said that don’t forget to add compost, compost, compost!  Good quality compost has a neutral pH of around 7.0  Adding compost helps to bring either acidic or alkaline soil back to more veggie-friendly conditions by helping to make nutrients available to plant roots.

Different pH for different veggies?

As a broad principle, green leaf based veggies (spinach, lettuce, cabbage, kale etc.) prefer a pH in the more alkaline range, say 7.0 to 7.5.  Vegetables where the focus is on eating the fruit (tomatoes, capsicum, cucumbers, pumpkin) prefer a more slightly acidic soil around 6.0 to 6.8.  This helps to explain why tomatoes and pumpkins happily pop up in compost heaps where conditions are typically more acidic. Check out the below chart and promise yourself you’ll explore you soil’s pH this weekend!


What is Permaculture?

About 15 years ago I was participating in after-hours management studies at Deakin Uni.  During a coffee break I found myself talking about veggie gardening as a hobby with one of the other students.  He mentioned that I may be interested in ‘Permaculture’.  While the word was vaguely familiar I had no idea what it meant and was actually a bit put off by the word ‘cult’ in it!

So what’s it all about?  Permaculture was originally the marrying of two words: permanent and agriculture.  The concept evolved out of an intense working relationship between a young Perth student called David Holmgren and his teacher and mentor Bill Mollison, from Tasmania.  They were brought together during a radical environmental design course – radical because it was nearly 40 years ago – in Tasmania.  At the time there was plenty going on to suggest things couldn’t continue at the exponentially frantic pace; an international oil crisis and the hugely controversial Club of Rome report called Limits to Growth.

This course provided fertile ground for the then twenty-something Holmgren who penned the Permaculture concept, which along with Bill’s encouragement and experience became Permaculture One.  Agricultural in the true sense of the word, the first book provided ideas and blueprints that would ensure a culture could sustain itself without fossil fuels and chemical inputs.

Essentially, the pair came up with an idea that we would now call ‘design for sustainability’ – almost 20 years before that term took on its current meaning.

After the first book, David moved to Hepburn Springs (where he still resides) and set about creating a real-life example of Permaculture in action while continuing the intellectual development of Permaculture.  Bill with his big personality and unmatched life experience took Permaculture to the world, publishing several more books and becoming the ‘face of Permaculture’ until recent years.

Far better known overseas than in Australia, Permaculture ideas and concepts continue to filter into the mainstream; think worm farming, no-dig gardens, water tanks, chicken tractors/domes, food forests, passive solar house design, eco villages, no till cropping, herb spirals, bikes and of course organic veggie growing.  Check out these ‘chook domes’ from Africa!

Of course Permaculture didn’t invent these things, it simply provides a framework to link them all together and to help make the most efficient and ethical decisions in the first place.

During the time I’ve been involved in Permaculture education I’ve often had people tell me that “it’s all just common sense!”.  It’s truer than they think.  The origins of Permaculture thinking were largely influenced by pre-industrial long survived cultures.  You see, common sense used to be more common!

But perhaps the most appealing thing I find about Permaculture is that it encourages us to look at positive solutions for what may otherwise be depressing situations.  A very hands-on example, I have a minor leak with a garden tap.  No biggie but given the age of the tap I can see any backyard plumbing is going to cascade (pun intended) into bigger problems.  The alternative of a three figure plumbing bill also doesn’t appeal.   Approaching it with my Permaculture hat on turns the problem into the solution.  Hence I’ve planted mint under the tap which is growing wonderfully thanks to the occasional drip irrigation.  Sure I’ll have the tap fixed when there’s enough work justify getting a plumber to visit but in the meantime I’ve averted problems of unused water pooling, turned waste water into food and beautified a soggy looking part of my yard.

So whether it’s building a classic herb spiral or choosing a bike instead of car, I invite you to explore the evolving world of Permaculture, safe in the knowledge that it’s nothing to do with a cult! Oh, and apologies to anyone called Moonshadow out there…

Oranges and Lemons…

Eureka and Lisbon lemons are joined by the more recent Meyer variety – great if you’re more interested in the sweeter juice and hate thorny trees!

Try fitting this into your Corona…a great example of a Lisbon lemon

There’s also a myriad of orange varieties and mandarins available, including my favourite at the moment – the blood orange.  A recent discovery, blood oranges have an almost strawberry/orange taste and look great in desserts and mixed drinks.

I’ve grown two tahitian limes in Geelong and they love our frost free urban micro-climates and I’ve also had good results from a so called native lime which I actually think might be a ‘Kassia Lime’ as its flesh was a yellow/orange colour – not the usual green flesh.  Citrus trees make great sustainable gifts for weddings, new family editions and look spectacular in pots and who wants to part with $1 every time they want an organic lemon!?

Location, location, location – getting the most out of your citrus trees.

Citrus work really well in pots, as well as the ground.  The most important thing to remember is that their fruit often takes twelve months to ripen.  So unlike our stone fruit which are quite happy to be in shade all winter, your citrus trees need FULL SUN over the winter.  Just take a wander around your neighbourhood with a compass and I’ll guarantee the healthiest looking lemons are coming from trees with lots of access to the northern sun.

Even better is siting them in a courtyard or against a north facing masonry wall.  Remember the reason these varieties are grown commercially in Mildura is because of the long clear sunny days which aid ripening and help them get to market earlier.

Here’s a very happy looking Valencia orange backed onto a north facing wall

Planting tips

With the below average rainfall we experienced in recent history, the idea of planting new trees was met with some trepidation.  Would it survive?  Can I be bothered keeping the water up to the new tree with prohibitive restrictions?  Well after almost two years of fantastic rain, sub soil moisture is back and water restrictions have eased.  Of course we need to continue to be careful about our water use, but I also think we need to take advantage of the much improved growing conditions and get some trees established while the going’s good!

A good technique before planting is to dig the hole to the required size (usually twice the width and at least the depth of your pot) and to fill it with water.  See how long it takes for the water to drain.  If it’s several hours or more then you will have drainage issues and your tree may not survive – especially as we have nearly 6 months of rain ahead!   You can mix in some gypsum sand, compost and see how that works.  If still no luck then build up the soil and essentially plant close to ground level.

Lemons are also beautiful ornamental trees with scented flowers and lush foliage

Troubleshooting with citrus trees

Ants are usually a sign you’ve got scale or whitefly as they’re chasing the sweet secretions from other pests – use the white oil recipe below and make sure you cover tops and bottoms of the leaves.  The ants will be grumpy but it won’t kill them!

Prune any dead wood at the end of winter and fertilise around now (Autumn) with an organic based fertiliser or manure.  Oh, and if it’s acceptable in your household and not going to upset your neighbours, yes wee on your tree.  It provides liquid urea fertiliser…why give you nutrients away for free!

Most problems with citrus can be fixed using a homemade white oil recipe:

1 cup of vegetable oil

1/2 cup of water

Teaspoon of washing detergent

Mix vigorously in a bottle until white and cloudy.  This becomes your concentrate which you mix 1 part to 40 parts water in a sprayer bottle.

Look after you citrus trees, plant a few varieties and you’ll have access to your very own fruit all year round!

Raise your pitchfork to the sky…

Well, I googled ‘compost definition’ and of the 2,290,000 results this seems to be the most popular.

“A mixture of decaying organic matter, as from leaves and manure, used to improve soil structure and provide nutrients.”   The word compost comes from the latin compositum which basically means a mixture of different things.

So unlike soil which is really the result of rocks being slowly ground down over huge amounts of time, compost contains lots of goodies that were alive and kicking just a short while ago so to speak.

As the definition suggests compost helps our soil structure which means it can hold sandy soils together while helping clay soils to break down…clever stuff huh!  It will also help to hold water in your soil, far more important than putting a layer of mulch over your patch and hoping for the best!

Another increasingly important reason to make sure your patch has regular compost added is because it increases soil biology/life.  What this means is that it makes major nutrients such as phosphorous, nitrogen and potassium available to plants.  That’s right, even if you keep adding fertilisers, if the soil has no life your plants can’t access it!  It’s another major reason for making sure you use organic methods that don’t upset soil life.

So now we know what compost is and why it’s so important, how do we make it?  There are basically two ways:

Anaerobic – this is also called cold compost, usually smellier (due to the methane produced) and harder to get the ‘right’ kind of bacteria involved.  This is a common method used currently by most Australians in the form of a static compost bin such as the famous Gedeye.  It’s been for as long as I can remember…check out the model’s clothes in the below picture if you don’t believe me!  You can greatly improve this type of compost by circulating the contents with a compost aerator.  Cold composting takes about 3 to 6 months to produce something you can use in the garden.

Aerobic – or hot compost uses a different type of bacteria which require air.  This means the compost needs to be turned every few days to oxygenate the pile.  Much faster, nicer to work with and the only kind I use.  The downside is you tend to need to have all ‘ingredients’ on hand to make it work well. Grass is almost the perfect balance of nitrogen and carbon and will break down without much help.  I usually add about 10% extra carbon material though to stop it forming into cow pats!  Hot composting produces compost in around 3 to 6 weeks!

Personally I tend to put most of my organic waste through chickens and worms leaving only grass clippings to be composted.  I currently use a tumble style compost bin which allows no way for rodents to enter the bin and produces compost faster than any other method I’ve tried.  This is especially important to note as normally a cubic metre (BIG) is required to get a hot compost pile going.

Smelly compost?

Main problem is too rich in nitrogen, which makes it too wet and hard to move, smelly etc.  Usually occurs because households produce far more ‘green’ waste than dry matter.  So add plenty of  straw, shredded paper etc. to keep the balance right.  A sprinkling of lime will also help to decrease the acidity and make things easier on your nostrils.

How to use your compost.

Compost is ready to work into your soil when it has a sweet smell, has cooled down (in the case of hot compost) and the ingredients are almost broken down.  Turn your compost into the top 20cm of your soil and leave for a week or so prior to planting new seedlings.  You can also ‘top dress’ garden beds with compost, especially over winter where it won’t dry out.

Portable Gardening


Going potty

When I planted these strawberry guavas, I knew a couple of things.  Firstly, I had a house for sale and I wasn’t sure whether the new owners would be as enthusiastic about my little Chilean beauties as I was.  Second, I knew they’d take a few years to produce fruit hence the combination of those factors lead me to get them in some decent pots until they found a permanent garden in the future.  I’ve picked some classic terracotta pots for these as they’re less fickle than high fashion glazed pots.  One thing I’d wish I’d done was to purchase pots with an internal coating to help maintain the moisture.  The neighbouring geraniums are in pots with such a coating and I really notice the way they hold onto their moisture much better.

Pots are also great because you can move them during the year to follow the shade or the sun or the rain depending on what they need.  Citrus and olives love the sun, so they’ll love being backed onto a north facing wall which may have other plants gasping in protest.  Upcoming  heatwave?  Well pots allow you to move everything into the shade for a few days meaning you don’t risk losing them.  Of course they can be quite heavy so only attempt this will the right tools e.g. a sturdy trolley and someone that can manage it (especially during heat waves!)

Knowing when to water

The great thing about containers is the ability for you to control the growing medium.  Generally potting mixes are a safe bet – you’ll notice they’re made up of larger ingredients such as pine bark which make bigger gaps meaning better drainage.  Of course the flip side of this great drainage is that you have to water more often.  I like to include compost  in the mix to ensure there’s lots of organic matter in the mix, and this also helps to hold the water better.

In a normal garden bed I usually stick my finger into the soil up to the second knuckle and by seeing if the soil sticks to my skin I can tell the soil moisture.  Pots can be a little tricky so I’ve found the best way is to tip the pot ever so slightly to see how heavy it is.  The more moisture the harder the pot is to move.  It’s amazing how light a full pot can be if the soil has started to dry out and indicates they need to be watered more frequently.

Want an example of how not to container garden?  Well I purchased a couple of these recycled half wine barrels a while back and planted up a valencia orange and tamarillo.  All good I hear you say, but unfortunately I forgot to check the drainage holes in the bottom of the tamarillo’s barrel and wondered why it was looking pretty average a few months later, especially when compared with the lush orange.  The soil mix was fertile and revealed a stack of worms as I pulled it aside to check what was going on.  As I dug down I noticed water starting to pool…hmmm.  Yes, I was drowning my poor tree!

Remember containers need drainage holes!

Feed regularly

The excellent drainage of pots also means the fertility will flush quickly through the soil.  I combat this by adding a good sticky compost which will hang onto the moisture and therefore the nutrition.  I also tend to ‘top dress’ the potting mix with organic fertiliser such as pelletised manure (dynamic lifter) or blood and bone.   Plus of course worm juice!

If you’re interested in learning more I’ll be giving a free “Growing Veggies in Boxes” workshop on Thursday May 10 from 1pm at the Cloverdale Community Centre, 167-169 Purnell Rd Corio.