Is it even possible to grow a healthy garden in alkaline soil?

You’ve watered consistently. You’ve planted at the right time. You’ve even made an effort to enrich the soil before planting…so why is it still not working?!

Anyone who’s planted a garden in alkaline soil will know this struggle all too well. But what exactly is alkaline soil and how does it affect my garden?

It’s simple science

Alkaline soils have high pH levels. Before your eyes glaze over, let’s get the science bit out of the way. It’s simple. Basically, the higher the pH levels the more alkaline your soil is. A pH level of 7.0 is widely considered neutral. Anything above that number is alkaline and anything under is more acidic. If you live on the coastal plain around Perth, chances are your natural soil will have higher pH levels. That’s because we’ve got plenty of limestone which is naturally very alkaline. The further inland you go, the more acidic the soil.

Why is this important?

From choosing your plants, fertiliser, and maintenance routines, pH levels will influence how you garden. Higher pH levels reduce the availability of important nutrients plants need to flourish. Knowing how to navigate alkaline soils will help you realise your best and brightest garden ideas no matter your soil type.

Test your pH levels

The first step is finding out what kind of soil you’re dealing with. This can be done by yourself with a DIY soil pH testing kit. Drop into your local garden centre- they’re bound to stock them. It’s possible to get it done professionally, but don’t deny yourself the fun of becoming a scientist for a day.

What’s the best way to improve alkaline soil?

Got a pH reading above 7 or 8? You’ll want to improve your soil by adding the right fertiliser, and additives to lower the pH levels. Here are some simple strategies:

  • Add iron sulphates. This is the most common technique for tackling alkaline soils and it’s super effective.
  • Choose ammonium-based fertilisers. These have a proven effect of lowering pH levels in the soil.
  • Add organic matter to your soil. Composting regularly will work to reduce pH levels. This won’t be as quick as chemical fertilisers, but it’ll work wonders over the long term.

What sort of plants should I choose?

If you’re gardening in alkaline soil, choosing plants that naturally thrive in higher pH levels can make all the difference. Plants that have naturally adapted to these conditions will be your best bet. Here are a few examples of alkaline soil tolerant plants:

  • Native Wisteria. This beauty is well adapted for the alkaline soils of Western Australia and is easily trained onto any surface, creating a rich burst of purple.
  • WA peppermint. You’ll see these growing happily all over WA’s coastline – a tasteful centrepiece to any garden or stick it on the verge for more privacy.
  • This Mediterranean flower easily adapts to higher pH levels. Include it wherever looks best.
  • Rottnest Island Pine. Built for Perth’s alkaline soils, use this keen little pine to line a fence or create a natural barrier.

Design your garden with your soil type in mind

Once you’ve tested your soil and chosen your plants, it’s time to organise your garden based on your goals. Here are some tips to help with your design.

  • If you’re relying on organic compost and organic matter to lower the pH levels, make it accessible, and don’t let any food scraps go to waste.
  • If you’re fertilising – always stick to the instructions – test your soil consistently and don’t over-fertilise.
  • Group plants according to their ideal pH levels. That way it’s easier to tend to them as a group.