Tried and acid tested

With Diar­muid Gavin Know­ing the pH of your soil is vi­tal when you are plan­ning which plants to grow next year

Star Courier (Surrey & Hants) - - FRONT PAGE -

The dor­mant sea­son is a good time for plan­ning and de­cid­ing which plants you’d like to grow next year. And one im­por­tant fac­tor when choos­ing new plants, in­clud­ing veg­eta­bles and fruit trees, is to know the pH of your soil. It’s an area of gar­den­ing that many find con­fus­ing as it im­plies you need to know more about chem­istry than plants, but it’s worth un­der­stand­ing the ba­sics so you can make in­formed de­ci­sions and grow plants which will be happy.

Some of our favourite edge- of­wood­land plant­ing, such as rhodo­den­drons, mag­no­lias and camel­lia, will only flour­ish in acidic con­di­tions, so let’s have a look at what that means and how to find out if your soil is suit­able.

The term pH is a mea­sure of acid­ity and al­ka­line on a scale of 1 to 14. The mid- point, 7, is neu­tral. Any­thing be­low that num­ber is acidic and above it al­ka­line. Most gar­den plants do best in a slightly acidic soil, which is be­tween 6 and 7. To grow rho­dos and camel­lias, how­ever, you want a level of 5 to 6.

If you’re not sure what your soil pH is, there are a num­ber of ways to find out.

If you have hy­drangeas, the flow­ers will be blue on acid soil but pink on neu­tral to al­ka­line soil.

You can test with lit­mus pa­per, which you can buy cheaply in art and craft shops. Mix your soil sam­ple with some dis­tilled wa­ter and dip the lit­mus pa­per in for a few sec­onds.

The pa­per will turn red for acidic and blue for al­ka­line. This will just give you an ap­prox­i­mate idea. To get a more ac­cu­rate read­ing, use a soil test­ing kit avail­able from gar­den cen­tres. You can also use a pH me­ter which is like a probe you stick in the soil.

Fi­nally, the Rolls- Royce method is the soil test­ing ser­vice avail­able from the Royal Hor­ti­cul­tural So­ci­ety. This costs £ 30 and they will an­a­lyse sam­ples of your soil – not only for acid­ity but for tex­ture and ma­jor nu­tri­ent lev­els.

So if you find you have acid soil, then there are some re­ally choice spec­i­mens to choose from. If your soil is al­ka­line you can still grow them in pots us­ing an er­i­ca­ceous com­post, which is acid.

Er­i­ca­ceous plants tend to be shal­low root­ing and can eas­ily dry out, so a good mulching ev­ery year will help with wa­ter re­ten­tion.

Leaf mould is ideal as this will help keep soil acid. Use er­i­ca­ceous feed – liq­uid or slow re­lease – and top up with se­questrene of iron to con­di­tion the soil.

If you try grow­ing these plants in or­di­nary soil, you will no­tice the leaves go­ing yel­low – this is due to iron in the soil be­ing un­avail­able to plant roots in al­ka­line con­di­tions.

In years gone by, pas­sion­ate gar­den­ers would cre­ate peat beds so they would be able to grow these lovelies. How­ever, us­ing a lot of peat isn’t bril­liant for the en­vi­ron­ment – some­thing many gar­den­ers hardly con­sid­ered 20 years ago.

In the end, it’s best to know what soil type you have and then to gar­den in har­mony with it.

Here are some of my favourite acidlov­ing plants, also known as lime­haters...

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