All about the acid lovers of the plant world…

Hello lovely gardening readers. It’s Wednesday again and here I am cracking on through the alphabet at a rate of knots, now turning my attention to the letter C and with it, the fussy old calcifuges.

My aim with my gardening jargon buster series is to try and demystify some of the copious amounts of jargon that spring up around what are (usually) fairly straightforward gardening ideas.

And, boy oh boy, does the calcifuge come jargon laden!

Its name, for a start, would be massively off-putting if you’ve not come across it before.

As I mentioned in my first post on acidity and alkalinity (aka soil pH), certain plants prefer to grow in certain alkaline or acidic soil conditions.

And that is all that calcifuge means: a plant that prefers to grow in acidic soil.

The name literally means “chalk fleeing” – eg a plant that does not like chalky (otherwise described as limey) soil conditions

But the jargon doesn’t end there! You might also come across these plants referred to as ericaceous, which is just another way of saying the same thing. I only just found this out myself this second by checking Wikipedia, but the “ericaceous” name comes from the Erica family of plants (heathers) which are, as you would expect, chalk haters (or lime haters, or acid lovers, or calcifuges. Pick your moniker as you so choose…)

Now that’s out the way, there isn’t actually a huge amount more you need to know about calcifuges.

Obviously, as they require acidic soil conditions, you need to make sure you give that to the plant.

You can do that in a number of different ways. First of all, check the pH of the soil in your garden. If it’s 6.5 or below (eg, ranging down towards 4 which is the most acidic soil you’re likely to come across) then calcifuges are going to be pretty happy.

You might want to “top up” the acidity levels by adding some sort of acidic mulch to the top of the soil, such as pine needle mulch or pine bark mulch.

(Also recommended as an ericaceous mulch is sphagnum peat moss, but I’m not going to suggest you use that because of all the peat issues.)

If your soil is too alkaline, however, or if you want to grow a plant that requires even more acidic soil, then – my advice would be – just grow it in a pot. Fill the post with an ericaceous compost and top up every now and again. Simple. Certainly far more simply than trying to alter your soil pH.

And if you really fancy growing a certain plant actually within a bed or border and not in a pot, then you could sink a pot into the ground and just fill that with the right compost.

You can also use a range of acidic fertilisers, which will ensure the plants receive exactly the right nutrients they need. (Their problem with alkaline soils is actually that they are unable to take up the correct amount of iron from the soil, which becomes “locked up” in soils with higher lime content.)

One final note: tap water has lots of calcium in it (eg chalk) so it’s always best to water calcifuges with collected rain water instead.

Growing in the wrong conditions

So what will happen to all these calcifuges if they’re grown in soil that’s too acidic? In short, they will most likely die.

First of all, expect to see yellowing leaves (the scientific term for this is lime-induced chlorosis), the plant will grow more slowly, might fail to flower and, eventually, will just give up the ghost.

If you’re growing any of the plants in the list below and they’re showing any of those symptoms, it might be a good idea to check whether the soil they’re in ic acidic enough.

Calcifuge plants

Finally, a quick overview of some of the most common calcifuges and their preferred pH.

I would definitely recommend with any plant, however, checking the RHS online plant finder and getting all the info you need on what the plant likes to grow, from soil pH to soil type, exposure, sunlight etc etc.

Rhododendrons / azaleas: If you’ve read my blog for a while you might remember that my garden was full, absolutely stuffed full, with rhododendrons. (I think there were 40 plants originally…) One of the reasons I wasn’t that keen to keep them is that the soil isn’t very acidic, only about 6.6. So without constant pampering, the rhododendrons would soon get unhealthy. They prefer a soil pH of 5-6

Blueberries: I’ve been meaning to grow blueberries for years and I think this year will be the year! (Though, I almost certainly said that last year.) They are some of the most acid-loving of all, requiring a soil pH of 4.5-5.5

Camellias: Personally, I am not a camellia fan, but I know I’m really rather alone in this opinion. Irrespective of my views of them, camellias like an acidic soil of around pH 5-6.

Acers: All acers (maples) prefer a slightly acidic soil. The ever popular (and ever beautiful) Japanese maple, Acer palmatum, tends to do best in a soil pH of 4.5 to 5.5.

Blue hydrangeas: this one is especially crazy. Pink hydrangeas will turn blue if the soil pH is below 5.5.

Heathers: there are a few heathers that will survive in soils with a pH higher than 6.5, but most prefer acidic conditions, ranging from 4.5 to 6.5.

Pieris: A lovely plant this, in my opinion, and one that I hadn’t come across until a few years ago. They prefer a pH of 5 to 6.

Magnolias: most magnolias require acidic conditions, with the exception of Magnolia stellata (ahem, which is the magnolia in this photo, since this is the one in my front garden…)

And that’s about it. There are many others, of course, but these are some of the more commonly grown calcifuges.

So, I hope that was vaguely helpful. Was there anything I’ve missed out, or do you have any other tips on growing these acid-loving plants? (Or any questions about something I’ve not covered?) If so, please do leave a comment below.

Til next time then, when I’m going to be talking about deadheading…