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"The soil is a
wonderful thing...." That one liner by one
of Britain's great radio gardeners, the late Fred Streeter, says it all. "It all
starts in the zoil", I can just hear Fred saying that on a Sunday morning on the BBC,
in his rural Sussex accent. Many of my media gardening peers still send Fred Streeter up,
because of his quaint manners and great simplicity as a presenter, however if you want to
grow citrus there are some very simple measures that must be adhered to. You must get very
serious about the soil and its nutrition, right from the start.
Young citrus of all sorts are demanding delinquents. Sure
they age and frequently get forgotten, but as youngsters, they need more attention than
most other fruit trees in the backyard.
In the main, citrus love a free draining friable soil. A
sandy loam that drains and yet retains moisture, is perfect. Few of us garden on such
ideal citrus soils as the commercial areas of the South Australian Riverland, Victorian
Sunraysia or Queensland's Mundubbera Shire. The home gardener has to take a plot of
builder's rubble or clay and make a garden to suit an enormously wide range of plants. We
must be fools, when you think about it! Anyhow fools that we are, citrus need sun and good
drainage. If you have clay soil then it will have to be dug and gypsum incorporated into
it, if your garden soils are on the alkaline side. That's because gypsum leaves the soil
pH where it started, where as dolomite which also changes soil structure just like gypsum,
but it makes the soil more alkaline in the process. That's no drama if your garden soil is
on the acid side, in fact it's an advantage, by bringing the pH back closer to neutral,
where most fruit and vegetables thrive. But if you use dolomite on soils with a pH of over
8 it will make them even more alkaline and serious nutrient deficiencies will appear,
especially on citrus!
Gypsum and dolomite open up the soil structure, allowing
better drainage to take place and preventing root rot. It's one of the plant kingdom's
great ironies, that all nutrient exchange takes place through the medium of water and yet
when most plants are water-logged they turn their toes up. Citrus are very particular
about wet feet. They hate it. So good drainage is imperative. They don't however do well
on very light sandy soils either, because the nutrients move pass their roots too quickly
and keeping such soils moist enough to get loads of nutrient, is too taxing.
That's why I recommend to anyone who wants to establish
citrus in pots, tubs or containers, they will need to add some loam to the premium potting
mixture. Most premium potting media that you buy for potting up your hanging baskets and
filling terra cotta tubs, is very free draining. It's been make from loads of rotted pine
bark and depending on the price you paid for it, with small quantities of shredded copra
or peat moss to retain moisture. The simple fact is that to make the ideal potting mix
that drains freely and retains plenty of moisture, would price it out of the market or
make the product too heavy for the super market and garden centre shelves. That's why I
recommend you add 20-30% of loam and a handful of Zeolite to your premium potting media
for container-grown citrus. The loam not only retains more moisture due to its greater
surface area, but combined with Zeolite it grealty aids the cation exchange of essential
plant nutrients, where compounds that contain calcium, magnesium and potassium are
concerned. Quite simply the tiny particles of loam provide more surface area for the
nutrients to get way-laid before they leach from your pots. So the fertiliser that you
paid for, gets used by the citrus in the tub.
If you don't have a pH testing kit to check the soil
alkalinity or acidity, just scoop up a handful of the soil and smell it. If it smells
sweet then it's predominantly alkaline and if it smells sour, it's certain to be acidic in
reaction and if you can't tell, then it's either neutral or time to give up smoking! The
soil pH is critical when growing citrus because most of the essential nutrients or
chemical compounds that they feed on are only taken up by the plants during their growing
season, when the soil is moist and within narrow bands of alkalinity or soil acidity. In
very alkaline soils the uptake of iron compounds is very irregular and tapers off quite
markedly at pH 8.5, so that your citrus start to develop lime-induced-chlorosis (LIC) or
iron deficiency. Adding mineral iron or horseshoes will do very little to alleviate the
situation either, since plants cannot access ferrous iron. While there is frequently
plenty of iron in the red clay alkaline soils, the alkalinity ties up the iron so that
it's not available to the plants. That's when it's advisable to add iron chelates
(pronounced kelates) to the soil, to turn those yellow leaves with the decidedly green
veins, back to uniformly healthy green leaves. Unfortunately when you spot the LIC
symptoms there are often other nutrient deficiencies on your citrus too. That's why it is
frequently recommended that iron chelates be applied at the same time as a complete
mineral mix or with one of the special citrus fertilisers that have been formulated to
deliver the broadest band of citrus nutrients. It's not really feasible to have a nutrient
analysis done on your home garden soil, because of the cost and the fact that when you
grow a wide range of plants, each has its particular requirements. You are hardly going to
want to trudge around the garden dispensing minuscule quantities of nutrient to a host of
different plants, even if you were an organic chemist or soil scientist. That's why we
take the middle road and use a range of nutrients even if there is a degree of over
application. It's akin to the Medico not being able to diagnose your illness and
prescribing a broad spectrum anti-biotic that will knock lots of your gastro-intestinal
micro-flora out, and hopefully the one that is causing you the most discomfort. Then the
task is to re-establish the overall vigour by building up the balance. In your body that's
by eating a wide range of foods and micro-flora-rich yoghurt. In the soil or in your
containers, it's by adding the micro-flora found in well rotted compost. Compost is the
panacea of the garden. It seldom contains or releases any nutrient of great worth, but
it's the sponge through which all nutrient exchange takes place. Even the chemical
fertilisers work better when there's plenty of organic material in the soil for a rapid
nutrient uptake. More on the nutrients themselves a bit later, under the ehading,
"Feeding your citrus". This nutrient-speak needs to be digested slowly. |
