54 SEPTEMBER 2019 GARDENING AUSTRALIA
M
ost plants we grow in our
home gardens enjoy a bit of
a feed. But what, how much
and how often varies widely.
Roses and citrus are examples of ‘gross
feeders’, meaning they enjoy generous
amounts of fertiliser, regularly. Productive
plants such as vegetables are likely to
grow better if they have access to extra
nutrients, while indigenous plants grown
in their natural environment won’t need
fertiliser to perform at their best.
The nutrients that plants require in
the greatest quantities are nitrogen (N),
phosphorus (P) and potassium (K), and a
fertiliser containing all three is described
as a complete fertiliser. Many other
nutrients – even minute trace elements –
are just as essential for growth, although
they are required in lesser amounts.
Most of these nutrients are absorbed in
the water taken up by the plant’s roots.
Generally, it’s best to monitor your plants
and fertilise only when they are in active
growth or about to start growing. Container
plants must be fertilised regularly, though,
because some nutrients leach out easily,
and the ongoing breakdown of organic
matter in potting mix competes with the
plant for nitrogen.choosing a fertiliser
Plants such as shrubs, trees and
ornamental grasses can be fed with a
general-purpose fertiliser. This can also
be used for slower growers, such as
orchids, succulents and indoor plants, but
at much-reduced levels and frequency.
If you’re unsure, choose a fertiliser
that’s labelled for a particular plant type.
Lawn foods, for example, are relatively
high in nitrogen because nitrogen
promotes leafy growth, which is exactly
what your lawn wants. Citrus and rose
foods promote growth and production,
but rose food often has added potassium
because it enhances disease resistance. PHOTOSRACHEL HENDERSON,PHOTOGRAPHY BY NATSKYPLANTS
A healthy
for
Fertilisers can be confusing. How do
you choose the right one? Is it all
marketing? What if you don’t bother?
JUDY HORTON explores the options