Maximum Yield Australia/New Zealand March/April 2019 | Page 41

F
ragrant, zingy, and an essential culinary ingredient,
citrus is not a crop to be left out of the hydroponic realm.
While we may be more used to thinking of expansive
orchards of spreading citrus trees grown in sun-drenched
climates, with a little modification citrus can be a valuable
and productive specimen for the indoor garden. By
selecting high quality, grafted, and dwarf varieties of citrus,
a thriving crop can be grown all year indoors, avoiding
the limitations of cold outdoor environments and the risk
of frost damage. As an added bonus, citrus flowers are
highly fragrant and the glossy, deep-green leaves make an
attractive display within any hydroponic system.
Citrus Types
Often overlooked
in hydroponic
growing, many
citrus varieties
make for excellent
indoor growing
cultivars and reward
horticulturists with
some tasty fruits
and fragrances.
While a wide range of citrus is grown commercially using
hydroponic methods, these are largely long-term outdoor
systems with drip irrigation. Some citrus such as Makrut
lime (also called k-lime), grown largely for its fragrant
leaves, are produced in greenhouses where heating is
applied to extend the harvest season. With a smaller indoor
garden, the objective is to maximise yields and fruit quality,
while at the same time growing a healthy and attractive tree.
To achieve this, investing in dwarf, grafted trees of known
cultivars is the best option, as although citrus can be grown
from seed, the characteristics of the resulting tree are highly
unpredictable. The time to first flowering is often many years
and fruit is generally inferior and lower yielding than that
of named varieties on grafted plants. There are even some
types of grafted trees with two or three different types of
citrus grafted onto the one root stock, making more efficient
use of valuable growing space. Grafting tends to produce
superior trees and crops as the root stock provides additional
vigour and disease resistance. Citrus trees are great
specimens for restricted spaces as many varieties, such as
lemons and limes, tend to fruit relatively young and while
still quite small in stature. They can also be pruned and
trimmed to restrain excessive vegetative growth and kept
compact, while at the same time, still be highly productive.
If grown with a restricted root zone volume in limited-sized
pots, the height and spread of the tree can be minimised and
citrus can even be grown as fruiting bonsai specimens.
Hydroponic Citrus Varieties
The most commonly grown citrus for hydroponic production
are the smaller types of lemons and limes; however, there
are some more unusual citrus types which offer a unique
opportunity to grow a tree crop indoors. These include the
tiny-fruited orange kumquat, the limequat, the Australian
finger lime (Citrus australasica), blood limes, the strangely
shaped Buddha’s hand citrus, and the uniquely flavoured
calamansi. The Australian finger lime, often called citrus
caviar, is a relatively new specimen on the culinary scene
which is currently being prized by chefs worldwide and one
which is likely to become a valuable commercial hydroponic
crop. Finger limes are a relative of citrus, native to Australia,
but available from some citrus nurseries in the US. The fruit
are elongated and finger like, and are split open to reveal
rounded lime green, tart, and juicy vesicles which resemble
caviar. Finger limes require warm growing conditions and
are frost sensitive outdoors, thus well suited to the year-round
protected climate of an indoor garden.
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