Narrow-leaf ironbark

Eucalyptus crebra

Narrow-leaf ironbark (Clemson, p.53) is regarded by some beekeepers as a valuable pollen and honey tree, flowering usually late winter into spring.

The pollen from narrow-leaf ironbark is not of high quality for actively breeding and honey-collecting hives, it being 16% to 20% crude protein. The amino-acid profile of narrow-leaf ironbark is except for iso-leucine, satisfactory. The low levels of iso-leucine would reduce the digestibility of the pollen to equivalent pollen containing 15% digestible crude protein. This is below the desired 20% required by bees. (Table 18).

Under favorable conditions of a previous good summer rainfall, and a mild winter, the tree will produce large volumes of pollen and nectar. This will stimulate the bees to breed very rapidly and often swarm. However, these bees will not be high protein bees.

Bees working narrow-leaf ironbark are working under high stress conditions because of: low temperatures (as narrow-leaf ironbark flowers late winter into spring), nosema (as late winter into spring is the main problem time for this disease), and a heavy work-load due to the good honey flow.

Although the bees are overstimulated to breed and often swarm, the protein level of the pollen is too low to allow the bees to develop into high protein bees. These hives populations have been known to collapse. If given access to high-protein pollen such as hill gum directly after the narrow-leaf ironbark has finished flowering, hive populations will maintain themselves. This is often the experience of beekeepers who work this floral source.

Table 18: Narrow-leaf ironbark Eucalyptus crebra
Minimum % of Amino-Acid from De Groot (1953)
Pilliga 1991
Kingaroy 1992
Kingaroy 1992
Threonine 3.0 3.4  3.6  3.4 
Valine 4.0 4.2  4.1  4.3 
Methionine 1.5 2.1 2.3  2.6 
Leucine 4.5 6.0  5.8  5.9 
Iso-leucine 4.0 3.4* 3.3* 3.7*
Phenylalanine 2.5 3.4  3.5  3.8 
Lysine 3.0 6.2  5.3  5.9 
Histidine 1.5 2.0 2.2  1.7 
Argine 3.0 6.4  6.5  6.7 
Tryptophan 1.0      
Crude protein   19.9% 18.6% 16.37%

* Low level of this amino-acid

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