Grafting Hakeas

David Beardsell, David Jones and Ray Kerr

The following article is reproduced from the March 1982 issue of the Society's journal Australian Plants. Although now some years old, the method described has been proven over the subsequent years and grafted hakeas now feature in private (and some public) gardens in many parts of Australia. Those interested should also see the article Grafted Hakea by Doug McKenzie.

Photographs illustrating grafting methods that were in the original article have not been reproduced here, but diagrams showing some of the procedures and terminology used can be found in the plant propagation by grafting section of the ANPSA website.



Grafting as a method of propagation of Australian native plants has been carried out by a number of workers with mixed success (Wrigley and Fagg, 1979; Elliot and Jones, 1980). However, the only plants which are grafted commercially are Lophostemon confertus cv. Variegata and Agonis flexuosa cv. Variegata because they cannot be readily propagated from cuttings, weeping standards of Grevillea x gaudi chaudi using Grevillea robusta as a rootstock, and the nut producing species Macadamia integrifolia and M. tetraphylla.

Many species of plants from Western Australia are very difficult to grow in the eastern States, possibly due to sensitivity to the root pathogen Phytophthora cinnamomi or lack of adaptability to poorly drained and acidic soils. In a number of genera, however, there are hardy species native to the eastern States which could be used as rootstocks for these difficult species.

   Hakea bucculenta
   Hakea bucculenta
Photo: Brian Walters

This work reports the successful adaptation of Hakea bucculenta, H.francisiana and H.multilineata to cultivation in heavy soils in southern Victoria by grafting onto Hakea salicifolia, a hardy species from New South Wales.

Materials and Methods

Young seedlings of Hakea salicifolia (syn. H.saligna) were potted into 13 cm pots and placed in a heated/cooled glasshouse in December 1975 and in December 1980, until they were actively growing with woody stems 4-8 mm in diameter (pencil thickness). In mid-January terminal shoots 6-10 cm long of Hakea bucculenta, H.francisiana and H.multilineata were taken from both young seedlings in pots grown under hard conditions outside and garden grown plants when dormant buds in the leaf axils were just beginning to swell prior to the onset of a period of active growth.

The grafts used were simple wedge (cleft) grafts, and as the scion wood was generally narrower than the rootstocks, the cambial areas (region of cell division directly under the bark) of rootstock and scion were carefully matched on one side only. The grafts were tied with grafting tape and the scion and top of the rootstock covered with a loose fitting polythene bag. The bags were left over the grafted plants for 10-14 days to help prevent drying out of the scions before union took place. If the bags were left on longer than this, buds were damaged by fungal infection. Although all leaves were removed from the scion wood in order to reduce water loss, a number of leaves must be left on the rootstock otherwise callus formation and graft union will not readily take place. Grafted plants were left in the glasshouse until the buds in the scions had produced several fully expanded leaves, approximately eight weeks after grafting. The grafted plants were then placed into a shade house for ten days of hardening off, after which they were placed into the open nursery area and the grafting tape was removed.

Using this method the percentage of successful grafts is above 80 per cent, with most failures occurring in the first two weeks after grafting.

Results and Discussion

It should be noted that although the percentage of successful grafts of the above three Hakea spp. when grafted onto Hakea drupacea (syn H.suaveolens) is also high initially, all grafts of this combination died within six months due to failure of the graft union presumably from incompatibility. Six years after grafting there have been no signs of incompatibility when using H.salicifolia as a rootstock.


Ruler
"Six years after grafting there have been no signs of incompatibility when using H.salicifolia as a rootstock"
Ruler

The growth of grafted H.bucculenta on H.salicifolia is very vigorous, resulting in a dense attractive bush. Unfortunately it has taken six years for grafted H.bucculenta to flower. This may be because of the extreme vigour or it may be simply the result of juvenility as young seedlings were used as scions in the initial grafted plants. Flowering will probably increase in the future, while in the meantime grafted plants of H.bucculenta can be admired for their foliage and form alone. In order to increase flowering, scion wood should be taken from plants which have flowered.

In contrast, grafted Hakea francisiana flowers prolifically while still growing vigorously, forming a very attractive bush. The growth has varied where different plants were used as sources of scion wood, however, one plant which has compact growth and produces many dark pink flowers has been selected as the source of future scion wood.

Hakea multilineata when grafted onto H.salicifolia has an open, upright growth habit and is not as attractive as H.francisiana, but still forms a neat, slender tree.

Conclusion

The three species Hakea bucculenta, H.francisiana and H.multilineata which are difficult to grow in the eastern states can be successfully grown by grafting onto H.salicifolia. The results are good enough to encourage nurserymen to carry out grafting of these Hakea spp. on a commercial basis.

References

  • Wrigley, J. W. and Fagg, M. 1979. Australian Native Plants. Collins, Sydney and London.
  • Elliot, W. R. and Jones, D. L. 1980. Encyclopaedia of Australian Plants Vol.1, Lothian. Melbourne, Sydney and Auckland.


Acknowledgement: We would like to thank W. Thompson for critically reviewing this work.


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