A preliminary report of results in growing breadfruit from stem cuttings by Len Muller at Mt. Mirinjo Farm, Woopen Creek, north of Innisfail
BREADFRUIT PROPAGATION - Past Endeavours
The traditional method of propagating breadfruit trees is from natural suckers which emerge from damaged roots, or from root cuttings. From Bligh of the "Bounty" to modern times, it was believed that breadfruit will not grow from stem cuttings.
In "The Propagation of Tropical Fruit Trees" (Commonwealth Bureau of Horticulture and Plantation Crops, Kent 1976), Patricia Rowe-Dutton reviewed experiments on the propagation of Artocarpus altilis, Breadfruit. The section on propagation by stem cuttings is discouraging. She notes, however, that it was achieved by J. Leon in Costa Rica in 1968. Other attempts failed or were laborious and complex. I have not read Leon's paper, so do not know his method.
I have found that striking stem cuttings under the climatic conditions we had this year from December to the beginning of March is actually very easy indeed. The period was one of wet weather, with temperatures 30°C max. temp. and 24°C min. temp.
MY SYSTEM, MATERIALS AND METHOD
Stem cuttings 20-25 cm long and 3 cm diameter were taken from a seedless breadfruit, var. 'Noli'. A pruning saw was used - not secateurs, which crush the tissues. The leafy ends of the branches were discarded. No growth hormones were applied.
Standard black plastic pots 20 cm in diameter and 20 cm deep were chosen, with six or eight large drainage holes around the perimeter of the base. The holes run up the side of the pot about 2 cm and permit some aeration of the potting mix as well as perfect drainage.
Peatmoss and coarse sand were used for the potting medium. We use German "Moorgold" peatmoss because it seems to be free of mould. The sand was from the Johnstone River and had been sieved by the supplier (Vince Reale, Innisfail), to remove stones and fine particles. The sand was mostly composed of quartz and basalt. No fertilizers were added to the mix.
The procedure was as follows: the cuttings were set on 13.12.90. The pots were filled with pure peatmoss (unsifted) to a depth of 4 cm. The cuttings were supported with their bases resting on the peatmoss, and the pots were filled with 50:50 mixture of coarse sand and peatmoss. They were then watered thoroughly and placed in the shadehouse and kept moist.
During the first month, light-coloured pores appeared on the surface of the bark at the exposed ends of the cuttings. Lateral shoots at the nodes began to enlarge and turn green. At two months, large creamy-white roots began to emerge from the bases of the pots. Two weeks later (1.3.91) the cuttings were repotted in 50:50 coarse sand and peatmoss. They had already grown several quite large leaves, and were well in advance of root cuttings set on the same day. They had numerous and vigorous roots.
After allowing the repotted plants to settle down for a week, they were moved into morning sun and given a weak mixture of "Thrive", a general purpose liquid fertilizer. A week later, full strength "Thrive" was applied as the plants were fully established in their pots.
BREADFRUIT TREES AND COLD WINTERS
I first saw the breadfruit tree almost 25 years ago in East Timor, Indonesia. The beautiful leaves seemed to express the wonder of the Tropics, and I decided that my life would seem empty unless I had a tree growing near me. I was able to buy a tree grown from a root cutting at Limberlost Nursery, Cairns, and took it back to Darwin, where I lived at that time. I began propagating them and selling them there, and once, even a lady from Tahiti came to buy one! People knew that breadfruit could only be grown from root cuttings and were willing to pay a good price. In Darwin the breadfruit tree flourishes, but it is not grown commercially. It is a tree which required hot wet conditions.
The wet areas around Innisfail and Tully, North Queensland, are ideal for breadfruit except that winter temperatures in some years make it difficult for young trees to survive after planting. At Woopen Creek, we may expect a few days as cold as 12°C. The record low is 8°C.
At 10°C., the life of a young tree is threatened, but they will survive 10°C. in a nursery.
Despite several cold winters at Mt. Mirinjo Farm, Laurie Smith and I have succeeded in growing several large trees which are bearing good crops for the second year in a row. Last year (1990) could be classed as a colder than average winter. We had 12°C and 11°C min. for a total of 8 cold days: 3 in June, 3 in July and 2 in August. During the cold spell, all of the young trees in our breadfruit block were severely affected, the symptom being numerous brown spots on the leaves and the young stems. If cold continues for some days, most of the parts of the plants above ground will die. The cultivar 'Noli' appeared to be hardier than the others. (This cultivar was obtained from Kamerunga Horticultural Research Station, Cairns in 1982, courtesy of Brian Watson).
Adult trees were unaffected, or only mildly affected. They are bearing good crops of fruit in March 1991. Mature trees also exist on other properties in the Innisfail- Tully area, so there are good grounds for expecting that the breadfruit can be grown commercially here. I therefore put forward the stem-cutting method of propagating breadfruit as a means of obtaining numerous plants at little or no financial risk.
Conclusion and Ongoing Projects
Growing breadfruit trees from stem cuttings is the 'fast-track' way of obtaining a lot of trees, and has been easy to accomplish. This makes them more of an expendable item, unlike the precious trees grown from root cuttings. Thus it seems worth while to propagate them madly and plant them anywhere where they have a chance of surviving.
Regarding previous negative findings on breadfruit stems as reviewed by Rowe-Dutton, I cannot comment at length, not having read the original papers. I suspect that cloggy, water-logged potting mixes have been used.
Out of interest, I am continuing the experiment on striking cuttings throughout the winter without artificial heat to see how important ambient temperature is in the rooting process. I am also working on Marang, Chempedak, and Jakfruit, using wood of similar size to the seedless breadfruit cuttings. Present indications are that the method as described is not suitable for these species. This is a preliminary report and the method is still being refined (March 1991).
DATE: July 1991
* * * * * * * * * * * * *