Root deformity and toppling in families of mountain ash up to eight years after planting.  J. A. Harris and F. Y. Kassaby.  August 1986.  17pp. (unpubl.)

SUMMARY

The incidence and causes of toppling in mountain ash saplings up to eight years after planting were studied at two forest sites, one near Toolangi and the other at Mt Disappointment to the north of Melbourne. At Toolangi the study area was a progeny trial in which 1317 seedlings representing 22 families were planted in 1976. At Mt Disappointment, the study area was a seedling seed orchard with sections planted in 1977, 1979 and 1981, involving a total of 11,882 seedlings from 40 families. All seedlings had been raised in FH 415 S paperpots. The root systems of saplings grown from seedlings raised in paperpots and hand-planted in the field were compared with those of saplings grown from seed germinated in situ at Powelltown to the east of Melbourne.

Toppling was rare within two years of planting, but was significantly higher in the third and subsequent years. Generally, toppled saplings lacked taproots, and had either predominantly one-sided root systems or had snapped off at the butt. There was significant variation in the extent of toppling among families of mountain ash, and the extent of the difference increased with the age of the stand.

It was concluded that root deformation resulted from a combination of distortion to root systems during transfer of a germinant from the germination medium (soil) to the paperpot (i.e. pricking-out), girdling of the lower stem by coiled lateral roots, and failure of paperpots to decompose readily. Root deformities may be reduced by either paying more care to the pricking-out process or sowing directly into paperpots, and by removal of the paperpot and trimming of the soil plug immediately before planting.