Farm Forestry New ZealandEucalyptus sphaerocarpa has only been grown in New Zealand and Northland for 20 years but the species is proving to have many desirable traits suggesting potential for commercial production forestry.
This species combines the resilience to wind exposure of the ash group of eucalypts with the good timber properties of the stringybark eucalypts. Indeed the timber is superior in strength and durability to blackbutt and the stringybark eucalypts and at an earlier age. Like tallowwood, this species produces durable and strong timber from an early age, but unlike tallowwood has a very narrow width sap band.
Health: Few insect or disease problems. Some leafminer damage to young trees in exposed sites.
Timber: The timber is pale brown, very strong, hard and very durable. Produces high density, durable and strong wood from an early age.
| Species | Density (dry) | Bending strength, MoR (MPa) | Stiffness, MoE (GPa) | Hardness, Janka (kN) |
|---|---|---|---|---|
| Eucalyptus sphaerocarpa | 750 | 100 | 13.5 | 6.75 |
Siting: Requires good soil drainage. Adaptable to fairly low fertility but best growth is on moderately fertile sites. The most wind-hardy of the recommended eucalypt species for Northland.
Steep slopes: Well suited to steep erodible slopes provided soil drainage is good and fertility reasonable. A coppicing species, i.e. the roots do not die but the stump stays alive after felling and re-sprouts. Coppicing species hold the soil from slipping even after harvest.
Species characteristics: Slower-growing at first than stringybark eucalypts, similar growth rate to tallowwood. Although called a "stringybark", this species is actually an ash eucalypt. Seed is available commercially from Northland stands and although a high initial stocking is recommended to ensure selection of the fastest growing trees with the best form, the species is well enough formed to grow at radiata stockings.
Recommended regime: Plant at 1200-1800 stems per hectare. Thin in 3-4 stages down to 400-600 stems per hectare. This gives a 3:1 thinning ratio. Because available seedlines are unimproved, a high initial stocking is recommended for a sufficiently high thinning ratio and greater selection for growth and form.
For clearwood production prune potential crop trees to 6-8m in 3-4 lifts and thin down to 300 pruned stems per hectare. However, although pruning improves grade recoveries from those logs, this is not necessary to produce clearwood because eucalypt trees self-prune provided tree stocking is sufficiently high to induce this. The tradeoff is between the cost of pruning and higher establishment costs. A higher thinning ratio also provides greater selection for growth and form.
Key message: High quality durable timber, adaptable to steep slopes with thin soils and wind.
NZFFA on facebook