The Narrogin arboretum was one of more than 50 demonstration plantings established by the then Forests Department, throughout the wheatbelt, in the 1950’s and 1960’s. The arboreta were developed to evaluate a range of local, regional, Australian and overseas species that were thought to have promise for planting in the wheatbelt and goldfields, with a focus on species for quality timber, dust control and for windbreaks.
Before this the only tree seedlings available were Sugar Gum-Eucalyptus cladocalyx, Brazilian Pepper-Schinus terebinthifolius, and Kurrajong-Brachychiton gregorii from the Forest Department Hamel nursery. I often see the first two trees at early farm homesteads. LIvestock don't eat them.
The Narrogin arboretum, smaller than most, was added to over several years as new species became available, with the last trees being planted in 1969.
In the last couple of years well established tree in the arboretum have died. As part of a search for possible causes I obtained the DBCA file containing the original planting map, and a report on arboreta success by George Brockway in 1965.
Brockway never ceases to amaze me: he is truly a legendary forester and conservationist, who initiated the arboretum project with a series of trials in 1946 as the Kalgoorlie District Forestry Officer.
Before this the only tree seedlings available were Sugar Gum-Eucalyptus cladocalyx, Brazilian Pepper-Schinus terebinthifolius, and Kurrajong-Brachychiton gregorii from the Forest Department Hamel nursery. I often see the first two trees at early farm homesteads. LIvestock don't eat them.
The Narrogin arboretum, smaller than most, was added to over several years as new species became available, with the last trees being planted in 1969.
In the last couple of years well established tree in the arboretum have died. As part of a search for possible causes I obtained the DBCA file containing the original planting map, and a report on arboreta success by George Brockway in 1965.
Brockway never ceases to amaze me: he is truly a legendary forester and conservationist, who initiated the arboretum project with a series of trials in 1946 as the Kalgoorlie District Forestry Officer.
Narrogin Arboretum. Red shade indicates dolerite clay soil
The Narrogin arboretum is more difficult than most to evaluate because it lacks a uniform soil type and planting date, and has an ephemeral creek running across its centre. Plantings range from 1955 at the eastern end to 1966 at the west. Soil types range from Marri loamy sand to the west grading downslope to York Gum clay loam in the east, and species have been roughly planted according to their reputed appropriate soil type.
Another complication is the warming and dryer climate. E. rudis-Flooded Gum trees, which grew on in sandy surfaced soil on the southern side of the arboretum have all died except for a clump below a street drain outlet on Range Road. Other apparently healthy large trees in Foxes Lair abruptly died in the last two years, including a large Tasmanian Blue Gum. Similarly a row of E. Lane-pooleii trees (with the exception of one adjoining a drain) on loamy sand on the western end of the arboretum died in the past 3 years. They survived for 70 years as attractive mini-versions of trees in their natural range. Despite this, some WA higher rainfall species have thrived and many Goldfields species have done poorly. Why do E. gomphocephala-Tuart (southwest coastal sand), E. preissii-Bell Fruited Mallee (south coast species) do so well here?
Another complication is the warming and dryer climate. E. rudis-Flooded Gum trees, which grew on in sandy surfaced soil on the southern side of the arboretum have all died except for a clump below a street drain outlet on Range Road. Other apparently healthy large trees in Foxes Lair abruptly died in the last two years, including a large Tasmanian Blue Gum. Similarly a row of E. Lane-pooleii trees (with the exception of one adjoining a drain) on loamy sand on the western end of the arboretum died in the past 3 years. They survived for 70 years as attractive mini-versions of trees in their natural range. Despite this, some WA higher rainfall species have thrived and many Goldfields species have done poorly. Why do E. gomphocephala-Tuart (southwest coastal sand), E. preissii-Bell Fruited Mallee (south coast species) do so well here?
Vigorous Sugar Gum row - Brockway noted that imported species tend to be more successful in arboreta than locals, because insect pests do not recognize them as being edible. This is very evident at Narrogin in excellent growth of most Eastern States trees, and perhaps the Tuarts. He specifically mentioned wood boring beetles, but termites and stink bugs are the main culprits at Narrogin. The damn stink bugs are everywhere. When I plant seedlings in Foxes Lair I have to cover susceptible species with fly mesh for a few seasons to stop the growing points being sucked dry.
Brockway also noted that tree plantings were more successful after a crop than in cleared bush. Factors involved include
- Seedling response to fertilizer, particularly phosphorus.
- Retained subsoil water
- Fewer insects
Pines, and Casuarina obesa-Salt Sheoak have grown very well, but some pines are approaching the end of their life.
Most mallees have thrived in the arboretum, particularly on the upper slopes. Oil mallees planted on heavy soil (E. kochii subspecies kochii and plenissima) have persisted on the heavy soil but are attacked by stink bugs. E. kochii subsp. kochii did not persist on a sandier row.
Most mallees have thrived in the arboretum, particularly on the upper slopes. Oil mallees planted on heavy soil (E. kochii subspecies kochii and plenissima) have persisted on the heavy soil but are attacked by stink bugs. E. kochii subsp. kochii did not persist on a sandier row.
Arboretum mallees, E. grossa in the foreground
Mallets are another story. These WA eucalypts are obligate seeders, which lack lignotubers and tend to grow on very hard setting and heavy clays, and breakaway slopes. E. spathulata-Swamp Mallet, was a Brockway recommendation, and I would have agreed twenty years ago. A once magnificent row (pegs 159-163) have mostly collapsed from termite infestation. The original map showed an earlier planted row further east in the arboretum on clay soil, which are just termite eaten holes in the soil.
 E. spathulata row 2005 |  E. spathulata row 2025 |
Other failed mallets are E. diptera, E.campaspe, and E.gardnerii. Three species have persisted: local E. astringens-Brown Mallet, E. Stricklandii (a straggly Goldfields species), and E. platypus- Moort.
Mallets appear to have a shorter life than trees and mallees.
E. spathulata has exquisite bark in autumn, and one of them was the official hugging tree. Alas, no longer.
Mallets appear to have a shorter life than trees and mallees.
E. spathulata has exquisite bark in autumn, and one of them was the official hugging tree. Alas, no longer.
 Hugging tree |  Alas no longer |
Moort is a small mallet which forms dense thickets on hard setting southern clay soils. It has adapted well to fire by excluding other plants while living and shedding huge amounts of seed when burnt.
Plants in the Narrogin arboretum row are continuously infested by termites that cause branches to snap regularly, but the moorts still thrive and flower prolifically.
Plants in the Narrogin arboretum row are continuously infested by termites that cause branches to snap regularly, but the moorts still thrive and flower prolifically.
 Jerramungup Moort thicket |  Arboretum Moort |  Moort flower |
Brockway also highlighted seedling survival problems due to overgrown seedlings with coiled roots. I don't think that it was a problem at Narrogin, but the problem persists today. My DBCA buddy Peter White who assists urban landcare groups in his spare time is frustrated by nursery produced overgrown seedling with coiled roots, which are a widespread cause of revegetation failure.