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Michael Eason hiking in Anza-Borrego Desert State Park to observe Washingtonia filifera in situ
Currently at San Antonio Botanic Garden, Michael's work has...
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Plant Focus

Quercus xjackiana acorns
The hybrid of Q. alba and Q. bicolor

Oak Trials in New Zealand

red oaks
Quercus texana and Q. kelloggii at Appletons Tree Nursery in autumn 2019

The IOS might be interested to hear about some oak trials being planned for New Zealand in 2021 and 2022.

The Oak Action Group of Farm Forestry New Zealand is planning to establish American Red Oak Timber Trial Blocks in three North Island locations in 2021. We are focusing our efforts on public land or covenanted blocks, so that eventually the plantations can themselves form seed orchards of elite trees for future selection. We have obtained initial agreements for 1-ha plots in eastern regions of the North Island: at Eastwoodhill Arboretum in Ngatapa, Gisborne; Guthrie Smith Arboretum at Lake Tutira near Napier; and at Rewanui in Masterton, owned by the Montfort Trimble Foundation. All sites have current stands of oak.

We have spent the last two years identifying the fastest-growing species of oak in New Zealand, with a focus on developing further alternative species for plantation timber. The American Red Oaks are a standout, as are many of the Mexican species. 

For these trials we have chosen to focus on seven species of American Red Oak: Quercus rubra, Q. ellipsoidalis, Q. pagoda, Q. palustris, Q. shumardii, Q. texana, and Q. kelloggii. Eastwoodhill Arboretum were able to collect substantial numbers of some species for us during the Covid-19 lockdown, as we were not able to travel regionally during early autumn. 

The seedlings for the trials are being grown by our nursery partner, Appletons Tree Nursery, who will supply field-grown 1-year saplings next winter as well as the best 2-year seedlings from existing stocks in the nursery. 

The plan is to cluster plant each of the 1-ha blocks in sets of five oaks at 12-m centers with alder as trainer trees (about 150 seedlings of each of seven species). Each site would have approximately 70 planting clusters. We will establish criteria for tree selection (form, vigor, lack of epicormics, and eventually growth stress and heart wood formation) and thin to select the best one or two trees at each cluster. The above trial/demonstration blocks will not only demonstrate what growth rates are possible on a range of land types under plantation conditions, but also serve as future seed stands for fast-growing Red Oak. We are considering two alternatives for these blocks: 

  1. plant species in pure stand clusters and select the best at each cluster site, to produce "pure" species progeny from elite trees
  2. plant every species at each cluster site, with a deliberate view of creating hybrid acorns from elite trees.

Comments from IOS members, on the relative merits of each approach, would be welcome!

oak trials
Eric Appleton and Eric Cairns (Oak Action Group) inspecting rows of 1 year seedlings at the tree nursery

We are also wishing to investigate ways of producing clones of superior trees through grafting and air layering techniques.  We have only a small selection of smaller, columnar growing varieties in New Zealand, and it would be nice to supplement these a little further down the track with imported selections from some of the excellent breeding and selection work being done overseas. Of course this will inevitably mean importing into quarantine facilities in New Zealand, but perhaps clonal production is a way to spread the extremely high initial up-front costs of importation. 

We plan to conduct similar trials on Mexican species in the next few years. We know very little about timber properties and performance of these species grown in New Zealand's conditions but are optimistic that their utility in their natural range bodes well for a plantation approach here. One avenue would be to make selections of fast-growing Mexican Red Oaks (including Q. laurina, Q. affinis, Q. crispipilis, Q. rysophylla, and a number of other ones). Test plots planted at Guthrie Smith Arboretum (woodlots) have been thinned from 40 trees per species down to 6–8 trees. Many of the remaining trees are doing 2cm/year DBH at age 15, on not very fertile soils, but with moderately high rainfall. This type of experimental plot needs to be tested on a range of sites. Some of these oaks might be suitable for farm plantings on erodible hillsides, possibly to replace poplar when it reaches its use-by date. Early investigations of wood properties from branch prunings show (in most species except Q. furfuracea) a high degree of tangential and radial shrinkage, which is worth exploring further.