Report: Trees for steep slopes
Sustainable Forest Solutions
Reviewed by Mike Marden, July 2018.
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Please note that the web report is regularly updated whereas the pdf download above is dated July 2018.
|Species rating *|
|Early growth rate||4|
|Root decay rate||7|
In a nutshellGiant sequoia is extremely wind firm and grows well in dry environments. It may have potential for exposed steeplands with thin soils in the North Island but establishment is slow for the first five years, requiring attention to releasing from weeds. May be particularly suitable for planting in exposed sites within coast redwood stands because it yields the same timber.
Giant sequoia (Sequoiadendron giganteum) grows on free draining soils at altitudes of between 830 m and 2700 m in its natural range in North America, with little rainfall in the growing season and significant snowfall in winter (Knowles & Miller, 1993). It is very cold hardy (Knowles & Miller, 1993). Large specimens are found throughout New Zealand, demonstrating its wide climatic adaptability.
Giant sequoia is highly tolerant of gale force winds (Brown, 2007), tolerating much greater exposure than coast redwood (Knowles & Miller, 1993). Giant sequoia resists uprooting even in extreme winds such as during Canterbury windstorms in 1975 (Knowles & Miller, 1993) and again in 2013 (G. Fleming, pers. comm) both of which severely damaged other species including radiata pine, but with little or no damage to giant sequoia.
Trials were planted in New Zealand in the late 1970's near Gore, Geraldine and Hamner Springs in response to observations on its wind firmness. These have all grown well, with another at high elevation near Arthur's pass looking like it may have potential (Libby, n.d.). Brown (2007) suggested that giant sequoia should be more widely planted in the South Island.
Giant sequoia tends to grow best on slopes and where there is good soil drainage, with wet soils resulting in butt rot (Knowles & Miller, 1993). In New Zealand giant sequoia has established without shelter and in extremely dry conditions in Otago and can grow in much drier conditions than coast redwood (Knowles & Miller, 1993). It will grow on exposed barren ridge tops but prefers some intact topsoil (C. Low, pers. comm).
Giant sequoia, like coast redwood, responds well to being released from weed competition (Knowles & Miller, 1993). Growth can be slow for the first ten years or so, but then increases significantly (Knowles & Miller, 1993). Even on better sites growth is slow for five years, "but then height increases by 80-90 cm per year and can achieve 90 cm diameters at 25 years old" (C. Low, pers. comm).
Little is known about silviculture of giant sequoia, but like coast redwood, this should aim to minimise branch death and formation of black knots, while also minimising branch size (Knowles & Miller, 1993). Trees can become very large, with specimens in New Zealand achieving over 3m diameter at 120 years old and the species offers fast diameter growth even as it ages (Knowles & Miller, 1993). Giant sequoia has a more consistently good form than other conifer species (Knowles & Miller, 1993).
Only stumps from young trees sprout coppice growth (Libby, n.d.).
Rooting of cuttings becomes more difficult as parent trees age, however there is some evidence that clonal stock can be rejuvenated, which can then be hedged to produce large quantities of cutting material (Knowles & Miller, 1993). Seedlings are prone to botrytis disease in the nursery whereas cutting material isn't (Knowles & Miller, 1993).
Giant sequoia has been found to be healthy and relatively pest and disease free in cooler regions of New Zealand. However, "flagging" caused by Botryosphaeria dothidea occurs in younger trees under some circumstamnces. In Nelson this occurs on drier sites and is attributed to seasonal drought rather than generally dry conditions (R. Appleton, pers. comm). Flagging is more prevalent in warmer climates such as found in the Nelson region, whereas cooler areas such as high elevation central North Island has little flagging and healthy trees (D. Tantrum, pers. comm).
Giant sequoia foliage is generally unpalatable to browsing and possum damage, less so than coast redwood, however the bark may be stripped by cattle and goats (Knowles & Miller, 1993).
The wood of plantation giant sequoia is similar to coast redwood (Libby, n.d.), but is slightly coarser in texture, darker in colour and possibly with slightly better mechanical properties (Knowles & Miller, 1993).
Disclaimer: The opinions and information provided in this report have been provided in good faith and on the basis that every endeavour has been made to be accurate and not misleading and to exercise reasonable care, skill and judgement in providing such opinions and information. The Author and NZFFA will not be responsible if information is inaccurate or not up to date, nor will we be responsible if you use or rely on the information in any way.