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flowers

Natural populations

Leptospermum polygalifolium extends along the east coast from Cape York, Queensland to the south coast of New South Wales. It usually grows in sandy soil or on sandstone rocks but sometimes on basalt soils and rocks [28]. Six subspecies [28] are recognised by the National Herbarium of New South Wales [43]:

Bean (1992) notes that this is a very variable and complex species and while it is true that some distinct forms do exist, there appears to be widespread inter-gradation between them [27]. There are 3 known forms of subsp. tropicum, propagated from natural populations from the Windsor Tableland, Cardwell and Hinchinbrook Island in North Queensland, which are used as garden plants [125].

Flowering and seeds

The main flowering is in spring – early summer. Seed is periodically released from fruits over time. Thompson (1989) recorded the main flowering times for each of the subspecies as: Subsp. polygalifolium – November to December; Subsp. montanum – November to January; Subsp. cismontanum – September to October; Subsp. howense – November to January; Subsp. tropicum – August to September; Subsp. transmontanum – August to January [28]. Leptospermum polygalifolium germinates easily from seed [10] with no pre-treatment, at an optimum temperature of 20°C [90].

Cultivation and uses

This plant is a valuable river stabiliser as it lies down in a flood, of high wildlife value and widely used as an ornamental [1]. Within the range of subsp. transmontanum, variation in drought and frost tolerance is suspected, emphasising the need to source seed locally. Northern populations of subsp. montanum require frost free conditions, while populations in the central inland areas of New South Wales would tolerate light to moderate frosts. Leptospermum polygalifolium tolerates slightly acidic to neutral soils, with low level intermittent waterlogging but will not tolerate permanently wet ground

Key descriptors:

Subsp. polygalifolium:
Climate parameters
Mean annual rainfall: 650-2150 mm
Rainfall distribution pattern: uniform
Mean annual temperature: 9-19 °C
Mean max. temperature of the hottest month: 20-31 °C
Mean min. temperature of the coldest month: -3-8 °C
Frosts (approx. no. per year): greater than 20
Frost intensity: light to moderate (0 to -5°C)
Altitude: 10-1400 metres
Soil factors
Texture: loam, sandy loam, sandy clay loam or sand
Soil depth: skeletal to shallow (less than 30 cm) or moderate to deep (30-100 cm or greater)

Subsp. cismontanum:
Climate parameters
Mean annual rainfall: 650-1700 mm
Mean annual temperature: 13-24 °C
Mean max. temperature of the hottest month: 25-32 °C
Mean min. temperature of the coldest month: 2-11 °C
Rainfall distribution pattern: summer or uniform
Frosts (approx. no. per year): greater than 20
Frost intensity: light to moderate (0 to -5°C)
Altitude: 0-450 metres
Soil factors
Texture: loam, sandy loam, sandy clay loam or sand

Subsp. howense:
Climate parameters
Rainfall distribution pattern: summer
Frosts (approx. no. per year): frost free or more or less frost free
Altitude: 100-900 metres
Soil factors
Texture: loam, sandy loam, sandy clay loam
Soil depth: skeletal to shallow (less than 30 cm)
Tolerance of extremes in climate
Wind: tolerates salt-laden coastal winds

Subsp. montanum:
Climate parameters
Mean annual rainfall: 800-2250 mm
Rainfall distribution pattern: summer
Mean annual temperature: 7-18 °C
Mean max. temperature of the hottest month: 20-29 °C
Mean min. temperature of the coldest month: -2-7 °C
Frosts (approx. no. per year): greater than 20
Frost intensity: light to moderate (0 to -5°C)
Altitude: 300-1550 metres
Soil factors
Texture: loam, sandy loam, sandy clay loam
Soil depth: skeletal to shallow (less than 30 cm)

Subsp. transmontanum:
Climate parameters

Mean annual rainfall: 550-1100 mm
Mean annual temperature: 10-23 °C
Mean max. temperature of the hottest month: 24-33 °C
Mean min. temperature of the coldest month: 0-8 °C
Rainfall distribution pattern: summer
Frosts (approx. no. per year): greater than 20
Frost intensity: light to moderate (0 to -5°C)
Altitude: 150-1250 metres
Soil factors
Texture: loam, sandy loam, sandy clay loam
Soil depth: moderate to deep (30-100 cm or greater)

Subsp. tropicum:
Climate parameters

Mean annual rainfall: 700-4100 mm
Rainfall distribution pattern: summer
Mean annual temperature: 16-25 °C
Mean max. temperature of the hottest month: 26-32 °C
Mean min. temperature of the coldest month: 5-19 °C
Frosts (approx. no. per year): frost free or more or less frost free except high elevation occurrences
Altitude: 300-1550 metres
Soil factors
Texture: loam, sandy loam, sandy clay loam or sand

References

[1] Carr D (1997) Plants in Your Pants: a pocket guide for the identification and use of the common plants of the northwest slopes. Greening Australia NSW, Armidale.

[8] Bonney N (1997) Economic native trees and shrubs for South Australia. Greening Australia, South Australia.

[10] Wrigley JW, Fagg M (1993) Bottlebrushes, Paperbarks & Tea Trees and all other plants in the Leptospermum alliance. Angus & Robertson Publishers, Sydney, NSW.

[27] Bean AR (1992) The genus Leptospermum (Myrtaceae) in Northern Australia and Malesia. Austrobaileya 3: 651.

[28] Thompson J (1989) A revision of the genus Leptospermum (Myrtaceae). Telopea 3: 396-402.

[43] National Herbarium of New South Wales (2008) PlantNET - Flora of New South Wales. (Online http://plantnet.rbgsyd.nsw.gov.au/floraonline.htm Accessed: February 2008).

[90] Flynn S, Turner RM, Dickie JB (2004) Seed Information Database (Release 7.0, October 2006). (Online http://www.kew.org/data/sid/ Accessed: July 2007).

[125] Australian Society for Growing Australian Plants (1999) Australian Plants Online - Leptospermum polygalifolium . (Online http://asgap.org.au/l-pol.html Accessed: February 2008).

Internet links

Australian National Botanic Gardens - Growing Australian Plants: http://www.anbg.gov.au/leptospermum/leptospermum-polygal.html

Australian Society for Growing Australian Plants: http://asgap.org.au/l-pol.html

PlantNet NSW Flora Online – species description & distribution: http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Leptospermum~polygalifolium

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