Where is it originally from?
What does it look like?
Very large resinous evergreen tree with thick bark that is reddish-brown underneath, and rough and furrowed when mature. Branches sit horizontally, and are in irregular whorls, while branchlets usually droop. Ridged shoots are light to dark brown with short hairs. Shiny purplish-brown winter buds (to 1 cm long) are narrow and sharp. Needle-like leaves (15-38 x 1-2 mm) are clustered in twos, whitish beneath, have edges that are often rolled, and are orange-scented when crushed. Male cones (12-20 mm long) are catkin-like, while papery cylinder-shaped female cones (5-10 cm long) are downward-pointing. Seed scales are large and broad, bract scales are longer and thinner than seed scales, and are 3-pointed, with the centre point longest.
Are there any similar species?
Alternatives: If you are a conifer fan, there are plenty of non-weedy alternatives available to replace weedy species. Your local garden centre will be able to recommend other non-weedy alternatives that will grow well in your area.
Why is it weedy?
Douglas fir is one of a group of conifers that are 'wilding' in parts of New Zealand and rapidly invading high country land, costing millions a year to control. It can produce 20,000 wind-spread seeds per tree every year, and seed can remain viable for years. Wilding species such as Douglas fir can change landscapes completely, threatening fragile grassland and herbfield ecosystems.
How does it spread?
Seed is spread by wind in autumn and winter, with seedlings establishing most readily on well lit sheltered sites where there is no competition from other vegetation. Seldom spreads onto land where vegetation cover is dense.
What damage does it do?
Invasion and suppression of grassland and regenerating shrubland, invasion of low-stature plant communities including herbfield and tussockland. Can also threaten landscape character and recreation value. Major wilding conifer species in southern areas.
Which habitats is it likely to invade?
Lowland, montane and subalpine habitats, growing in sites with low-moderate fertility. Found in scrub and forest margin communities, shrublands, tussockland and light wells in forest.
What can I do to get rid of it?
1. Handpull small seedlings (all year round). Leave on site to rot down.
2. Cut down (all year round): cut low enough to remove all green needles. Leave on site to rot down.
3. Stump swab (all year round): cut down close to ground and paint stump with metsulfuron-methyl 600 g/kg (1g/L) or picloram gel. Don't need to remove all green needles if using this method.
4. Bore & fill (all year round): drill 1 hole every 150 mm around the trunk, and fill with metsulfuron-methyl 600 g/kg (1g/hole).
5. Cut and squirt (all year round): make one cut every 150 mm around the trunk, and fill with metsulfuron-methyl 600 g/kg (1g/cut).
6. Frilling (all year round): with a sharp chisel or axe, make a deep cut into the sapwood at regular intervals around the base of the tree, taking care not to ring-bark the plant. Immediately apply metsulfuron-methyl 600g/kg (1g/L) to each cut using a paintbrush or squeeze bottle.
7. Spray (spring-summer): glyphosate (100ml/10L) or metsulfuron-methyl 600g/kg (5g/10L)
What can I do to stop it coming back?
Continue to monitor and remove further infestations as seedlings appear.