WEEDBUSTERS

Weedy in the wrong place

NZ Lifestyle Block - - Contents -

Lo­ca­tion: na­tion­wide Dis­tinc­tive fea­tures: blue-grey fo­liage, bright yel­low fluffy flow­ers from July to Septem­ber, fol­lowed by straight, hair­less seed pods (5-10cm long). Why is it weedy: pro­duces many long-lived seed and suck­ers when roots are dam­aged. Grows rapidly, and tol­er­ates hot to cold tem­per­a­tures, poor soils (fixes own ni­tro­gen), damp to dry con­di­tions, and dam­age. Pos­si­bly al­lelo­pathic (able to pro­duce tox­ins that poi­son the soil to dis­cour­age growth of other plants).

Sil­ver wat­tle is a prob­lem depend­ing on where you are. DOC con­sider it a weed, but con­trol is only rec­om­mended where wat­tle is a re­cent threat, of low in­ci­dence or poses a high eco­log­i­cal threat, eg to na­tive bush.

It can be any size, from shrub to large tree. Its frond-like leaves (20-30cm long) are ar­ranged al­ter­nately on stems and have bluish, nar­row leaflets, hence the name. Big clus­ters of nu­mer­ous fluffy yel­low flow­ers ap­pear from July to Septem­ber, fol­lowed by straight, hair­less seed pods.

It’s a prob­lem when it forms large, dense, long-lived stands in dis­turbed habi­tats. Na­tive for­est species es­tab­lish un­der wat­tle so long-term im­pacts are usu­ally con­fined to open and low-grow­ing veg­e­ta­tion types. Rot­ting mat­ter af­fects wa­ter qual­ity. Large stands in­crease wa­ter run-off in win­ter, less in sum­mer, caus­ing sea­sonal drought and flood­ing.

HOW TO CON­TROL IT

1. Hand pull or dig seedlings (all year round). En­sure min­i­mum soil dis­tur­bance. 2. Cut and squirt (all year round): make 1 cut ev­ery 100 mm around the trunk, ap­ply tri­clopyr 600 EC (5ml) per cut.

3. Bore and fill (all year round): make 1 hole ev­ery 200 mm around the trunk, ap­ply met­sul­furon-methyl 600g/kg (3mg) or tri­clopyr 600 EC (10ml) per hole.

4. Cut down and paint stump (all year round): tri­clopyr 600 EC (100ml/l) or Yates Hy­dro­cotyle Killer (500ml/l) or met­sul­furon-methyl 600g/kg (5g/10l) or Vig­i­lant gel. 5. Spray (spring-sum­mer): tri­clopyr 600 EC (30ml/10l) or Yates Hy­dro­cotyle Killer (15ml/l).

2 THINGS WAT­TLE DOES WELL

• Wat­tle pro­vides good cover for tall-grow­ing na­tive species so these sites can be left to re­gen­er­ate (20-40 years) if it’s in the right place (with a seedbed of tall na­tives). • It is a great fire­wood, grow­ing fast in tough con­di­tions (salty ar­eas, drought) and can be cop­piced.

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