WILLOW HERB
Epilobium ciliatum – Tall willow herb
Epilobium nummulariifolium – Creeping willow herb
DESCRIPTION
These are two closely-related weed species. The creeping kind is a NZ native, and is unusual among native plant species in that is has become a serious weed, including in orchards and vineyards. The tall kind is, unsurprisingly, taller than the creeping kind, and is not a native; it’s originally from North America.
Both species are perennials. Neither of these willow herb species is related to the similarly-named willow weed Persicaria maculosa, which is the subject of a separate Rainbow & Brown Weed File.
Tall willow herb is an erect weed, growing from a rosette. It can be up to 2 metres tall, but more usually half that height. Flowers grow singly atop the erect leafy stems, are about 1cm in diameter, four-petalled, and pink to purple. The erect stems are hollow and quite thick, and reddish in colour. Leaves are long (9cm), slender (3cm), and very dark green. The root system is fibrous and spreading.
Creeping willow herb is a sprawling creeper, rarely taller than 12-15cm, but growing in dense patches to a metre or so in diameter. It’s a very common garden weed in NZ. Flowers are white and very small, appearing from spring to autumn. Leaves are nearly circular, a bit over 1cm in diameter, and a flat green colour with dark red to purple edges. The creeping stems are a pale purple colour, and readily take root at the nodes, enabling the creeping-and-spreading habit of the species. Root system is weak and fibrous.
Both species have long (4-8cm) seed pod capsules that split when mature to release many small seeds.
Distribution is pretty much NZ-wide. Both species prefer damp conditions, including gardens, drains and the edges of waterways, roadsides and cultivated or bare land (hence their enthusiastic appearance in orchards and vineyards).
Creeping Willow Herb photos below
MANUAL CONTROL
It’s fairly easy to pull out isolated specimens and smaller patches by hand, which should be done before seed capsules mature and split. All material must be removed from the site to minimise regrowth from viable root or stem fragments.
Both species are unlikely to establish successfully if the site is well covered with pasture species or other good ground cover. It’s normally only in bare or cultivated sites where these species are able to flourish.
HERBICIDES TO CONTROL WILLOW HERB
These species are relatively tolerant of glyphosate. It will kill the seedlings and smaller plants, but mature plants will usually die back but then recover and regrow. This is why these weed species are a problem in orchards and vineyards. Spraying with glyphosate kills everything else between rows (except clover), but the glyphosate does not harm the willow herb seeds that are present, and has no residual effect to prevent their germinating & establishing successfully in their ideal bare-ground conditions.
Herbicides to Kill Willow Herb in Orchards & vineyards, berry fruit
- GA200 (glufosinate-ammonium) is effective against willow herb species at all growth stages, although spraying before seed maturity is obviously the way to go. And GA200 is one of the safer sprays to use around vines and orchard trees. It also has the added benefit of taking out the clover, as well as the general weeds that would be controlled by glyphosate.
Use the equivalent of 7.5L of GA200 per hectare, and add SprayWetter at 100ml per 100L of water used.
Tall Willow Herb photos below
