Annual broad-leaved plant that is a member of the mallow family
Large heart-shaped, leaves which are velvety and soft (hence the name velvetleaf). Leaves are also clammy to the touch and smelly
Can grow 1–2.5 m in height, although may be less in cooler, southern regions
Large (3 cm across) buttery-yellow flowers appear in spring to autumn and only open for a few hours
Seed capsules are large and distinctive, forming a cup-like ring of 13 woody and hairy segments, about 2.5 cm across. Segments remain intact at maturity and each releases 1-3 seeds through a slit on the top of the capsule.
Biology
Origin
Originally from Asia (China and India) and used as a fibre crop in India as long ago as 2000 BC
Currently used in China and other Asian and North African countries to produce a jute-like fibre. It was first imported into New Zealand as a potential fibre source but did not become naturalised and spread at that time
Discovered again in New Zealand in two locations in summer/autumn 2007-2011. One outbreak (Helensville, near Auckland) was contained, but the other was more widespread, over 10 farms between Waitoa and Waihou in the Waikato. It was found in maize silage and in crops and dairy pastures, where maize silage had been fed out (- see references under ‘Further Information’)
In 2016 velvetleaf seed was accidently imported with fodder beet seed and planted on over 600 properties throughout most of NZ. Inspections have found velvetleaf plants on about a third of the at-risk properties with many more yet to be inspected
The incursion plants differ from the crop biotype in several important areas;
The plants are shorter and more branched, thus producing many more seeds
They mature earlier
The seed pods are black on the weedy type and yellow on the crop type.
Life-cycle
Germination occurs over a long period during summer, mostly from seeds in the top 25 mm of soil; seeds cannot germinate when buried below 150 mm
Even small plants, produced from seed germinating in late summer, can flower and set seed
Seed matures about 6 weeks after flowering
Seedlings are vigorous and the plant grows rapidly in its first few months
Root growth is rapid and the plant can grow in lightly shaded conditions
High digestibility and high crude protein in comparison with other broad-leaved and grass weeds (such as yellow bristle grass and fathen). However, stock tend to avoid grazing it
Seeds are spread by farm machinery when harvesting grain (e.g., maize), through livestock, and as a contaminant of grain or silage.
Impacts
As velvetleaf is a new weed incursion, its impacts on pasture, crops and livestock in New Zealand are currently unknown
Overseas literature highlights the longevity of the seed and that as a result large numbers of seed can accumulate in the soil seed bank
Velvetleaf is known to produce allelopathic chemicals that can inhibit water uptake and chlorophyll production in many crop plants
Even moderate infestations that emerge the same time as the crop does can reduce production by 25% or more.
Control
Control in pasture is by phenoxy herbicides such as 2,4-D or MCPA if there are many plants but hand pulling is easier when there are only few plants
Good control can be achieved in maize with a combination of pre- and post-herbicide applications
Control in many crops is difficult due to the long period over which the weed can emerge The only way to guarantee 100% control it the inspect the crop on a row-by-row basis and hand pull any surviving or late germinating plants
Burying seeds may help to prevent them from germinating, but burial will not kill seeds as they can remain dormant for decades.
Popay AI, Champion P, James TK 2010. An Illustrated Guide to Common Weeds of New Zealand. New Zealand Plant Protection Society, Christchurch, New Zealand.
Warwick SI, Black LD 1988. The biology of Canadian weeds. 90. Abutilon theophrasti. Canadian Journal of Plant Science 4: 1069-1085.
Young S 2013. New Zealand Novachem agrichemical manual. Agrimedia Ltd., Christchurch, New Zealand. 767 p.