Greg Hoskins Senior Biosecurity Officer Auckland Council
Velvetleaf (Abutilon theophrasti), also known as butter-print, is an invasive species that has been confirmed in the Helensville and Waikato areas.
It is an erect, annual shrub-like herb from the same family as hollyhock, to which it bears some resemblance. The plant can reach a height of 1-3m. The velvety, heart-shaped leaves are alternate, about 3-15 cm long. The seeds are brown/black and hairy, and about 3mm diameter. It has a long taproot.
Velvetleaf originates from China and Tibet, where it was grown as a fibre crop and medicinal plant. Since being introduced as a crop in Europe and North America, velvetleaf has come to be seen as an invasive species. It is one of the most detrimental weeds to corn, causing decreases of up to 34% of crop yield if not controlled.
The first record of velvetleaf in this country was in the late 1940s, when it was imported by the Ministry of Agriculture and Fisheries for testing as a fibre plant. Its presence was later noted in the 1950s as a contaminant of soya bean seed for trials. These were in Wellington and Lincoln respectively, and were isolated records of the plant.
Velvetleaf was recorded in NZ in 1978 at Ararimu, near Papakura, in pasture and cultivated land. It was believed to have come into the country as a seed contaminant.
Velvetleaf has recently been identified in the Waikato area in maize and in feedout lines from silage, and also on two properties in the Helensville area. The owner of one Helensville property believes the velvetleaf may have come onto this property as a seed contaminant in poultry manure that he spread over his farm.
This plant is one of the worst agricultural weeds in corn, sugar beet and soya bean crops in North America. It competes strongly with those crops for light and water, and releases allelochemicals that reduce the growth and emergence of neighbouring plants. Viability of seed in the soil is for 50-60 years, with 500–10,000 seeds/plant produced. The seed also survives in silage and passing through animals.
The plant blooms in summer (January-February) with flowers approximately 1-2cm wide. The flowers have five petals. The yellow to yellow-orange blooms are quite attractive and are on short flower stalks (pedicels) in the upper portions of the plant, in the axil of the stem and leaf, or where the leaves branch off the stem. The plant has distinctive 2cm-diameter circular seedpods. These have a ring of 'prickles' around the upper edge and have a series of crimps along the sides that resemble those of a piecrust edge. Hence, another common name for this plant is "pie-maker".
Small populations and single plants can be easily pulled or dug up before they go to seed, so early detection and rapid response is a key to controlling the plant. However, because seeds can remain viable in the soil for 50 years or more, velvetleaf can be very difficult to eradicate if infestations are allowed to persist and produce seed. It is important to watch carefully for this plant and remove it as soon as it is found. All plant material should be bagged and disposed of safely, to avoid spreading the seeds.
If any equipment is used where this plant occurs, clean it carefully before working in a new area. Return to the same area each year and look for new plants germinating from the seed bank.
Established populations will take much longer to eradicate because of the long-lived seeds. Plants can be manually dug up or pulled, or they can be mowed close to the ground while the plants are still small. Crop rotation can help prevent favourable growing conditions for velvetleaf.
Chemical controls are generally effective only when velvetleaf is less than 10cm tall. Velvetleaf leaves tend to droop or wilt in the late afternoon, so spraying is more effective in the morning or midday