A creeping, mat-forming, leafy perennial up to 30 cm tall with no smell from its crushed leaves
The stems lie along the ground and root at the nodes
The flowers are tubular, with dark violet petals, arranged in compact cylindrical heads 2-5 cm long at the tops of the stems
The flower head has two leaves at its base
Plants flower between November and April
Leaves are oval, slightly hairy, arranged in opposite pairs
Each leaf is up to 6 cm long and 2-3 cm wide. The lower leaves have stalks, the upper leaves are almost stalkless
The flowers are occasionally pink or white
Usually found in moist or damp lawns and damp, lime-deficient pastures.
Biology
Origin
Originally native to temperate northern hemisphere regions
Introduced to many parts of the world, either because of its medicinal properties or accidentally as a contaminant in grass seed
Probably introduced into New Zealand, either deliberately or accidentally, in the early days of European settlement
Now common throughout New Zealand.
Life cycle
A perennial species which normally remains green throughout the year
The flowers appear to be self-fertile.
Benefits
Plants have considerable value as herbal remedies for a wide variety of ailments
In western medicine it is used externally for treating minor injuries, sores, burns, bruises and can also be used as a mouthwash to treat mouth ulcers
Impacts
Impact on turf and lawns
Selfheal can be very problematic in turf and lawns where it is seen as unsightly and is difficult to remove due to its creeping habit.
Impact on pasture
Not readily eaten by livestock and therefore can replace more valuable pasture species
Neither is it readily eaten by porina caterpillars so these will tend to encourage the spread of the weed when other pasture species are weakened.
Impact on livestock
There are no known adverse impacts on livestock, which are reluctant to eat the plants anyway.
Control
Cultural control
Management of selfheal is very similar to that for penny royal, i.e. harrowing to rip up the stolons, improving drainage and possibly an application of lime to raise the soil pH.
Grazing management
Appropriate pasture species for the region, suitable fertiliser regimes and good grazing management are the best ways of controlling any weeds in pasture.
Chemical control
This species is not easy to control selectively with herbicides in either turf or pasture
The usual remedies, MCPA, 2,4-D, clopyralid or triclopyr, are relatively ineffective and some of these can severely damage clovers
A safest approach is an application of 2,4-D, applied during flowering in spring. Note however that use of 2,4-D at this time may injure adjacent susceptible crops, especially grapes and kiwifruit
A triclopyr/ picloram mixture will also give control, but even this is not a long-term solution. Note, however, that this mixture will also kill all clovers and if used in turf may kill some turf species.
Further information
Popay I, Champion P, James T 2010. An illustrated guide to common weeds of New Zealand. New Zealand Plant Protection Society, Christchurch, New Zealand. 416 p.
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