Garden weeds - Principles of Horticulture - page 219

species may grow at altitudes up to 1700 m. It is
most common in neutral pH conditions but may occur
on slightly acid or lime soils, especially when bare
patches have been left by machinery, sports footwear
or rabbit damage.
Life cycle . Creeping buttercup may grow up to 60
cm in height at flowering time. Horizontally growing
runners develop above ground in May and develop
roots along their length, representing the main problem
to turf grass. Each new rooting point gives rise to a
new plantlet during the summer months, so that after
a few years of uncontrolled growth, the buttercup
colony occupies a large circular area of turf. The low
growing point of this weed keeps it out of reach of
most lawnmowers. Its long, fibrous roots reach deep
down into the soil, giving it resistance to dry weather,
and represent a problem for herbicidal control.
Spread . The two-year-old plant produces bright yellow
flowers from May to August, and an average of 700
seeds are produced by each plant. The plant dies
after seed production, but leaves behind developing
daughter plants. Seeds may fall to the ground and
survive for seven years in the soil, or may be eaten by
birds and thus spread.
Control . Cultural controls include weeds being
carefully uprooted with a small fork (ensuring that
the growing point and main roots are removed) while
raking up the weed's runners before cutting the grass
helps to reduce spread. Autumn spiking and drainage
of lawns lead to less weed establishment. Selective
weedkillers such as those containing a mixture of
2,4-D , dicamba and fluroxypyr penetrate down to
the weed's roots without killing turf. In bare ground,
buttercups may be controlled by glyphosate herbicide.

to the surface of the soil. However, eradicating it
completely needs constant attention as the small
pieces of rhizome remaining in the soil can develop
into a new plant.
One rather prolonged but effective control measure
involves the temporary removal and potting of shrubs
and herbaceous border plant from the weed-affected
areas. This procedure is then followed by placing over
the area a large sheet of thick, opaque black plastic
that starves the weed of light and moisture. It is
recommended that this sheet is left in position for a
year to achieve control. It may be necessary to repeat
this procedure if the weed emerges above ground
again.
When this weed is found in lawns and growing
independently (i.e. not linked to another ground elder
plant by a rhizome), regular weekly mowing of the
grass with a low blade cut will gradually starve the
weed of its stored food reserves.
Chemical controls include:
X Glyphosate is a translocated herbicide that is
effective against ground elder. The chemical
moves down from the leaves to the underground
roots and rhizomes, thus killing the whole
plant. Three important points should be noted:
glyphosate kills all types of plants - any sensitive
garden plants need to be protected at the time of
spraying; use a sheet of polythene in order to avoid
any spray drift reaching them; gel formulations
that are wiped onto the weed will be less likely to
cause a problem.
X Mid - summer sprays achieve the best results as
the weed has considerable leaf at this time. In this
way, the chemical is deposited over a large area of
foliage, and there will be more internal movement
of the chemical down to the roots and rhizomes.
However, a second spray may be applied in late
summer, if the weed has not yet died.
X Spraying in the evening is more effective because
the chemical is absorbed by the leaves more
effectively at this time.

17

Ground elder ( Aegopodium
podagraria )

This belongs to the Apiaceae family. Ground elder is
so-named because it has a leaf shape superficially
resembling that of the elderberry shrub. It is, however,
not related to this species.
Damage and location. This weed is perennial, and can
rapidly form a dense matt of foliage that crowds out
plants in beds and borders (see Figure 17.1).
Life cycle . Ground elder produces white underground
rhizomes (see p. 92) under the soil but close to the
surface. These invade gardens by creeping under
fences from neighbouring garden and wasteland.
The weed may also be present in the compost of
introduced pot plants that are then grown in the garden.
Control . Cultural controls include carefully removing
rhizomes with a garden fork, as they occur close

Couch grass ( Agropyron repens )

Belongs to the plant family Poaceae (Graminae).
Damage and location . This grass is thought to
have been introduced to Britain and Ireland 2,000
years ago by the Romans as a medicinal plant. It is
sometimes called 'twitch', and is a widely distributed
and important weed found at altitudes up to 500 m. It
quite often takes over bare plots and those growing
ornamentals, vegetable or fruit.