Page 125 - Updated SuDS Design & Evaluation Guide-Newham V3 Spreads

P. 125

Detailed Design 9.10.3.2 Herbaceous planting Herbaceous planting, as well as fulfilling the Bioretention features are defined by Recent ideas about planting, including ‘prairie Detailed Design
planting style’, have influenced both the
aggregate filtration below specialist highly
Raingardens and bioretention features, in
choice of plants and the growing mediums
permeable soils. This can be a testing
particular, use herbaceous plants and
functional and aesthetic criteria of more
used in recent SuDS features.
environment for planting and so further
sometimes low shrubs to create an
general soft landscape design, must protect
requirements exist:
These new approaches combine a new
the SuDS network, by means of the following
ornamental appearance or planting that is
■
palette of herbaceous plants and grasses
Bioretention planting, located in public
appropriate to a formal landscape context.
criteria:
with the free draining soils recommended for
open space, must be resistant to damage
■
Flowing water can be a constraint to the
The planting must resist flow, encourage
and neglect. Certain evergreen suckering
planting of SuDS features. Raingardens and
the trapping of silt and pollution as well as
shrubs and ornamental grasses can resist
on green roofs and modified bio retention
bioretention are examples of smaller basin
collectively be attractive all year.
features.
occasional damage and require simple bioretention structures and are being trialled
structures with less dramatic flows that allow ■ Unlike general amenity planting, the maintenance.
an ornamental planting approach to be taken. Plants chosen to withstand dry conditions of
planting must be either evergreen or have
This is helped if there are inlet aprons or ■ If tree planting, consider fine leaved free-draining soil profiles may be from many
a presence at ground level year-round.
other erosion controls where water enters the species that do not generate heavy leaf sources.
feature. ■ Plant selection must take into account fall.
In these cases, a deep stone drainage layer
that the raingarden will be dry most of the
Plants can be evergreen (e.g. Geranium ■ Select drought tolerant species. overlain by an open graded growing medium
time and although it will be inundated in
macrorhizum and Phlomis russeliana) or based on crushed stone with 15 - 20%
most rainfall events will usually return to ■ A regular mulch of coarse organic matter
plants that shrink back to a visible clump (e.g. organic matter and about 10% of loam added
empty within around 24 hours. is also important to keep the soil healthy
Alchemilla mollis and Rudbeckia fulgida and the surface of the soil open. to the mix may be used. This soil layer is then
‘deamii’) or with winter-present foliage such ■ Herbaceous plants should be selected topped by crushed stone.
as grasses like Miscanthus and Stipa. This with a fibrous root system to hold the soil Road runoff is largely managed by the very
119 planting usually needs a minimum of one together. large surface area of very free draining soil 120
strim in February and some weeding during
■ Planting choice should avoid the reliance rather than a dense planting mix.
the growing season.
on herbicides, pesticides and fertilisers to
protect receiving watercourses.
Facing: Herbaceous and grass planting used
to dramatic effect at Australia Road SuDS
Park.

Attractive and wildlife friendly herbaceous
planting by Sheffield City Council in a
crushed stone bioretention substrate.

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