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Commentary on another Level 2 Garden Planning Question
by Janet Prescott - Wednesday, 15 January 2020, 3:07 PM

This one from R2112 Feb ‘19

Q5a) Identify THREE different plant groups, for different situations within a pond. [ 3 marks]
b) Name ONE example of an aquatic plant for EACH of the plant groups stated in a). [3 marks]
c) Describe TWO methods of controlling blanket weed in a pond.[ 4 marks]

This question relates to the following part of the syllabus:
Outcome 5. Understand the planting and maintenance of a garden pool.
5.1 Name TWO AQUATIC plants from each of the following groups: floating, deep-water,
marginal and bog plants.
Examples could include: Floating: Stratiotes aloides Deepwater: Nymphaea ‘Chromatella’
Marginal: Caltha palustris Bog garden plant: Gunnera manicata

5.3 Describe the annual maintenance of a garden pool including possible controls for algae
including blanket weed.
Seasonal maintenance tasks to include: Water/vegetation balance, role of oxygenator
plants; maintenance of water levels in summer; control of vigorous growth and invasive
pondweeds, division of plants; netting against leaves, management of ice formation.
Controls for algae to include pond balance, use of barley straw or other additives and
manual methods of removal.

The first part of the question is looking for plant groups rather than plant examples. Three of the
groups listed on the syllabus could be used, i.e. floating, deep-water, marginal or bog plants. The
examiners’ comments also suggest oxygenators as another correct answer.
The examples could be those listed on the syllabus. Further examples suggested in the examiners’
comments are:
Nuphar lutea – deep water
Hydrocharis morsus-ranae – floating
Myriophyllum verticillatum, Lagarosiphon major - oxygenators
Caltha palustris – marginal
Primula japonica – bog
Make sure you include typical examples and indicate the group they belong to. Some aquatic plants
may be included in different categories in different text books and websites. This is often the case
with marginal and bog plant examples.

Also, make sure you don’t give any examples that are invasive aliens. There are several that are banned from sale in the UK.

For part c), the examiners’ comments suggest the following as acceptable answers:
‘Blanket weed can be controlled by ‘twirling’ it around a cane or the handle of a rake and leaving it
at the side of the pond initially to allow any wildlife to return to the pond.
Floating a bale of barley straw in a mesh bag in the pond is an effective method of controlling
blanket weed. Approximately 50g of straw per m 2 of water surface is ideal. The straw is added to the
pond in spring and is removed after six months when it has turned black’.
As the question asks you to ‘describe’ you need to include a reasonable amount of detail.

Note on water plants from JP:

Banned plants include Elodea crispa ( syn.Lagarosiphon major) and E. nuttallii, Azolla filiculoides, Myriophyllum aquaticum and M. heterophyllum, Hydroctyle ranunculoides, Ludwigia grandiflora, Crassula helmsii, Alternanthera philoxeroides, Gunnera tinctoria, Eichhornia crassipes, Lysichiton americanum...

Elodea canadensis is not banned from sale. The RHS website currently says:  ' This plant is listed on Schedule 9 of the UK Wildlife and Countryside Act as an invasive, non-native species. While this does not prevent it from being sold in the UK, or from being grown in gardens, the RHS encourages those that do grow it to take great care with managing it and with disposing of unwanted material. The RHS also encourages gardeners to find alternative plants to grow to those listed on Schedule 9.'

Any water plant that establishes itself successfully can be 'invasive' in its own environment: Lemna minor and other duckweeds are native;  the native oxygenator Myriophyllum spicatum can choke a pond and kill off fish in a warm summer;  Typha latifolia, Iris pseudacorus and other natives will swamp more delicate plants if conditions suit them, and many bog garden ornamentals like Cyperus eragrostis can seed into the rest of your garden. They can all be 'weeds' when you don't want them outcompeting other plants.