1. RHS Level 2 Certificate
Week 17 – Review of
PGR and botanical
names; Environmental
issues in gardening

2. Learning objectives
1. State the role of Plant Growth Regulators in plant growth and development.
2. Name the principle plant growth regulators
3. Identify the principle plant growth regulators from a description of their
effects
4. State the importance of botanical/horticultural nomenclature.
5. Define the meaning of ‘family’, ‘genus’, ‘species, ‘subspecies’, ‘variety’ and
‘cultivar’.
6. Explain and apply the conventions for writing botanical names, including use
of italics and standard script, cultivar and hybrid indicators etc.
1. Environmental issues in gardening. Identify and explain the
environmental protection issues in relation to the following:
1.1 Growing media
1.2 pest and disease control
1.3 non-native plants
1.4 water usage and water disposal
1.5 soil cultivation

3. Plant Growth regulators - review
 Control
plant physiological processes –
principally cell division and differentiation and
tissue development (progress to maturity and
senescence)
 Their effects depend on their concentration,
combination and the location of the cells or
plant tissues in question (roots or shoots
etc).

4. Plant Growth Regulators review 2
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Auxin – elongation of cells and fruit formation
Cytokinins - promotes cell division (mitosis), delays the
senescence of leaves.
Gibberellins - cell division and elongation of stems.
Promote flowering and also bolting in ‘long day’ plants
and seed germination.
Ethylene - ripening of fruit and senescence of leaves
and flowers. Induces abscission of leaves in deciduous
plants (the process of leaf fall).
Abscisic acid maintains dormancy in seeds and possibly
in buds. It also is responsible for causing the closing of
stomata – produced in response to ethylene(?).

5. Botanical names – naming structure
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Genus - A group of species that bear close
resemblance to each other.
Species - A group of individuals that are very closely
related structurally and functionally. Individuals in a
single species interbreed freely and breed true to
type.
Variety – a naturally occurring distinct sub- population
within a species that will either come true from seed
or can be reproduced vegetatively (for example by
cuttings).
Cultivar – a man made variety.

6. Botanical naming conventions
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Genus and species in italics (underlined when
handwritten). Genus name starts with a capital letter,
species name starts lower case.
Variety names are in italics
Cultivar names are in inverted single commas and in
normal script. Not underlined when handwritten.
Hybrids – indicated by an X. Placed between the
genus and species names in inter-specific crosses and
before the genus name in inter-generic crosses.

7. Environmental issues – growing media
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Peat is a problem – why?
Useful in many ways – light, moisture retentive, low
in nutrients, open structured and clean to use and
handle
However, cutting peat means destroying
irreplaceable natural habitats and their plants, birds,
animals and insects.
What are the alternatives? Coir, composted bark,
composted green waste, bio-solids.
Do they work? Yes, provided cultivation techniques
are adapted, particularly watering and feeding.

8. Methods of pest and disease control risks to the environment
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One man’s pest is another creature’s dinner –
destroying garden pests can have an effect on food
webs in the garden
Resistance and withdrawal of products mean that
the choice of chemical controls is becoming very
limited. For some pests (e.g. greenhouse whitefly)
there is no effective chemical control available to
amateur gardeners.
Some chemical controls pose a threat to the
operator and to beneficial insects.

9. Methods of pest and disease control –
alternatives to chemical controls
 Correct
care of plants and the environment –
well grown plants that are not under stress are
less likely to succumb to pests and diseases.
 Toleration of some damage
 Barriers, traps, biological controls and ‘organic’
plant based sprays
 Integrated Pest Management – use of
chemicals only as a spot treatment in response
to a problem, coupled with biological and
cultural controls

10. Non-native plants – environmental
issues
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Most UK plants are strictly speaking non-native – the Ice Age
left very few true natives.
Some non-native plants however are invasive and
uncontrolled by natural processes in this country e.g. Fallopia
japonica
Such plants can cause physical damage to buildings and
block watercourses; crowd out native species and provide
little or no habitat for native insects, birds and animals
Do not buy ‘problem plants’, do not dispose of them in green
waste (burn them); do not give them away or dump them.
If you want to attract more insects and birds to your garden
choose ‘native’ plants.

11. Water management and conservation
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Save rain water for use in the garden
Water effectively. No point wetting the soil to
depths below the root zone, or watering anywhere
other than at the roots. No point watering mature
lawns.
Give the plants what they need – pay attention to
rain fall and do not water if it is unnecessary.
Choose plants that need little additional water.
Mulch – used to conserve moisture in the soil,
prevents evaporation.

12. Learning outcomes
State the role of Plant Growth Regulators in plant growth and development.
2. Name the principle plant growth regulators
3. Identify the principle plant growth regulators from a description of their
effects
4. State the importance of botanical/horticultural nomenclature.
5. Define the meaning of ‘family’, ‘genus’, ‘species, ‘subspecies’, ‘variety’ and
‘cultivar’.
6. Explain and apply the conventions for writing botanical names, including use
of italics and standard script, cultivar and hybrid indicators etc.
1. Environmental issues in gardening. Identify and explain the
environmental protection issues in relation to the following:
1.1 Growing media
1.2 pest and disease control
1.3 non-native plants
1.4 water usage and water disposal
1.5 soil cultivation