GREEN ROOF COURSE
Growing Green Skills
ENDORSED BY THE EUROPEAN FEDERATION OF GREEN ROOFS (EFB)
Monitor and Control the Growth of Plants on a Green Roof Level 4 (UK Level 3)
GREEN ROOF PROJECT Growing Green Skills
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GREEN ROOFS Monitor and Control the Growth of Plants on a Green Roof Before any maintenance is carried out on a site an environmental assessment must take place, this isn’t the same as an environmental survey as it just covers the site you are to work on, the type of issues you may come across could be nesting birds, mice, bee hives, wasp nests etc. These may affect the maintenance work for example maintenance shouldn’t take place when birds are nesting (only carry out maintenance after chicks have fledged), you may want to record any nesting insects as these may be pollinators or dangerous (wasps) and shouldn’t be disturbed. Under Health and Safety at Work Act a Risk Assessment for the area you are to work on must be carried out. (For more information on the 5 Steps to Risk Assessment see bibliography for link) Step 1 Step 2 Step 3 Step 4 Step 5
Identify the hazards Decide who might be harmed and how Evaluate the risks and decide on precautions Record your findings and implement them Review your assessment and update if necessary
STAGES IN PLANT GROWTH There are different stages to plant growth and plant cycles, these are Annual, Biennial, Woody Perennial, Herbaceous perennial, bulbs these also come in categories of hardy, semi-hardy and tender it is important to know these so you put the correct plants on the roof, there are also monocotyledons and dicotyledons, the easiest way to identify these are that monocotyledons come from the grass-like family, having veins running parallel to the leaf, while dicotyledons have branching veins.
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Growing Green Skills
THE HEALTH OF PLANTS ON A GREEN ROOF Inspection of plants should be carried out in conjunction with specifications where these are provided as this gives a means to which standards can be verified, although they may be no written specifications these may be conveyed by oral explanation, some people may already posses this experience, being learnt over a period of time or a transferable skill from landscaping. In some situations e.g. biodiverse green roofs, it might be best to leave the plants alone, that way the plants that survive will be best suited to the environment they are growing in. On other green roofs where alien vegetation is excessive and poses a threat, some form of weeding will be required, in most situations this may be hand weeding the site making sure you eradicate perennial weeds by carefully digging out the roots. Larger sites may require spraying with chemical (MUST be qualified in the UK holding a PA1 and PA6 from FEPA), be very careful here as any run off will go directly into the drainage systems and may also be detrimental to the flora and fauna you are trying to attract, it is for this reason that chemicals should only be used as a last resort. Plants should be checked for ill health and where this is found and is assessed as being due to lack of nutrients a feeding regime must be put in place (see below). In most cases where plants aren’t surviving it may be they are the wrong plants. If it is decided that fertilisers are to be used these should be slow release fertiliser capsules these are recommended at the following rates; Intensive greening sites 8g N/m2 Extensive greening sites 5g N/m2 N= Pure Nitrogen Extensive roofs
have a low nutrient requirement and are only fed once per year in the spring
Biodiverse
Not required as indigenous species are being encouraged.
Semi intensive
More regular feeding is required as there will be a wider range of plants.
Intensive
As with semi-intensive.
Fertiliser Also don’t forget that fertilisers will also leach with excessive irrigation and/or fertiliser, causing problems elsewhere and extra cost to the company. Always measure fertilisers before adding to the roof and only use where absolutely necessary
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GREEN ROOFS Hierarchal methods used to control the health of plants for a green roof • Cultural – Plant selection, Weeding/pruning of unwanted vegetation • Physical – Hand weeding, mulching, hand picking of pests. • Biological – use of nematodes to reduce certain unwanted organisms e.g. Vine Weevil, encouraging natural predators e.g. birds, wasps • Integrated – Combination of all methods • Chemical – Where roofs haven’t been maintained for some considerable time, initially chemicals may need to be used, but only after careful consideration to the environment. METHODS OF HANDLING PLANTS. Where plants need replacing, particularly on some intensive green roofs, plants should be carried by the base of the plant, Tree braches should be wrapped as should bare-rooted specimens, where containerised specimens are used the growing media should be moist. Other contractors usually have a lack of understanding with regard to plants, this is difficult to avoid, but if you are on site, keep an eye on them. Also check any replacement plants for weeds, pests and/or diseases. Biosecurity; be aware of your environment so you don’t bring non-beneficial organisms onto the green roof as it could be very difficult to eradicate weeds, pests and/or disease extra vigilance here may cut down on ill health or damage to plants and the environment and so cutting down on costs. List the equipment and resources required to maintain a green roof.
It comes under the Health and Safety at Work Act to make sure everyone is trained in the variety of equipment and resources for the maintenance of a green roof and understands their uses and maintenance requirements. IRRIGATION REQUIREMENTS Irrigation is required for the initial establishment of green roofs, once plant cover is established irrigation with either be reduced (intensive, semi intensive) or stopped. It may be necessary for some intensive green roofs. The following factors may determine the amount of irrigation needed 1. The planting layers demand on water 2. The type and amount of water storage i.e. Growing medium, drainage layer 3. Precipitation patterns, some areas having more than others.
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Growing Green Skills
Sources of water can include; hoses, sprinklers, dribble hoses, overhead irrigation and automated systems. There are various systems available. The installation of irrigation equipment should be in line with the principles of BS 7562-3: 1995 Planning, design and installation of irrigation schemes – Part 3 Guide to irrigation water requirements. Other relevant standards; BS EN 15099 – 1:2007 – Irrigation techniques. Remote monitoring and control system, BS EN 15097:2006 – irrigation techniques. Localised irrigation hydraulic evaluation and BS EN 13742 – 1:2004 – irrigation techniques. Solid set sprinkler systems. Selection, design, planning and installation Maintenance of this equipment will depend on the type being used, basic maintenance will be checking for any visible leaks or wearing of joints etc, if any are found these should be reported to the line manager. Specialist companies may be contracted to carry out installation and maintenance on irrigation equipment. PROBLEMS THAT MIGHT OCCUR WHEN MAINTAINING A GREEN ROOF Over fertilising of the green roof can cause weak elongated nitrogenous growth, measuring the fertiliser and only using it where needed will cut down on the possibility of this happening. Breakage of plants, care should be used at all times when maintaining the roofs, any broken stems, branches etc. should be pruned out correctly. Contractors usually have a general lack of understanding with regard to plants, it is difficult to avoid this problem, but if you are on site keep a close eye on the work you have done. Missing plants and plants pulled out by birds or frost lift. DISPOSING OF ORGANIC AND INORGANIC WASTE Companies have their own policies with regard to waste, generally it can be said that all green or organic waste should be composted where possible, or taken away to be composted, inorganic waste such as stones, concrete, cans etc. should be put into their respective re-cycling vessels, any dangerous waste such as asbestos, oils etc must be remove by specialist contractors. The method of maintaining hygiene on a green roof is to make sure you clear up at the end of the day/job making sure nothing is left behind that may cause injury to others or animals that have been enticed onto the green roof and putting waste into the correct bins (see above). The type of records required for management and legislative purposes are, Risk assessments Accident records Chemical records Machinery records Working at heights records It is importance to maintain these records as they may be needed for legal requirements at a later date. It is important to be able to identify a range of living organisms that may occupy a green roof, with this in mind look up a list of local vertebrates, invertebrates and wild flowers identifying about 50 if possible.
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GREEN ROOFS MAINTENANCE OF A GREEN ROOF Extensive roof maintenance - < 100mm low nutrition substrate Irrigation: Post-establishment, irrigation should not be required for most extensive green roofs, although the water storage capacity of the system and the plants’ water demands should be appropriately assessed. Fertilisation: Extensive green roofs typically have low nutrient requirements and are therefore often fertilized on an annual basis, each spring, using a slow-release fertiliser. Plant management: Removal of undesirable plant species and fallen leaves should take place twice each year General: Drainage outlets (including inspection chambers) and shingle/gravel perimeters to be cleared of vegetation, twice yearly
Biodiverse – very low to low nutrition substrate Irrigation: Typically not required Fertilisation: Generally not required, particularly where indigenous species are being encouraged to replicate native habitats. Whilst a low vegetative density is common, zero vegetation is generally undesirable Plant Management: A maintenance programme should be drawn up to follow the biodiversity hypothesis, ensuring that no materials are removed from the roof that may adversely affect the biodiversity potential of the roof General: Drainage outlets (with inspection chambers) and gravel/shingle perimeters should be inspected twice yearly and cleared of any living or dead vegetation
Semi intensive – 100mm to 200mm low to medium nutrition substrate Irrigation: Periodic irrigation is expected, depending upon the plant specification and the climatic and microclimatic conditions prevailing at roof level. Fertilisation: With a wider range of planting, using a more fertile growing medium, more regular fertilization is required. Plant management: Removal of undesirable vegetation on the greened area twice yearly. General: Drainage outlets (including inspection chambers) and shingle/gravel perimeters to be cleared of vegetation, twice yearly
Intensive – 200mm + medium nutrition substrates and top soils Irrigation: Regular irrigation is often required, subject to the plant specification and the climatic and microclimatic conditions prevailing at roof level. Fertilisation: With a wider range of planting, using a more fertile growing medium, more regular fertilization is required. Plant management: The intensive maintenance of lawns, hedges, borders etc is required on a regular basis, so as to maintain the roof aesthetics. Undesirable vegetation should be removed from the green areas at least twice yearly. Failed plants in excess of 5% of the plants installed should be replaced. General: Drainage outlets (including inspection chambers) and shingle/gravel perimeters to be cleared of vegetation, twice yearly. Where excessive substrate settlement has occurred, this should be replenished.
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Growing Green Skills
BIBLIOGRAPHY The Health and Safty Executive – 5 steps to risk assessment http://www.hse.gov.uk/pubns/indg163.pdf GRO Green Roof Code – Groundwork Sheffield, ISBN: 978-0-9568378-0-6
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GREEN ROOFS
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