This handy guide to everything you need to know to keep your lawn healthy was created by Lawnscience.
For further advice please email mark@lawnscience.co.uk.
What makes a great lawn?
Soil
Soil is really the foundation of your lawn, and the type of soil you have under your lawn will influence not only the quality of your lawn but will also dictate the type of treatments you need to apply to your lawn in order to keep it in good condition. The “soil structure pyramid” demonstrates how the main constituents of soil, i.e. clay, silt and sand combine to make up the various soil types.
In the UK there are five broad types of soil:
Peat based soils contain a high level of organic material due to the high acidity level slowing down decomposition. This soil can tend to retain water and may benefit from a drainage system. It also tends to contain low levels of nutrients, but if fertilised correctly can provide an excellent growing medium for turf.
Chalk based soils tend to contain stones of varying sizes and have the added disadvantage of drying out quickly in the summer. Normally alkaline, these soils tend to block trace elements such as manganese and iron. Lawns grown on chalky soils will require regular fertilisation due to leaching.
Loam based soils are perfect for the development of a quality lawn; normally rich in organic matter they tend to retain moisture and nutrients.
Sand based soils created by the breakdown of rocks they tend to drain rapidly drying out in sustained periods of warm weather. Fertilisers tend to leach through these soils creating the requirement for a regular fertilisation regime
Clay based soils are the opposite of sandy soils, containing very small amount of air spaces within their structure they tend to hold on to water and have a tendency to compaction.
Soil and PH
PH is the measure of the relative acidity or alkalinity or soil. In certain cases, it can have a significant effect on the quality of your lawn. It is measured on a scale of 1-14, 1 being highly acid, 7 being neutral and 14 being highly alkaline. Generally, peat-based soils tend to be acid whilst chalk based soils tend to be alkaline and clay soils tend to be neutral at around 7.
Lawns tend to favour soils with a PH of around 6-7 and in most gardens this is normal
A PH of 6.5 is the point where nitrogen, phosphorous, and potassium (N-P-K) and trace minerals are most easily available to grass in order to feed it
Soil and microbes
There are literally millions of microbes in the soil beneath your lawn and they supply an important service to your grass.
Their main role is to decompose organic materials such as roots and leaves, within the root zone, releasing previously organically bound Nitrogen and Phosphorous in an inorganic or mineral form which can be utilised by the roots of your grass. Lawnscience have available a series of soil conditioner treatment which can help stimulate microbial activity within your soil.
What your lawn needs to thrive
Lawns, like most plants require 3 things to thrive, light, water, and food. We’ll explore the importance of these three inputs below:
Light
Sufficient light is important to healthy grass growth. Without becoming too technical, a healthy grass plant needs a large, deep root system to prosper. To create a healthy root system the roots require carbohydrates which they cannot produce for themselves because they don’t contain chlorophyll. So the root system depends on the grass above the surface to supply it with carbohydrates.
Light falling on the grass above ground level, helps to achieve photosynthesis, which in turn produces carbohydrates. The more carbohydrates produced within the plant, the more are moved within the plant to the root system, creating healthy, deep roots. So simply put, poor light equals poor roots and poor roots equal weak grass. Now you understand why grass in shady areas tends to be weak and sparse, and quite often full of moss.
If you have grass in shady areas it may be possible to improve its chances of survival by over-seeding with a more shade tolerant variety.
Water
All plants need water to survive and grass is no exception. The amount of water a lawn needs depends on three main factors:-
The Climate
In warm periods grass can lose valuable water by evaporation and by transpiration. Evaporation is the water lost from the surface of the soil and as with most lawns the surface of the soil is hidden beneath the grass this tends to be limited. Transpiration is the water lost from the plant itself similar to a human sweating. The level of transpiration is determined by the relative humidity of the air, if it’s humid less water is lost, if it’s arid more water will be lost.
The type of grass
Different types of grass have difference rates of transpiration, this is more exaggerated in the USA where they have warm and cold season grasses, an issue we do not have in the UK.
The type of soil
Sandy soils have a poor water holding capacity and the water not utilised by the root system can quickly drain away. Clay soils tend to hold water on the surface in puddles which evaporates before it can reach the root system. Loam based soils tend to provide the best balance between allowing the soil to percolate down into the root area but holding onto it long enough for the roots to have time to capture it.
How often to water is best decided by looking at the grass itself. The first sign of lack of water will be the grass losing its springiness; this is the time when you should start watering. If water is not applied the grass will lose its bright green appearance and develop a grey-green hue, at this stage it’s really crying out for water and delay in watering will encourage the grass to turn yellow and eventually a pale straw colour.
It is better to give the lawn a good soaking, say down to a depth of 4 inches, once a week than to lightly water every day. Letting the grass dry out between watering will encourage air to enter the soil and encourage deeper rooting of the grass.
The best time to water is in the early morning before the sun is high in the sky. Watering during the day only leads to high evaporation levels and the grass missing out on some of the water. Watering in the evening reduces evaporation but tends to keep the grass canopy wet for long periods which encourages fungal disease.
Food or fertilisation
Grass is primarily composed of carbon, hydrogen and oxygen, these three elements being obtained from water and carbon dioxide in the air. It is generally accepted that there are an additional 14 mineral nutrients required for a healthy plant and these are obtained through the root system.
The main or “macronutrients” are Nitrogen (N), Phosphorus (P), and Potassium (K).
Nitrogen (N)
The element used in the greatest quantity by grass and a major part of any fertilisation program. Nitrogen is a component of many of the biochemical constituents of the plant and plays a key part in chlorophyll production. An indication of nitrogen deficiency is the yellowing of the grass, know as chlorosis. It also plays an important part in the growth process and therefore another indicator is the slowing down of the plant growth rate.
Phosphorous (P)
Plays a key role in many of the plant compounds that are essential for the growth of the plant. Its primary role is the storage and transfer of energy and without it normal development and growth cannot take place. A lack of Phosphorous will also have a impact on root development. On the other hand adequate phosphorous will promote disease and drought tolerance.
Potassium (K)
Plays a role in photosynthesis and carbohydrate production, but it main purpose is in plant stress and disease reduction. It also aids in the retention of water within the plant. Lawnscience provides a balanced fertilisation regime for your grass we amend our fertilisation programs depending on the season, weather and other relevant factors.
Grass
Quite often we tend to think of grass as just being grass, but there are many different varieties or species of grass and they each have differing characteristics. Your lawn will be made up of a mixture or blend of different grasses this is done to blend the different characteristics such as texture and colour it also gives the lawn a resistance to diseases. Differing types of grasses have different characteristics, below are some of the popular types used in lawns:-
Perennial Ryegrass (Lolium perenne)
A tufted grass is has a dark green appearance, good tolerance to wear and tear and requires a medium level of fertilisation. Normally a lawn will contain some Ryegrass as it provides a good strong base.
Chewing’s Fescue (Festuca rubra spp. Commutate)
A dense grass that grows in tufts has a medium green appearance, moderate tolerance to wear and requires low levels of fertilisation. One of its main characteristics is that it can survive very close cutting, down to 5mm and therefore is often used in mixtures for golf greens.
Brown top bent (Agrostis tenuis)
A creeping grass, producing slender stolons and rhizomes, these are shoots that run horizontally along the surface and just below the surface of the soil. Good tolerance to wear and requiring a medium to low level of fertilisation. Again, this grass can be mown very short at 5mm and is regularly used in quality lawns.
Seed blenders create different mixes of grasses to deal with differing circumstances. There are mixes for heavy wear areas, mixes for fine ornamental lawns, for utility lawns and for shady lawns.
Quite often lawns in shaded areas become quite weak, this may be because the mix of grass sown was not suitable for a shady area.
Weed control
Someone once defined a weed as “a plant growing where it was not wanted” so I suppose weeds are a personal issue. Some people don’t mind the odd weed in a lawn, some spend ages inspecting their lawns and removing every last one. But whatever your view in the long term if you are to have what is commonly regarded as a quality lawn weed control will need to be managed.
There are two approaches to weed control, physical removal and chemical management. Physical removal requires the complete removal of the plant root and all, which can be no mean feat as many weeds produce strong deep roots which tend to break up in the ground during removal. This makes the task all the more difficult as it is essential to remove all of the root, if not the root remaining can spawn new weed life and you are back to square one. Chemical removal is achieved by the application of a “selective” herbicide; these products attack weeds whilst leaving grasses unaffected. The way the work is by entering the weed plant and moving through the plant (translocating), they interfere with the hormonal balance of the plant impairing food movement within the weed and eventually the weed dies.
Disease and pest control
Lawns can get attacked by pests and diseases if preventative action is not taken to protect them. In the UK there are three pests and three diseases which cause the most problems.
Red Thread
Red thread infection can occur on all lawn grasses but is particularly common on ryegrasses and fescues. Mild, damp weather is favoured by this fungus, Laetisaria fucifrormis. Red Thread used to be prevalent on under fertilised lawns but recently we have noticed this fungal disease even on well fertilised lawns. Red Thread is quite easy to identify by the red shards that grow outwards from the leaf.
Fusarium
The most common UK lawn disease, caused by the fungus, microdochium nivale. Cool and wet conditions are favoured by this fungus and also grasses which are weak as a result of lack of nutrition. All UK grasses can succumb to fusarium patch but the disease is normally seen first in Poa annua due to its shallow rooting. Initial infections are small but these can rapidly enlarge. The disease can be recognised by the white or pink gossamer like mycelium on the leaf surface.
Rust
Rust can attack all UK lawn grasses but is particularly attracted to perennial ryegrass and Poa pratensis. It can occur throughout the year but is normally seen during early summer to late autumn during mild humid weather. Rust is easy to identify the affected grass appears rust coloured due to the spores present on the leaf.
Leatherjackets
During August/September you will normally see swarms of daddy long legs (Crane flies) bouncing about your lawn having hatched from their pupae state. 24 hours later the female lays her eggs in lawns, providing her young with a short-term food source. After a period of about two weeks the larvae hatch and start to feast on the roots of your lawn creating havoc. Normally the first signs of damage is disruption to the grass surface caused by birds attempting to make a meal of the feasting leatherjackets, other signs are a yellowing of the grass. Leatherjacket damage can be disastrous to a lawn and in some cases can completely destroy it. Protection against Leatherjacket attack is available from Lawnscience by applying a pesticide the insect can be killed before any damage is caused.
Chafer Grubbs
The garden chafer is the larval stage of the May Bug; they normally cause most damage to lawns in August and September in a similar way to the leatherjacket they feed off the plant roots. Normally healthy turf can suddenly wilt and die.
Worms
Worms are great for soil. They create large channels that encourage gas exchange and allow water and nutrients to penetrate deep into the soil. They also act as a little aerator benefitting the soil structure and they actually help to decompose thatch. However, they do cause problems when they surface, normally in the wetter winter months, they produce casts, which are little heaps of soil that have passed through the worm. These casts tend to smear on the lawns surface covering the grass beneath them and creating idea seeding ground for weeds and moss.
Moss control
Moss is one of the major problems with lawns and in England a regularly recurring issue. The reason why moss gets into a lawn is that for some reason the grass thins and creates a space within the lawn for moss to inhabit. The main reasons for the thinning of the lawn are:-
Compaction
High levels of thatch
Shade
Close mowing
Insufficient soil depth
The best way to manage moss is to make sure that it does not get the opportunity to infest the lawn in the first place; this can be achieved by maintaining a thick lush lawn. In order to achieve this we recommend the following approach to moss management:-
Correct mowing height
Mowing grass too short weakens the plant by reducing the leaf area which in turn reduces the amount of light taken up by the plant. There are some species of grass which can survive with close mowing; examples would be slender creeping red fescue, Chewings fescue and Broad top bent, these grasses can survive mowing to a level of 5mm. These grass types would be used in seed mixtures for golf greens because of their ability to survive close mowing, the problem is that most domestic lawns do not contain a high proportion of the types.
The mowing height also affects the depth of the root system, the deeper the roots the better the plant will deal with issues such as wear and tear, disease. For more information on mowing heights see the section on mowing below.
Regular scarification
Scarification is the process by which thatch is removed from the top surface of the lawn. Thatch is basically decomposing organic matter and the living roots, crowns and stems of the grass, which lays on the surface of your lawn forming a dense spongy mat. Excessive thatch can cause disease issues within lawns as it creates a good media for turf pathogens and insects to survive in. it also acts like a sponge absorbing moisture and preventing its movement to the root zone where it can be absorbed by the grass roots.
Depending on the condition of your lawn it may be advisable to over-seed your lawn after scarification, this process inserts new seed into your lawn creating a thicker more lush appearance.
Aeration
Over time lawns deteriorate as a result of soil compaction. Compaction is literally the squashing together of soil particles reducing the spaces between the soil particles. This affects the root development of the grass because there is little or no space for the roots to develop and also a reduced supply of oxygen, essential of healthy roots. The process of aeration improves the gas exchange between the soil and atmosphere, increases the rate at which thatch naturally breaks down. There are basically two types of aeration, solid tine and hollow tine. Solid tine aeration is achieved by driving solid tines into the lawns surface promoting gas exchange. Hollow tine removes a core of soil which has the added benefit of reducing compaction in the soil.