Introduction
The grass family contains over 5000 different species. Only a minority of these can be used for sports surfaces.
To assist with the identification of different grass species, a form of classification has been produced that is based on based on botanical features.
The scientific names of many turf grasses have been written in Latin and are based on a binomial system which was originally devised by the Swedish botanist Linnaeus in 1753.
Structure of the Grass Plant
The diagram above illustrates the various parts of the typical grass plant.
Stolons
The surface creeping stems are known as Stolons, and all plants that have them exhibit a stoloniferous mode of growth. The stems root at the nodes (a joint like section). They also produce foliage at these points, and if cut will produce a new individual plant.
Rhizomes
The underground stems are termed Rhizomes and turf grasses exhibiting these are termed rhizomatous. The stems occur at the base of the plant and bear scale leaves which produce rhizomes which will eventually reach the soil surface.
Growth Pattern
The grass growth pattern during the year is as follows:
October
Ground Temp below 18 deg. The roots are still dormant but some leaf growth takes place relying on stored carbohydrates.
November
Ground Temp above 18 deg. Good root development with good leaf growth.
December
Full development of the plant.
January
Full development of the plant.
February
Full development of the plant.
March
Temp dropping to 22deg and below. Root activity resumed as in November, and whatever damage was done in the warm months is repaired. Leaf growth is still sustained.
April
Root expansion stops as ground temperature drops below 18 deg although the roots are still actively absorbing water and nutrients. The leaf growth slows down.
May
Root expansion stops as ground temperature drops below 18 deg although the roots are still actively absorbing water and nutrients. The leaf growth slows down.
June
Ground temperatures are no longer significant. The leaf growth has virtually stopped, but the plant is still producing carbohydrates. The roots are still active.
July
Ground temperatures are no longer significant. The leaf growth has virtually stopped, but the plant is still producing carbohydrates. The roots are still active.
August
The roots are still active and continue to store Carbohydrates in the stems and bulbous roots. Vertical leaf growth Resumes.
September
The roots suddenly retract. This is known as Root Die Back. No hair roots are observed since the roots are inactive. Vertical leaf growth is increasing even in frosted areas. No carbohydrates are being produced.
Photosynthesis
Like humans, turf grass needs food to grow and maintain its life processes. Green plants are unique because they have the capability of manufacturing their own food from two simple raw materials, carbon dioxide and water.
These low energy compounds are built-up, or synthesised into an energy rich plant food sugar known as glucose (carbohydrate). This synthesis or “putting together” of plant food uses the radiant energy from the sun as its energy source (photos, light + synthesis, putting together).
The only other prerequisite for photosynthesis to occur is a green colouring matter known as chlorophyll. This material is directly responsible for giving grass its characteristic green colour.
CARBON DIOXIDE (CO2) + WATER (H2O) + SUNLIGHT = PHOTOSYNTHESIS.
When this process is completed the plant in turn releases OXYGEN back into the atmosphere.
An actively growing patch of grass measuring 15 x 15 metres releases enough OXYGEN to meet the needs of an average family of four every day.
Roots
In order to maintain vigorous growth in turf grass on a bowling green the root system must be able to absorb and provide a regular supply of nutrients to the leaves.
The root system will regulate its own size, depth, and density according to the following:
- The demand for nutrients.
- The supply of nutrients available in the soil around the roots.
A vigorously growing plant with a large leaf area needs all the nutrients it can possibly obtain. If the demand should diminish because the greenkeeper has reduced the mowing height to the extent that the leaf area does not require so much food then the root system will retract. This illustrates the relationship between the mowing height and the extent of the root development.
Other Factors that Influence the Size of the Root System
- The texture of the soil. The roots are there to absorb the processed fertilisers and will only reach down into the soil to a depth where the conversion of the fertilisers takes place, i.e. as far as the air can reach.
- Soil with larger particles will enable the water and air to penetrate deeper than in finer textured clayey soils.
Sandy soils = Deep roots.
Clay soils = Shallow roots.The greenkeeper must encourage the deepest root system possible, considering the soil conditions and should not actively do anything that will inhibit or retard maximum root growth.
The diagram above illustrates the difference between shallow and deep root growth. Should the root growth be shallow then the following problems are likely to occur:
- Heat scald can take place.
- Compaction will reduce root growth.
- Fungi, disease and pest can cause a reduction in growth.