- Plant material is a very important component of landscape development, and planting design is integral to any landscape plan.
- Designing with plants requires awareness and knowledge of a broad range of aspects including ecology, botany, horticulture, aesthetic value, growth and survival, and use of plants to address environmental and ecological concerns.
1) Plant Material
- The major sets of factors that influence the choice of plant material are related to the characteristics, both botanical and physical of plant material and the context in which the plant material is to be used.
- The inter relationship of these sets of factors is the basis for developing a sound approach to the process of designing with plants.
i) Physical and Botanical Characteristics of Plant Material
- The information on plant material should be available in a systematic format to include definition, significance and design implications of the following aspects:
- Nomenclature (botanical and trade name);
- Origin, family and natural habitat;
- Growth characteristic and form as a function of habit;
- Physical characteristics, for example, bark texture, foliage, etc;
- Propagation and maintenance; and
- Use in landscape design.
ii) Vegetation Types (Evergreen and Deciduous)
- Some examples of the functional implications of using evergreen and deciduous plant material for specific situations are:
a) Evergreen trees
- For places requiring shade throughout the year,
- For strong visual screening,
- As part of windbreak or shelter planting, and
- For areas where leaf litter is to be discouraged.
b) Deciduous trees
- For greater visual variety,
- As partial visual barrier,
- For areas where under-planting is to be encouraged (for example, grass),
- For emphasis on branching and flowering pattern, and
- For areas where shade is not required throughout the year.
iii) Growth Rate and Age of the Vegetation
- Growth rate is directly related to the life-span of a tree and slower growing trees have a life-span extending to hundreds of years. The fast growing trees to the exclusion of slower growing varieties is not recommended. Landscapes are developed to sustain future generations; slow growing long lived native trees shall be emphatically included in all major planting schemes, specially those related to institutional campuses and large urban development. However, fast growing species have a limited role, and are appropriate in situations, where,
- quick effects are required, for example, in shelterbelts;
- immediate results with regards to stabilization of soil, etc are necessary, for example, in soil conservation schemes; and
- used as .nurse to protect slower growing sensitive species, when necessary. The slower growing species would generally be appropriate in situations where sustained environmental benefits are required such as roadside planting, campuses, townships, industrial areas, and other public landscapes.
iv) Growth Habits of Various Kinds of Vegetation and their Form
- The overall physical form of a plant is usually the result of the foliage density and branching pattern.
- It may also be expressed as the proportionate relations between height and canopy spread.
- The latter is direct expression of growth habit.
- A number of classifications of tree by their overall form exist, but it is almost impossible to have a variety according to regional conditions.
- The following classification into basic types may be useful:
a) Trees of fastigiated or columnar habit .
- Examples of trees of this type are:
- Casuarina equisitifolia (Beet-wood)
- Grevillea robusta (Silver oak)
- Polyathia longifolia (Ashok)
- Populus species (Poplar)
- Though the branching pattern of each is different, the overall shape is similar.
b) Tall trees with broad canopy .
- Examples of trees of this type are:
- Dalbergia sissoo (Sheesham)
- Tamarindus indica (Imli)
- Terminalia arjuna (Arjun)
- The canopy shape does not fit into any specific geometrical category.
c) Trees of spreading habit .
- Examples of trees of this type are:
- Delonix regia (Gulmohar)
- Lagerstromia flosreginae (Pride of India)
- Pithecolobium saman (Rain tree)
- Though these trees vary greatly in size, their basic form is similar.
d) Trees of weeping habit .
- Examples of trees of this type are:
- Callistemon lanceolatus (Bottle brush)
- Salix babylonica (Weeping willow)
- The above classification is helpful in choosing various combinations of the above types to achieve desired function and visual objectives.
v) Foliage Characteristics of Plant Material
- Visual effects imparted by vegetation, for example the perceived visual textures of plant forms depend on:
a) Leaf size and shape . Examples of plants with large leaves and bold foliage texture are:
- Neolamarckia cadamba (Kadam)
- Ficus lyrata (Fig)
- Plumeria acutifolia (Temple tree)
- Pterospermum acerifolium (Kanak champa)
- Leaf shape can also determine the appearance of the foliage of the plant, as for example:
- Callistemon lanceolatus (Bottle brush) . Narrow leaves giving a feathery appearance
- Polyalthia longifolia (Ashok) . Long narrow leaves
- Salix babylonica (Weeping willow) . Narrow leaves giving a feathery appearance
b) Leaf texture .
- The textural appearance of a plant is the result of the play of light and shade on the foliage. Plants with larger leaves generally appear bolder in texture than smaller leaves plants as the areas of light and shade are larger and therefore more clearly differentiated.
c) Leaf and foliage colour .
- Most trees in India have foliage in varying shades of green with variations in colour at the time of leaf fall and at the period when the tree is newly in leaf, when the leaves are fresh and much lighter in colour. Examples are:
- Lagerstroemia speciosa (Jarul) . Leaves acquire reddish tinge before falling
- Polyalthia longifolia (Ashok), Delonix regia (Gulmohar), Erythrina indica (India coral tree), etc . Leaves turn yellow before falling
- Ficus infectoria (Pilkhan), Mangifera indica (Mango) etc. . Young leaves have reddish tinge
d) Foliage density and distribution.
- An important consideration is the way in which particular kinds of vegetation are perceived. Tree masses are usually seen from greater distance than shrub areas; foliage texture of different distinctive kinds of trees growing together has to be markedly distinctive for individual species to be recognizably apparent. In shrub areas subtle differences in foliage texture may suffice for creating the required visual effect.
2) Flowering Characteristics of Plant Material
- Important considerations while identifying plant material according to flowering characteristics are as follows:
- Density and distribution of flowers on the plant,
- Botanical characteristics of flowers (for example, single/cluster, etc),
- Colour, and
- Presence or absence of foliage during flowering period.
- For the purpose of understanding the visual effect of flowers, tree species may be divided into two types:
- Trees on which flowers appear in profusion and therefore have a very strong visual impact, for example, Delonix regia, Cassia fistula, Lagerstroemia flosreginae.
- Those on which flowers are less profuse, or perhaps last for a shorter period and visual impact is more subtle, for example, Thespesia, etc.
- Aromatic/Non aromatic . for example, Plumeria An additional consideration when choosing shrubs for their flowering quality is the visual appearance of the flowers themselves, as shrubs are usually seen from quite close. Distinctive flowers are those of, i) Beleperone guttata (Shrimp plant), ii) Hibiscus rosa-sinensis (Clinex hibiscus), iii) Jasminum sambac (Chameli), iv) Tabernaemontana coronaria (Cape jasmine), v) Thevetia peruviana (Yellow oleander)
- The olfactory characteristics, that is, odour, of flowers may be an added benefit of flowering plants. Flowers with distinctive scent include those of Nyctanthes arbor-tristis (Har-singar), Jasminum pubescens (Chameli), Cestrum nocturnum (Raat ki rani), etc.
- Flowering characteristics of plant material may be classified as per the following format:
3) Growth Requirement of Plant Material
- Information about growth requirements of plant material applicable in landscape design pertains to the ability of particular plants to survive in specific environmental situations. These environmental conditions may arise from a number of aspects as given below.
- Capacity of plants to grow in cultivated situations is related to the environmental conditions obtaining in their natural habitat.
i) Soil conditions
- Physical as well as chemical properties of the available soil are important. These may or may not be amenable to change, they would therefore affect the choice of plant material considerably. Physical properties include consideration of light (for example, sandy) and heavy (for example, clayey) soils, and their structure. Chemical properties pertain to the presence or absence of nutrients and salts; soil, alkalinity or acidity. A preliminary soil analysis is essential for implementing effective planting schemes.
ii) Availability and quality of water
- The water requirement may be derived by data of humidity and rainfall of plants. natural habitat. The water table of the area where the plantation is to be done has a crucial bearing on the design with plants as well as a financial implication for reduced maintenance if planted appropriately.
iii) Availability of sunlight
- The growth rate of plants is directly related to sunlight requirement and availability; such as plants that require:
- (a) full sunlight; (b) partial sunlight; (c) predominantly shade; and (d) complete shade.
iv) Quality of air
- Growth may be affected by chemical pollutants, such as sulphur dioxide or physical pollution such as dust. Certain plants have the ability to withstand pollution, such plants are imperative for industrial areas, roads, highways, etc.
- The success of a designed landscape depends upon the growth of vegetation over an extended period of time; therefore maintenance of landscape is also a design component. Maintenance needs and practices in any given situation arise out of the inter-relationship between the growth requirements of plant material chosen and the environmental conditions existing on site. The likely degree of maintenance should be assessed based on the following:
- Scale of the design project,
- Financial and manpower resource,
- Availability of manures,
- Future intensity of site, and
- Environmental conditions.
- In small scale projects, such as gardens and small parks, the natural environmental conditions can be changed and maintained by management practices such as irrigation and application of fertilizers. The choice of plant species is therefore not very strictly limited by the existing environmental conditions. On larger scale schemes, such as very large parks, campuses and townships, this kind of intensive maintenance may not be possible. The process of choosing plants shall therefore respond to the existing environmental conditions, and also in such cases the choice of plant material is restricted by these conditions and suitable species become limited. The type of treatment adopted, as given below, may also serve as a guide to the degree of maintenance required: