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Horticulture

Shrubs

Shrubs are defined as woody, semiwoody or herbaceous perennial plants, branches arise from the base of the plants, and grow up to a height of about 0.5 to 4 metres. The plants are usually erect and bushy. Most of the shrubs are very hardy, require little attention and grow in all types of soil. Although some plants flower almost throughout the year, in most cases it is seasonal and selection can be made in such a way that some plants flower almost throughout the year, in most cases it is seasonal and selection can be made in such a way that some plants in the shrubbery will be in bloom in different seasons of the year. Shrubs flower regularly every year and produce flower of almost all the important colours-white, light yellow, golden-yellow, pink, scarlet, salmon, crimson, rose, violet, light blue, deep blue and some are sweet scented.

According to the requirement of sunlight for growth and flowering, shrubs can be classified into three groups:

  • Show normal growth and flowering in full sun.
  • Grow only in partial shade.
  • Can grow well both in sun and semishade.

Most of the tropical flowering plants are sun loving and growth and flowering are greatly affected by shade and it is also observed that lack of morning sun shows much more adverse effect than the afternoon sun. Plants like Magnolia mutabilis, M.pumila, M.fuscata, species of Pentas, Olea fragrans. In full sun these plants show signs of scorching during the hot weather and do not thrive. Shrubs show great variation in height, tall shrubs usually reach a height of 3 to 4 meters and dwarf shrubs grow only up to 0.4 to 1 meter and thus plants can be chosen from a large selection for growing in various places according to their suitability and utility. In addition to their utility as flowering plants, shrubs are also used for hedges and screening. Acalyphas from the most colourful hedge, Dodonia viscosa, Duranta plumerii, Clerodendron inerme are usually grown as hedge plants. They are quick growing plants and stand severe and frequent pruning. Hibiscus rosa-sinensis, lxora chinensis, Bougainvillea, Barleria, Jasminum pubescens and Murraya exotica are also used as hedge plants and produce showy flowers. Cesturm, Bougainvillea, Jasminum pubescens, Murraya exotica, Jacquinia ruscifolia can be grown for screening. Hardy dwarf shrubs like Lantana depressa, L.sellowiana, Russelia, Euphorbia splendens, Gardenia fortunei, Vinca rosea, Turnera etc. are usually grown in rockery to add colour and also Adenium, Jatropha podagrica to break the monotony of succulents.

Selection, planting and cultivation of shrubs

Selection of shrubs depends on availability and duration of sunlight at the site of planting, maximum height and spread of the plant, utility of plants i.e. foliage or flower, deciduous or evergreen and colour of flowers and season of flowering. It is always safe to plant shrubs during early monsoon. In the next two to three months of rains it will not only establish in the soil but will also start new growth and such plants thrive much better in the hot months of the year. Except hydrophytes garden plants are very susceptible to water logging and well-drained site should always be selected. Waterlogging for few days or very wet soil grown plant cannot be obtained in such a place.

In gardens, shrubs are usually planted in three ways

    1. In the form of shrubbery, on a long strip of land where taller shrubs are grown at the back, those with medium height in the middle and dwarf ones at the front. In this design upper portions of all the plants in the shrubbery bearing flowers become clearly visible. Colour of flowers and time of flowering are also considered so that the shrubbery remains colourful throughout the year with bloom and foliage.
    2. In small garden or to break monotony of open space shrubs are often grown in-groups and in this case few plants of the same variety or of different species are selected.
    3. Shrubs are also grown as a specimen plant or in only one row along the border of the garden or a wall.

In order to give a brighter appearance in the rockery dwarf and hardy shrubs are also planted. Distance of planting in a shrubbery depends on a size of the plants. Tall and bushy shrubs are generally planted at a distance of 1.5 to 2.5 ms. Shorter plants with less spreading habit can be grown at a distance of 0.5 to 1.5metre. Shrubs are watered in winter and more frequently in summer; slight wilting due to dry soil may cause defoliation and affect the growth of the plant. It is always advised to give thorough soaking to all plants then to sprinkle every day. Soaking of only surface soil encourages production of shallow root system, which not only prevents utilisation of nutrient from lower level of the soil but also makes the plant more susceptible to drought. Shrubs should be manured during the rainy season. Well decomposed farm yard manure can be dug in around the root region; use of bone meal or hoof and horn meal once or twice a year also shows excellent result.

Description and cultivation

Acalypha: (Euphorbiaceae) Eng. – Copperleaf

Acalyhpa are colourful foliage shrubs used for many purposes. Most of the species are varieties have colourful shrubbery. These do best in full sun while in partial shade, growth is affected and colour becomes less attractive.

Clearodendron macrosiphon

It is very free flowering dwarf shrub 1.0 high and produced mass of white flowers in several flushes during summer and rains. C.macrosiphon should be grown in the front row of a shrubbery. Propagated by cutting or layering.

Duranta plumeri (Verbenaceae)

Tall much branches shrub with axillary spines, about 2.5 to 3.0m high.

Var.: Alba – flowers white.

Var.: Variegata – flowers blue, foliage variegated.

It is usually grown as hedge and forms an impenetrable barrier.

Fortunella japonica (Rutaceae)

Tall handsome ornamental plant when in fruit, reaches a height of 2.4m. Flowers small, scented. Flowers usually appear in the early rains and the fruits turn yellow in winter. It is very easy to grow and likes full sun. Propagation by air layering.

Hibiscus (Malvaceae)

These are the most useful flowering shrubs in Indian gardens. For species, H.mutabilis, H. schizopetalous, H.collinus and the varieties of H. rosa-sinensis are commonly grown in tropical gardens.

Pink flowers

Ixora chinensis var: Rosea. A plant about 1.4m high. Flowers pale pink becoming reddish in age.

Ixora rugosula – Compact growing habit with small crowded bunches of flowers, deep pink in colour.

Scarlet flowers

Ixora coccinea – A compact shrub about 1.5m tall. Flowers deep scarlet.

Ixora chinensis – A small shrub about 1.5m high.

White flowers

Ixora barbata – A large shrub about 3m or more. Flowers white.

Ixora undulata – A large evergreen shrub. Flowers white, sweet scented.

Lawsonia inerme (Lythraceae)

Tall, often growing up to 3.6 to 4.6m.

Var: Alba – petals light yellow

Var: Rubra – petals rose on light green sepal.

Both the varieties grow tall and appear to be small trees with stout woody stem. Crown is much branched and spreading and bears large panicle of numerous small flowers in the summer and rains. Propagation by seed and cutting. Lawsonia is usually grown as hedge.

Changeable rose-Hibiscus mutabilis

Hibiscus mutabilis is a large perennial shrub with only a few straight branches. The green branches become woody with age and then the plant acquires the look of a small tree. In the early cold weather the plant produces single or double white flowers (10-12cms in diameter) that change to pink in the course of the day. Hibiscus mutabilis, commonly called the ‘changeable rose’ comes from South China. In the US the plant is known as the ‘confederate rose’ or the ‘cotton rose’.

The plant prefers high humidity and a porous soil. It is host to some troublesome insects like scales and aphids. Manual removal of insects, though cumbersome, is a better method to maintain the health of the plant. Proper trimming after flowering is recommended for a second flush of flowering and to keep the plant in shape during the non-flowering season. The plant is propagated through seeds and cuttings. Seed raised plants have a tenacity to produce only single flowers. Being a large shrub with a good number of showy flowers, Hibiscus mutabilis is space filler and a colourful plant for the last row of a mixed shrubbery.