Shrubs

WHAT ARE SHRUBS AND TYPES OF SHRUBS

Shrub or bush is multiple stems, short height only 5- 10m or even 2m tall. Shrubs have no trunk. Some shrubs have trunk whose multiple stems grow close to ground level. Some shrubs are deciduous, they shed their leaves annually as per seasonal changes such as Hawthorn whereas some shrubs are evergreen in nature, for example Holly (llex).

Sub shrub: The kind of shrub whose size is less than 2m as Periwinkle (Vinca) and Lavender (Lavandula) are small garden varieties of rose.

The shrubbery is a style of pleasure-garden grown with creativity, keeping in mind designing of shrubbery border, selective height, flower and foliage color, and flowering season and leaf retention time.

Shrubbery Border

Shrubbery border is that particular area where shrubs are grown.  Shrubs are grown in row or in rectangular shaped pattern where partitions are done by using hedges.

Types of shrubbery borders

Single faced: Tall- Medium- Dwarf (Built at the corner of the garden).

Double faced: Dwarf- Medium- Tall- Medium Dwarf (Built in the middle of the garden).

Following are some points to be kept in mind before lying out shrubbery:

• Best results are achieved by planting shrubs towards south or east facing.
• An attractive and pleasing effect can be obtained by planting shrubbery in front of trees.
• The shades of trees should be avoided as far as possible to keep the shrubbery healthy.
• Taller height is required when shrubbery is away from the house and vice versa.

How to grow shrubs

Garden soils are highly preferred for growing shrubs. Soil amendments can be made by removing the top layer of soil up to 45 cm and again refilled with fertile soil. Height and rate of growth also depends on types of soils. Bougainvillea spp., Thevetia peruviana, Nerium indicum, Russelia equitifolia are salt tolerant shrubs.

Preparation of ground: Ground should be prepared at least 15 days before planting. Pits of 60 cm deep are prepared and then exposed to sun for at least 2 weeks. Pits are refilled with mixture of soil and farmyard manure (2-4 baskets per pit). Chlorpyriphos @ 5 ml/l of water should be mixed with soil to prevent attack by termites. Fill the pits 10-15  cm higher than general level to avoid the formation of depression after first irrigation.

Propagation of Shrubs

Two methods for growing shrubs

1) Sexual method

2) Asexual method

                  Sexual method

In this method shrubs are grown by using seeds. Using seeds is the inexpensive way to grow shrub masses. Many shrub seeds generate dormancy around them which help them to survive under unfavorable conditions as warmth of spring. For the germination from seeds it is required for the seeds to break their dormancy. So seeds are sown in autumn so that with chills of winter seeds become able to break their dormancy. Sometimes we break dormancy artificially. For this purpose we chit the hard coat using knife, nick the seed coat or sowing the seeds in warm water for 24 hours.

Keep in mind:

• Too much soaking can cause rotting of seeds

Many seeds have multiple coating; they only germinate in second spring after cold and warmth. Using warm and cold stratification methods as subjecting the seeds to warm spell followed by cold moist make the seeds to germinate in first spring after sowing .E.g. Fraxinus

Cold moist stratification

• Take a plastic bag filled with moist composted bark, coarse sand perlite or vermiculite, in equal parts, putt seeds in it and seal the bag
• Keep the bag in refrigerator below 5°C (40°F) for four to 20 weeks. Time period depends upon the type of seeds.
• Shake the bag periodically, if seeds are germinating sow them immediately

Warm moist stratification

• As in cold moist stratification method, putting all mixtures along with seeds in bag, keep it in a warm place at 18-24°C (65-75°F) for up to 12 weeks before giving a period of cold stratification

• Sowing the seeds in pots and place in heated propagation.

Requirement for asexual propagation:

Selection of seeds

Fully ripened seeds dry them and store in airtight containers.

Sowing Time 

June and July (rainy seasons).

 Time of planting the shrubs

Seedlings are transplanted in two seasons

Rainy season:  during July and August (for mass planting).

Summer Season: Feb and March.

Planting the shrubs is based on type of shrub

• Evergreen shrub: Feb-March & July-Aug.
• Winter deciduous: Jan-Feb (Before sprouting or in dormant phase).

Some common examples are- Stenolobium stans, Thevetia peruviana, Calliandra spp. etc.

PLANTING REQUIREMENTS OF SHRUBS / MAINTENANCE OF SHRUBS

Planting distance:  Based on height and spread of shrub.

For tall shrubs: Distance of 150-180cm. For more attractive look two or more shrubs can be planted together.

Medium shrubs: 90-120cm in front line 30vms away from inner edge. For graceful look they can be planted in groups 4-6 plants in length of 3.0-4.5 m.

Asexual method or Vegetative method ( Propagation of shrubs)

In this method plants are propagated using stems of existing shrub. The new plant will grow separately with separate root system. Shrubs can be grown by this method during Feb- March season if there is no hindrance of water supply otherwise rainy season is the best season to grow shrubs by vegetative method.

Following asexual methods are used to plant shrubs

1) Cutting method

From the outer branch of parent shrub, a healthy stems of size 15-20 cm is striped off with thicker end, treated with rooting hormone than buried pots or sand beds in selected place. They are generally grown in Feb and March. The shrubs propagated by cuttings are Hibisicusrosa-sinensis, Jasminum sambac, Hamelia patens, Cestrum diurnum, Cestrum nocturnum etc.

Cutting types to be taken

 Soft wood cutting

Cuttings are taken during July and Aug.

Size: 3-4 inches stem.

Some commonly grown cuttings are Plumbago capensis, Tecomacapensis, Durantagoldiana, Russeliajuncea, Pentascarnea etc.

Hardwood cutting

These stems are taken during fall and winter from mature stems, firm wood resists bending.

Size: 6-9 inches (pencil size thickness).

Evergreen shrubs- Planted during Feb-March and July-August (Hamelia patens, Dombeya spectabilis, Hibiscus rosa-sinensis are common examples).

Winter deciduous shrubs- Ideally planted during Jan-Feb such as Lagerstroemia indica, Lawsoniainermis, Punicagranatum.

Semi hardwood cutting

Theses cuttings are taken during summer season (July – Aug) from the shrub which is partially matured.

Size: 6-7 inches.

E.g: Ervatamia divaricate, Ervatamiacoronaria, Duranta variegate, Hibiscus rosa-sinensis, Nerium indicum, Malvaviscusarboreus tris tis, Cestrum nocturnum.

Soft Terminal cutting

Grown in July- august.

Size: 3-4 inches

Some commonly grown cuttings are Plumbago capensis, Tecomacapensis, Durantagoldiana, Russeliajuncea, Pentascarnea.

2) Layering

In layering method, all low hanging branches, located near the ground are selected. Here we use that section of shrub still attached to the parent plant and starts it new root system. Bark of 2.5-3.0 cm is removed and wrapped with moss grass or coco peat or with garden soil and sand mixture. Time they are propagated during mid-June to mid-July. S E.g; Calliandra callicarpa, Gardenia jasminoides, Ixora parviflora, Cassia biflora, Bougainvillea, Ixora sp, Jasminum multiflorum etc.

Types of layering

Simple layering

This technique is suitable for those plants which has low growing branches. Here

The flexible stems hanging near earth surface are selected. Bending theses stems and buried in soil keeping other branches and tips in vertical position. The bended part may be wounded from where roots will start growing to form a new plant. Egs. Climbing roses,forsythia, boxwood, azalea, wax myrtle.

Time of planting:

• Early spring: using dormant branches.
• Late summer: using mature branches.

Keep in mind:

• Monitoring periodically moisture content and root formation.

 

Tip layering

In this Technique, selecting any tip of shoot near to surface. Fixing these tips into holes of dept 4-5 inches. Here initially tip will grow downward than again start rising upward as like normal plants. Re curved tip will become new plant. When it has grown remove it and plant during early spring. Some of the common examples are: Purple and black raspberries, and trailing blackberries.

Compound layering

It is similar to simple layering. In Compound layering technique a single long flexible stem is selected. This stem to is buried into soil alternatively keeping one part exposed and other part buried into soil. Keeping one bud out of surface and one bud buried under the soil surface. Each lower side is wounded, will grow up with new roots and shoots to form several stems and branches. Plants like heart-leaf philodendron, pothos, wisteria, clematis, and grapes can be grown by this method.

Mound layering

This method is used for shrubs with heavy stems that grow close together. Here put a cut 1 inch on the stem, above the soil surface in dormant season. Dirt is mounded around the base of the shrub. When there is spring season new roots and shoots will start emerging at the base of young plant. Mount layering can be applied to grow apple rootstocks, spirea, quince, daphne, magnolia, and cotoneaster.

Air layering

This technique is applied on stems one foot from tip down to stem. Stems of pencil size or more are selected for air layering technique. Choosing that area on stem where bud is present and proving cut 3-4 inches above the bud area. For monocot plant 1-1/2 inches and for dicot plants 1 inches bark of ring is removed. Using knife put a cut on specific area. Keep the wound open. Soak moist, unfilled sphagnum moss in water squeeze it and apply it to wounded part of stem. Keep it fixed using plastic paper or silver foil. Pot the layers when new shoots start emerging from wounded part. Woody ornamentals plants such as azalea, camellia, magnolia, oleander, and holly can also be propagated by air layering.

Keep in mind

Moisture content should be monitored regularly

3) Division of root system

Time: July-Aug. Jasmine sambac, Russeliajuncea, Plumbago capensisets are some common examples.

Care and maintenance of shrubs

Watering: Immediate watering after planting is essential for the establishment of shrubs.

Filling of gaps: Weak or dead plants should be uprooted as soon as possible and replaced with the new plants.

Irrigation: Irrigation should be done at regular interval and depends on various factors like soil texture, season etc. Under Punjab condition,  irrigation is not required in rainy season. From September to march, irrigation should be done at monthly intervals. After that it should be done fortnightly.

Weeding: during rainy season, one or two weedings are required to keep the area weed free. After that occasional weeding should be done.

Pruning: Careful pruning involves cutting back the growth of shrubs to improve the performance of plants. Method of pruning and trimming depends on the form and age. All the superfluous growth, old or weak branches arte best cut at ground level or as low as possible without leaving the stub. Winter flowering shrubs e.g., Poinsettia pulcherrima, Holmskioldia spp. and Doembeyaspp etc. are pruned at the end of summer season whereas others are pruned at the end of the winter season.

Following are some examples of shrubs/ hedges grown regionally with flowering/ fruiting time throughout the year.

Specimen

Botanical Name	Region	Flowering time
Hibiscus rosa-sinensis	Tropical	Throughout year
Hamelia patens	Tropical	Throughout year

Shrubs for avenue

Botanical Name	Region	Flowering time
MurrayaPanniculata	Tropical	March-Oct
Bougainvillea sp.	Tropical	Throughout year

Tall ornamental hedges

Botanical Name	Region	Flowering time
Thujaorientalis (mor pankh)	Tropical	–
Nyctanthes arbor-tristis (harshingar)	Tropical	Sep-March
MurrayaPanniculata	Tropical	March-Oct

Dwarf ornamental hedges

Botanical Name	Region	Flowering time
Acalypha spp.	Tropical	Mar-June

Tall protective hedges

Botanical Name	Region	Flowering time
Euphorbia splendens	Tropical	Throughout year
Opuntia sp.	Tropical	March-April

Shrubs for rockeries

Botanical name	Region
Euonymus japonica	Temperate
Lantana sellowiana	Sub-Tropical
Thuja spp.	Sub-Temperate+ Tropical

Shrubs for moonlit gardening

Botanical Name	Region	Flowering time
Jasminum auriculatum	Tropical	March-Oct
Ervatamiacoronaria	Tropical	Throughout year
Jasminum sambac	Tropical	Mar-Oct
Murraya paniculate	Tropical	Mar-Oct
Gardenia jasminoides	Tropical	Mar-Oct
Nyctanthes arbor-tristis	Tropical	Sep-Mar

Shrubs with ornamental fruits

Botanical Name	Region	Flowering time
Euonymus japonica	Sub-Temperate	Winters
Durantaplumieri	Sub-Temperate	Oct-Nov