Growth Habit Adaptations

Question 1

Why do plants have different growth forms?

Answer 1

A plant’s growth form is an adaptation to survival within a particular environment

Question 2

Why do we need to know growth forms?

Answer 2

to make an impact, to improve biodiversity. Using these different plant forms and combining them is a key
element in planting design.

fundamental to the habitat-building needed for biodiversity, as nature
needs the different layers provided by trees, shrubs, climbers and perennials.

Question 3

Growth form for Berberis darwinii

Answer 3

Accept the showy flowers and multi stemmed base. Fills in the space well.

Question 4

Growth form for Salix alba

Answer 4

Coppicing for colour of stems in winter.

Manipulation

Question 5

Evergreen variations in leaf size

Answer 5

LARGE LEAFED EVERGREENS: typically a strong dark green, packed full of chlorophyll to make the most of low light levels on the woodland floor. Not sun tolerant

SMALLER FOLIAGE: more typical of drought prone habitats. These are plants that can deal with exposed conditions.

Question 6

Why is regeneration important for growth habit?

Answer 6

The ability to regenerate and to produce lots of new branches after being cut, are factors that have made certain shrubs or trees very important for hedging and similar effects.

Shrubs you can hard cut to reshape/regenerate. Some trees (Tilia cordata LIME) it grows suckers which usually are trimmed. However, eventually a ring of trees will form around original and regenerate.

Question 7

Hedging for growth habit

Answer 7

species that can be clipped and which form dense twiggy growth in response to that clipping. Yew (Taxus baccata) and Box (Buxus sempervirens) are the classic examples for high quality hedging.

deciduous trees and shrubs have been used as well, particularly Beech
(Fagus sylvatica) and Hornbeam (Carpinus betulus), which if frequently cut, hang on to their leaves during the winter.
This is because their juvenile growth typically does this, and by continually cutting, we are keeping the foliage in that juvenile state. It all falls off in the spring when the new leaves grow, but the fact that the leaves hang on during the winter prevents the hedge from being completely see-through.

Question 8

Hedge examples

Answer 8

EVERGREEN: Taxus bacatta and buxus sempervirens.

DECIDUOUS: Beech (Fagus sylvatica) and Hornbeam (Carpinus betulus)

Question 9

Define Pleaching

Answer 9

variation on hedging, whereby you keep trunks up to a particular height,
and then having “a hedge on stilts”.

It is a way of having a screen at a particular height. Hornbeam can be used for this. However, more usually it is various varieties of lime (Tilia species).

Question 10

What is a subshrub and why is it different?

Answer 10

Will not take hard pruning.

Attractive, low growing EG

Woody, persistent above ground growth.

typical of Mediterraneantype habitats, where fire is a particular part of the ecology. Most of these species
regenerate rapidly from seed after fire.

Lavender, salvia, thyme

Question 11

What are clonal shrubs?

Answer 11

particularly members of the Ericaceae, the heather family), which are long-lived, and in many cases clonal.

tend to be plants of poor acidic soils that are able to form dense, long-lived
colonies. They are virtually all evergreen.

with very small leaves
closely pressed to the stem. These are very good reducing water loss in a very exposed windy environment.
Other clonal evergreens, such as this Pachysandra terminalis, are extremely useful for ground cover, particularly in shade.

Question 12

Perennial growth patterns

Answer 12

good spreaders. This Geranium x
oxonianum is a particularly good one. It has a long flowering season and a great ability to get a little bit bigger every year

Other perennials we grow more for more dramatic impact. These are tighter clumpforming plants.

Agastache foeniculum, a short-lived perennial. It will live for a number of years and unless it seeds around in your garden will die after that time.

Question 13

What are cushion plants (alpine)?

Answer 13

Not truly herbaceous because they have persistent above ground growth, but non-woody. They are very typically plants of alpine environments and therefore low growing with little stem growth.

Good for roof gardens.

Silene acaulis

Question 14

What is a cespitose grass?

Answer 14

Tight, clump forming grass that reaches a certain size and remains there.

Calamagrostis brachytricha

Question 15

What is a clump forming grass?

Answer 15

May start of tight and then slowly spread over 2-3 years.

Spreads steadily, dense growth, mat forming.

Carex pennsylvanica

Question 16

What is turf (sod)?

Answer 16

Rapidly spread through tillers/rhizomes. May be invasive.

Question 17

Ground cover plants

Answer 17

Vinca spp.
Erica cinerea (heather moorland)
Bergenia spp.

Ability to cover the ground with EG foliage.
Vigorous spreading rhizomes

Question 18

Example of a woody ground cover

Answer 18

Pachysandra terminalis

Tech. a shrub, spreads via rhizomes but low cover.

Question 19

What are some good green roof plants?

Answer 19

Saxifraga, Androsace or Raoulia

Question 20

What is a PROSTRATE WOODY Plant?

Answer 20

Branches that grow almost horizontally forming a dense carpet. Can be either Dec. broadleaf (willows) or Conifers (Mostly juniper).

Once popular groundcover for large scale but dull to look at and not biodiverse.

Question 21

Why are Evergreens mostly a conical shape?

Answer 21

EG’s have adapted to avoid the branches breaking due to heavy snow.

Question 22

Define fastigiate?

Answer 22

Tall and narrow trees, good in limited space.

Populus nigra ‘Italica’ or
Prunus ‘Amanagowa’

Question 23

Define Pendant shape tree

Answer 23

Weeping willow
Salix babylonica

Question 24

What is a multi-stem tree?

Answer 24

Good for confined space. Small but branches out

Acer palmatum

Question 25

What is pollarding?

Answer 25

Cut above 2-3 meters for basket weaving or to reduce plant sizes. Salix alba

Question 26

What is coppicing?

Answer 26

Cut at base of plant for either basket weaving or often to reduce plant size and especially foliage effects.

Salix alba (red stems in winter)

Question 27

Are there any trees that don’t need trimming for a hedge?

Answer 27

Thuya occidentalis ‘Emerald Green’

Eventually may need trimming but will grow slowly and well

Question 28

Advantages of shrubs for gardens?

Answer 28

Vital for screening,
Create visual mass
Source of flower/fruit for biodiversity
CAN be hard pruned to regen from base

Pruning reduces flowering

Prune lower branches to produce more interesting space and the opportunity to plant below.

Question 29

Topiary needs

Answer 29

Evergreen with tight branching pattern
Buxus sempervirens
Taxus bacatta

Question 30

What is growth adaptation?

Answer 30

Different plant growth forms adapation to enable plants to survive and compete effectively in different environments.

Understanding relationship between form and environment is crucial in making appropriate plant selection and managing appropriately.

It’s important to spot the adaptation and make the most of it for the garden.

Question 31

What are the growth adaptations?

Answer 31

Low to ground (alpines)
Herb. Perrenial
Perennial (EG, Deciduous)
Subshrubs
Trees/shrubs/climbers

Question 32

What is a geophyte?

Answer 32

Perennial that dies down which includes bulbs, corms etc. A plant with underground storage organs.

Question 33

Why are herbaceous plants important?

Answer 33

Annual/biennial produce many seeds.
Visually impressive
New shoots - rhizomes are CLONES

Question 34

IS Piet Oudolf style good for biodiversity?

Answer 34

Yes as seed heads, but without woody everything dies back and biodiversity is lost as habitat is lost.

Question 35

Are climbers good ?

Answer 35

Persistent growth
WEAK: Clematis or Lonicera
STRONG: Hedera Helix or Ilex aquifolium

In wild climbers can damage trees. In gardens usually grown on house (good insulation) or pergola.

Important to understand growth patterns to give the right size plant for the pergola.

Question 36

How is growth habitat integrated into horticulture?

Answer 36

1. Forms and longevity and spread are important decision on selection and maintenance.
2. Design gardens with different plant forms. Be sure to integrate a variety - good visually and biodiversity.
3. Understanding growth habits enables species to be chosen to fulfill functional uses of groundcover, screening, rain gardens, green roof etc.

Question 37

List some Warm-climate non-woody plants with persistent growth

Answer 37

Agave
Aloe
Yucca
Cacti

No secondary growth. Non woody, but continue to grow.

Question 38

List THREE characteristics common to all subshrubs. Give THREE name examples of species often used in gardens and designed landscapes.

Answer 38

a. CHARACTERISTICS:
a.i. Limited growth size
a.ii. Evergreen
a.iii. Often grow in poor soil and cannot take hard pruning.

b. EXAMPLES:
b.i. Lavandula angustifolia
b.ii. Salvia rosmarinus
b.iii. Erica cinerea

Question 39

List THREE common plants frequently used for hedging. Outline their basic characteristics which make them good hedge plants.

Answer 39

a. Buxus sempervirens: Common Box has tight branching pattern of leaves which will be tightly compacted and evergreen leaves.
b. Fagus sylvatica: Beech is a deciduous dense plant that will showcase a variety of colours throughout the season., specify dead leaves hanging on in winter as a useful feature.
c. Taxus baccata: Yew. An alternative for Buxus sempervirens. (The size difference between the two rather limits this comparison.)

Evergreen tightly branched plant that does well being trimmed into topiaries. Tolerates alkaline soil.

Question 40

What is a cushion plant? What environments are they typically from? And where would they traditionally be grown in the garden?

Answer 40

a. A cushion plant is a low growing plant that can withstand strong winds, intense sun and reduced soil depth. It has persistent growth with minimal stems, rosettes of leaves and a rounded cushion type habit.
b. Cushion plants are considered an Alpine plant.
c. Traditionally alpine plants were found in rock gardens; however they are now considered good plants for green roofs as they are low growing and can withstand the harsh environments.

Question 41

What is coppicing? Name one species where coppicing is useful in horticulture.

Answer 41

a. Coppicing is the horticultural technique of cutting a shrub down to the ground to regenerate growth.
b. Coppicing is often done to keep a plant size down, provide willow stems for basket weaving or most often for the winter beauty of the juvenile red stems.
c. Example: Salix alba

Question 42

Being evergreen allows a plant to photosynthesize all year round? What are TWO other advantages for the plant. And what are some of the advantages for the gardener and garden owner?

Answer 42

a. ADVANTAGES FOR THE PLANT:
a.i. The plant does not need to waste energy regenerating leaves in the spring after a harsh winter.
a.ii. The leaves on the plant are reduced in size (needles) to reduce water loss small leaves often are evergreen but this does not really answer the question -
evergeen leaves often unattractive for animals to eat
b. ADVANTAGES FOR THE GARDENER/GARDEN OWNER
b.i. GARDEN OWNER: Colour, beauty, privacy and shading year round.
b.ii. GARDENER: Reduced maintenance as leaves are not dropping

Question 43

Name and briefly describe two habitats where there are many evergreen species.

Answer 43

a. Harsh winter/treeline or moorland locations. Heavy snow, wind and cold temperature.
b. Subtropical broad leaved evergreen trees are found mostly in lower latitudes

Question 44

A hot dry site is one where we will want drought-tolerant plants. The summers brought about by climate change will exacerbate the stress plants face. Describe how you might choose plants for such a situation. What type of plants will you choose? Provide at least FOUR named examples. How will you expect the planting to develop over a ten-year period? If you were doing this for a client, what information would you provide them for the longer-term management?

Answer 44

a. Plants would need to be drought tolerant: You could say a little bit more about the plant categories likely to dominate: sub.shrubs. evergreens, grasses, their origin (eg. Mediterranean, steppe) being a good guide for suitability.
a.i. Silver/Grey colour subshrub with long narrow leaves. Lavandula angustifolia
a.ii. Perennial Evergreen: Ceanothus arboreus
a.iii. Grasses: Festuca californica
a.iv. Succulents: Agave americana
b. Over a 10-year period I would expect the subshrub – Lavandula angustifolia would need replacing as their lifespan is approximately 10 years. The Agave americana would continue to grow and would most likely need nothing. The Festuca californica would grow to its maximum size and would likely need cutting back early in the spring each year. The Ceanothus arboreus would need trimming to keep the shape. This does not follow, whats wrong with their natural shape?
c. The upkeep of the garden would be minimal.