Growth Habit Adaptations Flashcards
Why do plants have different growth forms?
A plant’s growth form is an adaptation to survival within a particular environment
Why do we need to know growth forms?
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.
Growth form for Berberis darwinii
Accept the showy flowers and multi stemmed base. Fills in the space well.
Growth form for Salix alba
Coppicing for colour of stems in winter.
Manipulation
Evergreen variations in leaf size
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.
Why is regeneration important for growth habit?
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.
Hedging for growth habit
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.
Hedge examples
EVERGREEN: Taxus bacatta and buxus sempervirens.
DECIDUOUS: Beech (Fagus sylvatica) and Hornbeam (Carpinus betulus)
Define Pleaching
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).
What is a subshrub and why is it different?
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
What are clonal shrubs?
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.
Perennial growth patterns
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.
What are cushion plants (alpine)?
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
What is a cespitose grass?
Tight, clump forming grass that reaches a certain size and remains there.
Calamagrostis brachytricha
What is a clump forming grass?
May start of tight and then slowly spread over 2-3 years.
Spreads steadily, dense growth, mat forming.
Carex pennsylvanica
What is turf (sod)?
Rapidly spread through tillers/rhizomes. May be invasive.
Ground cover plants
Vinca spp.
Erica cinerea (heather moorland)
Bergenia spp.
Ability to cover the ground with EG foliage.
Vigorous spreading rhizomes
Example of a woody ground cover
Pachysandra terminalis
Tech. a shrub, spreads via rhizomes but low cover.
What are some good green roof plants?
Saxifraga, Androsace or Raoulia
What is a PROSTRATE WOODY Plant?
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.
Why are Evergreens mostly a conical shape?
EG’s have adapted to avoid the branches breaking due to heavy snow.
Define fastigiate?
Tall and narrow trees, good in limited space.
Populus nigra ‘Italica’ or
Prunus ‘Amanagowa’
Define Pendant shape tree
Weeping willow
Salix babylonica
What is a multi-stem tree?
Good for confined space. Small but branches out
Acer palmatum
What is pollarding?
Cut above 2-3 meters for basket weaving or to reduce plant sizes. Salix alba
What is coppicing?
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)
Are there any trees that don’t need trimming for a hedge?
Thuya occidentalis ‘Emerald Green’
Eventually may need trimming but will grow slowly and well
Advantages of shrubs for gardens?
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.
Topiary needs
Evergreen with tight branching pattern
Buxus sempervirens
Taxus bacatta
What is growth adaptation?
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.
What are the growth adaptations?
Low to ground (alpines)
Herb. Perrenial
Perennial (EG, Deciduous)
Subshrubs
Trees/shrubs/climbers
What is a geophyte?
Perennial that dies down which includes bulbs, corms etc. A plant with underground storage organs.
Why are herbaceous plants important?
Annual/biennial produce many seeds.
Visually impressive
New shoots - rhizomes are CLONES
IS Piet Oudolf style good for biodiversity?
Yes as seed heads, but without woody everything dies back and biodiversity is lost as habitat is lost.
Are climbers good ?
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.
How is growth habitat integrated into horticulture?
- Forms and longevity and spread are important decision on selection and maintenance.
- Design gardens with different plant forms. Be sure to integrate a variety - good visually and biodiversity.
- Understanding growth habits enables species to be chosen to fulfill functional uses of groundcover, screening, rain gardens, green roof etc.
List some Warm-climate non-woody plants with persistent growth
Agave
Aloe
Yucca
Cacti
No secondary growth. Non woody, but continue to grow.
List THREE characteristics common to all subshrubs. Give THREE name examples of species often used in gardens and designed landscapes.
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
List THREE common plants frequently used for hedging. Outline their basic characteristics which make them good hedge plants.
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.
What is a cushion plant? What environments are they typically from? And where would they traditionally be grown in the garden?
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.
What is coppicing? Name one species where coppicing is useful in horticulture.
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
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?
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
Name and briefly describe two habitats where there are many evergreen species.
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
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?
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.
