Understanding Your Plants - South Australia

1. Understanding Your Plants
All plants require some water to grow, regardless of how waterwise they are. Some plants
obtain their water directly from the air, and other aquatic plants grow in a saturated
environment. However, most plants get their water through fine roots growing in the soil. In
a garden, water is usually added to the soil through rain or irrigation. Although trees and
large shrubs and a few other garden plants may be very deep rooted, the feeder roots of
the majority of garden plants are around 300mm deep. It is this zone that is therefore
critical for plant health. Water is gradually lost from the soil surface through evaporation
and is also transpired through the leaves of plants as they grow. Water can also run off the
surface and drain through the soil past the root zone. Understanding this process and
knowing the needs of your plants is vital if you are to irrigate in a waterwise way.
Transpiration Understanding your plants
Transpiration keeps plants cool, drives the The rate at which plants lose water through
‘engine’ by which water and nutrients are transpiration varies with the type of plant.
distributed through the plant’s tissues. Important steps towards saving water include:
Transpiration is essential for plant life. However,  Using water efficient plants where possible,
this constant water loss means they must equally such as plants adapted to Adelaide’s dry
constantly replenish their supply of water. conditions.
Depending on the type of plant and the rate at
which it is growing this water loss varies. When  Designing your garden so plants with similar
combined with soil evaporation, this is called water requirements are grouped together into
evapotranspiration. The rate of evapotranspiration separate watering zones, in appropriate areas.
increases:  Placing plants in the correct soil and
 In higher temperatures; microclimate position to meet their growing
needs – the right plants for the right place.
 In stronger winds;
 When there is low humidity;
Plant adaptations to drought
 When there is no protective mulch; and/or
Plants have many different adaptations to help
 When high and medium water-use plants are them preserve water. If you learn to identify these
planted. adaptations you can select waterwise plants at
Your challenge as a gardener is to manage your nursery and also provide extra water to the
watering so there is just enough water in the root plants in your garden which lack these
zone for your plants to stay healthy. adaptations.
Improving your soil, mulching, placing your plants Hard, thick or waxy coated leaves are common
in the right location and installing an efficient characteristics of waterwise or drought tolerant
irrigation system will help you achieve this. plants. Others have small or needle-like leaves
Remember, in shade plants lose about 50% less and therefore fewer pores or stoma through which
water through transpiration. water is lost by transpiration. Hairy or felty leaves
and silver or grey foliage are other indications of
drought tolerance. Some plants have fewer, or

2. virtually no leaves, as in the case of cacti, or shady area of an Adelaide garden. A waterwise
fleshy leaves that store water, a characteristic of gardener might consider replacing these species
succulent plants. with more waterwise plant choices as they die or
High water use plants mostly have soft, dark the garden design is changed.
green leaves. Some plants, including many Most established gardens contain a mixture of
deciduous trees, transpire a lot. However, they plants that originate from many different parts of
have a deep tap root or an extensive root system the world and are diverse in their ability to adapt
to draw water from a large volume of soil. to reduced rainfall.
Some but not all Australian natives, and many Few of us want to tear up our existing garden and
Mediterranean plants (eg. lavender and many start again from scratch. But when plants need
herbs), South African plants (eg. Proteas and replacing or when planting new garden beds,
Diosmas) and Californian plants (eg. Oenothera consider choosing low water use plants suited to
or Evening Primrose and Ceanothus) are adapted your conditions and group plants with similar
to dry climates. water needs together.
In Adelaide the indigenous or local native plants
are largely waterwise, easy care plants that also
make an excellent habitat for native birds, animals
and insects.
Some exotics, including established Roses,
Murraya, Photinia, Nandina, Bougainvilleas and
Camellia sasanquas have proven to be relatively
tough survivors during extended dry periods.
Many new release strappy leafed and
architectural plants such as Cordylines, flaxes and
yuccas are relatively drought tolerant.
Garden planning
If you are planning a new garden, invest some
time in getting to know its aspect and
microclimate, particularly its exposure to sun and
hot summer northerly and westerly winds and how
that affects plant placement.
Divide the garden into watering zones. Group
plants according to their water use needs. This
also helps you to choose plants that are
appropriate for particular microclimates in your
garden. By grouping plants, such as medium
water use trees, shrubs and perennials, each
grouping will benefit from an optimal watering
schedule incorporating thorough soakings that
encourage deeper roots rather than light surface
watering.
Flowering annuals, vegetables and fruit trees are
mostly high water users that like plenty of sun.
They generally need more frequent watering. If
you have an irrigation system, they may need
additional hand watering on occasions, especially
when it is hot. Use shade to create appropriate
summer microclimates for these plants.
Shade loving, high water users such as Impatiens,
Hydrangea and Fuchsia should be grouped
together, and only grown in a well sheltered,

3. Water stress symptoms
The following table can help you identify if you have water stressed plants.
Symptom Image Description
Leaf curl Leaves may curl during the day as a defence mechanism against
heat and the sun. The leaves should uncurl at night.
Wilting Drooping of the leaves and stems occurs in the non woody parts of
the plant.
Chlorosis Also known as yellowing of the plant. This predominantly occurs in
high water use plants. The tissue turns yellow, and the veins will
eventually brown. It can also be an indication that the plant is lacking
in iron. If chlorosis is visible treat your soil with iron chelates to
correct the deficiency.
Leaf This is where the leaves of the plant drop off. Older leaves (those at
abscission the bottom of the plant) will fall off first. But leaf abscission is also a
natural part of plant growth. Look for other symptoms of water stress
as well, such as those in this table.
Glossy Plants which have a glossy leaf surface may lose their glossy
leaves appearance when water stressed.
Glossy
Dull
Wrinkled Leaves of succulents may acquire a wrinkled appearance when
leaves water stressed

4. Some water saving tips: Keep your soil moist
 Plant trees and shrubs where they create Adelaide’s soils are prone to drying out in the
natural shade and windbreaks to reduce long, hot summers. Once dry, it is very difficult to
evaporation. get water to sink into the soil where the plant roots
 Take advantage of sheltered spots to grow more can use it. You can avoid this problem by
sensitive plants, particularly out of the hot ensuring the soil does not dry out completely, by
summer winds. monitoring moisture at depth. Dig a small 20cm
deep hole with a trowel and check for moisture.
 Avoid very large, broad-leafed plants and trees By using mulches and ground cover plants,
that need lots of water to survive summer. introducing structure such as rocks, logs and
 Choose water efficient plants. ponds, and following your watering schedule you
 Some selections of Australian grasses and can ensure some moisture is retained. On
strappy leafed plants such as Lomandra and particularly hot days, make an additional check of
Dianella are waterwise plants and are excellent your soil condition by pushing your finger or a
in landscapes, particularly in an Australian small trowel into the surface soil. If the soil
modern style garden. appears too dry below the surface, water
according to any current restrictions or bucket
 Plant low water using plants in an area that your shower or washing up water onto the beds.
tends to be dry, such as near walls or fences or Preventing the soil from drying out will avoid
hard to access area. costly and time consuming measures to wet it
 Consider putting moisture loving plants in low again.
lying, shady and sheltered areas.
 Control weeds because they compete with Pulsing your watering effort
garden plants for water.
Adelaide’s clay soils allow water to soak in at a
 Most vegetables are high water use plants that very slow rate, compared to a sandy soil (see
need a sunny position. Root vegetables are Impact of Soil Factsheet for details). If you apply
generally less demanding and can be grouped water at a higher rate than the soil’s ability to soak
separately from those that use more water. it up, it will pool and either run off or evaporate
 In Adelaide, to get the best results and save before it can reach your plants’ roots. When
water, leafy vegetables can be grown under setting up an irrigation system, ensure your
50% white shadecloth during January and installation professional takes this into account
February. and pulses your watering. This means water is
applied then left to soak in before another pulse is
 Plant in autumn so that plants become
delivered. This is also easy to do using a hose if
established during winter and will require less
you follow a series of simple steps.
water the following summer
Simply water individual small areas of your garden
 Remember to continually improve your soil (see
beds (1m² patches) until you see water start to run
‘The Impact of Soil’ fact sheet).
off or pool on the surface. Once this happens,
move on to another area, then return and keep
Watering Habits and Techniques watering once the surface water has soaked in.
Keep track of how long you spend on each area,
Choosing appropriate plants and improving your
to ensure that your garden’s overall watering
soil are two effective ways to decrease the
needs have been satisfied, as per the instructions
amount of water your garden needs, however
contained in your WaterRight webtool report. By
using appropriate watering techniques is also very
doing this you will ensure that all the water you
important. Regardless of whether you are using
put on your garden is going where it is needed,
drippers, sprinklers or a hose, timing and directing
into your plants’ root zone.
your watering will allow you to use water efficiently
on your garden. The Irrigation fact sheet and an
irrigation schedule from the WaterRight webtool Plant selection
will help you choose the best method of watering
There are many different resources listed in the
your garden.
links and resources section of the WaterRight
Gardens webtool, which can help you choose

5. garden plants on the basis of their water  Couch (Santa Anna, Casablanca and USA
requirements and regional soil and climate needs. Fancy Couch)
Specialised Australian native plant nurseries, local  Soft Buffalo varieties
garden centres and local Council nurseries are a  Native grass varieties (seek professional advice)
good source of advice on water efficient plants
suitable for gardens in your area. They can also
advise on plants that may become weeds in your Tips on watering lawns
local area.
 The better the soil beneath your lawn the
Some garden centres have their own signage deeper the roots and the less water needed.
about the water requirements of specific plants.
 Only water your lawn if it is showing signs of
The Adelaide Botanic Gardens and the Society for
stress, such as losing colour (in summer) or if
Growing Australian Plants (http://asgap.org.au)
the grass wilts or leaf blades roll or fold in half
are other good sources of information. The
lengthways. Another way to tell if your lawn
Botanic Gardens has excellent examples of how
needs watering is to step on it. If the footprints
to set up an Australian Native, SA Water
remain visible after you have stepped on it, it
Mediterranean Garden or Succulent garden,
needs a good soak.
including design, layout, plant choices and other
great tips.  Use pulse watering if your lawn requires
irrigation (see ‘Irrigation method’ Fact Sheet)
 Especially in summer, try leaving your lawn a
Lawn
little longer when you mow. Try to only mow
Lawn plays a key aesthetic and recreational role one-third of the leaf blades each time, keeping
in gardens. Although you can reduce your lawn blade length to 20mm. Longer blades shade the
area by using permeable paving or planting hardy root zone, reduce evaporation and assist deep
ground covers requiring less water, turf can still rooting.
have a place in waterwise garden design.
 Brown patches on grass suggest a compacted
The most commonly planted turf species in the or water repellent soil. Aerate your lawn
Adelaide region are warm season grasses such regularly to ensure that rain or irrigation
as Couch and Buffalo, including new soft leaf penetrates efficiently and evenly. Treat with a
types such as Palmetto and Sir Walter, and soil wetting agent.
Kikuyu. Be careful however, when using Couch
 Brown patches can also suggest scarab grub
and Kikuyu, as they can invade other garden beds
damage in the summer months. If the soil is not
and also waterways and natural areas.
dry and birds are pecking at the lawn, then
Warm season grasses can survive on relatively these signs indicate you have grubs chewing on
infrequent watering if grown in good soil that the root system on your lawn. Consult with your
fosters deep rooting. local nursery worker about the most appropriate
If you refrain from watering your lawn and let it pest control strategy.
brown off during extended dry periods, you will
discover it has an excellent capacity to recover Pot plants
after rain.
Potted plants, even drought tolerant ones, will
If you feel you must water your lawn, water require regular watering, as they have less soil to
infrequently but deeply. This encourages deep draw water from. Here are some tips to minimise
root penetration and maximum drought tolerance. their water use:
Some excellent low water use grasses suitable for  Grouping pots helps to keep them cooler. Group
South Australia’s climate are now available. them according to their watering needs,
Always seek advice from a lawn specialist before especially if you are watering them with an
planting to make sure your choice is right for you. irrigation system.
Also consider using native grasses and
 Use a quality potting mix. Look for the Australian
groundcovers to give your garden interest, or as a
Standard logo on the bag. A premium mix is
lawn substitute in low traffic areas.
advised for most potted plants. The compressed
As a rough guide, the following grasses are suited coir or coco peat potting mix bricks that you
to Adelaide’s cool winters and hot summers: rehydrate have very good water storing

6. capacity. They can be used on their own or
mixed with another potting mix to improve water
retention and air filled porosity.
 Mulch the surface of the potting mix. Use an
organic (eg: bark or coir) or inorganic (eg:
pebbles or scoria) mulch.
 Potting mix can become water repellent,
especially if allowed to get dry. Water running
down the sides of the soil or straight out the
bottom indicates this. Treat with a soil wetter, or
soak the container in a larger container of water
with some soil wetting agent added until it stops
bubbling.
 Larger pots are generally more water efficient
than smaller pots. Avoid pots that are too large
for the plant as this may make the soil water
logged.
 Allow the top 20mm of potting mix to dry out
between watering. Many potted plants are killed
from over watering.
 Unglazed terracotta pots are very porous, losing
water readily. Line them with plastic, ensuring
you cut out drainage holes, or treat the inside of
the pot with a sealant.
 Protect hanging baskets from drying winds.
 Self watering pots work well if used correctly.
Water them from above and allow the water to
drain through into the well. Plants draw water
from the well by capillary action. Don’t place a
very small plant in a very deep container, as the
roots will not be strong enough to draw water up
from the well. Tall containers require a more
open potting mix for capillary action to work.
Use a premium potting mix and consider adding
some coir to the potting mix.
 Consider watering your pots by soaking them in
a large container full of water. Each pot will only
absorb as much water as is needed to saturate
the soil. This is the best way of conserving
water.