Transcript of "Understanding Your Plants - South Australia"
Understanding Your PlantsAll plants require some water to grow, regardless of how waterwise they are. Some plantsobtain their water directly from the air, and other aquatic plants grow in a saturatedenvironment. However, most plants get their water through fine roots growing in the soil. Ina garden, water is usually added to the soil through rain or irrigation. Although trees andlarge shrubs and a few other garden plants may be very deep rooted, the feeder roots ofthe majority of garden plants are around 300mm deep. It is this zone that is thereforecritical for plant health. Water is gradually lost from the soil surface through evaporationand is also transpired through the leaves of plants as they grow. Water can also run off thesurface and drain through the soil past the root zone. Understanding this process andknowing the needs of your plants is vital if you are to irrigate in a waterwise way.Transpiration Understanding your plantsTranspiration 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 dryconstantly replenish their supply of water. conditions.Depending on the type of plant and the rate atwhich it is growing this water loss varies. When Designing your garden so plants with similarcombined with soil evaporation, this is called water requirements are grouped together intoevapotranspiration. 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 atYour challenge as a gardener is to manage your nursery and also provide extra water to thewatering so there is just enough water in the root plants in your garden which lack thesezone for your plants to stay healthy. adaptations.Improving your soil, mulching, placing your plants Hard, thick or waxy coated leaves are commonin the right location and installing an efficient characteristics of waterwise or drought tolerantirrigation system will help you achieve this. plants. Others have small or needle-like leavesRemember, in shade plants lose about 50% less and therefore fewer pores or stoma through whichwater 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
virtually no leaves, as in the case of cacti, or shady area of an Adelaide garden. A waterwisefleshy leaves that store water, a characteristic of gardener might consider replacing these speciessucculent plants. with more waterwise plant choices as they die orHigh water use plants mostly have soft, dark the garden design is changed.green leaves. Some plants, including many Most established gardens contain a mixture ofdeciduous trees, transpire a lot. However, they plants that originate from many different parts ofhave a deep tap root or an extensive root system the world and are diverse in their ability to adaptto 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 andMediterranean plants (eg. lavender and many start again from scratch. But when plants needherbs), 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 toor Evening Primrose and Ceanothus) are adapted your conditions and group plants with similarto dry climates. water needs together.In Adelaide the indigenous or local native plantsare largely waterwise, easy care plants that alsomake an excellent habitat for native birds, animalsand insects.Some exotics, including established Roses,Murraya, Photinia, Nandina, Bougainvilleas andCamellia sasanquas have proven to be relativelytough survivors during extended dry periods.Many new release strappy leafed andarchitectural plants such as Cordylines, flaxes andyuccas are relatively drought tolerant.Garden planningIf you are planning a new garden, invest sometime in getting to know its aspect andmicroclimate, particularly its exposure to sun andhot summer northerly and westerly winds and howthat affects plant placement.Divide the garden into watering zones. Groupplants according to their water use needs. Thisalso helps you to choose plants that areappropriate for particular microclimates in yourgarden. By grouping plants, such as mediumwater use trees, shrubs and perennials, eachgrouping will benefit from an optimal wateringschedule incorporating thorough soakings thatencourage deeper roots rather than light surfacewatering.Flowering annuals, vegetables and fruit trees aremostly high water users that like plenty of sun.They generally need more frequent watering. Ifyou have an irrigation system, they may needadditional hand watering on occasions, especiallywhen it is hot. Use shade to create appropriatesummer microclimates for these plants.Shade loving, high water users such as Impatiens,Hydrangea and Fuchsia should be groupedtogether, and only grown in a well sheltered,
Water stress symptomsThe following table can help you identify if you have water stressed plants.Symptom Image DescriptionLeaf 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 atabscission 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 glossyleaves appearance when water stressed. Glossy DullWrinkled Leaves of succulents may acquire a wrinkled appearance whenleaves water stressed
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 keepWatering 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 wateringsoil are two effective ways to decrease the needs have been satisfied, as per the instructionsamount of water your garden needs, however contained in your WaterRight webtool report. Byusing appropriate watering techniques is also very doing this you will ensure that all the water youimportant. 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 efficientlyon your garden. The Irrigation fact sheet and anirrigation schedule from the WaterRight webtool Plant selectionwill help you choose the best method of watering There are many different resources listed in theyour garden. links and resources section of the WaterRight Gardens webtool, which can help you choose
garden plants on the basis of their water Couch (Santa Anna, Casablanca and USArequirements and regional soil and climate needs. Fancy Couch)Specialised Australian native plant nurseries, local Soft Buffalo varietiesgarden centres and local Council nurseries are a Native grass varieties (seek professional advice)good source of advice on water efficient plantssuitable for gardens in your area. They can alsoadvise on plants that may become weeds in your Tips on watering lawnslocal area. The better the soil beneath your lawn theSome 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 ofThe Adelaide Botanic Gardens and the Society for stress, such as losing colour (in summer) or ifGrowing Australian Plants (http://asgap.org.au) the grass wilts or leaf blades roll or fold in halfare other good sources of information. The lengthways. Another way to tell if your lawnBotanic Gardens has excellent examples of how needs watering is to step on it. If the footprintsto set up an Australian Native, SA Water remain visible after you have stepped on it, itMediterranean Garden or Succulent garden, needs a good soak.including design, layout, plant choices and othergreat tips. Use pulse watering if your lawn requires irrigation (see ‘Irrigation method’ Fact Sheet) Especially in summer, try leaving your lawn aLawn little longer when you mow. Try to only mowLawn plays a key aesthetic and recreational role one-third of the leaf blades each time, keepingin gardens. Although you can reduce your lawn blade length to 20mm. Longer blades shade thearea by using permeable paving or planting hardy root zone, reduce evaporation and assist deepground covers requiring less water, turf can still rooting.have a place in waterwise garden design. Brown patches on grass suggest a compactedThe most commonly planted turf species in the or water repellent soil. Aerate your lawnAdelaide region are warm season grasses such regularly to ensure that rain or irrigationas Couch and Buffalo, including new soft leaf penetrates efficiently and evenly. Treat with atypes such as Palmetto and Sir Walter, and soil wetting agent.Kikuyu. Be careful however, when using Couch Brown patches can also suggest scarab gruband Kikuyu, as they can invade other garden beds damage in the summer months. If the soil is notand also waterways and natural areas. dry and birds are pecking at the lawn, thenWarm season grasses can survive on relatively these signs indicate you have grubs chewing oninfrequent watering if grown in good soil that the root system on your lawn. Consult with yourfosters deep rooting. local nursery worker about the most appropriateIf you refrain from watering your lawn and let it pest control strategy.brown off during extended dry periods, you willdiscover it has an excellent capacity to recover Pot plantsafter rain. Potted plants, even drought tolerant ones, willIf you feel you must water your lawn, water require regular watering, as they have less soil toinfrequently but deeply. This encourages deep draw water from. Here are some tips to minimiseroot penetration and maximum drought tolerance. their water use:Some excellent low water use grasses suitable for Grouping pots helps to keep them cooler. GroupSouth 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 anplanting 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 Australiangroundcovers to give your garden interest, or as a Standard logo on the bag. A premium mix islawn substitute in low traffic areas. advised for most potted plants. The compressedAs a rough guide, the following grasses are suited coir or coco peat potting mix bricks that youto Adelaide’s cool winters and hot summers: rehydrate have very good water storing
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.