Written By: Dee Pigneguy

Planning for Drought Conditions

New Zealand is not short of water as its average rainfall is between 640 mm and 1500 mm, making it a great place for horticulture and agriculture.  In fact between 70% and 80% of our water is used by these two industries.

Although statistics show we get plenty of rain, there are times when many places face drought conditions.  So when water is in short supply what steps can you take to drought proof your garden for those long hot days of summer?

When planning a garden it is important to consider not only the climate and seasonal rainfall but also your lifestyle and the time available to be the gardener!  Recently I visited a veganic gardener who had established a “jungle garden” mimicking natures’ best ideas for both wet and dry conditions. If it rains too much the tree roots absorb water and the terracing stops erosion.  If there are drought conditions the diversity of plants mulch the ground, while the shade and shelter provided by the taller plants keeps the garden from drying out. His trick to keep soil moist and his garden in top growing condition was to mulch everywhere, not with grass clippings—he didn’t have any lawn, but with all the clippings and plant material from his own garden.  Amongst the profusion of plants, four small ponds provided a water source for visiting wildlife and a cool moist retreat in the heat of summer.

The Clues Hidden in Plant Leaves

Plant leaves often give the clues to how the plants will perform in drought conditions.  Small leaves like those on rosemary and thyme shed heat without loosing water. Artemisia with grey leaves like wormwood and dusty miller indicate drought resistance. Lamb’s ears shade themselves with the hairs on their leaves. Sages have leathery leaves, which loose less water than fleshy soft leaves.  Pittosporums reduce transpiration with shiny waxy leaf surfaces.  The fleshy succulent leaves like those of aloe vera and agaves can store moisture for dry conditions.  Plants like sea holly and teasels have spikes, which help keep the plant cool, while aromatic plants contain volatile compounds, which cool foliage as they evaporate.

When densely planted and mulched many flowers like marigolds, cornflowers, chrysanthemums, bird of paradise, red-hot pokers, yarrow, amaranth, globe artichokes, Jerusalem artichokes, rue, statice, strawflower, alyssum, cleome and daylilies will withstand dry conditions.

Many flowers will withstand a hot summer if they are close planted and mulched:

Storing Water in the Soil

Soil is important in drought proofing your plants.  Building rich soil by incorporating organic fertilisers, leaf mould, green waste and compost.  Compost is full of humus, an organic material which acts like a sponge, soaking up available water and releasing it slowly for the plants.

Now that you have a soil that will hold water, use mulch to provide shade, stopping soil from drying out and helping to moderate the soil temperature.  While working to retain the soil moisture, the mulch will also suppress weeds also competing for available moisture. .  Mulches like pea straw and dried grass clippings will cut down watering by at least 50%.  Every time you hoe garden soil you expose it to the heat of the sun and the drying winds, so practice the “No dig gardening” techniques to reduce water loss. 

Plants need to be fed regularly to keep them strong, healthy and pest resistant, but avoid using fertilisers or pesticides. Instead use nature’s fertilisers, comfrey, seaweed and nettle to make your liquid manures.  And don’t forget that magic liquid produced by your worm farm.  Permaculture principles like growing plants on fences and built structures, helps to shelter them from drying winds, while providing shade from the burning midday summer sun.
 

Harvesting and Using Water

After storing water in the soil by enriching it with organic matter and mulch, the next step in drought proofing the garden is to install rain water tanks and water butts on every downpipe on your house or garage, in order to harvest as much rain as possible.  Make sure all water containers are covered to prevent mosquitoes from breeding and to keep out leaves and debris.

You can also consider using grey water—the water from washing dishes and clothes, but make sure the soap you are using is truly biodegradable and does not contain enzymes or fabric softeners.  Do not store this water, but use immediately on flowers, fruit trees and ornamentals.
 

Using Irrigation

Installing a soaker hose or a drip irrigation watering system avoids water wastage and delivers water close to the root zone where it is needed. The new Eco-seep uses standard fittings, doesn’t clog, can use recycled water, is suitable for plants that don’t like to get their leaves wet, and can be laid along the surface of the soil.  Also known as micro-irrigation, drip and low-flow watering systems are extremely efficient.

All irrigation systems need maintenance to run smoothly and come at a cost considering all the black plastic piping. Perhaps you can show the children how much fun it is to use a watering can!

In my garden I grow strawberries in pots grouping them together and placing them directly onto the soil.  This allows water to percolate through the roots and then into the garden soil.

Water Stress

Water is critical to plant growth and when plants are stressed they wilt and eventually die.  It is better to water in the early morning as plants need the water during photosynthesis. Wilting stresses the plant, so when vegetables show signs of wilting they need to be watered. To avoid disease and mildew problems I do not water in the evening.  When watering by hand pull back mulch and make sure water is getting to the root zone.  Don’t be stingy when watering; remember the larger the plant the larger the root zone.  Tomatoes, corn, pumpkin and cucumbers laden with fruit require large amounts of water.

Signs to look for when you think your plants may be suffering from water stress due to prolonged drought or lack of water

• Blossom and fruit drop
• Spider mite infestations
• Increased insect damage
• Blossom end rot in tomatoes and peppers
• Yellowing and browning of leaves
• Undersized fruits and vegetables
• Lack of growth
• Terminal die back in fruiting shrubs and trees

How Do Plants Use Water

Plants are just like water pumps. Driven by the energy of the sun, plants cycle large quantities of water every day. In a process called evapotranspiration, moisture in the soil is drawn through the roots and up plant stems before being lost through stomata on the underside of the leaves. The heat lost in the process of converting the water into vapour reduces overheating in plant tissue. 

Transpiration rates are influenced by the leaf shape, size, stomata, and waxiness of the leaf surfaces. Plants transpire huge quantities of water, and it is calculated that only 1% of water absorbed by the plant is actually used in photosynthesis, the rest is lost in transpiration. This process is all part of the water cycle, but when water levels are too low to maintain transpiration the stomata close, photosynthesis stops, plant tissues overheat, and leaves wilt.

My garden is dedicated to growing fruits and vegetables and is a very thirsty place. I use a lot of water during the summer months and have installed water butts and a 5000 litre water tank. I prefer not to use the council water on my plants because of the chemicals it contains.

Featuring Water in The Garden

Water is not only essential for plants, but also for the wildlife that will visit the miniature wildlife refuge you will create when adding decorative pools to your garden.  Pools, ponds and water features provide endless fascination for both children and adults.  Visiting insects, birds, dragonflies, lizards, and even frogs will provide many photographic opportunities for the budding photographer. Informal pools and ponds can be made simply by lining a hollow with black plastic sheeting, covering it with sand and stones and anchoring the edges with rocks or bricks or wooden surrounds. Flexible pond liners allow you to create your own designs or you can buy pre-formed plastic ponds.

  More formal above ground pool structures made of concrete, stone or bricks are also available.  Or you can be creative with recycled hot tubs or half barrels.

Although pools need dappled light to keep the water from overheating it is best not to site the pool under trees, as falling leaves and roots will create problems. You may have to use netting to keep falling leaves out of the pond as they remove oxygen from the water as they decay.  Overhanging vegetation around the margins, rocks, driftwood and artwork can all be used provide shade and create a unique water feature that suits your garden setting.

Depth should be between 40 and 80 centimetres but consider a shallow area for frogs which may come to stay and lizards that will come to drink.  Submerged rocks or pockets of brick or stone will allow for varying depths, and can be provide a base to grow water plants, or you can use sunken pots or wire baskets.

Plants and Pools

Although it will take time for a new pool to develop into a balanced ecosystem while the pondweeds, water lilies, plants, frogs, fish and insects get established, small backyard ponds do not need pumps and filters. Water plants will do the job, especially the oxygenators, which exist almost entirely under water where they supply oxygen.

These plants are placed at the bottom of the pond and the foliage can grow to the surface, absorbing carbon dioxide and releasing oxygen as they grow.  If they grow too quickly remove excess growth and add to your compost heap.

Be careful planting the commonly known oxygen weeds—the Egeria, elodea, hydrilla and lagarosiphon families are mostly all noxious weeds.  They clog filters, grow rampantly overpowering other submerged plants and when fish feed on them they produce algae forming waste.

When buying submersibles ask for Ludwigia Repens, Saggittaria Subulata, Myriophyllum Propinquum, or Cardamine Hydrocotyle.  It is common for these plants to be planted on the boggy margins allowing them to grow into the water where they will grow on the bottom of the pond. Always check to see if the plant section has Glenbogal Aquatic display.

Many plants grow well in ponds, but even submerged plants need sunlight, protection from strong winds and still water.  They do not have stomata like land plants but obtain the water and minerals they need directly through their leaves.  The floating leaves also absorb carbon dioxide directly from the small amount dissolved in the water.

As well as the oxygenators you will be able to grow plants around the margins. 

Create swamp or bog conditions by extending the edges of the pond making pockets to fill with soil. Native grasses are a varied and beautiful group and can be used in mixed plantings.  Some varieties are low growing and adapted to boggy conditions.  Grasses can be both upright and weeping, are easy care and have attractive foliage, colour and form.  Choose reedy native varieties such as Juncus or Isolepis Papyrus, long used by the Egyptians for making paper, has slender graceful stems growing 2-3 metres tall providing a focal point either in the pond or around the margins. When used in smaller ponds it should be grown in containers and placed underwater.

The large veined Taro leaves resembling the ears of an elephant are a spectacular pond plant. It will tolerate being grown in water or along the margins of your pool.   
Ferns require rich soil that is moist and well drained. Mulching will help retain soil moisture as well as a cool root run.  A lightly shaded position sheltered from wind also helps maintain humidity.  Ferns and pools belong together.

Water lilies can be planted in containers and sit on the bottom or on submerged rocks. Their leaves have long slanting stalks that can alter the leaf position in the water, and the waxy upper surface resists wetting.  Unlike land plants, water lilies have their stomata on the upper surface of the leaves.

Plan to clean your pond once a year in the spring. If you change the water too often when establishing a new pool it will only delay the development of the balanced ecosystem. There is no need to completely drain it, just remove all plant debris and divide and repot plants.  Always fill your pond with rainwater.

Swimming Pools

Swimming Pools provide a wonderful area for entertaining with the whole family. Pools can provide a pleasant place for exercising and relaxing and if properly planned can blend into the landscape. The ideal site is one that gets maximum sunshine and minimum wind. Landscaping need not be a problem with the wonderful array of New Zealand natives available—flax, hebe, kaka beak, kowhai, nikau, puka, renga renga lily, native grasses.
Or there are many visually stunning plants like the agaves, palms, bromeliads, cycads, and bird of paradise.

If you enjoy hanging making hanging baskets, gather these colourful flower arrangements into a group and sit them in containers of water.  They will last for months.

The list of plants is endless and depends mainly on your creativity as well as your preference for shade, shelter and colour.  With proper care and attention all your garden plants can be visually stunning.

Article Courtesy of New Zealand's Mitre 10 Projects Magazine: