Drip Irrigation – How Professionals Lay and Space the Drip Irrigation Pipes

Drip irrigation is probably the single most effective tool for water conservation at the dry climate gardener’s disposal. Unfortunately, many, perhaps most home gardeners do not know how to space and lay down the pipes, in order that the system provides adequate moisture to the plants, while saving water as much possible.

A Common Mistake

The worst error is to snake a dripper line in a long loop around the plants. There are three reasons why this is wrong.

*Firstly, a long, looping line will reduce the operating pressure of the system, causing the drippers at the end of the line to emit far less water than those at the beginning. Remember that the aim of efficient watering is to provide water as evenly as possible.

*Uneven coverage makes it impossible to calculate the volume of water necessary for any given watering, and then to use just that amount. For as quantities are determined by area, (i.e. 3 liters per square meter a month for established, drought tolerant trees and shrubs) it follows that each part of the irrigated area should be receiving the same amount of water.

*A looping, snaking dripper line is unsightly. Lines that are straight, taught, and parallel to each other, catch the eye less, and give a more ordered look to the garden, until the plants cover them up.

Laying the Dripper Lines

The problems just outlined are avoided when the dripper lines are placed parallel to each other in short, straight lines, and where the drippers themselves are evenly spaced within any given line. But what is the optimal distance between the lines? The principle to follow is that they should be close enough to supply adequate coverage to the plants, but distant enough so that the amount of water emitted by the system per unit of time, is as low as possible. The purpose here is to allow the soil to absorb the water without run-off and wastage, or in technical terms, that the flow rate of the system be suited to the infiltration capacity of the soil. Here are some examples.

Shrubs and Bushes : For drought-tolerant bushes, choose a spacing of 1 meter (3ft) between the drippers and I meter between the lines. For less hardy landscape shrubs, 0.5*0.5 may be necessary. Add a circle of drippers around young trees at a distance of about 30cm (1ft) from the trunk.

Heavy Soil v Light Soil : Space the lines further apart in heavy, clay soil as opposed to light, sandy soil. For example, with flowers, a spacing of 30cm*30cm may be needed to supply moisture in light soil, whereas such a spacing in heavy soil will cause puddles to form very quickly. As water moves horizontally in clay soil, a spacing of 30*50 would be more appropriate.

Integrated Dripper Pipes : Although more expensive, it is always better to buy pipes that are pre-inserted with drippers, as opposed to adding individual drippers to a blind line. These come in varying spacings such as 30cm. 50, 70, or 100cm. Choose the appropriate spacing according to the principles outlined above, and make sure the flow rate (given for each dripper) is the lowest available.

Drip Irrigation – A Simple But Essential Maintenance Task Before the Onset of the Irrigation Season

The life span of dripper lines is usually up to 10-15 years, as mineral deposits in the water eventually make the line inoperable. However, neglecting to wash out the system periodically will significantly reduce their operable life span. I've seen drippers block up after 3 or 4 years when this simple routine task is ignored.

There are two ways to do this – a simple way and a better one. Needless to say, professionals choose the latter, but let’s start with the simple, obvious method. Where the drip irrigation lines have been closed-off and tied-up at their ends, simply open each end of line and after turning on the tap, allow the water to flow out for about 5-10 minutes. As you should do this separately for every single line, the method is both laborious and wasteful of water.

It is preferable then to connect the end of the dripper pipes to a “collector” pipe, just as they are connected to a “feeder pipe” at the head of the line. This creates a closed drip system, which not only makes for better operating pressure, but allows for the periodic flushing to be carried out far for efficiently. This is what you need.

Connect a short, 3/4inch vertical pipe to the end of the collector pipe via an elbow connector. At the end of the 3/4in pipe connect another elbow and on to that a cheap, plastic tap, which has threads on both ends, so that a hose can be attached to it.

When you are ready to flush out the dripper lines, turn on the main tap so that the pipes start to emit water, and then turn on the plastic tap to which, as mentioned, a short piece of hose is connected. Flush the line for about 5-10 minutes, while using the water coming out of the hose for some useful purpose such as watering new plants.

The great advantage of doing things properly is that they end up getting done! We all tend to give up on something if it becomes tiresome, time-consuming, and messy. That is what usually happens when the drippers are not made into a closed system as described. The simple task of flushing the lines is neglected and forgotten, only for the dripper pipes to block up far sooner than necessary. So as winter draws to a close, do not forget to carry out this irrigation maintenance task that is so simple but essential for a dry climate and water conserving garden.

Landscape Garden Design – Using Santolina in a Mediterranean Style Garden

Santolina as a Mediterranean native, is virtually a “must” plant for a dry, Mediterranean-style garden. It is a sub-shrub or woody perennial, growing to about 70cm (2ft) in height and a meter (1ft) in width. The best-known species is Santolina chamaecyparissus, or Lavender Cotton, with its grey colored, finely toothed foliage. Species with green leaves include S. pinnata and S. rosmarinifolia (virens).

Santolinas also flower profusely through the summer with their small, button, daisy-like blooms. The plants are best chosen however for their foliage and small-scale landscaping properties than for their flower color. They can serve as a stable element in a flowerbed; holding the border while perennials have been cut down, and annuals replaced, and are particularly effective as niche plants between rocks or flagstones.

Santolina, especially the grey-leaved Lavender Cotton, is not suitable for tropical gardens, looking singularly out of place with the lush, large leaves and course foliage texture typical of tropical plants. However, it combines excellently with the finely toothed foliage of Chrysanthemum, (some) Achillea, or Rosemary, and with flowering plants that have small blooms.

Its leaves are fragrant when bruised or clipped, and so it is a valuable addition to a herb garden, at least from a stylistic point of view. For most herbal plants, like Lavender, Sage, and Thyme, are also Mediterranean natives, and have similar leaf shapes and texture. A herb garden edged with a foot-high Santolina hedge, is perfect for more formal compositions.

Thought should also be given as to how the bedding plants associate with the trees and shrubs in the garden composition. In order to create as much unity as possible, the ground plane, i.e. the bedding plants, should link with the “walls and ceiling” of the garden, i.e. the trees and shrubs. Therefore, Santolina combines well with shrubs like Juniper, Melaleuca, and Grevillea, as well as with coniferous and Mediterranean trees such as Pomegranate and Olive.

Care and Maintenance

The most important thing is to clip them frequently in order to prevent them coming too woody and top – heavy. The clipping will reduce the number of flowers, but the plants will grow more densely and compactly as a result. Santolinas are not fussy plants, but they do need good drainage. Other than that, they perform perfectly well under a low watering regime, and so are ideal bedding plants for dry climate gardens.

Metrosideros (Pohutukawa) – An Excellent Landscape Tree or Shrub for a Mediterranean Climate Garden

Metrosideros is the botanical name for a genus of landscape trees and large shrubs known commonly by its Maori name as Pohutukawa, or New Zealand Christmas Tree. As a large evergreen plant, it is ideal for screening purposes, but is also highly ornamental with its fine form, attractive, leathery foliage, and showy annual flowers.

Pohutukawa is relatively drought tolerant, thriving on as little as 200mm (8in) of additional irrigation in near desert climates that receive no more than 250mm of rainfall a year. In semi arid Mediterranean climates that receive some 400mm (16in) of annual rainfall, it can get by on less water, but will look better for the occasional deep soaking in the summer.

It is also tolerant of wind and sea spray, is largely unaffected by pests and disease, although it is unsuited to areas that have prolonged frosts and chill. Metrosideros grows well in most soils, including the alkaline ones typical of many dry climates, providing there is reasonable drainage. It is not a plant for the impatient however, as it grows slowly during the first few years. The patient gardener however will be rewarded with a beautiful and dependable landscape plant.

Combinations and Associations

With which trees and bushes does the New Zealand Christmas tree associate comfortably? Its oval-shaped foliage is medium in size and texture and so it fits in well with landscape bushes with similar foliage such as Pittosporum and Viburnum. It is especially good with another New Zealand native – Coprosma repens whose varieties that have variegated or copper leaves, add a gentle contrast to the light-green foliage of the Metrosideros.

Thought should also be given to how the plant combines with trees that are larger than it is, and with low-growing shrubs as well. With this in mind, it combines superbly with tall Eucalypts and with small bushes such as Green Island Ficus, Dwarf Pittosporum, (“Wheeler’s Dwarf”) and Raphiolepis.

Pohutukawa, as a member of the Myrtle plant family, (Myrtaceae) has flowers with the prominent stamens typical of that botanical family. Therefore, it links up with other Myrtaceae plants like Syzygium, Myrtle, Acmena, and Callistemon.

Metrosideros is so attractive and useful as a screening plant, and is so adaptable to the arid conditions prevailing in Mediterranean climates (excluding very cold areas) that dry climate gardeners can hardly afford to ignore it.