Timed Irrigation: Removing the Guesswork

For larger gardens, substantial new planting schemes or clients who regularly spend time away from the property, manual watering may simply be impractical.

This is where a properly designed automatic irrigation system becomes valuable.

A timed system can divide the landscape into different irrigation zones and deliver water according to the requirements of each area.

Drip irrigation can be particularly effective within planted borders because water is delivered slowly and directly into the root zone. Individual emitters can provide known flow rates, making the quantity of water substantially easier to control than standing with a hose and estimating.

A carefully specified system might separately control:

• Newly planted trees

• Shrub and herbaceous borders

• Hedging

• Kitchen gardens

• Containers

• Greenhouses

• Lawns

Each has different requirements.

Automation should not, however, mean switching the system on in April and forgetting about it until October.

Seasonal adjustment remains important. A system operating during cool, wet weather at the same rate as it does through a July heatwave can waste significant quantities of water and potentially damage plants.

Rain sensors, soil-moisture monitoring and appropriately configured controllers can make automatic irrigation considerably more responsive.

Where Do Sprinklers Fit?

Sprinklers certainly have a place, but they should not automatically be the default method of irrigating a garden.

They are particularly useful when establishing newly seeded or newly laid lawns, where relatively even surface coverage is required.

Within established planting borders they are generally much less precise. Water can land on paths, walls and foliage rather than reaching the roots, while considerably more moisture can be lost through evaporation.

For this reason, the RHS considers sprinklers one of the less water-efficient methods of general garden irrigation and recommends targeted alternatives where possible.

A successful irrigation design often uses different methods within the same garden rather than attempting to make one system perform every task.

Using Wells, Boreholes and Stored Water

Where a property has access to a well, borehole, large rainwater store or other private water source, it may be possible to integrate this into the irrigation strategy.

The crucial component is not simply choosing a pump with the largest possible output.

The system needs to be designed around the available water supply, sustainable yield, required flow rate and operating pressure.

A professional specification may therefore consider:

• The available volume and recovery rate of the water source

• Pump capacity and pressure

• The vertical distance water must be lifted

• Pipe sizes and pressure losses

• Filtration

• Storage or break tanks where appropriate

• Irrigation zones and their individual flow requirements

• Protection against a pump operating when the water source runs dry

• Suitable controls and sensors

• Future maintenance access

A correctly designed pumped system should feel almost invisible in the finished landscape. What matters is that sufficient water arrives where required, at the correct pressure and quantity, without unnecessary waste.

Irrigation Should Be Designed With the Garden — Not Added Afterwards

We increasingly consider irrigation in the same way as lighting, drainage and other technical elements of a landscape.

It is most successful when it is designed alongside the garden rather than retrofitted once everything has been built.

During the design process we already know where the trees will sit, where thirsty planting is concentrated, where drought-tolerant planting is intended, where lawn areas begin and end, and where hard landscaping will restrict future access.

That information allows an irrigation layout to be coordinated with the planting plan.

Pipe routes can be planned before paving is installed. Valve positions can remain accessible without becoming visually intrusive. Different planting zones can be calculated separately, and provision can be made for future maintenance rather than burying an improvised network beneath a completed garden.

Where appropriate, an irrigation specification can be developed alongside the wider garden design, detailing irrigation zones, pipework routes, drip lines, sprinkler locations where required, valves, controllers, pumps, water sources and the intended method of delivering water to each area.

This is especially valuable for large gardens, extensive new planting, specimen trees, kitchen gardens and properties where regular manual watering would be unrealistic.

Designing for Establishment — and Ultimately for Resilience

The objective of good irrigation is not to make a garden permanently dependent on enormous quantities of water.

Quite the opposite.

Plant selection should respond to the existing soil, aspect, exposure and moisture conditions of the site. Once appropriate plants have developed strong root systems, many should require considerably less intervention.

But before a garden can become resilient, it first needs the opportunity to establish.

Those first months after planting are when the landscape is at its most vulnerable. Careful watering during this period protects the considerable work already invested in soil preparation, plant selection, sourcing, planting and design.

Because the success of a newly designed garden is determined not only by what we can see on the day it is completed.

It is determined by what happens below the surface in the seasons that follow.

Find some of our Irrigation specifications below

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