Night-time Irrigation: When It Works and When It Doesn't

Night-time irrigation is something customers often suggest, and it is only partly correct. It does reduce evaporation, but it is not automatically the best time to open the solenoid valves: this depends on the type of vegetation and how long the leaves remain wet.

When night-time irrigation works

The best time window for programming irrigation remains between 5 and 10 in the morning, when the sun is low and the air is cool: during this period, water has time to infiltrate the soil before temperatures rise, whilst leaves dry quickly in daylight. For drip irrigation or sub-irrigation systems that wet the soil rather than the foliage, a genuinely nocturnal start time (after midnight, before dawn) also remains an efficient choice, as there is no “prolonged wet leaves” variable to manage.

When night-time irrigation is wrong

The problem arises with sprinkler irrigation on lawns or plants with dense foliage: irrigation in the evening should be avoided, as leaves can remain wet throughout the night. The longer the foliage stays damp, the greater the risk of fungal development — the same principle by which a buried system that keeps the exposed leaf surface dry reduces the risk of fungal diseases.

The most common conditions favoured by prolonged wet foliage at night are generally attributable to:

• Rust (fungi of the genus Puccinia), typical on lawns but also on roses and other ornamentals, with yellow-orange pustules on the leaves.
• Powdery mildew (fungi of the genus Erysiphe/Oidium), recognisable by its white powdery coating on leaves and stems, very common on roses, hydrangeas, and hedges.
• Fusarium patch (Microdochium nivale), one of the most widespread leaf spots on turf, promoted by prolonged moisture and mild temperatures.
• Red thread (Laetisaria fuciformis), another typical turf disease, with pinkish threads visible on grass blades under persistent damp conditions.
• Brown patch/Rhizoctonia (Rhizoctonia solani), which affects lawns and flower beds when foliage remains wet for extended periods under warm and humid conditions.

Note: these are general agronomic guidelines recognised in phytopathological literature; definitive diagnosis and specific treatment remain the responsibility of an agronomist or plant health specialist.

The practical rule to take to every installation

• Drip/sub-irrigation targeting the soil → night-time or very early morning schedules; no wet foliage issue.
• Sprinkler irrigation on lawns/flower beds/hedges → the 5–10 a.m. window; never in the evening or the middle of the night.
• Mixed systems (lawn + flower beds + drip) → not a single schedule for the entire system, but differentiated programmes per zone, based on irrigation type and plant material.

Programming night-time irrigation by zone with the Vision App

The operational point is that no compromise is required: Vision range controllers allow start times to be differentiated per zone.

• With PRO mode, available on controllers such as Pure Vision BLD, Ionic Vision, and Zenit Vision, the high number of start times (6 per programme) allows the installer and maintenance engineer to manage medium-to-large systems with ease — for example, assigning a morning start to the lawn and a separate night-time start to the drip line.
• With ONE-BY-ONE mode, irrigation scheduling is entirely flexible and allows each individual solenoid valve to be managed independently, with a separate start time and frequency per zone: the most precise solution when a single system combines lawn, exposed hedges, and shaded flower beds, each with different requirements.

The right time is determined by the type of garden

In short, there is no universal rule for night-time irrigation: there is only the right time for each zone in the system. Differentiating start times during programming, instead of relying on a single schedule for the whole garden, is what distinguishes a merely automated system from a truly efficient one.