How to Keep Your Greenhouse Watered While You're Away
Short answer: for a weekend away, a tap timer with a drip line is usually enough. For a week or more — especially in summer heat, or with mixed plants — the safest option is a smart system that waters by soil moisture and lets you check in from your phone, because it adapts to the weather instead of running a fixed schedule. Below are five ways to keep a greenhouse watered while you're away, ranked by how long they realistically last.
Why you can't just leave a greenhouse
A greenhouse dries out far faster than an open garden. On a hot day the air inside can climb well above outdoor temperature, and soil in pots or grow bags can go from moist to bone-dry in 24–48 hours. Different crops make it harder still: tomatoes, cucumbers and seedlings all want different amounts of water, so a single "leave the tap on a bit" approach either drowns some plants or starves others. A week-long heatwave while you're away is one of the most common ways a season's worth of growing is lost.
Five ways to keep it watered — and how long each lasts
| Option | Cost | Unattended for | Adapts to weather? | Best for |
|---|---|---|---|---|
| Ask a neighbour | Free | Any length | Yes (a person) | Short trips, if reliable |
| Self-watering wicks / globes | €10–40 | 3–7 days | No | A few pots |
| Gravity / DIY drip from a tank | €20–80 | ~1 week | No | Off-grid, no tap |
| Tap timer + drip line | €15–50 | Weekend–few days | No (fixed timer) | Simple setups, short trips |
| Smart soil-moisture system (GRAAS iRigator) | from €380 | Weeks | Yes, automatically | Longer trips, mixed crops |
1. Ask a neighbour
Upside: free, and a real person can spot problems — a burst hose, a wilting plant, a door left open.
Downside: depends entirely on someone remembering, and on them judging how much water each crop needs. Fine for a long weekend; risky for two weeks in July.
2. Self-watering wicks and globes
Upside: cheap, no plumbing, good for a handful of pots for a few days.
Downside: they empty at a fixed rate regardless of heat, don't scale beyond a few plants, and give you no idea whether they've run dry.
3. Gravity or DIY drip from a tank
Upside: needs no electricity or mains water — just a raised tank. Great where you only visit once a week.
Downside: hard to dose accurately, pressure drops as the tank empties, and there's no feedback on what the plants actually need.
4. Tap timer with a drip line
Upside: inexpensive and reliable for short absences — set a schedule and the drip line waters on time.
Downside: it's still a clock, not a plant. It gives the same water on a cool, wet day as on a 35°C scorcher, so over a long, variable trip you get over- or under-watering.
5. Smart soil-moisture system — GRAAS iRigator
Upside: it waters each of 4 zones by real soil-moisture readings, so it adapts to the weather while you're gone — more on a hot spell, nothing after rain. It can draw from a water tank with a built-in pump (no mains needed), keeps a backup schedule so a cycle is never skipped too long, and lets you check soil moisture and history from your phone anywhere in the world. For most people that's the difference between "hoping" and "knowing" the greenhouse is fine.
Downside (honestly): the biggest upfront cost of the five; installation takes longer than a timer (though no specialist is needed); and remote check-in needs Wi-Fi or GSM.
The setup that actually survives a two-week holiday
The most reliable approach isn't one method — it's soil-moisture control with a backup schedule. The moisture sensor makes the day-to-day decision and waters only when the soil genuinely needs it; the backup schedule guarantees a cycle still runs if a reading ever looks off. On the iRigator, Eco Pro mode waters from sensor readings with minimum and maximum intervals you set, and Dynamic Pro adjusts the amount of water to how dry the soil is — the way an experienced grower would, but without anyone there to watch it.
Frequently asked questions
Who will water my greenhouse while I'm on holiday?
Your options range from a neighbour to an automatic system. For trips over a few days, a soil-moisture system like the GRAAS iRigator is the most reliable, because it waters based on the weather and lets you check in remotely — you're not depending on anyone remembering.
How long can an automatic system run unattended?
A tap timer covers a weekend to a few days. A smart soil-moisture system with a water tank can keep a greenhouse going for weeks, limited mainly by tank size, since it only draws what the plants actually need.
Does it work without mains water or without internet?
Yes — the iRigator can run from a water tank with its built-in pump, and the watering logic runs locally, so it keeps working with no internet. Wi-Fi or GSM is only needed for remote monitoring from your phone.