Start with an honest look at what you are leaving

Before you rig up anything clever, take ten minutes to assess your plants. A mature rosemary in a 30cm terracotta pot will shrug off a fortnight without you. A young tomato in a grow bag will collapse in a single hot day. Small pots, glazed or unglazed, hanging baskets and anything growing in a shallow tray dry out frighteningly fast, so give those the attention and let the tougher specimens fend for themselves.

Think about position, too. That balcony corner catching sun from eleven until six is effectively an oven, while a pot tucked against a north-facing wall loses far less moisture. If you can move plants into shade before you go, you have already solved half the problem without spending a penny.

Self-watering pots and reservoirs

Self-watering containers are the most reliable solution for a one to two week absence, and they are easy to make or buy. The principle is a sealed water reservoir below the compost, with a wick or a capillary column drawing moisture upwards as the compost dries. Roots stay consistently damp rather than swinging between drought and flood, which is what most container plants actually want.

• Purpose-built self-watering pots usually hold a week to ten days of water in a modest 25cm size. Fill the reservoir to the brim on the morning you leave.
• Wicking containers made from a plastic crate and a fabric liner can be set up at home. A strip of capillary matting or an old cotton towel running from the water chamber into the compost does the job.
• Upside-down bottle feeders work for smaller pots. Fill a one or two litre bottle, pierce two or three small holes in the cap, and push it into the compost, cap downwards. Test it for a day first — holes that are too big will empty the bottle in an hour.
• Terracotta spikes screwed into a wine bottle are neat and slow, but check the flow before relying on them. Some let water through so slowly that the plant never gets enough.

The one thing to avoid is standing pots permanently in deep water. Roots need air, and a saucer filled to the rim for a fortnight is a recipe for rot, especially with rosemary, lavender or anything Mediterranean.

Capillary matting and tray systems

Capillary matting is the quiet hero of holiday watering. It is a thick felt-like fabric that sits in a shallow tray of water and pulls moisture sideways and upwards into pots standing on top of it. It works best with plastic or glazed pots, since unglazed terracotta also sucks water through its walls and can soak up more than its share.

Set it up like this: line a gravel tray with matting, leave one end of the matting trailing into a separate container of water, then stand your pots on the matting with their drainage holes in contact with the fabric. Press the matting against the base of each pot so there is a good connection. Group pots of similar thirst together, and give the tray a test run for two or three days before your trip so you can see how quickly the reservoir empties.

An old towel or thick cotton sheet cut to size does a passable impression of shop-bought matting, and it is a good use for fabric that has seen better days.

Mulch is your cheapest insurance

Mulching is unglamorous and remarkably effective. A 2–3cm layer of material on the surface of the compost slows evaporation, keeps the top layer cooler and reduces the number of days your plants spend gasping. Do it a week before you leave, while the compost is already damp, so you are sealing in moisture rather than trapping dryness.

• Bark chips or composted bark suit shrubs, herbs and larger containers.
• Gravel or horticultural grit works well on succulents and alpines, and looks tidy on a windowsill.
• Hydroleca or expanded clay pebbles are excellent for houseplants and indoor herbs.
• Grass clippings should be used thinly and only on established plants, as a thick layer will heat up and go sour.

Push the mulch aside to water, then replace it. Never water through a dry gravel layer and assume the compost below has had a drink.

Shade, grouping and the days before you go

Two simple moves buy you days. First, group all your pots together, tightly enough that the leaves touch. This creates a humid microclimate between the plants and cuts water loss from each one. Second, move the whole cluster somewhere out of the harshest midday sun — under an awning, beside a north wall, or indoors on a bright but sunless windowsill for houseplants.

Hanging baskets can be taken down and sat on a tray of damp matting, which makes an enormous difference. Grow bags benefit from being pushed against a wall and covered with a sheet of plastic with a few slits for air.

In the final days, water everything thoroughly and deeply, ideally in the evening, until water runs from the drainage holes. Then stop. Soggy compost followed by a fortnight of neglect is a faster killer than dryness. Remove any saucers that hold standing water.

On the day you leave, and when you return

Fill every reservoir, top up every bottle, and check that wicks and matting are properly in contact. If a neighbour is looking in, leave clear, simple instructions: one jug per pot, every third day, no ad-libbing. Overwatering by a well-meaning helper ruins more holidays than drought does.

When you get back, expect some limp leaves and a few crispy edges. Water gently, move plants back into their normal light gradually, and resist the urge to flood everything at once. Cut back anything clearly dead, feed once new growth appears, and make notes on what survived. A season or two of this and you will know exactly which plants to keep in small pots and which to hand over to a friend before you book the flights.