Before going away, the problem is not just filling the watering can: it is providing the right amount of water for each plant over several days, without waterlogging the roots. One simple method uses a water reservoir and an absorbent wick. It can work, but it is no substitute for testing it in advance or knowing what the plants need.
Can a piece of string really carry water?
Yes. A wick made from absorbent material connects a container of water to the potting compost. Through capillary action, moisture can travel along the fibres and reach the growing medium. The Royal Horticultural Society (RHS) recommends this method for large potted plants, and capillary mats for collections of small pots.
See the RHS guide to looking after plants while you’re on holiday.
However, the technique has no magic setting. The flow depends in particular on the material, its contact with the compost, the water level, the path taken by the wick and the plant’s needs. A synthetic string that absorbs little, or one simply placed on the surface of dry compost, may prove ineffective. Conversely, a continuous water supply can leave some roots too wet.
It would therefore be misleading to say that the plant takes exactly “what it needs”, or that the system automatically stops when the soil becomes damp.
How do you set up a wick system?
The University of Florida, through its UF/IFAS Extension service, describes a solution with a reservoir placed above a group of plants and cotton cords leading into the compost. It presents this as an option for an extended absence, without guaranteeing a set number of days for every household.
Read the University of Florida’s advice on plants while you’re on holiday.
For a first set-up, it is safer to start with just one pot, so you can check how the system actually works:
1. Choose a stable container large enough to hold an appropriate reserve, away from electrical sockets and surfaces that are sensitive to water. 2. Install a clean absorbent wick, for example one made of cotton or capillary fabric. One end must remain submerged as the water level falls; the other must maintain effective contact with the compost. 3. Water the pot as usual before putting the system into operation, then check that excess water drains away properly. 4. Monitor the moisture in the growing medium and the reservoir level for several days. Adjust the system if the soil stays waterlogged or dries out despite the wick. 5. Only use the system with other pots once you have checked their individual needs.
The proportions in this example are deliberately left open: no length of cord, basin height or reservoir volume is universally suitable for all plants.
Which plants cannot tolerate constant moisture?
Plants do not all have the same watering routine. Cacti and many succulents can tolerate a dry spell and may suffer from unsuitable continuous watering. Conversely, some houseplants need more consistent moisture, but that does not mean their roots should be left in water.
The RHS warns of the risk of waterlogging, rot, wicks shifting and reservoirs emptying. Conditions also change with the seasons: a pot away from a scorching window does not use water in the same way as one exposed to the summer sun.
A resource published by the University of Minnesota on 2 February 2026 also highlights the importance of using a pot with a drainage hole so that excess water can escape.
Read the University of Minnesota’s recommendations on houseplants.
Wick, capillary mat or someone you trust?
For a short absence, watering appropriately just before you leave and moving the pots into indirect light may sometimes be enough. It depends on the room temperature and the species being grown. A water reservoir is not necessarily the first thing to try.
For several small pots, the RHS suggests another solution: placing suitable containers on a capillary mat with one end in contact with a reservoir. The method requires good contact between the pots’ drainage holes and the damp surface. It is not suitable for all containers.
For longer absences, or when certain plants are particularly sensitive, horticultural organisations advise arranging for someone to come and check the moisture, the condition of the leaves and any pests. No homemade set-up can replace this inspection.
Testing before you leave makes all the difference
The main advantage of a wick is that it needs neither a pump nor a timer. Its main drawback is precisely the lack of fine control: if the water does not flow, the reservoir tips over or the soil stays saturated, nobody will automatically put things right.
The right set-up is therefore not one that promises to keep all plants alive “automatically” for weeks. It is one whose operation you have observed on the pots in question, in conditions similar to those they will face while you are away.
