Self watering planter: does a water reservoir pot work?
A planter with a water reservoir keeps soil evenly moist, but not every plant likes it. Read when it works, indoors and outdoors, and the smarter alternative.
A planter with a water reservoir keeps the soil evenly moist for longer, because the plant draws water from a storage space at the bottom. It suits houseplants that like steady moisture, but not plants that dislike wet feet, and outdoors you need to watch out for rain and frost.
How does a planter with a water reservoir work?
The base of the pot holds a separate water chamber, divided from the potting soil by a grid or false bottom. Through a wick, a capillary cone or simply through the roots, the soil pulls water upwards as it dries. You refill it through a small filler tube or an opening at the rim, and often a gauge or float shows how much water is left.
The idea is simple: the plant takes what it needs and you reach for the watering can less often. That sounds ideal, but it only works when the soil keeps getting air. If the roots sit in water permanently, the plant gets the same problems as in a pot without drainage. See also how that works for a planter with or without a drainage hole.
Which plants do well with a water reservoir?
A reservoir suits plants that like to stay evenly moist and cope with small swings. Think of peace lily, calathea, ferns, ivy and many herbs on a windowsill. If you are regularly away for a few days, it also saves a lot of fuss.
It is less suitable for these plants:
- Succulents and cacti: they want the soil to dry out between waterings.
- Orchids and other plants with air sensitive roots: they prefer dry to wet.
- Mediterranean plants such as lavender and rosemary: constantly moist soil leads straight to root rot.
- Plants in a fresh pot: the roots first need to explore the soil before they reach the reservoir.
What are the pros and cons of a reservoir pot?
The main advantage is regularity. The soil does not swing between soaking wet and bone dry, which most houseplants prefer. You also water less often, which helps in a warm summer or in an office where watering easily slips.
The drawbacks are less visible. Reservoir water can turn smelly if you never refresh it. Fungus gnats and rotting roots are close by when the soil stays too wet. Reservoir pots are also often plastic, with limited choice in shape and look. And a pot with a fixed reservoir is hard to clean or repair when something goes wrong.
Can a planter with a water reservoir stay outside?
It can, with care. Outdoors, rain fills the reservoir quickly and too much water can build up. An overflow helps, but after a heavy shower the soil stays wet. In winter, water in the reservoir can freeze and crack the pot, especially if the material is not frost resistant. The KNMI shows when frost is coming, and from that moment you empty the reservoir.
If you want a pot to stay outside all year, choose a frost resistant pot with a drainage hole and first read what frost resistant really means. For a terrace plant in summer a reservoir is a luxury, not a necessity.
Is terracotta or earthenware suitable for a water reservoir?
Terracotta and earthenware are porous: they breathe and moisture evaporates faster. That is good for the roots, but a reservoir in such a pot empties sooner, and a built in reservoir is hard to make watertight. Plastic holds moisture longer and therefore suits a fixed reservoir better.
Do you have a beautiful decorative pot without a reservoir of its own? Then there is a smarter route, see below.
What is the alternative: an inner pot with a reservoir in a decorative pot?
For many houseplants the best combination is a plastic inner pot with a reservoir, placed inside a decorative outer pot. The plant sits dry and airy in its own pot, the water is in the inner pot, and the outer pot does not need to be watertight. A handmade mosaic pot can then simply stand on the windowsill or in the living room without worries about leaks.
Make sure the inner pot is a few centimetres narrower than the outer pot, so you can lift it out easily to let it drain. An inner pot of 24 cm, for example, fits an outer pot with an inside width of roughly 26 to 27 cm. We explain how in our guide to using an inner pot inside a decorative pot, and which size suits your plant is covered in which pot size you need.
How often should you refill or refresh the reservoir?
Check the gauge or the weight of the pot every week. Only refill once the reservoir is (almost) empty, and let it run dry for a day now and then so the soil can breathe. Refresh the water about every two to four weeks, preferably with rainwater or water that has stood overnight. Rinse the reservoir a few times a year to prevent algae and limescale.
In winter a plant needs less water. Lower the refill rhythm then, even when the pot stands indoors.
Frequently asked questions
Is a water reservoir better than a watering can?
Not necessarily. A reservoir gives steadier moisture and saves effort, but you check the soil less often. With a watering can you feel how wet the soil is yourself. For moisture loving houseplants a reservoir is handy, for plants that like it dry the can is better.
Can a plant drown in a reservoir pot?
Yes, if the reservoir stays full or the soil gets no air. You recognise rotting roots by a sour smell and limp, yellow leaves. Let the reservoir run dry for a few days, take the plant out if needed and remove the diseased roots.
Which pot needs a water reservoir in an office?
A large inner pot with a reservoir inside a decorative pot works best, because the plants can then go days or weeks without a refill. For businesses, Masr Potten & Vazen can make decorative pots to order, with a company logo in the mosaic.
Looking for a decorative pot that fits around an inner pot with a reservoir? Browse the collection of handmade mosaic pots from Masr Potten & Vazen, or request a no obligation quote for custom work in colour, model and size.
