Drip irrigation for pots, planters and roof gardens.
Pots and planters hold little soil, so in hot, dry weather they can need water every day, and on a roof they dry faster still. This guide helps you decide how to water them automatically: which pots share a zone, which emitter each pot gets, whether your tank gives enough pressure, and how long to run it, with a worked example.
Written for homeowners and estate and facility managers. Updated .
Key points
- Put pots and planters on a zone of their own, apart from the lawn and the beds, and keep pots in sun apart from pots in shade.
- Give every pot its own emitter, sized so that large and small pots finish watering in the same run.
- Water until a little runs from the drainage holes, then watch the plants for a week and adjust the run time.
- Before you rely on a roof tank, compare its pressure with what your emitters need; a tank only a few metres above the pots usually needs a small booster pump.
- On a roof, ask the building's engineer about the weight of wet pots and about the waterproofing before you start.
On this page
Why pots need a zone of their own
A hydrozone is a group of plants with similar water needs and similar rooting depth, in similar sun and soil, watered together on one valve with its own run time. California's landscape water rules define it as a section of the landscape with plants of similar water needs and generally similar rooting depth.
Pots are a hydrozone of their own. The smaller the pot, the more often it needs water, and pots on a roof, a balcony or beside paving also take the heat and wind of the hard surfaces around them, which Hunter's drip guide says raise plants' water needs.
Keep them off the lawn's sprinklers, and off the shrub beds' zone, whose established plants are watered deeper and less often. Among the pots, split sun from shade: Hunter's design guides draw zones by sun and plant type, and group planters only when they share the same plants and microclimate.
Zones for a whole home gardenZones for estates, hotels and offices
Sources: California Code of Regulations, Title 23, section 490.2 (2025), Model Water Efficient Landscape Ordinance: definitions of hydrozone and plant factor; UF/IFAS Gardening Solutions, University of Florida (checked 2026), Choosing a container for your plant; Hunter Industries (2015), Drip Irrigation Design and Installation Guide (LIT-496), pages 10, 12 and 18; Hunter Industries (2019), Residential Sprinkler System Design and Installation Guide (LIT-226), pages 9 and 26.
Plants for pots and planters
In a pot the roots can go no deeper than the pot, so its soil is the plant's whole store of water. NIHORT, Nigeria's National Horticultural Research Institute, warns that a pot too large can cause root disease, and one too small restricts growth.
NIHORT's guide to setting up an ornamental plant nursery favours tropical plants. From its lists, for example:
- For sunny pots: ixora (Ixora species), croton (Codiaeum variegatum) and plumbago (Plumbago auriculata).
- For colour: annuals such as marigold (Tagetes erecta) and cockscomb (Celosia argentea), which NIHORT says make colourful container plantings.
- For shade and indoors: dieffenbachia, aglaonema, dracaena and snake plant (Dracaena trifasciata, once Sansevieria trifasciata), which NIHORT says can live in the conditions inside a house. Snake plant takes drought and its roots rot if it is overwatered, so give it a smaller emitter than the others, or put it with the succulents.
- Succulents, such as crown of thorns (Euphorbia milii). They need little extra water and should dry out between waterings, so give them a zone of their own or water them by hand.
Drip for succulents and other dry-garden plantsHerbs and vegetables: the kitchen garden guide
Sources: NIHORT, National Horticultural Research Institute, Ibadan (posted 2020), Setting up an ornamental plant nursery: plant types, pot type and size; NIHORT, National Horticultural Research Institute, Ibadan (posted 2020), Techniques of ornamental plants propagation: annuals; UF/IFAS Gardening Solutions, University of Florida (checked 2026), Succulents; NC State Extension, Gardener Plant Toolbox: Dracaena trifasciata.
How much water a pot needs
This series works out daily water in two steps. The first is ETo, the weather's drying power, in mm a day. For a dry-season month in the north and centre it uses 6 mm a day: a field study at Afaka, Kaduna State, found monthly averages of about 5.5 to 6.6 mm a day from December to March, and FAO gives 6 to 7 mm a day for a semi-arid climate at 15 to 25°C. The south and the rains run lower.
The second is the plant factor, the share of ETo the plants use. California's landscape rules give classes from the University of California's WUCOLS list: very low (less than 0.1), low (0.1 to 0.3), moderate (0.4 to 0.6) and high (0.7 to 1.0). The example below takes flowering pot plants as moderate. These Californian classes are only a guide, so watch your plants and adjust.
Water need in mm a day = ETo × plant factor, and 1 mm over 1 m² is 1 litre. So a pot needs that depth times the area its roots draw from: the pot's top, or the plant's spread if wider. Expect more on a roof, where heat and wind add to the need.
Sources: Onwuegbunam and others (2025), Actual crop coefficients and yield response factors of irrigated tomato in Afaka, Northwest Nigeria, Journal of Applied Life Sciences and Environment 58(1): study location and Tables 1a and 1b; FAO (1986), Irrigation Water Management Training Manual No. 3: Irrigation Water Needs, chapter 3, Tables 3, 5, 6 and 14; California Code of Regulations, Title 23, section 490.2 (2025), Model Water Efficient Landscape Ordinance: definitions of hydrozone and plant factor; FAO (1998), Irrigation and Drainage Paper 56: Crop Evapotranspiration, chapter 1, units; Hunter Industries (2015), Drip Irrigation Design and Installation Guide (LIT-496), page 12.
An emitter for every pot
Hunter's catalogue gives single-outlet emitters as a standard choice for potted plants. A supply pipe runs along the pots and each pot gets its own emitter, pushed into the pipe or at the end of a thin 6 mm tube into the pot. One multi-outlet emitter can also feed up to six thin tubes, for a cluster of pots.
Choose pressure-compensating (PC) emitters: they give the same flow over a range of pressures, so the last pot gets as much as the first. Hunter's come in fixed flows of 2, 4 and 8 L/h and more, so a bigger pot gets a bigger emitter, or more than one.
In a wide pot, set two or more around the plant: Hunter notes that in light, fast-draining roof mixes, water runs down rather than spreading sideways. Use polyethylene tube, which Hunter says suits warm climates. A long planter box can take rows of dripline instead: pipe with PC drippers built in.
- Tank on the roof: it stores the water, but on its own gives little pressure
- Small booster pump: gives the emitters the pressure they need
- Zone valve with a battery controller on it; a mains controller does the same where there is power
- Filter, with a pressure regulator: keeps grit out of the small emitters
- Supply line along the pots, with a thin tube climbing into each one
- Emitters in the mix: one in a small pot, two either side of the plant in a large one
- Drainage holes: a little water runs out at the end of each watering
What dripline isHunter HDL-PC dripline, for planter boxesHunter PLD fittings for dripline
Sources: Hunter Industries (2026), Product Catalogue Vol. 41, EMEA metric edition, pages 166, 185, 190 and 192; Hunter Industries (2015), Drip Irrigation Design and Installation Guide (LIT-496), page 7; FAO (2007), Handbook on Pressurized Irrigation Techniques, chapter 3, sections on drippers and pressure-compensated emitters.
Pressure from a roof tank
Flow is how much water passes in a set time, in litres per hour (L/h) for an emitter, or cubic metres per hour (m³/h) for a pump or a pipe; one cubic metre is 1,000 litres. Pressure is how hard the water pushes inside the pipe, measured in bar. Head is pressure given as a height of water, in metres: one bar is about 10 metres of head.
A tank gives pressure from the height of its water above the emitters. Hunter's PC emitters need 1.4 to 3.5 bar, about 14 to 35 metres of head, and its dripline 1 to 4.2 bar. A tank a few metres above the pots, on a roof or on a stand, gives only a few tenths of a bar, and less as it empties; below their range, PC emitters cannot hold their flow.
So unless your emitters' sheet says they work at less, plan for a small booster pump between the tank and the zone, chosen for the zone's flow (all its emitters' flows added together) and the pressure they need.
Raised tanks and pressureChoosing a pump for your water source
Sources: FAO (2007), Handbook on Pressurized Irrigation Techniques, chapter 4: System design; FAO (2007), Handbook on Pressurized Irrigation Techniques, chapter 3, sections on drippers and pressure-compensated emitters; Hunter Industries (2026), Product Catalogue Vol. 41, EMEA metric edition, pages 172 and 190.
Valve, filter and controller
Hunter's drip guide starts every dripline zone with three items: a zone valve, a filter and pressure regulation, and a zone of emitters needs them too. Small emitters block easily: Hunter's need water filtered to 150 mesh (100 microns), and its guide warns that even drinking water carries particles that can clog drippers. Its filter regulator does both jobs in one fitting, with a 150 mesh screen and an outlet pressure of 1.7 or 2.8 bar, both inside the emitters' range. A regulator only lowers pressure, so the pump must give more than its setting.
With no power point near the pots, a battery controller can run the valve. Hunter's NODE runs on 9 V batteries or a small solar panel, mounts on the valve or in its box, and has three programs of up to four start times each. It needs a DC-latching solenoid on each valve; the one-zone NODE-100 comes with one. Ask how the pump will start when the valve opens. Where there is power, a mains controller does the same job.
Hunter filter regulatorHunter NODE battery controllerHunter PGV zone valveHunter X-Core controller, where there is power
Sources: Hunter Industries (2015), Drip Irrigation Design and Installation Guide (LIT-496), page 10; Hunter Industries (2026), Product Catalogue Vol. 41, EMEA metric edition, pages 133, 169 and 190.
Working out a run time
Sources: Onwuegbunam and others (2025), Actual crop coefficients and yield response factors of irrigated tomato in Afaka, Northwest Nigeria, Journal of Applied Life Sciences and Environment 58(1): study location and Tables 1a and 1b; FAO (1986), Irrigation Water Management Training Manual No. 3: Irrigation Water Needs, chapter 3, Tables 3, 5, 6 and 14; California Code of Regulations, Title 23, section 490.2 (2025), Model Water Efficient Landscape Ordinance: definitions of hydrozone and plant factor; FAO (1989), Irrigation Water Management Training Manual No. 4: Irrigation Scheduling, Annex I, Table 8; FAO (1998), Irrigation and Drainage Paper 56: Crop Evapotranspiration, chapter 1, units; Hunter Industries (2026), Product Catalogue Vol. 41, EMEA metric edition, page 190.
What changes the run time
Water until a little runs from the drainage holes, as the University of Florida's extension service advises, but not while the mix is still moist: overwatering is the most common reason container plants die. Never leave pots standing in water, because soggy roots soon rot.
Hot, dry, windy weather dries pots fastest, so watch them closely through the dry season and the harmattan. Iowa State's extension service advises checking annuals in containers every day, and a few twice a day, as they dry out quickly on hot, windy days; Florida's says containers may need water daily in hot months and every few days in cooler ones. If a pot dries out before the next morning, add a second start time.
New plants need water every day or two until their roots fill the mix, as Hunter's design guide says of new shrubs, and it advises watering early in the morning, when it is least windy. In the rains, count the rain that falls on pots in the open. A coarse mix wants smaller, more frequent waterings, as sandy soil does.
Watering sandy, loamy and clay soilsPlanning for the dry seasonTopping up rain in the rainy season
Sources: UF/IFAS Gardening Solutions, University of Florida (checked 2026), Watering the vegetable garden: containers; UF/IFAS Gardening Solutions, University of Florida (checked 2026), Container gardening; UF/IFAS Gardening Solutions, University of Florida (checked 2026), Choosing a container for your plant; Iowa State University Extension and Outreach (2022), Yard and Garden: How frequently should I water annuals in containers?; FAO (1986), Irrigation Water Management Training Manual No. 3: Irrigation Water Needs, chapter 3, Tables 3, 5, 6 and 14; Hunter Industries (2019), Residential Sprinkler System Design and Installation Guide (LIT-226), page 26.
Signs and checks
- In the first week, feel the mix each morning: dry before the run, lengthen it or add a start time; still wet, shorten it.
- A little water should seep from the drainage holes near the end of each run; keep the holes clear and saucers empty.
- Wilting in a dry mix: the pot runs short, its emitter is blocked or its tube has pulled out.
- A mix that stays wet: shorten the run or clear the holes, because soggy roots soon rot.
- Weekly, while the zone runs: every emitter dripping, every tube in its pot, no leaks.
- Open and rinse the filter's screen weekly to begin with, as the maintenance guide sets out, and at least yearly flush the supply line from its far end. Change the controller's batteries before the dry season.
- On a roof, ask the building's engineer whether it can carry the pots with wet soil, and how pots, pipes and drainage should sit on the waterproofing.
Irrigation maintenance through the season
Sources: UF/IFAS Gardening Solutions, University of Florida (checked 2026), Container gardening; UF/IFAS Gardening Solutions, University of Florida (checked 2026), Watering the vegetable garden: containers; UF/IFAS Gardening Solutions, University of Florida (checked 2026), Choosing a container for your plant; Hunter Industries (2015), Drip Irrigation Design and Installation Guide (LIT-496), page 26.
When to ask for a site-specific design
A few pots on a balcony can be set up from this guide. Ask for a design when there are many pots or several levels, when the tank or pump also serves the house, or when pipes must cross the roof's waterproofing. The tank's height, the pump, the pipe run and how many pots one zone can feed all depend on the site.
To design it, we need:
- Your state and town.
- How many pots, how wide each is across the top, and which stand in sun or shade.
- The water source: the tank's size and the height of its base above the pots, or a borehole or town supply.
- Whether there is power near the pots or the tank, any pump you have, and a few photos.
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