Watering groundcovers: drip grid or low sprays?
A groundcover bed is a carpet of low plants, so water must reach all of it, edges included. You are choosing between a grid of dripline under the plants and low-rate sprays over them. This guide covers the plants, their water need, laying out a dripline grid on a slope, and a run time worked from the weather.
Written for homeowners and estate and facility managers. Updated .
Key points
- Give groundcovers a zone of their own, apart from lawn sprinklers and from trees and shrubs, which root deeper.
- A dripline grid wets the whole bed and keeps water off paths and walls; new cuttings also need water from above until they root.
- Lay the rows across the slope, run a row close to each edge, and put an air valve at the top and a flush valve at the far end.
- Groundcovers range from low to high water need: zone them by class, then watch the bed and adjust.
- Water in short pulses, clean the filter, and flush the lines at least once a year.
On this page
A groundcover bed is a zone of its own
A hydrozone is a group of plants with similar water needs and rooting depth, watered together by one valve with its own run time. California's landscape water rules, which this series follows for the idea, define it so. Hunter's drip guide gives each hydrozone its own valve, set apart by plant type, spacing, sun, exposure and slope.
A groundcover bed on drip never shares a valve with lawn sprinklers: a drip zone starts with its own valve, filter and pressure regulator, and runs on another schedule. Trees and large shrubs in the bed use more water than the groundcover; Hunter gives them extra rings of dripline, or a zone of their own with bubblers. Group groundcovers by water class too: drought-tolerant ones on a drier zone, thirsty ones such as caladium on a wetter one.
Watering a lawn: sprays, rotors and run timesTree irrigation with bubblers and dripDrought-tolerant bed irrigation
Sources: California Code of Regulations, Title 23, section 490.2 (2025), Model Water Efficient Landscape Ordinance: definitions of hydrozone and plant factor; Hunter Industries (2015), Drip Irrigation Design and Installation Guide (LIT-496), pages 10 and 19.
Groundcovers and how they grow
Groundcovers are low plants that spread over the soil by runners, trailing stems or clumps. Notes from the Federal University of Agriculture, Abeokuta, give periwinkle, caladium, Begonia rex, Alternanthera and moss rose as groundcover examples, and purple heart (as Setcreasea purpurea) for planting along a building's foundation. Growth below is from North Carolina State University, water class from UC's WUCOLS list.
Their roots stay shallow: the University of Arizona puts mature lawn and garden plants' roots in the top 15 to 30 cm, shrubs' in 30 to 60 cm. Wet that depth, no deeper.
| Plant | How it grows | Sun or shade | Water class |
|---|---|---|---|
| Purple heart (Tradescantia pallida) | Trailing stems about 30 cm high and up to 60 cm wide; can overrun a bed | Full sun to part shade | Moderate |
| Madagascar periwinkle (Catharanthus roseus) | Upright to spreading, 15 to 45 cm tall; flowers through the heat | Full sun to part shade | Moderate |
| Mondo grass (Ophiopogon japonicus) | Grass-like tufts up to 30 cm, spreading by runners; takes foot traffic | Prefers shade, tolerates sun | Moderate |
| Caladium (Caladium bicolor) | Large coloured leaves from tubers, 30 to 60 cm tall; needs plenty of water while growing | Part to deep shade | High |
| Trailing lantana (Lantana montevidensis) | Trailing stems 30 to 45 cm tall, 0.9 to 1.5 m wide; used on slopes; spreads by seed and can become weedy | Full sun | Low |
Sources: Federal University of Agriculture, Abeokuta, HRT 507 Ornamental Horticulture lecture notes (Aiyelaagbe and Olosunde), pages 2 and 3: foundation plants and ground covers; NC State Extension Gardener Plant Toolbox: Tradescantia pallida (purple heart); NC State Extension Gardener Plant Toolbox: Catharanthus roseus (Madagascar periwinkle); NC State Extension Gardener Plant Toolbox: Ophiopogon japonicus (mondo grass); NC State Extension Gardener Plant Toolbox: Caladium bicolor (caladium); NC State Extension Gardener Plant Toolbox: Lantana montevidensis (trailing lantana); WUCOLS IV, University of California (2025), plant search database: ratings for the plants named; University of Arizona Cooperative Extension (2017), Watering Trees and Shrubs, AZ1298.
How much water groundcovers need
Water need in a day, in mm, is ETo times a plant factor. ETo is the weather's drying power: what a well-watered field of grass loses in a day. One mm of water over one square metre is one litre.
For a dry-season month this series uses an ETo of 6 mm a day. A field study at Afaka, Kaduna State, worked out monthly averages of about 5.5 to 6.6 mm a day from December to March, and FAO gives 6 to 7 for a semi-arid climate at 15 to 25°C. That fits the north and centre; the south and the rains run lower.
The plant factor is the share of ETo a plant uses. California's rules sort plants into 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 classes come from California and are a guide only. This guide takes 0.5 for a moderate groundcover, picked from the class range; start there, then watch the bed and adjust.
Not all the water reaches the roots. This series counts 90 percent for drip, after FAO, and 75 percent for sprays, the top of USDA's 60 to 75 percent for fixed sprinklers.
Irrigating tomatoes, peppers and onions: ETo explainedSupplemental irrigation in the rainy season
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 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; WUCOLS IV, University of California (2025), plant search database: ratings for the plants named; FAO (1989), Irrigation Water Management Training Manual No. 4: Irrigation Scheduling, Annex I, Table 8; USDA-NRCS (1997), National Engineering Handbook Part 652: Irrigation Guide, chapter 6, Table 6-4.
Dripline grid or low-rate sprays
Dripline is tubing with drippers built in at a fixed spacing; laid in parallel rows, it makes a grid under the whole bed. Hunter lists it for groundcovers and for narrow, curved or small areas beside walls, where it keeps water off buildings and walkways.
Flow is how much water passes in a set time, in litres per hour (L/h) for a dripper; pressure is how hard the water pushes inside the pipe, measured in bar. Hunter's HDL-PC dripline is 16 mm tubing with drippers of 2.4 or 3.8 litres an hour, 30 or 45 cm apart. They are pressure compensating: each gives the same flow from 1 to 4.2 bar, so the far end of a row gets as much as the near end. Ahead of it go the zone's valve and a filter of at least 120 mesh (the higher the mesh, the finer the filter); Hunter's filter-regulator has a 150 mesh screen and holds 1.7 or 2.8 bar. On a larger site, a disc filter near the water source protects every zone.
| Compare | Dripline grid | Low-rate sprays (MP Rotators) |
|---|---|---|
| Where the water goes | Into the soil under the plants | Over the leaves and the soil |
| Edges, walls and paths | Stays off them | Needs careful arcs to keep off them |
| Shapes it suits | Any shape, narrow strips and curves included | Open beds wide enough for the throw |
| New cuttings | Need water from above until they root | Watered from the start |
Hunter HDL-PC driplineHunter filter regulatorHunter HY filter, screen or discHunter PGV zone valveHunter MP Rotator nozzleHunter Pro-Spray pop-up body
Sources: Hunter Industries (2015), Drip Irrigation Design and Installation Guide (LIT-496), pages 5, 6, 10 and 24; Hunter Industries (2026), Product Catalogue Vol. 41, EMEA metric edition, pages 52, 169 and 172.
Laying out the grid
Water spreads further sideways in clay than in sand, so Hunter's drip guide sets dripper and row spacing by soil; the table gives its figures in metric, with the nearest HDL-PC dripline. Lay the grid like this:
- Start with the longest side and lay parallel rows to fill the bed; follow curves with returns or branches.
- On a slope, lay the rows across it, along the contours, fed from a supply pipe that starts at the top.
- Run the first and last rows close to the edges, a quarter of the row spacing in and no more than 10 cm: edges dry out fastest.
- Join the far ends with an exhaust pipe, with an air valve at the highest point and a flush valve furthest from the supply.
- Keep each row within the maker's maximum length: for HDL-PC at 2.4 litres an hour every 45 cm, 96 m at 1 bar.
- Pin the tubing about every 1.5 m and near every fitting, and flush the lines before the final connections.
| Soil | Dripper flow | Dripper spacing | Row spacing | Nearest HDL-PC |
|---|---|---|---|---|
| Clay | 1.5 L/h | 61 cm | 46 to 61 cm | 2.4 L/h at 45 cm |
| Loam | 2.3 L/h | 46 cm | 41 to 56 cm | 2.4 L/h at 45 cm |
| Sand | 3.8 L/h | 30 cm | 30 to 46 cm | 3.8 L/h at 30 cm |
- The zone's own valve, then a filter and a pressure regulator
- The supply pipe down one side, fed from the top of the slope
- Rows of dripline across the slope, level along it; the arrow points downhill
- The first and last rows run close to the wall and the path, where the edges dry out fastest
- An air valve at the highest point
- A flush valve at the far, low corner, opened to wash out the lines
- The groundcover, covering the whole bed, so the drippers must cover it too
Where the soil is unknown or varies, Hunter uses the closer spacing and the higher flow. On slopes steeper than 5 percent it zones the top, the slope and the foot apart, or widens the rows on the bottom third by up to 25 percent.
Sources: Hunter Industries (2015), Drip Irrigation Design and Installation Guide (LIT-496), pages 8, 9, 11, 12, 14, 17 and 27; Hunter Industries (2026), Product Catalogue Vol. 41, EMEA metric edition, page 172.
Run times: a worked example
Pulse the water: for any run over 12 minutes, Hunter recommends several shorter runs a day, so water spreads through the soil instead of saturating it; an X-Core's Cycle and Soak does this. Water early in the morning, with least wind and heat.
Hunter X-Core controller, with Cycle and Soak
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 (1989), Irrigation Water Management Training Manual No. 4: Irrigation Scheduling, Annex I, Table 8; USDA-NRCS (1997), National Engineering Handbook Part 652: Irrigation Guide, chapter 6, Table 6-4; Hunter Industries (2015), Drip Irrigation Design and Installation Guide (LIT-496), page 25; Hunter Industries (2026), Product Catalogue Vol. 41, EMEA metric edition, pages 52, 105 and 172; University of Arizona Cooperative Extension (2017), Watering Trees and Shrubs, AZ1298.
New plants, soils and seasons
- New cuttings. Water them from above as well, by hand or with sprays, until their roots reach the drippers: typically three to six weeks, Hunter says. Keep the soil moist meanwhile and check the bed often.
- Soil. Sand takes closer drippers and rows; on clay, use wider spacing and pulses with time to soak in. The soils guide covers how often to water each.
- The dry season and the harmattan. Plan the whole season with the dry-season guide.
- The rains. ETo falls and rain does much of the work. A rain sensor such as the Mini-Clik halts scheduled watering once a set amount of rain has fallen, and lets the controller water again as it dries; between storms, the rainy-season guide shows when to top up.
Watering sandy, loamy and clay soilsPlanning dry-season irrigation in NigeriaSupplemental irrigation in the rainy seasonHunter Mini-Clik rain sensor
Sources: Hunter Industries (2015), Drip Irrigation Design and Installation Guide (LIT-496), pages 8, 9 and 24; Hunter Industries (2026), Product Catalogue Vol. 41, EMEA metric edition, page 155; Hunter Industries (checked 2026), Mini-Clik rain sensor: product page.
Signs and checks
- Dry, thin edges: move the edge row closer.
- Dry soil, wilted or curled leaves, older leaves yellow or brown: too little water.
- Soil that stays damp, pale young leaves, wilted young shoots, algae or mushrooms: too much water.
- After watering, a thin rod slides through wet soil and stops at dry soil, at the bottom of the roots.
- Wet spots of even size along every row while the zone runs, and no pools or leaks.
- The filter cleaned, and the lines flushed at least once a year through the flush valve, watching the water that comes out.
- Pressure at the valve and the flush valve measured when new and noted, for later comparison.
- A cut or punctured line cut back and rejoined with a barbed connector.
Irrigation maintenance through the seasonSeven causes of drip irrigation failure
Sources: University of Arizona Cooperative Extension (2017), Watering Trees and Shrubs, AZ1298; Hunter Industries (2015), Drip Irrigation Design and Installation Guide (LIT-496), pages 12, 23, 24 and 26.
When to ask for a design
A drip layout depends on the site: the flow and pressure the source gives, which set how many rows one valve can feed; the bed's shape and slope; and the soil. HDL-PC's check valves hold water in the line up to 2 m of height; Hunter's drip guide splits taller slopes into separate zones. We design and supply garden drip systems, and installation can be quoted. To plan one, send us:
- State and town or local government area
- Crop, or the type of site
- Area, in hectares, acres or square metres
- Where the water comes from, and how much you think you have
- How you pump today, and what powers the pump
- When you want the system working
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Sources: Hunter Industries (2015), Drip Irrigation Design and Installation Guide (LIT-496), page 17; Hunter Industries (2026), Product Catalogue Vol. 41, EMEA metric edition, page 172.
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Planning a groundcover bed?
Send us a sketch or photos of the bed, its slope and edges, and tell us where the water comes from. We design and supply garden drip systems, and installation can be quoted.