Nursery and greenhouse irrigation has advanced far from the initial days of hand watering. These days there are a multitude of ways to irrigate your nursery or greenhouse. From spray stakes, to overhead options, to misting and fogging, nursery and greenhouse irrigation has never been so efficient and effective. Greenhouses present their own set of problems, the closed environment can foster disease growth, and it is very important to control the climate in the greenhouse to ensure warmer temperatures during propagation and cooler temperatures during the vegetative and fruiting stages.
The following article will focus on the methods to irrigate your nursery or greenhouse with low pressure drip irrigation. Multiple methods and styles will be covered with links to products and more information included throughout the article.
Spray stakes are perhaps the most popular method we see used today, particularly for container plants. Spray stakes can consist of individual emitters attached to a stake, or to stakes that connect to the outlet of a specific dripper. When using spray stakes, it’s common to have one per plant.
There are many types of spray stakes and emitters on stakes available used in these applications. Let’s cover a few of them below.
Adjustable Emitters on Stake
Adjustable drippers/sprayers/bubblers are a popular choice for many nursery and container plant applications. The short, 6” stakes can be secured right in the container and the adjustment knob allows for some customization of water volume for different stages of plant growth. The adjustment knob also influences throw distance, allowing them to be used in a variety of container sizes. Adjustable emitters are available in a reasonable variety of spray patterns, from 360° umbrella type patterns, to 360° vortex fan patterns, to 90° and 180° options. The vast majority of these emitters connect to ¼” microtubing via the ¼” barb on the stake.
Because these are adjustable over a wide range of flow rates, it is important to keep in mind that, at higher settings, these can create a very heavy flow load on a system. The standard umbrella pattern adjustable dripper on a 6” stake has flow rates from 0 to 19 GPH, whereas the adjustable bubbler has potential flow rates of up to 31 GPH. Given this wide range, it’s
possible to get great performance on lower settings, but quickly overtax the flow rate of your water source or the ability of your mainline tubing to accommodate such heavy flows at higher settings. If the higher settings are to be used, careful planning will be required.
This video illustrates the spray patterns of our adjustable emitters, starting at 45 seconds in: Adjustable Emitter Spray Patterns
Spot Spitters were among the very first nursery specific spray stakes and have been a popular choice for nursery irrigation since their inception. They remain one of the most economical, effective and efficient options available. Spot Spitters are available in several different sizes: Short, Regular, Tall, and a Downspray model to accommodate almost any growing container. Their flow rates range from 3.6 GPH to 17.4 GPH.
With their unique design, there really isn’t a comparable emitter, Spot Spitters get a category they can almost call their own. Spot Spitters have a handy shut-off feature that allows individual spitters to be shut-off when no longer needed. You simply remove the stake from the soil, turn it over and insert the shut-off barb into the tubing. Though there are more modern options available, there is something elegant and very effective in the simplicity of their design and use.
Spot Spitters should not be used with vinyl tubing; the vinyl is a bit too soft and will pop off the barb. Be sure to use poly tubing if you’re using Spot Spitters to save some hassle.
Note: Spot Spitters, unlike most of the other emitters in this article, connect via ⅛” Microtubing rather than ¼” microtubing. The barbs on them are too small for ¼” tubing, be sure if you plan to use Spot Spitters that you get or already have ⅛” (0.125" ID x 0.185" OD) poly tubing. Available spray patterns depend on which Spot Spitter (short, regular, downspray or tall) is used; available options are 90°, 160° and 360° on the regular Spot Spitters.
Antelco CFd Downspray
Antelco's CFd Downspray is rapidly becoming a favorite in nurseries across the country. They create a gentle 360° spray that sprays downward at about 45° to help reduce the effect of wind on the spray and minimize damage to foliage. They are available in three color coded flow rate options: ddd
Black, Low Flow: 4.8 - 7.2 GPH
Brown, Medium Flow: 6.0 - 8.6 GPH
Blue, High Flow: 7.0 - 10.5 GPH
They are available pre-assembled on a galvanized stake assembly with 36” of tubing, or as just the emitter on quick threads to be connected to a Rigid Riser. The CFd Downspray Assemblies come equipped with a handy shut-off clip to stop flow when an individual downspray is no longer needed.
Netafim Spray Stakes
Netafim's Spray Stakes are a fairly new concept, and the first pressure compensating emitter in this category. They incorporate Netafim’s classic quality and ingenuity to bring us a spray stake that operates like none other.
These spray stakes are available in several color coded flow rates, 3.2, 6.6, 7.9, and 10.6 GPH and come equipped with a check valve. The spray stakes themselves also require the corresponding Netafim’s Dripper Tubing Assembly. This means if you get the 3.6 GPH Netafim Spray Stake, you’ll also need the 3.6 GPH Netafim Dripper Tubing Assembly.
The Netafim Dripper Tubing Assembly consists of 36” of poly tubing, the connection cap to connect the tubing to the spray stake, and, most importantly, a pressure compensating dripper to provide uniform distribution.
These have the option of coming as a standard spiked stake, or with the use of a 12 gauge metal rod. The dripper is installed into the wall of ½” or larger poly tubing, and the tubing ran over to the spray stake which is placed at the plant or in the container. This provides one of the most precise irrigation and fertilizer injection possible. Their uniformity is unmatched by almost any other option in the spray stake category. The check valve prevents low head drainage, an important feature when chemicals are injected into the lines or the plants have precise watering demands.
The spray stakes come with a side mounted secure shut-off so that stakes that are no longer needed can be shut off, while others remain in use. The side mounted shut-off makes it easy to spot which stakes are currently not in use.
In addition to unparalleled uniformity, these have the option of coming in a “bow tie” spray pattern which effectively doubles their spray distance, something beneficial for coarse soil mixes or large pots. This allows for one stake to essentially do the work of two.
Overhead and Inverted Emitters
Overhead and inverted irrigation has been a popular option for nurseries, greenhouses, and shade houses for some time; emitter technology has advanced enough that the efficiency of inverted emitters isn’t that far off from button drippers. Emitters like Senninger’s Wobbler, BowSmith’s Inverted Fan Jets and Antelco’s Inverted Rotor Sprays, operate at low, efficient pressures to deliver consistent, uniform results.
If you’ve done any research on greenhouse and nursery irrigation, you’ve no doubt ran into Senninger's Wobbler. They are among the most popular inverted options due to their uniformity, potential for large diameter, high volume and gentle, rain-like droplets. The inverted wobblers work at low pressure (20 - 25 PSI), making them a water-saving choice compared to traditional methods such as high pressure impact sprinklers.
Though they are capable of putting out a high volume of water, they do so over an equally large area, meaning the soil has time to absorb the water before more is applied. The droplets are gentle and rain like and thus experience low evaporative loss and are less likely to damage foliage.
Senninger produces several accessories that improve the already excellent performance of their Wobbler lineup. Head drainage is always a concern in overhead applications; for this reason, Senninger offers the Drain Stop Plus. The Drain Stop Plus serves as a check valve to prevent head drainage after system shutdown. This is particularly useful for the precise delivery of fertilizer or other injected treatments. The Drain Stop has three settings: Open, Check and Closed. This allows individual wobblers to be turned off when they are no longer needed.
Drop Adapter Assemblies are available for simple and fast installation of Wobblers and other inverted microsprinklers, foggers and misters. Senninger drop assemblies are available with two different barb sizes: 0.270” for lower flow emitters, and 0.345” for higher flow emitters. They are available in either a barbed or ½” MPT connection to fit a variety of systems. Riser Adapter Assemblies, for upright applications, are also available with similar options.
If you’d like to learn more about Wobblers, the Wobbler buying guide is available at this link: Wobbler Buying Guide
BowSmith Inverted Fan-Jet Assembly
BowSmith's Fan-Jet emitters have been around since 1977. Since that time they’ve undergone many revisions, and what was always a good emitter has only continued to improve and is now available inverted for overhead applications in greenhouses and high tunnels.
The inverted fan-jet assemblies include a PVC drop tube to provide stability. They connect to poly tubing via a convenient ¼” barb. Like other options mentioned in this article, these are a low-pressure solution, operating between 10 and 30 PSI. Flow rates start at low as 4.4 GPM (black nozzle at 10 PSI) and go as high as 29.4 GPM (red nozzle at 30 PSI).In addition to their large wetting pattern and consistent delivery, what makes these unique is the sheer variety of spray patterns available to match almost any project’s needs. The chart below illustrates many of the patterns available.
Antelco Inverted Rotor Spray Mini Sprinkler
Antelco's Inverted Rotor Spray Mini-Sprinkler is the inverted version of their popular Rotor Spray lineup. Designed specifically for overhead greenhouse and nursery irrigation, it is a low pressure, low flow emitter. Available flow rates are: 10.5, 13, 22, 30, 35.5 and 43.5 GPH. Note these flow rates are in gallons per hour rather than gallons per minute, making this the lowest flow option available amongst the inverted sprayers and microsprinklers listed in this article. Throw diameters range from 13.2’ to 24.4’.
This emitter’s droplets are gentle, as you’d expect most low pressure options to be. This significantly reduces the chance that delicate foliage or starts will be damaged by the spray from the emitter. Each rotor spray is equipped with 10-32 UNF threads to be threaded into a Rigid Riser or Shrub Riser Adapter. The rigid riser or shrub adapter promotes stability when used in an overhead application.
Jain Twist Weight with Pressure Compensating Dripper
Note: Jain is updating the appearance of the dripper, images are not current.
The Jain Twist Weight PC Dripper Assembly is a dripper assembly frequently used in both overhead and bench nursery and greenhouse applications. Other than the Netafim Spray Stake, it is the only pressure compensating solution in this category, but is also available in non-pressure compensating. The pressure compensating dripper can compensate between 12 and 40 PSI. Available flow rates for the pressure compensating model are 0.5, 1.0 and 2.0 GPH, 1.0 GPH for the non-pressure compensating model. Available tubing lengths are: 12”, 18”, 24”, 36” and 48”.
This is attached to ¼” or larger poly tubing via the ¼” barb on the dripper end of the assembly. The weight, where water emits from, is then either suspended above the container it is irrigating or simply placed in the pot if the tubing is at ground level. The attached weight provides stability for either installation. The weight also serves as an on/off. The weight can be twisted (hence the Twist Weight title) to shut-off flow when the emitter is not needed.
In addition to overhead greenhouse and nursery applications, this emitter sees a lot of use for overhead baskets and similar hanging containers. This makes it a flexible emitter that is compatible with many irrigation projects and needs.
Other inverted emitter options are available at this link: Inverted Emitters
Most overhead accessories focus on two issues that vex many growers who have attempted overhead irrigation: stability and head drainage. These solutions include weights that are used to stabilize overhead emitters that are apt to experience movement during pressurization and operation, and check valves that help prevent low head drainage.
Senninger One Weight -- When more weight is needed to ensure stability, this 0.85 lb zinc alloy weight is one of the go to options.
Hunter HCV -- This adjustable check valve is available in ½” or ¾” NPT, making it small enough to fit in drop assemblies, PVC mainlines and more. It is adjustable to hold head height between 4’ to 32’ with an opening pressure of 2 to 17 PSI. If low head drainage is a problem, this check valve can solve it.
Senninger Magnum Weight -- Like the Senninger One Weight above, this 0.85 lb weight is perfect for drop assemblies that require more stability. Compatible with the i-Wob, Xi-Wob, LDN and Super Spray. A threaded option is available for the i-Wob.
Senninger Drain Stop Plus -- Linked above as well, this serves as an on/off valve and check valve in one. Opens at 22 PSI and closes at 6 PSI when in Check mode. Features a standard ½” MPT inlet and ½” FPT outlet that allows it to be used with almost any brand’s emitters.
Netafim SlimLine EZ Close Plastic Weight -- This weight is similar to the Jain weighted assemblies mentioned above but works with Netafim’s Woodpecker PC Drippers and 0.125” Inside Diameter (⅛”) tubing. Like Jain’s, this one allows for on/off functionality at individual emitters.
Drip Arrow Sticks and Multi-Outlet Manifolds
Though two different products, Drip Arrow Sticks and Multi-Outlet Dripper Manifolds work together to create efficient irrigation for nursery containers. They allow a single emitter to irrigate multiple containers. This can be particularly useful for plants that need low volumes of water or those that need frequent watering cycles. The multi-outlet manifold fits on over the outlet barb of compatible drippers. ⅛” (0.125” ID) tubing is then connected to the outlet barb(s) on the manifold, which is in turn connected to the arrow stick that is placed in the container. Multi-outlet manifolds are available with 2 and 4 outlets. In this way, a single 1.0 GPH dripper can act as four 0.25 GPH drippers.
Drip Arrow Sticks
Drip arrow sticks are available as angle or straight sticks to fit a variety of needs. These are sometimes referred to as labyrinth stakes. This is due to the labyrinthine passage the water has to pass through in the stake; the labyrinthine passages provide for greater uniformity, similar to the flow path found in button drippers. All of the arrow sticks we currently carry are compatible with ⅛” (or 0.125” Inside Diameter) tubing and will not work with ¼” tubing. The multi-outlet manifolds they work with are also compatible with ⅛” tubing.
The multi-outlet manifolds are available with two, four or stacking four outlets. The inlets are designed to connect directly to the outlet barb on compatible drippers, and the outlet barbs to ⅛” Poly Tubing. These essentially split an emitter into multiple emitters, allowing one to feed multiple plants or in multiple places around a single plant. For example, using the 4-way splitter would allow you to split a 4.0 GPH dripper into four individual 1.0 GPH emitters.
While not strictly required, the ⅛” tubing that runs from the outlet barb on the manifolds typically connects to a drip arrow stick or similar. This provides for greater uniformity than simply using uncapped ⅛” tubing.
Multi-Outlet Drip Manifolds
The Multi-Outlet Manifolds, though similar to the multi-outlet manifolds discussed above, are different enough to mandate their own section. Multi-outlet drip manifolds see most of their use in landscape applications, however due to their flexibility, nursery use in particular has seen a significant increase.
The vast majority of our multi-outlet drip manifolds connect via a ½” female pipe threaded inlet that is compatible with ½” Male Pipe Threaded PVC Risers. We have a couple of them that have a convenient ¼” tubing barb at the bottom to connect to ½” or larger poly tubing.
Multi-Outlet drip manifolds typically have between four and nine barbed outlets. The outlets are compatible with ¼” (.170” inside diameter) tubing. There are two types of drip manifolds that fall into this category: those that are regulated or controlled and those that are not. Those that are regulated often have flow control at each outlet, handy if uncapped tubing will be used, and pressure compensation capabilities.
Regulated drip manifolds are typically used with uncapped ¼” tubing, unregulated drip manifolds typically end with a dripper attached to the ¼” tubing run to regulate the volume of water emitting.
*Octa-Bubblers can change the Flow Control Device to provide individual outlet ports with different pre-set flow rates.
Dripline and Emitter Line
Dripline isn’t just for vineyards and row crops anymore. We’re seeing dripline used more frequently used for nursery and greenhouse irrigation applications.The most common use for it is in making rings that go into a container or around a plant. Less common, but by no means rare, is simply running the dripline down a row of containers or trays and suspending it above the plants.
The ring method is sometimes known as “Tree Rings”, however it is by no means limited to trees. To create a dripline ring, you simply use a ¼” tee to close off the loop of 1/4" Dripline. This allows for emitters to be placed at each side of the plant’s root zone or each side of the growing container. This promotes even root growth and a robust and healthy root system.
¼” Dripline is available with 6”, 9” or 12” to accommodate a wide variety of container sizes and spacing needs. Like other options, it is a low pressure solution and operates optimally at 25 PSI, but has an operating pressure range of 5 to 30 PSI. ¼” dripline is an economical solution, the dripline itself and the ¼” fittings are inexpensive when compared to larger emitter line and fitting sizes.
½” Dripline and Drip Tape
½” Dripline and ⅝” Drip Tape also see some use in nursery/greenhouse applications, but not to the same extent as ¼” dripline. Larger dripline sizes and drip tape are not flexible enough to make tight rings like ¼” dripline. When larger dripline/drip tapes are used in nursery/greenhouse applications, it’s almost exclusively done so suspended above the containers or trays in a long straight row. These larger sizes are viable, however their applications are more specific in their uses. When used in this way, they are typically suspended with Tubing Support Hooks or Tubing Curls.
Netafim NetBow ***New***
A new product at the time of this writing (December 2020), the Netafim NetBow is similar to drip line, however it comes with its own unique advantages. The NetBow features 8 evenly spaced outlets in each 10" diameter ring and is primarily for container applications in which the container is at least 12" diameter. Each outlet delivers approximately 0.53 GPH at 14.5 PSI, however the NetBow can be used with a "hub" dripper to customize its flow rate. A hub dripper is similar to what you see what drip arrow sticks, Netafim Spray Stakes and multi-outlet manifolds. Tubing that connects to the NetBow will connect to the outlet barb on the hub dripper. The hub dripper will commonly be inserted into the wall of 1/2" or larger tubing. The hub dripper should be between 0.53 GPH and 2.11 GPH.
Using a hub dripper allows the flow rate of each of the 8 outlets to achieve very low flow. When using a hub dripper, you multiply its flow rate by 8 to get the flow rate per emitter. This means a 1.0 GPH hub dripper used would make each outlet on the NetBow to deliver approximately 0.125 GPH. These factors ensure uniform application, which is of utmost importance to growers.
The emitters used in the NetBow are Netafim's Typhoon emitters. Typhoon emitters are used in systems designed to last at least twenty years, systems with poor water quality and sub-surface drip irrigation systems, mostly due to their superior clog resistance. This allows the NetBow to be used with a wider mesh than most drip irrigation systems; this can be beneficial in systems in which pressure loss is a concern, as wider mesh filters typically lose less PSI than those with a tighter mesh or smaller micron.
The NetBow is easy to install. The NetBow, as noted above, can be connected to the outlet barb of a compatible hub dripper. Alternatively, it can be connected to a barbed fitting that's inserted into a punched hole in 1/2" or larger poly tubing. The tubing that comes with the NetBow is equivalent to our 1/8" tubing, with an inside diameter of approximately 0.125".
The Exoskeleton you see on the NetBow provides protection from root intrusion and keeps the emitters elevated out of the growing medium. This slight elevation helps reduce the already minimal risk of clogging.
The largest advantage in using the NetBow is it's even, uniform coverage. This provides a good air/soil/water balance and helps ensure even root growth. In the images below, you can see actual photos taken of a container plant grown without the NetBow, and one grown with the NetBow to see the difference.
Misters and Foggers
Misters and foggers serve multiple functions in a greenhouse irrigation system, from climate control (temperature and humidity), to propagation, to pesticide and fungicide delivery. The primary difference between a fogger and a mister is in water droplet size. Foggers create finer particles than misters. The difference in particle sizes makes them suited for slightly different applications in a greenhouse context. Foggers see more use indoors than misters, but misting nozzles indoors or in a greenhouse is by no means rare.
In addition to climate control, misters are used for the propagation of rooted cuttings. By the time they are rooted, most cuttings aren’t quite as delicate as they were prior to rooting, and misting nozzles provide for good coverage of the leaves and stems, leaving them moist but not soaked or waterlogged. When used for climate control it is primarily evaporative cooling, and to a lesser extent, humidity control, that they are used for.
Foggers excel at evaporative cooling. Foggers tend to have finer water droplets than misters, making them the go to choice for delivery of pesticides and fungicides; the fine particles are better at infiltrating in between leaves and other foliage and the lighter particles are less likely to immediately settle and fall after release. Foggers also excel at irrigating non-rooted cuttings; the small, gentle droplets are the least likely to cause damage to delicate starts and cuttings.
General Fogging/Mister Information
To achieve the exceptionally small droplet size they’re capable of, fogging and misting nozzles have very small orifices. This can lead to clogging, particularly in systems with hard water. There are a couple methods one can employ to ameliorate this, but the most important is ensuring the system is flushed before and after use. This prevents sitting water from settling and depositing its mineral content in the tubing or emitter orifices. Water treatments and/or special filters can also help with nozzle clogging. A filter like this one can filter out particles as small as 5 microns: Calcium Inhibitor Filter. If the nozzle is already clogged, or close to clogged, water treatment that targets calcium and other minerals can get them up and running: Hydro-Cleanse by EZ-Flo.
Similar to the overhead options mentioned earlier in this article, head drainage and leaking are always a concern for growers using the foggers/misters. For this reason, items like the Stop Drain from Senninger linked above, and check valves are invaluable for these types of emitters. Some fogger and misting nozzles come with leak or drainage prevention features built-in, such as the Jain Fogger and the Netafim CoolNet Fogger. Note, leak prevention devices like these also improve uniformity. Since they require a minimum PSI to open, they don’t begin emitting water until the lines are pressurized, meaning that the emitters will all begin operating at approximately the same time during system start-up.
It is worth mentioning that both foggers and misters typically run at higher pressures than other drip irrigation components. Many of them create a finer mist/fog at higher pressure. This means some careful planning in regards to pressure regulation will be necessary if these will operate on the same zone as drip emitters.
If you’d like to read more in depth, our fogger and misting buying guide can be found at this link: Fogger and Mister Buying Guide.