Hibiscus Plant Care

How to Add a Timer & Fertilizer Injector to your Drip System

Control the Drip

Once you've built or planned your drip system, you need to decide how best to use the system. Drip systems can be controlled manually, but that is missing one of the big advantages of having such a system. It is easy to control the watering schedule using a battery powered timer and a special valve called an "electric solenoid valve." The timer tells the valve when to open, allowing the water to flow into the system, then when to shut, cutting off the water from the system. We set ours to open for one hour in the early morning. By the time we first see the garden in the light of dawn our hibiscus are already fully watered for the day. Before this, we had to find at least an hour every day to walk around with a hose, watering each of the over 100 plants one at a time. Some days we just could not get to it, other times we felt rushed and would give each plant only the minimum amount to keep it alive. Forget going away for a vacation! Now, with the timer activating the drip system automatically each day, we are free to enjoy the garden whenever we want without being tied to the job of watering it every day in summer.

Fertilize With the Drip System

Fertilizer Injector
Fertilizer Applicator/Filter (DIG Brand)
We all know about best intentions. Fertilizing our hibiscus is one of those jobs we all intend to do but... Fortunately, once a drip system is set up, the job of fertilizing our plants can become much easier and faster. The DIG Company offers an inexpensive addition for drip systems (available at Home Depot and elsewhere for under $15) that will handle fertilizing for you. It is not entirely automatic, but all you have to do is twist off the top of the unit and pour the HVH Special Blend fertilizer or Booster into the unit until full. Twist the top back on and you're done! The next time the drip system is used the fertilizer will dissolve in the water as it passes through the unit, and will be carried by the drip system to all the plants on the system. This Fertilizer Unit is also a filter for the system and filters out small particles that can clog the drippers. Whether used for fertilizing or not, this unit serves an important function all the time by filtering the water that enters the drip system. It can be used with either manually controlled or timer-controlled drip systems and is we recommend it highly!

Types of Timers

Timers come in all flavors, from hugely complicated ones that can control all sorts of devices throughout a large nursery, to simple, inexpensive ones that only do one thing. This latter is what we want for a home garden. Some timers can be hardwired into the home electrical system. A few are even solar powered. But the one we use and recommend for its ease of installation and low cost runs on one 9-volt battery that lasts 1-2 years before needing to be replaced. No wiring is required! This timer activates an electric "solenoid" valve. Although these valves are available separately from timers, it is easiest to buy one that is already attached to a timer and sold as one unit. As mentioned before, these units, along with all other parts for the drip system, can be purchased economically at Home Depot, Lowe's, or at a specialty irrigation store. Many smaller hardware stores also carry them. We purchased our DIG Model 7001 Battery Operated Irrigation timer timer/valve unit at our local Home Depot for less than $50.


Drip Irrigation Timer
Irrigation Timer (DIG Brand)
The installation for both the timer and the fertilizer injector/filter is easy and done at the same time. The fertilizer injector/filter comes packaged with several different types of connectors so that it can be installed in most situations without additional parts. The timer is first connected to the water source for the system, and the fertilizer injector/filter is then connected to the timer on the downstream side of the timer. The downstream side of the Injector/Filter is then connected to the drip system pipe.

To better describe the flow of water to your drip system, think of it like this - the water flows from your hose faucet or from the manual valve on a direct PVC system to the timer, then from the timer to the fertilizer injector/filter, and from there into the drip system and out the individual drippers to the plants. Along the way fertilizer is added if you have filled the fertilizer reservoir, and all small particles are removed by the filter. It is the timer that allows the water to enter the system by opening a valve at the time you select, and then closing it at the time you select to stop the flow of water.

If your system is connected to a hose faucet or to a hose, all you have to do is screw the adapters that are included into the timer, and then screw the other end of the adapter onto the faucet or hose. If your drip system is connected directly onto PVC pipe, there is also a connector included with the timer that screws directly onto the pipe.

The Fertilizer/Filter unit also has adapters included that allow it to be connected directly to the timer on one end and directly to the poly water pipe on the other end. It may take some fiddling with parts to get everything connected together, but once you figure out which parts connect the system together, it is a fairly easy task to hook them up.

Install the Battery

Drip System Timer Installation
Fertilizer Injector & Timer Installed
Black Unit at top is Fertilizer Injector
(Unscrew to fill with fertilizer.)
Blue Unit at Bottom is Timer
(Blue cover opens to set timer.)
The timer uses one 9-volt battery to operate. This battery must be purchased separately but will last for at least a year. The timer part of the timer lifts off of the lower part of the unit which houses the valve. It remains connected by a cord, but removing it allows for you to stand up or sit comfortably nearby while inserting the battery and setting up the timer. The battery compartment door is on the bottom of the timer, the side opposite the settings. After opening the battery door insert the battery into the compartment, attaching negative and positive connections to the appropriate poles. This is marked inside the compartment and described in detail in the directions that come with the timer. Close the battery door and get comfortable so you can set the timer without feeling the strain of squatting in an awkward position.

If you feel thoroughly confused by all this, don't worry! These timers and fertilizer injectors come with excellent, clear instructions that are easy to follow. In an article like this, it's impossible to provide instructions for every type of component you might buy. If you understand the basic concept, installing the parts will be easy.

Setting the timer

OK, we've now got the entire system in place. The question now is, how do we use it? The timer, consisting of a timer and a valve, is easy to set. The directions included with the timer you buy will walk you through the steps using diagrams and words that are very user friendly. For instance, it will show you how to set the time of day you want the timer to open the valve and start the water. It then asks you how long you want the water to flow. In our conditions with the plants we have, one hour works great. Then you select the days you want the system to operate. In summer every day is best, although in rainy climates every other day may be better. There is also a button that lets you skip one day anytime that button is pushed, so on a rainy day you can push that button and no water will flow thru the system until the next day. There is also a manual on and off switch that you can activate anytime that turns the system "on" for whatever length of time is already set for automatic operation. This is useful for many tasks such as checking the drippers to see if the amount of water dripping out of them is what you want.

Special Tip For Potted Plants

There is no reason not to put potted plants on a drip system. All our greenhouse plants are in pots and they all have drippers in the pot. The main difference compared to in the ground hibiscus is that most pots do not contain sufficient soil to keep them from drying out during hot summer days. Large pots almost always have large plants in them and they will get sucked dry of water just as fast as the smaller pots with smaller plants in them. So what is the solution to keeping potted hibiscus happy, growing, and flowering in midsummer? Set your timer for more than once per day. Instead of the deep soak for an hour that in-the ground-plants need, use a shorter time such as 10 minutes for the system to drip water into the pots. BUT, set the timer to do this 2 or even 3 times per day, and watch the difference this will make to your potted hibiscus. University research has proven this to be the best way to water pots in nurseries, and if you try it, your results will almost certainly bear this out.

The Final Results

Hibiscus Garden
Plenty of Water Makes Plenty of Hibiscus Flowers!
Once the timer is set, watering becomes automatic. You can change this anytime you want, but until you do, the hibiscus will receive water every day that you set the timer to water them - automatically! This is the very best way to water your garden. Dripping water into the root zone for about an hour a day will make a huge difference in the appearance of your plants. We knew this from watering with a drip system in the greenhouse, but were surprised at just how much better our garden plants looked and bloomed with an automatic drip system in the garden. The difference is impressive, and well worth the time and cost to install the system.

We often hear people complain about a lack of blooms in midsummer, which is always puzzling because our hibiscus in the greenhouse never stop blooming, despite the extremely high summer temperatures inside. My best guess is that most people do not provide adequate midsummer water to their hibiscus and our experience with our own garden seems to confirm this. Sure you need to keep insects such as thrips from causing bud drop, and you need to keep fertilizer levels up, but by far the most important influence on the hibiscus in summer is deep, regular watering that keeps moisture available in the root zone at all times.

Sometimes people say, "The soil is moist, I can feel it, so why should I add more?" A little known fact is that hibiscus roots can only obtain enough moisture from soil or potting mix when that soil is 50% or more saturated. When the moisture level drops below 50% saturation, the roots have to compete with the soil for the water and cannot take enough out of the soil to fulfill their needs on a hot day. Only when the level is over 50% saturated can the hibiscus roots easily obtain what they need from moist soil. Think about a wet dishrag. When it is first wet it is almost totally saturated. If you wring it out, then you get a lot of water easily. But even though it feels moist after wringing when you squeeze it again you get at most just a few drops of water. Soil is a lot like that - there has to be ample water in it for the hibiscus to be able to get it.

Of course, there are more things you can do with your drip system now that you have it. You can add in little soaker hoses for ground cover areas, or bigger emitters for trees, or little sprinkers for grassy or mossy areas. Once you have the basic system in place and know how to add things to it, you'll find yourself getting very creative with it. There's nothing like building it yourself to give you the confidence to tailor it to the needs of your own yard! So have fun, and good luck with your new watering system! We know you will thoroughly enjoy having a watering system in place and that your hibiscus will flourish like never before!