Hibiscus Plant Care
Giant, colorful exotic hibiscus flowers like this 'Belle du Jour'
require large amounts of water to develop
Hibiscus are water-loving plants. They have lots of large leaves, and the blooms are big and full of moisture themselves. In the tropical areas where hibiscus originated, mostly islands or coastal areas, the air is humid and rainfall is plentiful. Most of us are not growing our hibiscus in the tropics, so we need to simulate as much as possible the natural conditions where hibiscus originally developed. That means plenty of water during the warm times of the year. Hibiscus are not built for cold temperatures and don't know what to do with too much water when it is cold. During cold weather, we continue to water, but we water quite a bit less.
There are two basic aspects to watering well. The first is how often water is applied and the second is how much water is applied. Hibiscus need to be watered often when the weather is warm, and even more when it is hot. In most locations, that means daily watering, unless sufficient rain makes watering unnecessary on a particular day. How much water to apply is determined by how much is required to thoroughly wet the soil around the roots of the plant. In a pot that is easy to determine, but for plants in the ground it is harder. If the hibiscus is growing well, with lots of green foliage, you can assume it is getting sufficient water.
The quality of tap water is an issue in some areas. The pH (acidity) and the amount and kind of minerals in the water can affect plant growth. Hibiscus are fairly tolerant of variations in both these measures of water quality. They grow best in areas where the water is slightly acid (pH 5.5 to 6.5) and where dissolved minerals are low, but will grow OK within a range of pH from 5.0 to 7.0 and with moderately hard water. If you know your water is outside these ranges, either very high or low in pH, or very hard with lots of minerals, consult your local County Dept of Agriculture for advice on how best to deal with local water conditions. A Master Gardeners group in the area is also a good source for advice about water quality.
How Often Should I Water?
Water Before Stress Shuts Down Growth and Blooming: However you water - whether by hose, watering can, sprinkler or drip system - the water must be applied before the soil or potting mix around the roots dries out too much. When the plant cannot get enough water from the media it is growing in, many growth and blooming processes begin to shut down. At first this shut down is not visible, but it is still happening and will affect the plant's growth and blooming. If allowed to continue, the hibiscus will visibly wilt. Once water is applied, the wilt will disappear and the leaves will once again appear green and crisp. When this happens, don't be fooled. Yes, the hibiscus has recovered from the near-death experience, but its future growth and blooming will be affected.
Water more in hot weather to keep hibiscus
like this 'Cindy's Heart' blooming prolifically
Water According to the Weather: Water often, but adjust how often according to current conditions. Hotter, drier, sunnier, and windier conditions dry out pots and soil more quickly. Cloudy, rainy, cooler conditions make water last longer. Be flexible about watering. If drying conditions are present, water more often. When wetter conditions prevail, cut back on watering. We have watered as often as three times per day when conditions called for it, and cut back to once a week during rainy, cool times. Winter does not mean not watering at all. Hibiscus survive cold temperatures best if they are well watered before the cold hits. Dried out hibiscus are vulnerable to both cold and insect attack. So don't let them become too dry! One of the better ways to help hibiscus deal with a frosty night is to sprinkle them with tap water that is well above the cold temperatures of the air.
As a general rule, water hibiscus once per day when summer temperatures are in the 70's and low 80's, and twice per day when they reach the upper 80's and 90's. If you cannot water them twice per day, then grow them under shade cloth or in larger pots that hold more water. Placing saucers underneath the pots and filling them with water will also help during the hottest times of year. Self watering pots are also available that contain a reservoir that sends water to the potting mix as it dries out. Drip systems run by timers are the very best way to control how often hibiscus are watered. Drips systems are not as hard to build as you may think! Go to this page on our website for do-it-yourself instructions on How to Build a Drip Watering System.
How Much Should I Water?
Remember, when watering it is necessary to apply sufficient water to saturate the growing media around the roots. When watering with a hose or watering can, be patient and water each plant thoroughly. Spend enough time watering each plant so that the water soaks all the way through the root zone and does not run off the top or out the bottom holes before soaking the root zone. An excellent way to make sure you apply enough water is to water each plant twice. The first application will soak partly through the root ball and make it easier to wet the entire root zone with the second application made shortly after the first. Flooding a pot quickly does not give the best results. Some of the water may flow off the top and the rest of it is likely to take the path of least resistance through channels the water creates in potting mix over time and then out through the holes in the bottom. Much of the potting mix is left dry and untouched if you just flood a pot quickly once with water.
For potted plants, you can check your results by tipping a few plants out of their pots after watering. If not enough water was absorbed by the rootball, you will see a definite line where the water penetrated to and stopped. The soil will be darker above the line where it is wet and lighter below the line where it is dry. When potted plants are watered correctly the entire root ball will appear dark and wet, with no visible line between wet and dry areas. Expect a surprise when you first do this check! What seems like enough water is usually not enough to soak the entire root ball. Try it yourself until you are sure that the amount of water you are applying is sufficient to wet the entire root zone.
For plants in the ground, digging a shallow well around the base of the plant is the safest way to make sure water seeps down through the whole rootball. The well should be wider than the root ball of the plant all the way around. When you fill the well with water, the water will fall straight down through the soil, and water only what is directly under it. So it's important for the well to cover the whole rootball and extend past it above the ground where your hibiscus will grow new roots. If you fill each well once, let it soak in, then fill it a second time, you should get the entire root zone well saturated with water.
A drip system works best to water many hibiscus plants.
These 'High Voltage' hibiscus in pots are on a drip system.
By far the best way to apply the right amount of water to either pots or hibiscus planted in the ground is to set up a drip watering system that drips water into the pot or ground slowly enough that the root zone becomes wet through and through.
Fertigation - the Best Watering Technique for Healthy, Blooming Hibiscus
Fertigation means combining the tasks of watering and fertilizing into one. It can be as simple as mixing fertilizer into a watering can and using this mixture to water your hibiscus. By applying a small amount of fertilizer with every watering, your hibiscus get a steady diet of the nutrients they need, and do not experience famine and feast cycles. Having a steady and regular supply of water and nutrients allows hibiscus to maximize their potential for growth and blooming. If you have more hibiscus than can be watered by a watering can, you can buy a simple hose end attachment, often called a proportioner, that mixes fertilizer and water together as the water passes through the proportioner. All your hibiscus can be watered using the hose proportioner and receive a supply of needed nutrients with every watering. As we have described in the article on drip systems, anyone with a sufficiently large number of hibiscus can be freed from the daily watering task by using a drip system with a fertilizer injector attached to it. Each of these methods of fertigation will help you grow the most attractive, best blooming hibiscus possible!
Water often and water thoroughly for best results with your hibiscus. Combine fertilizer with the water for optimal growth and health of your plants. Adjust water according to weather conditions. If you stick with these guidelines your hibiscus will reward you with great growth and many bright and colorful blooms!