Posted by Brent Wilson on 11/11/2016 to Fertilizing & Watering Tips
When planted right and in the right spot, Hardy Hibiscus plants, such as Confederate Rose and the "dinnerplate" type, are exceptionally easy to grow.
Here's a breakdown of what you need to know to be growing Hibiscus like the pros...
Perennial Hibiscus adapt to a wide range of soils, including clay, but prefer a moist but well-drained soil of average fertility. In the event of a prolonged summer drought, water as needed to maintain a healthy plant. Perennial Hibiscus will let you know when they are thirsty. If you see leaves wilting, water the plant generously and it should perk up within 30 minutes or so.
How To Test Soil Drainage
If you are uncertain about soil drainage in the area you intend to plant your perennial Hibiscus, it's well worth taking the time to test the drainage before planting. To test soil drainage, dig a hole 12" wide by 12" deep in the planting area. Fill the hole with water and let it drain. Then, after it drains, fill it with water again, but this time clock how long it takes to drain. In well-drained soil the water level will go down at a rate of about 1 inch an hour. A faster rate, such as in loose, sandy soil, may signal potentially dry site conditions and the need to amend the native soil with topsoil and/or other organic matter to help retain moisture. A slower rate indicates poor draining soil. Though Hibiscus will tolerate a consistently moist soil they do not like standing water.
Perennial Hibiscus will grow in a wide range of soil pH from around 5.5 to 7.5 on the pH scale. They do best in a range from 6.0 to 6.5. Most average garden soils fall between a pH range of 6.0 to 7.0.
Testing Soil pH
Soil pH is a measurement of the alkalinity or acidity of soil and is measured on a scale of 1-14, with 7 as the neutral mark. Any measurement below 7 indicates acid soil conditions, and anything above 7 indicates alkaline.
If you're unsure about the pH of your soil, and whether or not it's suitable for growing Perennial Hibiscus, it's a good idea to test the soil pH in the planting area. You can quickly test soil pH with an inexpensive soil pH tester probe. To raise the pH (make more alkaline) you can add pelletized limestone to the soil. To lower the pH (make more acid) you can apply Soil Sulfur, Aluminum Sulfate, or Chelated Iron. Adding organic compost to the soil or using compost as mulch can also help to increase acidity and maintain acid soil conditions.
Learn More: What is Soil pH and How To Adjust It?
Perennial Hibiscus thrive in full to mostly sun however will tolerate some light shade. For best flowering and overall performance, 6 hours of direct sunlight per day is suggested.
How To Plant A Hardy Hibiscus
Scroll down for container planting instructions and care tips
Start by digging your planting hole at least two to three times as wide and as deep or not much deeper than the root ball of your Hibiscus. The wider the hole the better. Place native soil removed from planting hole around the perimeter of the hole, in a wheelbarrow, or on a tarp.
Depending on the type, fertility and porosity of the soil in the planting area, it might be beneficial to mix in some compost or a soil amendment to the native soil removed from the planting hole. When planting in heavy clay or poor soil it is beneficial to thoroughly mix in a good soil conditioner such as bagged top or potting soil at a 50/50 ratio with the soil removed from the planting hole. When planting in very sandy, quick-draining soil, top soil and/or other organic matter can be added to help retain moisture. When planting in moist but well-drained soil of average fertility there's no need to amend soil.
To remove your Hibiscus from the container it was growing in first squeeze the sides of the container. Then grasp the base of the plant with your fingertips and very gently try to lift and remove the plant from its nursery pot. If the root ball is stuck in the pot it's best to use snips to cut the container away. Gently loosen some feeder roots around the surface of the root ball.
Set your Hibiscus in the planting hole so that the top edge of the root ball is at or slightly above ground to allow for settling. If necessary, add some backfill soil to the bottom of the hole to achieve proper planting height.
After setting your Hibiscus in the planting hole, use one hand to hold the plant straight and your other hand to begin backfilling your soil mixture around the root ball, tamping as you go to remove air pockets. When you have filled the hole to the halfway point you can soak the soil. Then continue backfilling to the top edge of the root ball. To avoid suffocating your plant, avoid placing any soil on top of the root ball.
Step 6 (Optional)
When planting your Hibiscus far away from a water source, you can use remaining soil mixture to build a 2 to 3 inch high water retaining berm (catch basin / doughnut) around the outside perimeter of the planting hole, as shown in the illustration above. This basin will help to collect water from rainfall and irrigation often reducing watering frequency. The berm can be removed after a growing season.
Next, deeply water the planting area, including the root ball, to a depth equal to the height of the root ball. For an extra boost, you can water your newly planted Hibiscus with a solution of Root Stimulator, which stimulates early root formation and stronger root development. Root Stimulator reduces plant shock and promotes greener, more vigorous plants.
To help conserve moisture and suppress weed growth, apply a 1 to 2" layer of shredded or chipped wood mulch or straw mulch around the planting area. As the mulch decomposes it will add vital nutrients to the soil that your plant will appreciate. Avoid using freshly chipped or shredded wood for mulch until it has cured in a pile for at least 6 months, a year is better. Avoid placing or piling mulch directly against the base of your plant as this could cause the bark to rot.
How To Plant A Perennial Hibiscus In A Container
Perennial Hibiscus growing in pots appreciate a consistently moist but well-drained soil. Therefore, use a quality potting soil or potting mix, or a 50/50 combination thereof and a container that has at least one drainage hole.
Choose a container that is large enough to allow for 2 to 3 years of growth before shifting up to a larger size container. This might mean your planting pot would be 8 inches or more in top diameter than the root ball of your plant.
Container color will matter as well. Not only will you want to pick a color of container that goes well with the flower and foliage color of your Hibiscus, you'll also want to pick a container that matches the style of your home or other structures and other plants in the surrounding environment.
Many nursery & garden centers offer a wide variety of containers to choose from. Before heading out to buy a container take pictures of your home and the surrounding environment. Doing so will help you to choose just the right color and style.
Container Planting Instructions
Before filling your container with the soil mix, we suggest lining the bottom of the pot with shade cloth or a porous landscape fabric. This will keep the drain holes from becoming stopped up with soil. If you place gravel or other materials in the bottom of the pot lay the fabric over it.
To remove your Hibiscus from the container it was growing in first squeeze the sides of the container. Then grasp the base of the plant with your fingertips and very gently try to lift and remove the plant from its nursery pot. If the root ball is stuck it's best to use snips to cut the container away.
Pour a small amount of soil mixture in the bottom of the container. Set the root ball of your plant in the container and make necessary adjustments by adding or removing some soil so that the top edge of the root ball will sit 1" or so below the rim of the container.
Backfill with your potting soil around root ball, tamping as you go, until the level of potting soil is even with the top edge of root ball.
Water thoroughly until water starts to drain from the holes in the bottom of the container. After watering, add more potting mix if settling occurs.
Step 6 (Optional)
Apply a 1/2" layer of wood chips or sphagnum moss to soil surface to help conserve moisture.
How To Care For Perennial Hibiscus
Feeding - Watering - Pruning
Hardy perennial Hibiscus are very easy to grow and care for. Follow the advice below and you'll be growing them like the pros.
How To Fertilize Hardy Hibiscus Plants
Hardy Hibiscus will benefit from fertilization.
In Ground: Feed Hibiscus plants growing in the ground as directed on the product label in late winter or early spring with a quality slow-release shrub & tree type fertilizer or a natural organic plant food.
In Pots: Feed plants growing in pots, planters and other containers as directed on the product label with a granular or water soluble (liquid) all-purpose plant food that is listed for use on plants growing in containers.
Soil pH - Perennial Hibiscus will grow in a wide range of soil pH ranging from around 5.5 to 7.5 on the pH scale. That said, they thrive in a soil pH ranging from 6.0 to 6.5. Most average garden soils fall between a pH range of 6.0 to 7.0.
Learn More: What is Soil pH and How To Adjust It?
How To Water Perennial Hibiscus
Note: When watering with an automated irrigation system it's best to set your timer to water during the early morning hours and not in the late evening or at night, which can lead to the onset of fungus and other foliage diseases. During the first few weeks after planting, check soil moisture often and adjust irrigation time if necessary or apply additional water by hand to maintain a moist root ball and surrounding soil.
At Planting Time
Immediately after planting deep soak the soil in the planting area to a depth equal to the height of the plants root ball. For an extra boost, you can water your newly planted Hibiscus with a solution of Root Stimulator, which stimulates early root formation and stronger root development. Root Stimulator reduces plant shock and promotes greener, more vigorous plants.
During the First Active Growth Season
In average garden soil you should not have to water your newly planted perennial Hibiscus every day. Water only as needed to maintain a moist root ball and surrounding soil. Keep in mind that deep soaking less frequently is much better than splashing just a little water on the plants every day.
When established, only during periods of summer drought will perennial Hibiscus require supplemental water. If you see leaves wilting this is a sign your plants could use a deep soaking.
When watering dormant hardy Hibiscus plants during winter, when there are no leaves on the plant, whether in the ground or in pots water only enough to maintain a damp soil.
How To Prune Hardy Hibiscus Plants
Perennial Hibiscus do not require regular pruning. Spent flowers can be removed to keep plants tidy, but is not necessary. A stray or broken branch can be pruned any time of year by making your pruning cut just beyond the point of the break or dead plant part.
An annual pruning when new growth begins to emerge in spring is suggested. At this time, use sharp bypass hand pruners or loppers to cut off any dead plant parts. In colder climates plants usually die back to the ground.
Winter Care of Confederate Rose Hibiscus
Confederate Rose Hibiscus plants growing in the ground do not require any special care during the winter month when they are dormant (without leaves).
NOTE: We suggest waiting to prune Confederate Rose until early to mid-spring, right when or shortly after new leaves begin to emerge. At that time, prune off all dead plant parts.
Confederate Rose Hibiscus plants growing in the pots are safe to leave outside as long as the temperature stays above 20 degrees F. Otherwise, if temperatures are forecast to drop below 20 degrees F we suggest moving the pot to an unheated interior space that stays above 20 degrees, such as a garage or shed, until a point in time temperatures go back up. If you have to keep the plant in a heated indoor environment it might begin to emerge from dormancy. In this case you might need to wait to move the plant outdoors until low temperatures are forecast to stay above 60 degrees F in spring.
Plant Long & Prosper!
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