How to prune hibiscus plants

As past president of the Australian Hibiscus and the International Hibiscus Society, there’s no one better to teach us how to prune hibiscus plants than 87-year-old Over60 community member, Jim Prudie.

“This month we will look at the subject of pruning your plants, as this is advisable here in Australia seeing that this is the month that spring arrives and the plants begin to wake from there winter sleep and the sap begins to flow causing the plants to start getting new shoots and if you prune the bush at this time you will get a good shaped bush and better flowers. People in the southern states should wait until the danger of frosts has passed and in the northern hemisphere you will have to adjust the month to coincide with your spring.

This condition is brought about by a few things – the most important being that the daylight hours begin to get longer as the sun on its 
journey begins to get closer to your country, where ever you may live, be it in the northern or southern hemisphere, and as the sun gets closer, the weather begins to warm up and this causes the sap to flow and in so doing it causes the roots to start drawing more nourishment from the surrounding soil, and the plant goes into growing mode and new shoots begin to appear at the eyes, as opposed to the bare sticks we have been looking at during the winter.

We prune our plants for a variety of reasons, and I have listed the most important reasons to get a better bush.

1. To train into a desired shape.

2. To maintain the bush to a manageable size, and open up the bush to the sun by pruning away the middle branches which have grown into the middle thus blocking out the air and light.

3. It helps in the control and to be able to see any attacks of insects.

4. It will encourage stronger growth, as when you shorten the branches when you prune them, it will cause the plant to send out more branches, and as I always say more branches, more flowers.

5. It will get rid of old and weak branches, and those which grown in a crisscross fashion causing a cluttered plant, as well as those that have grown out of shape.

6. If you prune your plants in the spring you help the bush to promote larger and better blooms of good shape and size. Hibiscus thrives on being pruned in the spring, and you do not have to get a stepladder to see the flowers, as the branches get too long. When you prune the tops of the branches, it causes the plant to start shooting down lower and instead of bare sticks you will see a plant covered in nice green leaves, and more branches, and “more branches more flowers”.

This happens because when you prune the tops off, it stops the growing cycle from the tip. 

Whenever I start to prune I try to think how the bush grows, and prune the plant according to the way it grows, by that I mean if the plant is an average grower, I will prune off about a third of the bush, if the bush is a tall fast grower I will prune off about a half, and if the plant is a slow low grower, I will just prune off the tips, otherwise it takes too long to recover if you give it a hard prune, and you will miss out on the flowers for the season and have to wait until next year to see some blooms.

I always cut off the low lying branches, usually leaving a 12 inch space under the bush, which allows you to keep under the bush clean and also if there are low lying branches, and a flower appears it drags in the dirt and there is a danger of snails causing damage to the petals.

I prune just above an outward pointing eye, using a slanting cut away from the eye, so any water will run away from the eye, and also 
encourages the new shoot to grow outwards instead of into the middle of the plant, and as I always try to end up with a pruned bush which is in the shape of a vase.

Make sure your secateurs are kept clean and sharp, so that they will give a clean cut, and I like to dip my secateurs into some alcohol or methylated spirits between bushes to prevent spreading disease.

Some members do not prune all the branches at one time so they are able to have blooms while they wait for the new growth to flower. These remaining branches can be pruned once the new growth commences flowering.

If you are growing in pots this is a good time to think about a root prune at the same time as you prune the top of the plant, and repot into some fresh potting mix, with some slow release fertilizer included in the mix, either into the same size pot if it is the biggest you want to go to, or the next size pot if it is in a small pot.  Do not make the pot size too big, When the bush is putting out a lot of new growth this is when I apply a fertilizer high in nitrogen to promote the new growth, and apply this until you see new buds starting to form and then I use a fertilizer higher in potash than nitrogen to promote flowers instead of nice green leaves.

A fertiliser I recommend after you have pruned the plants in the ground is the following: two ice cream containers [or two litres] of Blood and Bone, two of superphosphate, one of sulphate of potash, half a can of magnesium sulphate [epsom salts], a quarter of can sulphate of iron. Mix all this all together and apply a good handful around each bush. Then I cover this with good mulch about two to three inches thick to keep the roots cool in hot weather to come and also to prevent the loss of moisture. Later when the blooms appear I use a soluble fertiliser higher in potash than nitrogen with my FertiGator and apply it from the hose attached to the 5000-litre tank with an electric pump.

If you follow these instructions you will be well on your way to seeing a healthy bush and plenty of flowers.

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