Q. My hibiscus plant, transplanted from a pot to my outdoor flower bed, is blooming like it should. But the leaves are not getting any bigger than 1 - 1½" long and ¾" wide. The new leaves also only get to that size. I water and fertilize if with Miracle Grow regularly, but that does not help. Any suggestions?
A. The appearance of plants will be different when grown in different climate zones. I am now on my farm in the Philippines where we have Roselle hibiscus (commonly called Red Zinger) growing. I checked the size of the leaves in response to your email. I normally don’t pay much attention to leaf size just flower production.
|Roselle growing on our Family Farm in the Philippines|
The leaves of our Roselle vary in size from the narrowest at about 3 to 4 inches in length and about 2 inches wide to the largest being 6 to 8 inches long and 4 to 5 inches wide. The largest leaves are growing in partial shade. The smaller leaves are growing in full sun.
|Tropical hibiscus growing in the Philippines in a tropical climate.|
Appearance can also be impacted by your management practices. Let's cover a few of these.
Climate and microclimates. Plants grown under high light intensities have a different appearance than plants grown under lower light intensities. The principal differences are in leaf size, color and thickness.
Leaves growing under higher light intensities, provided they are getting enough water and nutrients, will be dark green, smaller, thicker or tougher and develop a thick waxy coating on the leaf surface.
The same plant growing under lower light intensities will have larger and thinner leaves with a waxy coating that is not as thick. If light intensities get extremely high then we will see leaf discoloration, yellowing or bronzing, on some plants because the light intensity is actually damaging the leaves.
|Red hibiscus growing in rock mulch in Las Vegas|
If the same plant does not receive enough light then the plant will become “leggy” with large distances between the leaves and thin stems that will not support its own weight. The plant will become "floppy".
Our job as a manager of this plant is to find a good location in our landscape that provides the right microclimate which provides enough light for flowering and an appearance close to what we expect.
Because we are in a desert, Hibiscus will not look similar to those grown in semi tropical or tropical climates but we can approach that look if we are careful where we plant it.
Soil. Organic matter such as compost mixed into the soil at the time of planting and applied annually to the soil surface surrounding the plant will encourage larger and healthier leaves. I have seen this numerous times on a number of plants particularly in parts of the plants that are shaded such as lower leaves.
|Red hibiscus growing in rock mulch in Las Vegas showing signs of leaf drop, leaf yellowing and branch dieback.|
Fertilizer. Fertilizer will influence the kind of growth. We know that phosphorus fertilizers are very important for flowering, fruiting, root development and production of oils in plants. If not enough phosphorus is present it will impact these types of growth.
We do not need to apply phosphorus to a soil very often unless it is extremely sandy or growing in hydroponics.
Nitrogen is different. Nitrogen is important for developing dark green color in leaves and stems and for "pushing" new growth. It is important in producing good leaf size and in the number of leaves and supporting stems produced.
Nitrogen in soil available to plants also dissolves easily in water. Nitrogen is easily does not dissolve in water easily and is slowly released to plants.
In your case you want to make sure that nitrogen is applied regularly through the growing season to maintain dark green color and "push" new growth. Combined with moderate amounts of shade, nitrogen will encourage more leaves and larger leaves.
What should you do? Understand that if your hibiscus is in a very hot, bright location that this location will limit the plants ability to produce larger leaves. Moderate amounts of shade will encourage larger leaf development, particularly in a microclimate that gets morning sun but afternoon shade.
Apply a 1 inch layer of compost and scratch it into the soil surrounding the plant as much as you can. When you’re done doing this, apply another 1 inch of compost to the soil surface and thoroughly wet the soil deeply. Apply a 1 inch layer of compost to the soil surface every year.
Apply high nitrogen fertilizer at the beginning of the growing season. Apply a high phosphorus fertilizer after it is finished blooming. If you apply fertilizers at other times of the year, apply liquid fertilizers to the leaves.
Do not apply any nitrogen fertilizers to the soil after August 1 if you are concerned about winter freezing damage.