Green thumb
Who knew that plants could communicate by semaphore with insects.
Many plants have flowers that change colour as they mature, this creates a stunning multi-floral display on a single plant and wonderment of how nature can preform such splendour.
Nature brings about this effect through a number of processes, senescence or ageing which causes fluctuating amounts of the pigments, anthocyanin, carotenoids and betalanins. Some of these pigments are less stable in heat and the flower colour will often fade in the midday summer sun.
Changes in the pH of the soil can also effect a change in flower colour and we see that in hydrangeas where alkaline soil will produce pink flowers and acidic soil blue flowers.
Some plants have the ability to signal to pollinators that the insects have done the job and the plants have already been pollinated. The flowers change colour, and sometimes shape to show they have been pollinated and subsequently, the insect are no longer attracted to the flower and do not waste time trying to find nectar on an empty anther, the flower is also warning them not to try to steal nectar from the flower’s pistil, (the female organ of the flower).
Who knew that plants could communicate by semaphore with insects.
The seaside daisy, Erigeron karvinskianus is a good example of a flower that changes colour following pollination.
This daisy is a hardy ground cover and because it readily sets seed it can become invasive if not controlled. The white flowers turn pink when pollinated and the mosaic created of masses of white and pink flowers blanketing the ground or hanging over a rockery is stunning.
The seaside daisy is native to arid Mexico and as such requires good drainage, it will not grow in waterlogged areas. Flowering will improve if the soil around the plant is mulched with compost regularly. Few pests bother this hardy ground cover and it is said to repel mosquitoes.
Hibiscus tiliaceus, the native hibiscus tree’s flowers open early in the morning with bright yellow petals and deep maroon centres. As the day progresses the flower colour gradually changes from yellow to orange then red before they fall in mass and create a floral carpet beneath the tree’s leafy skirt This tree grows naturally in riparian and seashore areas and when the flower laden branches sometimes overhang the water’s edge the spent flowers fall into the running tide where they bob around like tiny lanterns before they are gulped up by fish herbivores; another wonder of nature.
Hibiscus mutabilis is an old fashioned plant that once had pride of place in most front yards. The large, 15cm double white flowers gradually darken throughout the day through shades of pink and ultimately to red before they crumple and fall to the ground.
H. mutabilis flowers from autumn into winter and should be pruned back hard in early spring to promote compact growth.
Without doubt Brunfelsia latifolia, ‘yesterday, today and tomorrow’ is the most popular medium sized shrub that makes a multi-floral display. The small, single, flowers open blue before quickly fading to lavender then white.
Flowering is prolific and the shrub is completely covered in a mass display as senescences caused the colour change.
A number of Camellias have flowers that open pink and darken to cerise once they have been pollinated signalling to insects that their nectar has been taken.
Camellias are hardy shrubs but good drainage is essential. Select C. sasanquas species for the tropics as they perform best in warmer conditions. The smaller leaf and dense foliage of sasanquas species provides more protection for the flowers. Unfortunately, the flowers are not long lived and will shatter and fall after two days creating a caret of petals around the shrub. Flowering occurs in the winter months.
Tibouchina Noelene is another colour changer, it will grow to 2.5 metres and needs, light, early pruning, for compact growth.
T. Noelene flowers from winter into early spring and the large single flower petals open white, deepen to mauve then pink and magenta. The flowers totally cover the bush with a stunning multi coloured display.
Good drainage is essential for all tibouchina and it is best to prune them lightly as heavy pruning in the tropics often results in dieback. Mulch around the plants in summer but not close to the trunk and feed with an organic fertiliser enriched with sulphate of potash throughout the warmer months, this will ensure good flowering when the weather cools.
Last of all the most spectacular tropical shrub of all Gardenia tubifera.
This golden gardenia is native to South-East Asia, it grows 2-3m high and has a spread of at least 2m. The flat pin wheel flowers open white, turn to pale yellow and then to a deep mustard yellow.
The flowers are deeply fragrant and the perfume fills the air over the flowering time of this hardy, tropical shrub.
Flowers appear spontaneously throughout the year and last for around two weeks. This is a plant that can take pride of place in any front yard.