Hibiscus Longiflora produces abundant summer blooms. PICTURE / SUPPLIED
This summer so far has been a bit skint on heat, with quite a few southerly orientated winds. Though we have had fine sunny days here in Whanganui, the temperatures have sat a bit cooler than in other years.
Like people, plants all react differently to the heat and some plants thrive in it.
In gardens where there is shelter from the wind, a hot microclimate ensues. This encourages spectacular flowering in plants such as bougainvillea, mandevillea, silk trees, jacarandas, petunias, tropical impatiens, flame vine and tropical hibiscus. I have seen some good examples of some of these in our city. It is during these hot months that these plants come into their own.
Other plants don't react well to the heat — hellebores, chatham island forget me nots, rhododendrons, azaleas and camellias can all end up with scorching on their leaves from excessive sun.
The summer months can be a time that substantial growth can be made if they are kept moist. If you are growing plants to create privacy, then ensuring they are well watered and well fertilised during the summer months will encourage much faster growth than during cooler times of the year. Plants such as pittosporum, griselinia and many other natives, evergreens and deciduous trees will react in this way.
A way to help plants during the summer months is to mulch the soil around them. Mulching is the spreading of a layer of organic matter on the surface of the soil with the aim to improve moisture retention, suppress weeds and provide a cooling effect on the soil and root system.
Mulching will improve soil structure and encourage earthworms and microbial activity, giving better results for new and existing plantings. As the saying goes "the answer lies in the soil" in regards to success or failure in the garden. If you have seen the growth that can be achieved particularly in Taranaki soils or Westmere loam then you will agree with this statement.
There are a number of different mulches available that will best suit different plants and soil types. At the garden centre we have bulk landscape supplies of these and other products and it has been an interesting exercise to source and develop products suitable to specific plant types and categories.
Some of the options available for mulching are poultry compost, natural bark feeding mulch, mushroom compost, peat moss and barley straw in bales.
One of the heat loving plants of summer is hibiscus.
Hibiscus are amongst the most favoured shrubs for tropical, subtropical or warm temperate gardens. In Whanganui some grow more vigorously and bloom better than others. In selecting hibiscus keep an eye on nearby gardens for robust, free flowering plants to give you an idea of suitable plants for your situation. Hibiscus, if regularly fed and watered, respond with healthy growth and displays of superior flowers. They have a strong appetite and need to build energy reserves for constant flower production. An annual feed with Novatec Fertiliser is recommended.
Some early references claim the geographical origin of hibiscus rosa-sinensis, which literally means "Rose of China". Various forms eventually found their way to England. Others suggest it hailed from India. Captain James Cook and other Pacific explorers later found a double red form being cultivated in several island groups. Early botanists suggest Polynesian migrants may have brought hibiscus with them from South East Asia and then to Hawaii, Tahiti and Fiji. Earlier crossing of Chinese and native Hawaiian species has resulted in the development of most of the thousands of hybrids grown today.
If you enjoy hibiscus, I encourage you to find space for one more. If you are just beginning and have yet to experience the delight of picking a hibiscus bloom from your garden then consider giving one of these a go.
Hibiscus grow best in maximum sunlight. They will grow in the shade but need full sun for optimum flower production. If you can, avoid placing them with other plants which compete for available root space and nutrients.
Growing hibiscus in containers is an ideal way of enjoying this beautiful plant at close range. In reasonable conditions they will thrive on sunny patios, balconies, by swimming pools, etc. Ceramic or wooden pots are best with a minimum size of 50cm diameter. Use a good quality potting mix with a long-term slow release fertiliser incorporated. Select lower growing varieties such as the 'hibiscus longiflora' range to plant as they take longer to overcrowd their container. Re-potting is necessary after two years. Appropriate feeding, pruning and pest control is desirable. Regular watering is essential and a fitted irrigation micro-tube with adjustable micro spray or dripper fitting makes this easy to manage.
Annual pruning of hibiscus is encouraged for healthy growth, good flower production and neat compact plants. When the season begins to warm up in the spring remove about one third of the previous season's growth. Use sharp secateurs and make an angled cut above the outward pointing bud. Completely remove crossed or wayward branches or any which overcrowd the centre of the bush. Trim off branches within 30cm of the ground to create clearance for mulching, fertilising, etc. Bushes soon grow into vigorous new stems.
There are a few different hibiscus types that are available to home gardeners today including Fijian, Clarks Hybrids, Hawaiian, Syriacus and Longiflora.
Hibiscus Longiflora is my pick of the hibiscus types. This type produces many more flower blooms than other varieties. Top quality breeding has resulted in flowers produced in profusion at cooler temperatures, blooming earlier in the season and continuing for a longer period. To add to the flower power the blooms of longiflora varieties typically last 3-4 days as opposed to 1 day which has been the norm for hibiscus. The longiflora varieties have a compact growth habit about 80cm to 1.2m high by 80cm wide. Enjoy the week!
Gareth Carter is general manager of Springvale Garden Centre
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