Hibiscus enjoy the summer heat

COLOUR: Take a trip to the tropics with beautiful hibiscus. PICTURE / SUPPLIED

Like people, plants all react differently to the heat. Some plants relish in it — the hot days really encourage a spectacular flowering in plants such as bougainvillea, mandevillea, silk trees, jacarandas, petunias, impatiens, flame vine and tropical hibiscus. Look out for these and others as you drive around the city. It is during these hot months that these plants really come into their own. Read more about hibiscus below.

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 if they are overly exposed.

At the same time for many plants, if they can be kept moist during the summer months it is the time that substantial growth can be made. 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, improve soil fertility and structure, provide a cooling effect on the soil and root system below and suppress weeds.

If you are looking at doing some major planting in the autumn then mulching an area during the summer is a way to start improving soil structure and encouraging earthworms and microbial activity, giving better results later when plantings are going to be made. 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 Pea Straw in bales and bags.

Hibiscus — Summer Delight
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 to obtaining good plants for your situation.
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.

The story goes that a bloom worn over a girl's right ear could suggest that she's in search of a mate, while over the left ear indicates mission accomplished. Hibiscus became the national floral emblem of Hawaii in 1923. The history and legend is somewhat fascinating and I hope it serves as an introduction and appreciation of the diversity of form, colour and sheer beauty of hibiscus flowers.

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. There are a few different hibiscus types that are available to home gardeners.

Fijian Hibiscus
Cold hardy shrubs that normally retain their leaves during winter. Blooms are slightly smaller than Hawaiian, but the shrubs tend to be larger. More solid colour shades.

Clarks Hybrids
New Zealand bred varieties by Jack Clark that are ideally suited to temperate conditions. They are a cross between Fijian and Hawaiian hibiscus.

Hawaiian Hibiscus
These are smaller growing, cold tender shrubs with huge flowers, they like to be grown in a warm, sheltered and sunny spot. The varieties come in multi colours of almost every shade except blue.

Hibiscus Longiflora
This is a more recently developed range that is small and compact. The compact growth habit makes them ideal for pots and patio containers. The flowers are produced in profusion with flowers typically lasting 3-4 days as opposed to one day which has been the norm for hibiscus up till now.

Hibiscus Syriacus
A cold, hardy, deciduous variety ideal for those whose gardens get heavy frosts. These tend to have smaller flowers and smaller leaves and come in a range of colours, including a spectacular deep blue.

Position
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. An open, sunny, frost-free garden bed devoted exclusively to hibiscus is ideal.

Planning
After three years in your garden most nursery cultivated hibiscus stock will have reached a height of 1.5-2m and about 1 metre wide. Allow sufficient space for growth and easy maintenance, and allow sunlight to reach every plant. Arrange colours effectively and position lower growers in front for visual effect and best sunlight.

Hibiscus in Containers
Growing hibiscus in containers is an ideal way of enjoying beautiful hibiscus 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 generally take longer to overcrowd their container. Repotting is generally 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.

Feeding
Hibiscus if regularly fed and watered responds 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.

Pruning
Annual pruning 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.
Enjoy the week!
Gareth Carter is general manager of Springvale Garden Centre