Our native hibiscus deserve a special place in our home gardens
Puarangi is easy enough to grow provided you give it good drainage and plenty of sunshine. Plus, it fits in well with mixed planting schemes. Hibiscus belongs to the Malvaceae, a large international plant family best known for the large-flowered tropical hibiscuses. This article discusses two true native species in New Zealand, one of which is classified as a non-resident native. It also discusses how to save these native herbs and how to grow them in your garden. Finally, it looks at the possibility that Hibiscus trionum may have arrived via the Pacific islands, and its wide open flower and large central eye is widely loved by all who see and grow it.
Published : 2 months ago by Alan Jolliffe / NZ Gardener in
Hibiscus belongs to the Malvaceae, a large international plant family best known for the large-flowered tropical hibiscus. Many of these have been imported into New Zealand to add a tropical effect to gardens in the northern and warmer regions. They make a magnificent show for many months of the year. However, we should not ignore our New Zealand native members of this family.
We have two true native hibiscus species and one other is under a cloud of science as to whether or not it is truly native. We will get to that. As well, there is a tree species which is classified as a non-resident native.
This article is about the genus Hibiscus. New Zealand also has other members of the Malvaceae: Whau (Entelea arborescens), which is a really interesting small tree; the genus Hoheria which has seven species; and the genus Plagianthus which has three species. The botanical name Hibiscus is of ancient origin used by the Roman poet Virgil for the marshmallow plant.
READ MORE:
* Five healing native herbs and how to grow them
* How to grow hibiscus
* Save these natives - plant them in your garden
This common hibiscus lives in New Zealand under a scientific cloud. Hibiscus trionum is best treated as an annual but in warm, frost-free areas will live two to three years.
Easily identified by its wide open flower and large, black central eye, this annual is widely loved by all who see and grow it. I have seen it described by gardeners as their favourite native plant.
In late spring, it quickly grows into a small plant about 50cm high or higher, depending on shelter and location. During summer through to autumn frosts (in colder areas), it produces many flowers. The unfortunate thing is that the flowers generally last about a day.
Flowers open with their pale creamy lemon petals surrounding the black-maroon eye, and once open stay nice for some hours and then start to fade and the petals will assume a dark red pattern as they quietly wither away. Don’t worry though there will be more flowers the next day. Planted or self-seeded, in a group there will always be flowers out.
Seed is produced easily and the pods are surrounded by a lovely closed papery calyx which opens when the seed is nearly ripe to enable seed to easily disperse. Each year, save some seed and in spring sprinkle it directly into the soil in new locations. Self-seeded plants can also be transplanted early to new locations. Once you have it, plants will pop up each year and you won’t be disappointed.
For all its good qualities, Hibiscus trionum it is not considered by some botanists as native, although others state more work needs to be done. It is not recorded in very early New Zealand records but is recorded after 1860 by early botanists which may indicate it arrived about that time. It was first discovered in the gum digging settlements so the possibility exists it was brought here in material and equipment.
Another thought is that it may have arrived via the Pacific islands. Hibiscus trionum is also found in Australia and on islands throughout the Pacific, and it is known from western Europe, the US and Africa.
At this stage, scientists know that the New Zealand form is diploid (two sets of chromosomes per cell) while all other forms in the world are tetraploid (four sets of chromosomes per cell). There is a chance this plant may be classified as a New Zealand native plant after further research. It grows naturally here, and no matter what the botanists decide, it is likely to be considered by many gardeners and horticulturists as a native of New Zealand.
This species is a genuine New Zealand native plant and is also regarded as a native of eastern Australia. The flowers are usually creamy white to very pale butter yellow and may have some pinkish striping or colouring in the petals especially as they age.
In my Christchurch garden I notice the flowers of Hibiscus richardsonii do not open as wide as those of Hibiscus trionum, and it grows to about twice the height. The branches are somewhat bare with few thinner, deeply cut leaves.
As with Hibiscus trionum, the seed capsules are enclosed in a closed papery calyx which opens when the seed is nearly ripe. Seed of Hibiscus richardsonii is offered occasionally through specialist clubs or similar.
My own seed is heading to the Christchurch Botanic Gardens shortly so hopefully we will have some on display this year. It would be great to see more of this plant grown in gardens, and of course in the wild in reserves and conservation areas in its natural locations.
Let’s be upfront: This is not a New Zealand native tree. However, it has established itself in the northern parts of our country. It is classified by NZPCN as a non-resident native and was categorised as naturalised in New Zealand in 1964.
This tree has more than 20 common names and these names appear to be associated with a different island or community. The website iNaturalist (a social network of naturalists, citizen scientists and biologists) uses the common name sea hibiscus.
It grows well beside the sea and has occurred in mangrove swamps, beach areas and rivers here, and around the tropical zones of the world. Travel between the islands has probably spread them around because parts of the tree are useful for many things.
It is easy to work with and has been used for small boat building, wood carving and furniture. Plant fibres taken from the stems have been used in rope making and its bark has been used like cork for sealing cracks in boats. The flowers, leaves and bark were and are still used for medicinal purposes. The leaves can be used for food.
The flowers are quite large, and appear abundantly for a long period of time and are very showy. The petals are yellow, with a dark reddish brown-purple base. As the flowers age, they become orange-reddish brown, giving the effect that it has flowers of different colours.
The leaves are large and heart-shaped, somewhat similar to a lime tree, from the genus Tilia, hence its specific name – tiliaceus.
I have seen it growing north of Whangārei in a number of places, including in cultivation in seaside gardens. It is also very common as a coastal plant in Australia, often growing right out onto the beaches.
Swamp hibiscus, also known as prickly hibiscus, is a taller and more wiry, sprawling, tangled, thorny, shrub with flowers similar to Hibiscus trionum. The large flowers have a similar dark centre to H. trionum but with a more purplish colour, and a ring of light purple around the dark centre. Flowers only last about a day but there are usually blooms out when the sun is shining in late summer or autumn. Again, the seed is in the papery calyx which opens when seed is ripe.
Diversifolius describes a plant with differing or varied leaf shapes, which is from the Latin diversus and folium (leaves). Leaves are up to 100mm long and 80mm wide, with 3-5 uneven irregular teeth, on long thorny stalk. Hence, H. diversifolius differs from H. trionum by having leaves of various shapes and strong, almost woody stems with sharp small hooks.
Found in the northern parts of New Zealand, it has been located in other areas but likely planted by gardeners or others wishing to ensure its survival. It likes coastal wetlands and stream sides, and can be found growing with raupō in back dunes or close to brackish streams.
The plant grows naturally in dense thickets and makes an interesting, almost thorny barrier by stream sides and in wetlands. You can see the cultivated plant in a large bed in the hibiscus collection in the Auckland Domain.
H. diversifolius is also found in a range of countries, including tropical Africa, Australia, New Guinea, the Philippines, many Pacific islands, and Central and South America.