Lophomyrtus obcordata

Lophomyrtus obcordata is a flowering plant from the myrtle family, Myrtaceae. It is a tall bushy shrub whose size can reach up to c. 5 or 6 m.[1] This shrub has a smooth trunk beige hidden by pieces of greyish bark whose diameter is about 0.2 m.[2] The branches are spread out; the branchlets are numerous, erect, of the subcylindrical type, and slightly pubescent.[1]

The leaves are much smaller than those of other trees of the same genus (e.g. Lophomyrtus bullata).[3] These leaves are thick, heart-shaped, opposite or fasciculate, glabrous when adult (and pubescent before), and 5 to 10 mm long and wide. They are carried by petioles 1 mm long, rather fragile and brittle.[1]

The flowers are axillary and solitary, 6 to 8 mm in diameter, borne by fine pubescent pedicels about 20 mm long. It has four sepals, four white petals, and a large number of stamens (about 100 or more).[2] The ovary is inferior, meaning that it is surrounded by the receptacle and has two or three compartments and therefore two or three placentas (axile placentation) where there are a large number of ovules.[1]

The fruits are oval berries of bright red to dark red color, and their size is 6 mm long. The seeds are brown, bean-shaped, with a resistant, glabrous, and rather smooth seed coat.[2] They are produced in very large numbers.[4][1]

Trunk

Lophomyrtus obcordata is a species endemic to New Zealand.[3] Lophomyrtus was formerly placed in the genus Myrtus, a genus found mainly in South America. The genus Lophomyrtus is endemic to New Zealand.[1]

Lophomyrtus obcordata is an endemic species of New Zealand. It can be found on both, the North and South Islands, although it is found mainly on the South Island.[1]

It grows well in coastal forests and rather at low altitudes. For example, it can be found in the forest of Westland, where the rich and deep soils and the heat are conducive to its development, although this species is also rather tolerant to drought.[5]

Branches

Lophomyrtus obcordata is mostly found in coastal forests, but also in the montane forests - although more often present in coastal and lowland habitats.[1] Occasionally, it can be found in the alluvial forests of the eastern South Island.[1]

This shrub is found in the forest understory and in rock-like habitats.[6]

Flowers

Lophomyrtus obcordata grows in rich and deep soils, loamy, and possibly clay soils.[7] Loamy soils are very rich and fertile soils, conducive to the good development of plants.[7] These soils are rather light and heat up quickly during sunshine. However, these soils become depleted over time, which can harm the development of Lophomyrtus obcordata.

It prefers moist soils. It adapts quite easily to any type of pH, but its development will be limited in acid soils.[8]

Lophomyrtus obcordata has foliage and fruit that are very attractive to birds, insects, and pollinators such as bees.[7] These species may be endemic to New Zealand, or adventive.

Landcare Research-Manaaki Whenua gives a list of 14 species that are in association with Lophomyrtus obcordata.[9] They can be classified according to their order. For example, Lepidoptera and Hemiptera feed on the leaves and can therefore be problematic for shrubs.

There are no known parasites specific to Lophomyrtus obcordata. However, some parasites generally attack plants of the Myrtaceae family.

One of the biggest threats to this family is Austropuccinia psidii, the cause of myrtle rust disease. The rust spreads very quickly and destroys endemic species of the Myrtaceae family, particularly Lophomyrtus obcordata, but also another close species, Lophomyrtus bullata (ramarama). Unfortunately, even today the control of this disease is still inefficient, due to a lack of knowledge.[10]

Myrtle rust: what it is?

It is a fungal disease that can affect the plant of the Myrtaceae family. This disease forms bright yellow spots, like pimples. These are spores that spread from one plant to another. It quickly spreads over the entire surface of the leaf, starting from the underside. The oldest spores are brown and gray. If the disease spreads too much, the leaves may curl up, and necroses may appear.[11]