Brown spots on staghorn
An audience member asked Don about brown marks on her staghorn. This fern was situated on the verandah so didn’t get any rain. Don thought the problem was that the fern was drying out.
Staghorn (Platycerium superbum)
This is an epiphytic fern from the rainforests of Australia and Malaysia. The circular, grey-green sterile or ‘nest’ leaves are deeply lobed at the apex and act as collectors of nutrient-rich material. As new fronds grow each year the old ones at the back of the fern curl over to form a convenient basket shape. When the plant is well established, fertile, antler-like fronds 1-2m long are produced. The staghorn does not produce plantlets, but grows larger each season.
Don’s tips:
Fill the basket with sphagnum moss, compost, tea leaves, banana skins, or whatever organic material happens to be lying around.
Water the fern well. Don uses a mixture of 50% Nitrosol and 50% Seasol, diluted as normal. This mixture gives plants a boost: the Nitrosol encourages foliage growth and the Seasol aids root development.
Avocados
A question was asked about a mature avocado tree that was producing tiny little fruit.
Don explained that this was a pollination problem, and that avocados have a curious sex life. Some avocados (known as group A) have flowers that function as female on the first morning they open. When they reopen on the afternoon of the next day, they are functionally male. Opening and closing of the flowers is synchronised in all trees of the same variety. Other varieties (known as group B) have flowers that open on the afternoon of the first day as female, then close and reopen the next morning as male.
In warm areas of Australia two trees are needed for pollination to take place. In cooler areas the opening and closing of the flowers is not so well synchronised, so there is enough overlap for pollination to occur on solitary trees.
Avocados are wonderful fruit trees for the home garden. They are easily propagated from seed, however seedlings are unreliable and grafted plants from the nursery are a much better option. Grafted trees grow around 10-12m (30-35’) tall, but seedlings may reach 30m (60’) tall. Seedlings take around 15 years to mature and bear fruit, while some never bear fruit at all.
Grafted avocado trees are available in nurseries from spring. A plant in a 5 litre bag or 200mm (8″) pot will cost around $25, and will fruit in about 2 years.
