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YOUR GARDENING QUESTIONS THIS MONTH

Your questions answered

QMISSING HARVEST I grew sunflowers for the first time this year. When I was researching the plant, I had read that the seeds are ready for harvest when its petals dry up and fall off. Well, that’s happened, but I don’t see any seeds. How has this happened? JACK MOORE, KERIKERI

AIt’s possible that the flower wasn’t pollinated. Seeds won’t form unless pollination has occurred. If the weather was too cold and wet when the flower first opened, there may not have been enough bees about to do the job.

Another possibility is that the sunflower was a sterile variety selected for flower production rather than seeds. Check seed packets or catalogues – if a variety is described as pollen-free, the sunflower won’t set viable seed if grown on its own.

If you are growing sunflowers in order to harvest the edible seed, certain varieties are better for seed production. Try ‘Golden Toasted F1’ from Kings Seeds. Protect seedbearing blooms with a pillowcase or frost cloth to stop birds getting the seeds and harvest when the heads droop and the backs go yellow. Cut off the heads and allow to dry fully in an airy spot under cover. When the seeds loosen, scrape them off the seedhead and remove the

husks. Barbara Smith

QMISSION CONTROL This little butterfly flew into our kitchen the other day. It was very pretty, bright red, with dark almost black patches on its wings. I have been around nature a long, long time, and never seen one like it before. Do you know what it is? BUNNY DAVIS, ROTORUA

AThis colourful butterfly is actually the Cinnabar moth, Tyria jacobaeae, introduced as a biological control for ragwort, a pasture pest that’s toxic to horses and cattle.

In 1926, large numbers were bred in England and released over much of New Zealand but failed to naturalise. Another attempt was made in the 1980s and it’s now found over the central and southern North Island and in the northern South Island.

The caterpillars have bright orange and black stripes. The flamboyant colouring announces to potential predators that these caterpillars are full of toxic compounds ingested from their host plants.

Alas, there’s only one generation of caterpillars each spring and they prefer to eat each other instead of moving to new plants when the food supply runs low, so they’re not overly successful as ragwort controllers! Barbara Smith

QMYSTERY PLANT A friend of mine found this plant in a Dunedin garden. She said it smells like mustard. Do you have any idea what it could be? LEANNE MURPHY, LAVENDER SPRINGS

AJulian Matthews has identified it as Cantua

buxifolia – the rare, cream-coloured form. Usually it’s a deep pink to carmine red.

Margaret Barker grows it in the Larnach Castle gardens. Margaret describes the cream flaring flowers as the colour of mˉanuka honey faintly flushed with carmine.

The more usual carmine-flowered form of Cantua buxifolia grows at Larnach Castle too. It comes from high in the Andes of South America where it is known as the sacred flower of the Incas and is revered locally as the national flower of Peru.

The bushes can be a bit scruffy by the end of winter; foliage is sparse, with dead-looking twiggy bits. Then suddenly, mid-spring they’re dripping with 8cm pendant tubular, rich, carmine-coloured flowers that weigh down the arching branches.

Cantuas prefer shelter from the worst frost. At Larnach Castle the cantuas grow against a north-facing wall in well-drained, fertile soil with added compost.

Propagation is by cuttings of semi-ripe growth. New Zealand grown plants do not set seed as we don’t have hummingbirds to pollinate the flowers as they do in the Andes. Barbara Smith

QPALM PUZZLE This palm has flowered for the first time. Can you identify what palm it is? It is growing very close to a jacaranda tree – will either plant interfere with the other’s growth? ANGELA ESPLEY, AUCKLAND

AWe asked Stephen Dobbs from South Pacific Palms (southpacificpalms.co.nz) in Kerikeri to identify your palm.

He says it is Trachycarpus fortunei, the Chinese fan palm.

Stephen says palms can be hard to identify from pictures as there are closely related sorts, but if it was

Trachycarpus martianus, leaves would be divided evenly into segments to half the depth of each leaf. If it was

Trachycarpus wagneranus, the leaves would be smaller and more rigid.

But the jacaranda and palm are too close together, he says. The palm should be in full sun. It is showing stretched growth because it is in the jacaranda’s shade, which is leaning sideways because of the palm. Long term, it would be best to remove one.

Windmill palms are hardy, fast-growing and produce prolific amounts of seed which is dispersed by birds and gravity. Weedbusters warn that they can form dense stands that crowd out native plants.

On the other hand, jacarandas are fast-growing. A new one would soon reach a similar size in a new location if you decide to keep the palm.

South Pacific Palms grow 70 palms and cycads and offer a planting and landscape design service. Barbara Smith