There is no doubt that growing plants in the garden which are found locally is a safer bet, but there are always exceptions to the rule. For us here in the north the Pachystegia or "Marlborough rock daisy" provided with the right environment will perform pretty well.
At present there are three species of Pachystegia
Pachystegia insignis, Pachystegia minor and Pachystegia rufa all endemic to New Zealand.
Pachystegia insignis is by far the most common and wide spread within the genus's natural region which as the common name suggests is Marlborough. There it is found from the Wairau river in the north and to the south to the Waiau river North Canterbury and inland as far as Molesworth Station. The other two species, P. rufa and P. minor are also found growing within this range but are confined to much smaller areas. It is thought that P. rufa is only found in four small gullies all in close proximity.
Pachystegia would be hard to confuse with any other plant. It is handsome at all times and in late spring magnificent large flower heads rise above the foliage with classic white petals and a yellow disc in the centre.
Seeing plants in their natural environment has given us a much greater understanding of their requirementsGuy Bowden
In the wild most plants are found growing on steep rocky or stony sites composed of sandstone gravels. These rock types have a relatively high level of natural fertilizer especially calcium bound phosphorus (Ca.P). They are highly resistant to summer drought with their thick leathery leaves, dense felt like tomentum on the undersides and on young stems help to retain water. The root system of established plants is often extensive reaching into cool fissures on rock bluffs and outcrops.
We once had a magnificent plant growing in a very tall pot, it got quite large and flowered well year after year then quite suddenly started wilting and looking sick. Having hardly ever watered this plant I thought it was dry and started watering repeatedly which did not help. It wasn't until I turned the pot over that I discovered a large tap root had blocked the hole in the bottom of the pot.I had drowned it.
We recently visited Kaikoura and anyone who knows the road with the tunnels for both cars and trains will know the habitat of the rock daisy. They are perched all over the steep rock faces overlooking the ocean on this stretch of state highway one. Seeing plants in their natural environment has given us a much greater understanding of their requirements when growing them in cultivation.
In the garden Marlborough Rock Daisy will grow best in almost any dry well drained soil. Sometimes it's a good idea to build up the ground with a pile of rocks lifting it a little above the ground. It will also grow well on retaining walls. Our cold wet winters cause most problems, making it important to choose an open sunny site. The more wind the better; salt laden winds are no problem.
Pachystegia the species
At present three species of Pachystegia have been formally recognized (Molloy 1987)
Within each of these recognized species there are distinct variants reflected by the shape and dimension of the leaves..
A low growing, robust spreading shrub. The stiff branches spread up to 2 metres and may reach a height of 2 metres . The thick branches are densely clothed with small white hairs (tomentum). They tend to be bare from the base with leaves crowded towards the ends. The leaves (up to 20cm long by 10cm wide) are very thick and when mature are green and shining on top and like the branches clothed with white felt-like small hairs (tomentum). Flower heads up to 7.5cm in diameter are white with a yellow disc in the centre. Flowers late spring to early summer. P.insignis is distributed throughout its natural region of north Canterbury and Marlborough.
This is a much smaller plant than P. insignis and is ideal for small gardens. Plants seldom reach more than 30cm in height with approximately the same width. P. minor has smaller and darker green leaves than P. insignis. Flowers are the same colour and generally it flowers very well. Found in restricted coastal and inland locations of the Pachystegia general distribution.
This distinct species has only recently been discovered in four reasonably small gullies in Haldon Hills in Marlborough. Rather than the white hairs (tomentum) found on the undersides of P. insignis and P. minor the undersides and unopened flower heads of this plant are covered in brown or rusty brown hairs and the flower stalks are bright reddish in colour. Not yet common in cultivation, but I'm sure it would also make an excellent garden plant.