Chatham Islands forget-me-nots

Written by Gordon Collier

Chatham Islands forget-me-nots

13 July, 2020

It’s a safe bet that many of us at some time or another have tried to grow in our gardens the fabled Chatham Island forget-me-not (Myosotidium hortensia). It’s an equally safe bet that there have been numerous failures.

Only occasionally does one see the forget-me-not thriving when cultivated in New Zealand – isolated clumps perhaps but seldom a big drift of bright blue flowers held over broad, glossy green leaves. The place to see them in abundance is in their native home the Chatham Island’s. Early October is the best month and if you time it right what a spectacle!

A great place for viewing is near Kaingaroa, a tiny settlement on the edge of the sea. Hiking between thickets of the endemic Corokia macrocarpa (hokataka, whakataka) laden with large yellow berries, and past drifts of the unique Chatham Island sow thistle Embergeria grandifolia, the quarry is finally reached. Here these handsome plants grow between rocks and a prostrate hebe (Hebe/ Veronica chathamica), right at the sea’s edge.

According to the latest Threatened Plants of New Zealand book its natural habitat includes coastal cliffs, rocky outcrops and rock stacks, sandy and rocky beaches just above the strand zone, and in openings within coastal forest.

The forget-me-not is a member of the borage family. Myosotidium hortensia sharing its common name with Myosotis, the other forget-menots of the Boraginaceae. Myosotis is species rich, whereas Myosotidium comprises just the one Chatham Island species, and the two genera are not as close as once was thought. Surprisingly, recent DNA sequence evidence has concluded that the closest living relative to Myosotidium hortensia is the species Omphalodes nitida found far away in the Mediterranean (Heenan et al., 2010). The conclusion from this molecular work is that the ancestor of Myosotidium arrived on the Chathams through extreme longdistance dispersal, sometime between 3.6 and 22.5 million years ago.

Travelling around the main island it’s a fairly common sight tucked in against buildings, along hedge rows and always cultivated with tantalising ease. Coastal development destroyed the whiteflowered wild plants and these are now only known in cultivation.

“They grow like weeds – the rougher it is the better” Lois Croon says and goes on to give her recipe for success: “It’s a coastal herb; they like a light soil but will perform in a heavier one providing it’s not clay. They like wind and to be fed with seaweed, or lots of compost, or a liquid feed. Don’t plant them in the shade or love them to death. In summer an occasional drink of water would be appreciated. It’s normal for them to die down after flowering. They form tubers after a time and new plants can spring from these. Here on the Chathams the temperature is normally in the low 20s (ºC) so a cool site is needed for them on mainland New Zealand.” Lois has simple directions on how to grow new plants from seed, “seed moist and sow them fresh; expect them to germinate in 5–6 weeks. As soon as they are large enough, prick the seedlings out into PB2 bags using a good long lasting mix.”

The drastic decline of this special plant that once grew all over Chatham and Pitt Island is due in part to the introduction of pigs who love eating the tubers they form. Browsing, trampling and rooting by pigs, cattle, sheep, and horses also damages the plants. Possums and rodents are said to browse on their flowers and fruits. Lois Croon is fascinated by the huge leaves of these special plants. She notes their leaves have corrugated channels that help rain water run down to the roots.

References: de Lange, P.J.; Heenan, P.B.; Norton, D.A.; Rolfe, J.; Sawyer, J. (2010). Threatened plants of New Zealand. Canterbury University Press, Christchurch, New Zealand. 472 pp. Heenan, P.B.; Mitchell, A.D.; de Lange, P.J.; Keeling, J.; Paterson, A.M. (2010). Late-Cenozoic origin and diversification of Chatham Islands endemic plant species revealed by analyses of DNA sequence data. New Zealand Journal of Botany 48(2): 83–136. Matthews, J. and Collier, G. (1985). The New Zealander’s garden. Endeavour Press, Portland, OR 

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