Pseudopanax crassifolius (Sol. ex A.Cunn.) C.Koch

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Pseudopanax crassifolius, also known as horoeka or lancewood, is a heteroblastic tree belonging to the family Araliaceae. It is endemic to New Zealand and found throughout the country from sea level up to about 750 m in lowland to montane shrublands and forests.

The juvenile form, which lasts between 15 and 20 years, is easily recognised. The leaves are stiff and leathery with a prominent central rib, about 1 cm wide and up to 1 m long with irregular teeth, all growing downwards from a central stem. The young trunk has characteristic vertical swollen ridges. As the tree gets older the stem begins to branch, producing a bushy top. The leaves also become wider and shorter, losing their teeth. It is only when the tree is mature that it adopts a typical tree shape.

The difference between the juvenile and adult tree's appearance is so drastic that the two forms were initially described as separate species and even genera by early botanists, including the botanists accompanying Captain James Cook during his first voyage to New Zealand.

One of the theories about this curious change of appearance is that the young plant had to protect itself against browsing by the moa, a group of giant flightless birds that once roamed New Zealand's bush. Once above moa height, it was out of danger and turns into a "regular" tree. A study of leaf colour development in P. crassifolius found that leaves of seedlings would blend with leaf litter, while juvenile leaf colouration would draw attention to their spines. A closely related Chatham Island species, which evolved in the absence of moa, did not display these changes.

Closely related is Pseudopanax ferox, the toothed lancewood. It is similar to P. crassifolius except the leaves are more abundant and severely toothed, resembling remotely a bandsaw blade.

Description

Pseudopanax crassifolius is a heteroblastic plant, meaning that it has different leaf forms and growth habits depending on its growth stage. These growth stages, which are largely related to the plant height, are: seedling, juvenile, transitional, and adult.

A juvenile tree is single-stemmed with long and narrow deflexed leaves, typically below the height of 3–5 m.

As an adult, P. crassifolius can reach a height of 15 m. It appears as a round-headed tree due to being multi-branched, making it look more like a "typical tree" than its previous forms.

 

Pseudopanax crassifolius - Wikipedia

https://youtu.be/ImIXh-ecwZk?t=1451