Native Plant of the Month - December - Rimu
Rimu are some of New Zealand’s most distinctive large forest trees. They have graceful weeping foliage and develop intricate linear patterns on their bark as they mature. Rimu trees are either male or female and every few years the females fruit very heavily - known as a mast year. This mast fruiting triggers breeding in several of our rare native birds, including kākā and kakapō. The 2021/2022 summer is predicted to be a mast year so we are crossing our fingers for a great breeding season!
Rimu are endemic - they are found nowhere else on the planet. They are members of the Podocarp plant family, along with other forest giants such as kahikatea, totara, miro and matai. Podocarp species are more closely related to pine trees than other flowering tree species. They have needle-like leaves and produce pollen using cones. The name podocarp means fruit-foot. This might sound strange, but it is quite a good description of the fruit of many plants in this family. If you have ever seen a rimu fruit you will know that it looks like a shiny red berry with a single blue-black seed perched on the end, a bit like a kid on a moon-hopper. Unlike other types of fruit, the fleshy red tasty part of rimu and other podocarps’ fruit is actually a swollen section of stem. The seed develops on top of this swollen coloured stem, so the part we see as a fruit is more like a foot growing beneath the seed. This modified stem has evolved to create a tasty treat to attract birds who eat this colourful ‘fruit’ along with the seed that sits on top of it and then spread the seeds far and wide.
Rimu are slow growing and may live over 1000 years. They are described as emergent trees because when they are fully mature they are so big that they poke up and emerge above the forest canopy. This makes them really important parts of the ecosystem as they provide tall and complex habitat for a diverse range of native forest animals. Old rimu trees often host a variety of plant epiphytes among their branches, making them into giant hanging gardens. Canopy scientists study these ecosystems and it is thought that there may be many new species and interactions to discover high up in the branches of forest giants like rimu. Both the gardens of epiphytes, as well as their shaggy bark, make big old rimu into hot real estate for our pekapeka, or native bats. These cute little flying furballs often roost under bits of rimu bark, tucked in amongst epiphytes, or in hollows in tree trunks. Because rimu live such a long time they often develop lots of great roost spots for our pekapeka.
Rimu are a fantastic tree to plant for future generations to enjoy. They are slow growing and will do best in good soil that does not dry out in summer and is well shaded. You may need to keep your rimu trees watered and well mulched during summer, especially for their first few years in the ground as they are sensitive to drought. A healthy rimu in your garden will reward you with a lifetime of beauty and birds. If you are feeling really adventurous you can even tap into some of our early settler history and have a go at making a drink with rimu leaves. Captain Cook made New Zealand’s very first beer using rimu and manuka leaves - with the aim of preventing scurvy. His account describes the beverage as pleasant and refreshing, although recent commercial attempts to recreate this pioneering drink have not met with much palatable success!