UCPH experts decrypt plant legend’s garden

In a residential neighborhood of Kolding, Denmark, there lies an overgrown 7000 square meter garden once owned by legendary gardener and plant nursery owner, Aksel Olsen. It it safe to say that Olsen was a veritable plant nerd. For decades, he amassed a wide variety of seed from around the world, seeds that took root and became plants in his own backyard. Among his other means of acquiring seed, he asked Danish missionaries to bring seeds back from Asia and other corners of the globe.

Upon Aksel Olsen’s death in 1982, his daughter carried on the plant nursery business. After his daughter’s passing in 2014, Kolding Municipality intended to exercise an option to purchase the property, which they did in 2016.

To make the right decisions for the future of the garden, it was decided to convene experts to record the unique plant life that had come to rule his old-growth forest like garden prior to any thinning or plant removal. The decision has been a source of great excitement for the University of Copenhagen’s Lars Birck, day-to-day manager of the Royal Agricultural School Gardens, and Associate Professor Marian Ørgaard, of UCPH’s Department of Plant and Environmental Sciences.

"We have looked forward to each and every chance to spend time in the garden. Aksel Olsen collected seeds from all over the world that he germinated and crossed to develop new hybrids. The results are quite amazing and we have found many rarely seen species," says Lars Birck, whose manages the Royal Agricultural School Gardens and its 6000 different types of plants.

500 species expected
The two experts have been recording the plants since May 2017 and have spent a great deal of their free time verifying and registering the diversity of plants in the garden. The garden's densest sections, where plants grow in multiple layers and in every direction, have made it a huge and time-consuming task. They expect to find around 500 plants before finishing with the garden, an experience that has already prompted many a 'wow-moment'.

"You learn a lot by observing how trees and plants grow over the course of 50 years. For example, one of the largest paperbark maples in Denmark has been discovered in the garden, and it has been a joy to see such a massive specimen,” says Lars Birck.  

Paperbark maple is native to central and western China. Indeed, Asia, along with North America, are the parts of the world that Olsen was most fascinated with, an interest reflected in his garden’s vegetation. 

Rare trees, including ‘nikko maple’ and 'Japanese emperor oak' were also recorded. But the rarest find thus far is a shrub by the name of Viburnum erubescens, which probably doesn’t exist many other places in Europe, according to Marian Ørgaard.

With a brush cutter and pruning shears
The pair of plant connoisseurs estimates that the garden has been left untamed for roughly 15-20 years. This has allowed nature to unfold freely. In particular, blackberry, nettle, dwarf bamboo and elder have spread ubiquitously, making a brush cutter and pruning shears indispensable for getting through the garden.   

"It is exciting for us to see how plants and trees develop when they are left to look after themselves," says Marian Ørgaard, who, in light of the story of Aksel Olsen’s garden, has received numerous tips from people about other gardens.

Four students from the Department of Plant and Environmental Sciences have used the garden for study projects. Among other things, they have mapped the garden and its old paths and sharpened their plant identification skills.    

Alongside the recording of plants, Lars Birck and Marian Ørgaard have also started to make recommendations about the care of the garden in the future in such a way that will prevent overgrowth while maintaining its wildness.