Fern and Fossil glasshouse, tall tree ferns, moss, liverwort and rocks. Royal Botanic Garden Edinburgh
The Ferns and Fossils Glasshouse in April 2022, before work began.
[Photo: Kevin Bannon]

A different decant

Two years into the Edinburgh Biomes Project and we’ve already seen three large display Glasshouses emptied, along with the move of a massive collection of outdoor plants and multiple rearrangements of many of the potted glasshouse collections. In 2022, the Horticulture team fixed their attention on the Ferns and Fossils Glasshouse, home to an impressive species diversity from an ancient group of plants. The collection includes some tall Dicksonia antarctica tree ferns with liverworts and mosses like Hypopterygium tamarisci clinging to their trunks, along with giant horsetails such as Equisetum myriochaetum and various fern species of Blechnum and Cyathea, mixed with conifers of the Amentotaxus and Acmopyle genera. This glasshouse collection presented a whole set of different challenges to those encountered with the earlier decants.

Moss growing on the trunk of a large tree fern. Red new growth smaller fern.
Left: The moss Hypopterygium tamarisci thrives on the surface of Dicksonia antarctica.
Right: The vibrant new growth of Blechnum patersonii in a break of sunlight.
[Photos: Kevin Bannon]

A Glasshouse ‘decant’ involves more than the simple removal of plants; it’s the careful dismantling of a collection of plants that have grown together for years and have become an interwoven natural landscape.

The plants are shaped over time within the rocks and borders of the glasshouse; mature plants with their roots deep in the landscaped ground, layers of smaller plants that grow into the available spaces, topographies of stone and fossils, and sculptured pathways and water features. The decant of this landscape began with the creation of two lay-down (‘hardstanding’) spaces around the perimeter of the Glasshouse. You can read more about this early work in Hazel Frances’ Stories from the Biomes: Fern House Decant Begins.

The biggest are the first to leave

Following the creation of hardstanding on the south side of the house, plans were made to move five of the Dicksonia antarctica tree ferns to Logan Botanic Garden. Although they appear to be the type of large plants that should be left ‘til last, these tall ferns had to come out first.

Dotted around the house, towering above the rest of the collection were nine Dicksonia antarctica tree ferns weighing roughly 250 – 300kg each. All carefully lowered in their own unique way, the first five were moved and planted outdoors at Logan, while the other four were lifted and carefully potted on the hardstanding space created in the Temperate Lands Glasshouse.

The animation below is a before and after comparison showing how the planting beds had to be adjusted, and tree ferns removed, to allow the electric telehandler to enter the glasshouse. The success of this strategy meant that we could use the telehandler to help lower the remaining tree ferns.

Animated GIF of glasshouse overview
Each black spot represents the position of each Dicksonia antarctica originally planted within the Glasshouse. [Animation: Kevin Bannon]
Animated GIF of glasshouse overview
After the removal of some Dicksonia antarctica and portions of their beds, the telehandler is able to navigate within the Glasshouse. [Animation: Kevin Bannon]

Despite the help from the telehandler, there were challenges to overcome due to the tight awkward spaces we were working in. Much of the landscape around each tree fern remained intact while we moved these tall and extremely heavy tree ferns, so manoeuvring had to be slow and careful to ensure there is no damage to the surrounding collection.

Two horticulturists lowering giant tree fern.
A large Dicksonia antarctica rests on a narrow path. [Photo: Roween Seuss]

An interesting thing about Dicksonia antarctica tree ferns is that their trunks are made from roots; this means they can be moved without digging up a huge root ball. Instead, the trunk can be cut at the base, the roots kept moist, and then replanted in their new home. All five of the Dicksonia tree ferns moved to Logan Botanic Garden are cut in this way.

Two horticulturist beside root plate of tree fern. A horticulturist uses a chainsaw to cut tree fern trunk.
Left: The massive root plate of another Dicksonia antarctica after being lowered. [Photo: Hazel France]
Right: Roween Seuss uses a chainsaw to cut the stem for later planting and added ease of manoeuvring that fern out of the house. Despite being cut, the roots from the trunk will still grow and the tree fern will stabilise itself over time once planted. [Photo: Kevin Bannon]
Two horticulturist wrap tree fern trunk
The team wraps a tree fern trunk with damp hessian to keep moisture on the trunk, before reversing it out of the Glasshouse. This combined process is repeated for all the plants of height. [Photo: Kevin Bannon]

Machinery, materials and muscle

The manual labour of the horticulture team is the bedrock of any decant, and the purpose of machinery is to make it easier and safer. The team are trained on various machines to help with the project, ranging from a small manual pallet truck to a 5½ tonne electric telescopic handler (telehandler).

Digger and Dumper

Horticulturist operates digger and soil dumper, removing soil.
Excess soil is removed in order to lay ground guards for access into the bed, in order to remove further planting. Senior Horticulturist Neil Watherston uses a mini digger to transfer the excess soil into a mechanical dumper, which is then driven out of the glasshouse and the soil tipped into a nearby skip. [Photo: Kevin Bannon]

Pallet Trucks

Multiple horticulturist prepare to move large tree fern
The electric pallet truck acts as a pivot point while moving a large tree fern; the stem and crown are held by multiple members of the team as the pallet truck changes position. [Photo: Hazel France]
Multiple horticulturist prepare to move large tree fern
A tree fern is adjusted on a stack of pallets to enable the electric pallet truck to gain access. Often, due to conditions of the ground, a manual pallet truck is used, and this needs the strength of the team to adjust and move it. [Photo: Suzie Huggins]

Trollies and Ratchets

Horticulturist cutting plant material. Bags of compost, ratchet straps, pallets
Throughout the decant large trolleys and electric pallet trucks help to move around the variety of materials needed such as pots, hand tools, and stacks of compost bags. The image above shows Horticulturist Hazel France using a trolley while she clears a patch of the fern Woodwardia radicans. In the centre, we see a selection of ropes, ratchets and lifting strops used for the safe removal of the taller tree ferns. [Photo: Kevin Bannon]

Electric Telehandler and Attachments

Large telehandler reverses out of glasshouse
Senior Horticulturist Neil Watherston reverses the electric telehandler out of the glasshouse with only inches to spare. The flexibility of the telehandler makes it one of the most valuable machines for the decant process. [Photo: Kevin Bannon]
Telehandler attachment cuts under large plant
The Planting Plate attachment: the electric telehandler’s planting plate attachment slices under a large Thyrsopteris elegans. This relatively shallow-rooted fern is then lifted and can be carefully split into smaller pieces. This method reduces the damage to the roots. [Photo: Kevin Bannon]
Two horticulturist direct machine into glasshouse
The Lifting Hook attachment: reaching through the narrow access, strops tied around the trunk of the tree are attached to a hook attachment. Although at a challenging angle, here the telehandler can easily take the weight of the tree while it is manoeuvred into a better position. [Photo: Kevin Bannon]
Electric telehandler lifts large tree stump
The Bucket attachment: the telehandler bucket offers a hydraulic jaw-like action to grab and lift large objects. The photo above shows the strength of the bucket easily lifting a massive root ball. [Photo: Kevin Bannon]


Man operates jackhammer on area of stone.
Working close to one of the last remaining plants, Dicksonia arborescens, Neil Watherston uses a jackhammer to break down the concrete remains of a waterfall feature that once surrounded this small tree fern. Following, we were able to safely remove the fern. [Photo: Kate Miller]

Rocks, rocks and more rocks

A defining component of the fern house decant is the large amount of rockwork that needed to be removed. The Ferns and Fossils Glasshouse landscape contained over 1,000 rocks of all types and sizes, with many of the tall tree ferns anchored at their base by a halo of surrounding rocks. The true size of most of the rockwork is hidden beneath the soil, and this only becomes apparent when each planting bed is tackled.

Periodically, during the decant, a full day of work is focused on the removal of the rocks, calling on large numbers of the wider team to help in the strenuous work.

Multiple horticulturists work in a glasshouse to remove plants and planted area
Horticulturists Szymon Drozdek and Neil Watherston make use of both manual and mechanical devices when moving rocks out of the glasshouse. Here Neil loosens the rocks with the digger and then, using a sack barrow, Szymon transports them to the telehandler bucket waiting outside. [Photo: Kevin Bannon]
Electric telehandler moves piles of rock into tractor trailer
Once fully loaded, the rocks are transferred to a tractor and trailer and then transported to a storage area of the Nursery grounds. [Photo: Kevin Bannon]
Pile of rocks
The large and varied collection of rocks from the glasshouse now in the Nursery. [Photo: Kevin Bannon]

The (almost) last plants

Multiple horticulturists move a tall tree fern within a glasshouse
One of the last to leave, in January 2023 the team lifts a Dicksonia squarrosa tree fern and slowly moves it down to the entrance where they lower it and take it out of the glasshouse horizontally. [Photo: Kevin Bannon]
Two horticulturists guide a tall tree fern and an electric telehandler holds the tree

Where the plants go

As was the case with the decant of the Palm Houses in 2021, the plants from the Ferns and Fossils Glasshouse have to squeeze in amongst our other collections – with the largest of them destined for the tall Temperate Lands Glasshouse.

The decant process to leave the Fern House is effectively reversed when arriving at the Temperate Lands Glasshouse. We lay protective ground guards on the slabs outside the glasshouse, and on the floor inside. While still outside, we lower the tree ferns, brace them horizontally and manoeuvre them through the low door into the glasshouse. As we progress and add more plants, the space for manoeuvring within the glasshouse becomes tighter and tighter, requiring more and more precise planning and moving.

Illustration showing height difference in tree fern species. Kevin Bannon
An illustration comparing the different sizes of some plants that the team move and pot in their new home. The tallest is a Dicksonia squarrosa, which – due to its thin trunk – comes with the real possibility of snapping during the process of lowering, but thankfully, it endured and was safely potted. [Illustration: Kevin Bannon]
Horticulturist stands beside raised tree fern, held by electric telehandler
Cyathea australis in the Temperate Lands Glasshouse with Horticulturist Kate Miller and Neil Watherston. Nearing the end of the process, floor space becomes tight leaving just enough room for the electric telehandler to enter and carefully raise the plants into place. [Photo: Kevin Bannon]
Two horticulturists prepare a large airpot for potting of tree fern.
Kate Miller and Neil Watherston prepare some compost and a planter pallet, ready to pot the next fern. [Photo: Kevin Bannon]

The illustration below shows the basic process of how we are using Air-Pots®. First, a base layer is created using a strip of Air-Pot® material, and this is filled with compost. The plant is then carefully lowered onto this base and held in place while the root ball is wrapped with a larger piece of Air-Pot®. Next, compost is added with care so as not to damage the roots. With every plant, there is a need for adjustments in pot size, so the beauty of this system is we can tailor each of the pots to suit.

Illustration showing how to use an airpot. Kevin Bannon
A simplified illustration of the process of using an Air-Pot® to pot a large sized plant. [Illustration: Kevin Bannon]
A horticulturist pots multiple tree ferns
Horticulturist Hazel France finishes potting an Alsophila tree fern. Traditional pots are still used where possible, depending on root ball size, height, and weight of the plant. [Photo: Kevin Bannon]

When it came to the largest of the tree ferns, another method was necessary. Neil Watherston constructed six large boxes using treated wood, to give the added strength and stability required. Still using a plastic pallet as a base so they remain moveable, the box is fixed on top, and the inside is lined with plastic. The animation below shows the process of potting a large tree fern into one these boxes.

An animation showing how very large tree ferns were potted in custom built wooden boxes with pallet bases.
Potting a large tree fern in a constructed wooden box. [Animation: Kevin Bannon]
Tall tree fern in custom wooden box with pallet base
Wooden boxes constructed to support the largest tree ferns. [Photo: Kevin Bannon]

A good sign

Moving any plant is a risk, but this can be especially true for mature plants. The plants go through a lot of stress; they are being ripped from conditions they have become accustomed to over years, or in some cases, over several decades. They have their roots and foliage cut, and these particular ferns are placed in pots where the risk of drought or overwatering is increased. However, in the hands of a highly skilled horticulture team, the ferns are flourishing once again in their new home.

New fronds emerging from crown of tree fern
A flush of new, tightly packed fronds push free from the crown of Dicksonia sellowiana in its new glasshouse. [Photo: Kevin Bannon]
Multple tree ferns with new fronds, flush over bridge in glasshouse
As of July 2023, the tall tree ferns that were moved and potted are flushing new canopies high over the bridge in the Temperate Land Glasshouse. [Photo: Kevin Bannon]

With another glasshouse done and more to go, the horticultural team moves forward in laying the groundwork towards creating RBGE’s glasshouses for the future.

An illustration showing horticulturists moving plants of various size. Kevin Bannon
A parade of plants. [Illustration: Kevin Bannon]