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The Fern House, May 2022

So far, the iconic Temperate Palm House and the Tropical Palm House have been emptied of plants and are ready for refurbishment work to begin. The plants that could be kept have been dug up, potted and are now growing on. Plants from the Temperate Palm House are currently in the Temperate Lands glasshouse and Plants from the Tropical Palm House are split between the Orchid and Cycad glasshouse and the Tropical Support glasshouse.

Plants from the Temperate Palm house that were dug up and potted in the summer of 2021, now growing on pots in the Temperate Lands glasshouse, June 2022.

This is an example of the ‘decant’ process involved in the Edinburgh Biomes project, where plants have to be moved between glasshouses with suitable temperature/light/humidity levels for them, until building work is complete and they can be replanted. Complexities will arise as the plants grow and get bigger, but the available glasshouse space for them decreases, or changes, as the refurbishment project gets under way. 

The next public display glasshouse that the Horticulture team have begun work on is the Ferns and Fossils glasshouse, aka. the Fern House. We learned a lot about digging up, moving and potting large palm trees during the work on the palm houses and many of the same methods can be applied to the movement of tree ferns. However, the Fern House presents a new set of challenges. For example, in the palm houses the ground was flat and the paths straight, whereas the Fern House is on a slope with winding paths between densely planted beds, which limits the equipment we can use, and makes moving plants around more difficult. Also, the naturalistic display is built of hundreds of rocks which also need to be removed. 

Fern decant starts small

We began the fern house ‘decant’ process in April. We dug up one small area as a trial run to create a flat area of ‘hard standing’ in situ where the newly potted plants can be kept for the time being.

Bed before work began, April 2022
Digging up Blechnum gibbum for potting. (Pictured: Kevin Bannon)
The bed now emptied of ferns, ahead of the removal of rocks. We used the metal pinch bar in the foreground to lever the rocks loose so we could shuffle them out.
Rocks were removed and the soil dug out to bring the bed down to the level of the path. The area was then raked level, weed supressing membrane laid down, and potted ferns put back in place.

Tackling the Alsophila firma grove

The next area we tackled was a grove of much larger tree ferns, Alsophila firma.

The grove of Alsophila fiirma before work began in May 2022. Yellow tags show us which plants have been selected to keep, and red show which were to be removed.

We collected and sowed spores in May which, now at the time of writing in June, have germinated so we have a new crop of baby Alsophilas on the way. 

The underside of an Alsophila frond showing its spores; because we can’t keep all of the very large specimens, we collected and sowed spores to start off a new generation.

Three Alsophilas had been tagged to keep and the rest were to be removed. To do this, scaffolding was constructed so that the fronds could be removed and then the trunks cut down in sections.

Horticulturists Pat Clifford and Kate Miller cut down an Alsophila in sections. These tree ferns are very spiky which makes the job extra challenging!

With the larger tree ferns removed we had better access to carefully dig up the smaller ones that we wanted to keep.

The window of time for moving ferns is restricted by when they are flushing, ie. putting out their new fronds. These new fronds are very soft and prone to wilting and are easily damaged so we moved Alsophilas before they flushed so that they could unfurl their new fronds in peace in their new home.  We removed the old fronds to reduce moisture loss, but left the lower section of the frond (the rachis) intact to protect the emerging curled fronds, or crosiers.

Digging out an Alsophila for potting. We wrapped the ferns in hessian to protect them from water loss, and to protect us from their spiky trunks.

Alsophilas ‘pup’ which means in their case they send out a large rhizome (underground, horizontal trunk) that then pops up new ferns along the way. This means that what might look like several individual plants is in fact one large plant that is all connected underground; this can make digging them up more difficult than it first looks at the outset!

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Alsophila fima looking glamorous in hessian

One by one we dug them out and laid then on a flat-bed trolley, then wheeled them down to the Temperate Lands glasshouse.

Horticulturists Kevin Bannon and Kate Miller taking a fern from the Fern House to the Temperate Lands glasshouse

In the Temperate Lands glasshouse we potted up the Alsophilas in Air Pots® using a bespoke bark-based mix we designed for terrestrial ferns, with a slow release fertiliser mixed through.

Alsophila when first potted up in May 2022

We did this work on the Alsophilas in May and at the time of writing in June they are flushing their new fronds in the Temperate Lands glasshouse.

Alsophilas flushing in June 2022

The next stage with the Fern House work is to dig up and either pot or remove the remaining ferns in the Alsophila bed, and then remove the rocks and dig out the soil. We will then level the area to create a hard standing flat surface to keep the next set of plants that we dig up and pot from another area of the house.