Propagating Arbutus fruits collected from the Greek island, (Sapienza)
The National Collection of the genus Arbutus takes an interesting twist in the propagation process. It was an exciting prospect to know that I would have the opportunity to propagate from the fruits of Arbutus Andrachnoides, and Arbutus Unedo, collected from the Greek island of Sapienza by the owner of the National Collection in the cotswolds.
The Greek island of Sapienza is an offshore island in the south Peloponnese which is uninhabited, except for one of the last remaining lighthouse keepers in Greece.
Arbutus Andrachnoides is a hybrid of Arbutus Andrachne and Arbutus Unedo. Andrachnoides has an attractive deep red bark with a sharp tip on each individual leaf, and its beautiful ivory/white flowers appear from late autumn to early spring. When working in the 6.5 acre garden here in the cotswolds I often stop and admire the mature specimen which was sourced from Bodnant garden, Wales, in 1986.
This particular specimen has proven to be winter hardy at temperatures recorded down to – 12 last winter. I have recently written about this in the RHS Plantsman, spring issue, on the subject of the winter hardiness of the Arbutus from the National collection.
From purely personal experience I think the more you become involved in cultivating and propagating from a particular genus of plants, it’s likely that you become more passionate about it. Comparing the merits of the 14 species of Arbutus from the Ericaceae family has been a very interesting project over the last five and a half years. I recently embarked on what I hoped would be the best approach to the propagation of these seeds from the Greek island, and I knew, that it would be an interesting challenge to undertake.
MY FIRST QUESTIONS
I did wonder whether, if indeed I was successful in achieving some germination from these fruits, they would be less hardy in our temperate climate, bearing in mind the climate of their original country of origin. I also wondered whether, if I could germinate some of these seeds through the process of seed stratification – exposing them to extreme winter temperatures within a cold frame, it would produce hardier plants and trees in the longer term.
SOAKING THE FRUITS; SOWING THE SEEDS
The strawberry like fruits of Arbutus species need to be soaked in warm water at the initial stage of contact for 24 hours. I have undertaken this process with the fruits of other Arbutus species from within the garden, which have included Arbutus Unedo- Elfin King, Arbutus Unedo- Atlantic, and fruits taken from the mature tree of the common species, Arbutus Unedo. The first two are shrubby cultivars of the Unedo.
On average most fruits are the size of a marble and contain about 20 seeds. After the soaking period I carefully split open the softened fleshy fruits and sow the seeds into modular trays filled with a John Innes seed compost. (I covered this process in more detail in the spring issue of Plant Heritage.) I sowed all of the seeds within a two week period from early to mid Nov last year.
THE WAITING GAME
I knew from my previous experiences that I would need to be patient in waiting to see the first seedlings emerge, if indeed that were to happen as, of course, there are no guarantees. I recalled sowing a whole modular tray of Arbutus Atlantic seeds 84, in which only two germinated. However the same amount of seeds were sown of Arbutus Elfin King, and the result was an astounding 95 % germination, so who knows what would happen.
FIVE WEEKS AND THE FIRST SIGNS OF LIFE
After five weeks I was rewarded with the sign of the first two seedlings starting to emerge. This ran true to form with my previous sowing of Arbutus seeds which took about the same amount of time for germination to occur. These seedlings germinated in the propagation area of the glasshouse with the overnight temperature running between 10-15 degrees c.
THREE AREAS OF GERMINATION
I had sown equal amounts of seeds in three areas of varying temperatures. These were : In the propagation end of the glasshouse which runs at an overnight temperature of 10 – 15 degrees c
The cool end of glasshouse with a min night temperature of 8 degrees c
The cold frame- according to varying outside temperatures
I am very restricted in controlling the temperatures within the glasshouse because it is a large lean- to glasshouse measuring approximately 18 metres in length x 5 metres in height and it is heated by 240 volt fan heaters. It’s a lot of space to fill with a restricted system of heating. Therefore, if there is an extreme drop in temperatures, as we are currently experiencing, the overnight temperatures can drop several degrees lower than the desired temperature within each area.
GERMINATION RATE TO DATE
The rate of germination to date has surprised me with germination taking place in all three areas. See below my brief summary -
*Propagation Unit
Approx – 50% germination overall of both species, with about a 10% higher rate of germination of the Andrachnoides
Cool End
Approx – 70% germination overall of both species, with about a 20% higher rate of germination of the Andrachnoides
Cold Frame
Approx – 12 % germination overall with equal germination of both species
THE COLD FRAME
The germination in the cold frame took 10 weeks, that is twice the length of time it took in the glasshouse. The lowest outside temperature that I recorded has been – 8 degrees c. The seedlings spent just one night of that temperature within the cold frame, covered with another modular tray, and a double layer of fleece.
When I removed the various protective covers this morning the seedlings were still alive. I have now decided to move them into the cooler end of the glasshouse where I shall continue to grow them on, covering the trays at night with fleece. A move to the much warmer end of the the propagation unit would be too much of a shift in temperature, and too much of a shock to this new flush of life.
DRAWING COMPARISONS
The interesting comparison of the current results of the seeds from Sapienza is that of the Arbutus Unedo. I collected the fruits from the mature specimen in this cotswold garden in the late autumn of 2009, (this tree was originally sourced from Bodnant garden, Wales 1986). The seeds were sown soon afterwards and I achieved a 20% rate of germination. This narrowed down to what are now two small woody trees, both of which are about half a metre in height, currently in the propagation end of the glasshouse.
The rate of germination of the Arbutus unedo seeds collected from this cotswold garden is considerably lower than that of the seeds collected from the Greek island.
NEXT BLOG-
The late Graham Stuart Thomas is arguably one of the greatest gardeners and plantsmen of the last century. I would like to share with you my winter task 5, that of pruning roses. (an influence from G S T)
