Prunus x subhirtella ‘Autumnalis Rosea’

by Peter Williams

Timing is everything and plants that flower in the short dark days of mid-winter are always welcome in my garden.  Prunus x subhirtella ‘Autumnalis Rosea’, the pink winter-flowering cherry, does not always get its festive timing exactly right, but in most years including 2020, it is in flower on Christmas Day.  Buds are produced in early autumn and flowers appear during mild spells from October until April. 

Fig.1 – Prunus x subhirtella ‘Autumnalis Rosea’ at Christmas 2020

The origins of this and many other flowering cherry cultivars is not really known.  There is a story that it was discovered in the late 1600’s when a Japanese emperor noticed a single specimen flowering in a courtyard in Kyoto late autumn. Grafting material was taken to propagate more plants and the tree became known as Prunus ‘Jugatsu-zakura’ which translates as cherry of the tenth month – a reference to the time at which its first flowers can open. In most years the main flowering period is April and in very cold years like 2010-11, this is the only time that the tree flowers.

Fig.2 – Main flowering period in April

Winter-flowering cherries occur in pink and white flowered forms and are small, round-headed trees suitable for even the smallest gardens. Both white and pink forms are freely available but some nurseries still offer ‘top-worked’ specimens where the winter cherry is grafted onto a more vigorous rootstock at about chest height.   The rootstock always grows faster than the scion and the result is usually a rather ugly specimen with a disproportionately thick main stem.  Bottom worked cherries will have the graft union at the base of the plant and this results in a far better proportioned young tree and the graft union can easily be hidden by associated planting.

Like most ornamental cherries the winter-flowering sorts will grow happily in both acid and alkaline soils but they do not thrive in soils that become waterlogged over winter.  

The only negative features of the winter-flowering cherries are that the bark and autumn leaf colouration are not very striking. 

Peter Williams

December 2020

Obsessed with Aeoniums?

by Brian Denison

Aeoniums are natives of Madeira, the Canary Islands and North Africa, climates that do not experience sub-zero temperatures, consequently plants need protection in the UK during winter.

Fig 1: Greenhouse ready for winter

I insulated my greenhouse in November to accommodate them. I had to remove everything in the greenhouse to install the bubble wrap.

In Fig 1, I have just started to return the plants.

In the video below all the plants have been returned to the greenhouse and as you can see I have quite a few Aeoniums.

Many of them are the black  Aeonium ‘Zwartkop’ but I also have several of the bright green species A. arboreum. The display in Fig 2 highlights the contrast in colour of the two Aeoniums.

Fig 2

Another species I have is called A. ‘Blushing Beauty’ given to me by our late much esteemed member Roberto Renzi. This plant normally has pink tinges to the leaf tips, but it needs sun to develop the colour so the leaves are plain green in winter. My fourth and final species is A. ‘Sunburst’ purchased at Harrogate show last Spring (fig 3).

I have recently put together an arrangement of this Aeonium with Echeveria Peacockii (fig 4) . This is a succulent from the same family Crassulaceae and has similar cultural requirements.The display should look better when some growth occurs. The Echeveria was purchased from Merriments in East Sussex a couple of years ago. They had a superb display of several of them planted outdoors.  I have already propagated my plant from offsets which were used for the Fig 4 display. The original plant and remaining offshoots can be seen in Fig 5.

Fig 5: New Echeveria and babies

One of the problems with Aeoniums is their quick vertical growth but they may still look stunning, as seen in the examples in figures 6 and 7.

When Aeoniums get leggy the tops may be cut off with say 50 to 100 mm of stem and rooted easily in a cutting mixture. The cutting must be allowed to dry for a few days until the wound has calloused before potting up. I like to use an upturned plant pot to ensure the stem remains upright – see this video .

 Aeoniums are monocarpic, meaning they die after blooming. When Aeoniums form branches, not all the stems necessarily flower at once; the flowering stem(s) may be removed giving a good chance for the plant to survive. Out of interest Fig 8 shows an Aeonium in flower and fig 9 shows a flower on one stem which may be removed if desired.

It is also interesting to try to get Aeoniums to branch out. You can simply chop off the top (the removed stem can then be use as a cutting) and then ideally cut the stem down again leaving perhaps 50 to 100 mm of remaining stem which is then  allowed to regrow (Fig 10). Another technique is to carve out the growing point but this it is not easy as the leaves are tightly packed. If successful, the plant produces new shoots as illustrated in Fig 11.

Fig 12: Corner fuchsia display

I have several tender succulents, so my greenhouse is maintained at minimum 5°C (see Appendix 1). To justify the equipment and cost, I try and use the facility as much as possible to overwinter tender perennials, cuttings, Pelargoniums, and some half hardy Fuchsias. Some of the latter are now up to 4 years old, so are of decent size and give a wonderful display in summer. I use Fuchsias quite a lot for summer displays because I have lots of shade. Fig 12 shows Fuchsia ‘Voodoo’ in a shady north facing position in early August. I trim and defoliate all my fuchsias for winter storage.

Now my greenhouse is fully utilised for a variety of functions, perhaps I am not so fixated about Aeoniums after all.

Appendix

Fig 13: Novatec Thermostat

To maintain the greenhouse temperature at not less than 5°C, I use an electric fan heater. Although it has an anti-frost setting it does not control the temperature well enough. The Novatec thermostat in Fig 13 works incredibly well. The fan is set on the heat setting and is connected to the thermostat unit. It will only come on when the thermostat detects the temperature falling below 6°C. It will control temperature to an accuracy of +/- 1°C so will switch off the heater when appropriate.

In late spring the thermostat can be switched to cooling mode when required. The fan heater element is now switched off, but the fan remains operational. The thermostat is now set to an upper temperature limit which when exceeded automatically starts the fan to cool the greenhouse.

Fig 14: Weather Station

I can also monitor the greenhouse temperature in the house using a weather station (fig 14). I have two remote sensors one in the garden and one inside the greenhouse. I check every morning to see what maximum and minimum temperatures have been recorded.

Perhaps the most important implement however is the greenhouse door which is opened and closed as appropriate to hopefully minimise mildew etc as well as helping to control temperature.

Brian Denison