Growing mistletoe, Viscum album from seed
Like many households in the UK, our Christmas decorations in 1999 included a few traditional sprigs of mistletoe, Viscum album L. (Viscaceae/Loranthaceae).
For once, I decided to try growing something from them, realizing that this is a hit and miss process. My understanding is that there are several strains of mistletoe, some of which, at least, are quite fussy as to the host species they will grow on. I also understand that much of the mistletoe sold in Britain is imported from Normandy, France: Normandy is noted for its excellent cidre, so there must be many apple orchards. There is also British-grown mistletoe on sale, again primarily from apple orchards.
After Christmas, the sprays were left in an unheated greenhouse, and in mid-January I squeezed the seeds from the berries, and rubbed them firmly onto various parts of three separate apple trees. I made no incisions, but made a point of placing the seeds by pruning wounds (healed) and other wounds caused by the cat sharpening its claws!
A second lot of seeds was applied in mid-March, by which time the berries were yellowish and very shrivelled.Checking the seeds regularly, I was encouraged to see that most of the seeds remained firmly attached to the trees. Far more exciting though, was the discovery on 1 April that at least three seeds were germinating. This photograph (left) was taken on 2 April 2000. I will continue to monitor these seeds and intend to update these pages regularly, and to add photographs to record any further progress.
6 April 2000: The single radicle is curled hard against, but not yet penetrating, the bark. The radicles of all the germinating seeds emerge from one of the lobes of the heart-shaped seeds, not the pointed end. 26 April: not much progress with this seed, but the radicle is a little longer.
However, another seed has germinated, on a different apple tree, and this has produced two radicles, which I understand is fairly normal, as each seed contains, or may contain, two embryos ( photo right, taken 30 April).
According to Kerner & Marilaun (1903), the disappearance of the white seed coat coincides with the penetration of the host's tissues by the 'sinker' tissue of the mistletoe. Certainly by 8 June 2000, all the germinated seeds appear to be very firmly anchored to the trees.
24 October 2000: the germinated seedlings remain firmly attached to the apple trees, giving me hope that they may be making some growth beneath the bark. Hopefully there will be more to report next spring, but I infer from Kerner, that there may be no external growth until two years after germination.
8 February 2001:The germinated seeds remain firmly attached. I recently came across an article on mistletoe by Daltry (1875). He states that, while the seeds germinate readily on almost any substrate ("even ... an iron nail"), they may remain attached for a year without penetrating the bark, before drying up and falling off.16 April 2003: After a long time of inactivity, one seedling (that shown in the first photograph, above) is showing signs of growth (right), with a minute green eruption from the apple tree's bark, just below the original point of attachment of the seed. Cutting open the wood where another had been attached revealed vivid green tissues within the white apple wood.
During summer 2003, this plant developed its first leaves (left), as did a seedling I had previously overlooked, on another tree.
Same plant, 8 March 2004 (right). All three surviving plants have been pecked by birds. From the size of the damage, I suspect a blackbird or thrush. However, a fruiting branch that I optimistically hung in the same tree, in the hope that birds would take the berries and sow the seeds, was left well alone.
First flowers !
November 2005: two plants have flower buds - two buds on one plant and just one on another. Although still in tight bud (below), I suspect these are both females. On this plant, the flower has only one pair of bracts (move your mouse over the flower for an enlargement - this may not work in Internet Explorer: sorry, but it is fine in both Firefox and Opera browsers!)
14 March 2006: the petals of both plants are beginning to part at the tips, revealing that one is a male and one a female - how lucky is that?! Encouraged by this, in late March, I sowed berries from last Christmas on a wild crab-apple tree; several of these germinated by mid-April, although subsequently all have disappeared. I suspect that I sowed them on too old wood.
January 2007: there are two strong plants (a male and a female), and a much smaller third one – a late starter from the original sowing.
The habit is quite different at present. The male (left) is distinctly pendulous, although I do not recall having seen this mentioned elsewhere.
Although these two plants are on different trees,
they are only 10m apart, and in similar conditions.
By contrast, the younger growth on the female (right) is much more upright, although one of the older shoots is slightly pendant. This is the seedling shown in the first, third, fourth and fifth photographs above.
Hand pollination between the two larger plants in 2008 resulted in a single berry.
In 2009, I left them to their own devices. I did notice some tiny midge-like flies on the open female flowers (should have photographed them!), but I don't expect any fruits, as the male plant is about 15m away.
What I have noticed this year, though, is that there are adventitious shoots arising close to, but quite distinct from the existing main shoots on both the female and the male plants. One can be seen, just right of centre, in the photograph on the right.
December 2009: To my considerable surprise and satisfaction, the larger female plant has five berries this year, so I presume those tiny flies seen at the flowers found their way from the male plant - I didn't make any attempt to transfer pollen.
The two largest plants, one male and one female (on separate trees) show little or no difference in habit of growth now, both being more or less pendulous. They are both a good size: about 45cm across, although fairly sparsely branched, as shown in these photographs. I expect that, in time, the foliage will thicken up as more shoots arise from the base, or from further adventitious shoots.
Daltry, Thomas, W. (1875). The Mistletoe, in North Staffordshire Naturalists' Field Club: Annual Addresses, Papers, etc. Hanley: NSNFC.
Kerner, A. & F.W. Oliver (1903). The Natural History of Plants. London: The Gresham Publishing Company. Although rather elderly, this is a classic work and often repays study when seeking information on the unusual.