Perhaps the most widely planted of flowering cherry trees in Japan today is the Yoshino cherry, Prunus x yedoensis. Despite its popularity within Japan, and indeed around the world, this Japanese cherry blossom has a history that is relatively brief, and yet the specifics of its origins remain mysterious. Regardless, it is considered one of the most spectacular of flowering temperate trees in cultivation today largely due to its habit of simultaneously opening thosands of showy pink-white blossoms on bare branches – a sight to behold in person.
The Yoshino cherry is a fast growing tree in the first 20 years of its life, then slows down a bit, ultimately reaching heights of 12 meters or a bit more (~40-45 feet), and nearly as much wide. The uniform crown has a spreading, rounded, inverted vase shape with fine branching. Young trees tend to grow upwards, but around 30-40 year old trees begin to spread, with older trees developing attractive hanging branches. The dark reddish-brown bark is marked by prominent lenticels (lens shaped pores in the bark that allow gas exchange). Trees are typically single trunked.
The simple, broad leaves are borne alternately, are serrated, elliptic to ovate, and up to 15 centimeters long (6 inches). They flush directly after flowering has finished, remaining green until the fall when they turn yellow to orange or orange/red. Flower buds develop during the summer months, remaining dormant until warm days in late March or April trigger them to swell.
Without a doubt this tree’s greatest feature are its lovely pale pink to white blossoms which are borne in generous clusters all along its bare branches. Occasionally they can occur here and there along the main branches as well. Each flower is from 3-3.5 centimeters in diameter, sporting 5 broad petals, first opening pale pink and fading to near white as they mature. These occur in clusters of 5-6, and flower nearly simultaneously on any given tree. The round fruits (known as drupes) quickly ripen, starting out green, then turning red, and finally mature black. They are small (around a centimeter wide), mildly sweet, and not very tasty due to their high acidity (I know, I’ve tried them). Fruit formation is usually fairly modest in this tree.
Being of hybrid origin, Prunus x yedoensis is not found in nature – at least not these days. A little back story first: when botanists started to look at Japanese cherry varieties in a systematic scientific manner, they immediately found themselves in a complex quagmire. Trees that were thought to be species seemed to be possible hybrids, accepted species had different forms (for example upright and weeping), and differences between trees could be very subtle. Add to this mix the fact that Japanese horticulturalists had been selecting and hybridizing cherries for centuries long before the concept of a species (in the western tradition) was even recognized, and you’ve got a mess on your hands. And out of this situation arose the question – what is the Yoshino cherry actually? A species? A natural hybrid? An artificially produced plant?
We know one thing – the Yoshino cherry was known to be cultivated in Edo (the name for Tokyo during the Edo Period) in an area known as Somei around the middle of the 1800s. Beyond that, things get quite a bit fuzzier. The Somei growers called them yoshinozakura (meaning Yoshino cherry), after a famous cherry covered mountain in Nara Prefecture. This designation was in honor of the mountain only, not implying the origin of the Yoshino cherry. During the 1880s Dr. K. Fujino undertook a study of the cherry trees planted at Tokyo’s famous Ueno Park. He determined that the park contained three distinct species, one of which he called somei-yoshino – a name that has stuck to this very day in Japan. He published his report in 1900 and the following year Dr. J. Matsumura gave the tree its Latin name, Prunus yedoenis. Despite these facts nothing definitive about this tree’s origin was yet known.
In the meantime, trees of somei-yoshino found their way into both Europe and America. In 1910 largely due to efforts by private individuals from both Japan and the USA, 2000 cherry trees were donated by the city of Tokyo to be planted in Washington, D.C. Disappointingly, the trees arrived riddled with disease such that the U.S. Department of Agriculture determined they would have to be all destroyed, an order that the president, William Taft, reluctantly agreed to. In 1912 a second group of over 3000 trees was generously given, and so began the famous spectacle of cherry viewing along the Potomac River in Washington, D.C. In this group of cherries, both somei-yoshino and kanzanzakura (P. ‘Kanzan’ or P. ‘Sekiyama’) figured prominently.
To see this lovely tree flowering in Japan, watch this video:
In 1916 the famous English botanist Ernest Henry Wilson postulated that somei-yoshino was in fact a hybrid between two well known wild Japanese cherries – edohigan (P. spachiana f. ascendens) and ooshimazakura (P. speciosa). The question remained whether somei-yoshino was the result of natural hybridization or human manipulation. Then in 1933, another Japanese scientist asserted that somei-yoshino was in fact a natural hybrid found on the Korean island of Jeju (then called Quelpart) – an idea that was disproved by later research. Enter another Japanese researcher in the 1950s, Dr. Y. Takenaka. He strongly believed that somei-yoshino was a natural hybrid of the above mentioned species, probably originally from either (or both) the Izu or Bozo Penisulas, located midway up Honshu’s eastern coast. He undertook exhaustive hybridization experiments of various varieties (some which are still grown today in Japan), and combined with field observations, came the conclusion somei-yoshino was a natural hybrid from the Izu Penisula. To see a nice synopsis of his findings in English, check out this article taken from the Journal of Heredity (1963).
OK, I’ll cut to the chase. Japanese researchers (Innan, et. al, 1995), using DNA fingerprinting, determined that in all likelihood P. x yedoensis is indeed the result of crossing P. speciosa (syn. P. lannesiana) and P. spachiana f. ascendens (syn. P. pendula f. ascendens). They furthermore concluded that it was the result of just one hybridization, and that all plants produced subsequently were propagated through vegetative means, not by seed. So in the end, it seems likely that the tree we call P. x yedoensis was produced artificially by plants men in the Kanto area of Japan sometime in the 18th or 19th centuries. The exact details of this remain a mystery, at least until written documentation is ever found from that period.
To see the Yoshino cherry in its homeland, along with a wide variety of other commonly planted cherries in Japan, check out this video:
Prunus x yedoensis is a tree that has been planted on every main island of Japan, from southern Kyushu up to the warmer areas of Hokkaido. It is not found on any of the southern islands since winters are not cold enough there to properly vernalize the flower buds. The mass planting of this beloved tree began in earnest after WWII, and nowadays it is nearly impossible not to see them in flower just about anywhere during the cherry blossom viewing season (o-hanami). While Japanese people today consider somei-yoshino a national symbol with deep cultural meaning, we can see from the above history that idea doesn’t quite hold water. Certainly cherry trees, in particular P. jamasakura (wild mountain cherry) and P. spachiana (edohigan), have played an important roll in traditional Japanese culture, and can be found in art and poetry spanning the centuries, but the Yoshino cherry is not to be counted among these. Its popularity seems to be largely due to its fast growth rate and incredible flowering habit – something no other cherry can aspire.
Much has been said about this tree’s relatively short life span, especially in comparison with trees like P. spachiana which are known to live three centuries or more. Within Japan the common wisdom is that a tree typically looks good for around 60 years, and then goes into decline. This idea is somewhat supported by watching trees in the parks, riversides, and streets throughout the country. Many look pretty bad, however recent studies have demonstrated that trees in decline can be made vigorous again through pruning and care. Since most Yoshino cherries are planted in heavily trafficked public spaces, they are subjected to a fair amount of unintended abuse through damage to the sensitive bark, and compaction of the soil.
Confirmed specimens date back to over a hundred years, however, in all likelihood trees do their best within the first 80 or so years of life. The original trees brought in to Washington are all but a memory these days, supporting this idea. Having said that, assuming they are given proper cultural conditions, you can expect any given tree to live, flower, and grow nicely for at least 50 years. Of course disease problems left not managed can lead to reduced vigor and lifespan.
In researching this article I came across in the western literature various forms of this tree repeatedly, in particular the form ‘Akebono’. I found this curious since P. x yedoensis is assumed to be the result of a single hybridization, so how could forms of it result? This lead to a broader search that unearthed an astounding variety of supposed forms, most of which seem to be the result of hybridizing Yoshino cherry with other similar trees. Here’s a run-down of some of the more common forms.
‘Somei-Yoshino’ – these are the original type with the mysterious origin. They are available outside of Japan, but seem to have lost favor to some of the other varieties, at least in America. In fact though, they are the true Yoshino cherry.
‘Akebono’ (“Daybreak”) – this form has pinker flowers than the original type, and the petals are more frilled. In Japan it is called amerika (“America”) since indeed this is an American plant, an out-crossing made by W. B. Clarke of San Jose, California during the 1930s. He considered it an improvement over the original tree, at least in part to its pink flowers. It is funny that if people in the US were asked what color Japanese cherry blossoms are, most would probably respond “pink” – perhaps an artifact of this form becoming popular in the states. It is one of the most commonly sold Yoshino types in the USA today, and can be seen growing at the Tidal Basin in Washington, D.C. Another form, ‘Afterglow’ is a seedling tree of this cultivar.
‘Shidare Yoshino’ (“Weeping Yoshino”) – this a strongly weeping form, apparently of Japanese origin, dating back to the late 1800s. It is thought to be the result of hybridizing P. speciosa with the weeping form of P. spachiana, f. pendula (syn. P. subhirtella v. pendula and P. pendula), though I could find no record of its exact origin. It is also sometimes referred to as P. x yedoensis f. perpendens. The tree is characterized by its strong weeping habit, shorter stature, and brilliant white flowers. It appears to have entered the US sometime early in the 1900s, perhaps through one of the several donations of cherries by Japanese authorities to the the US. Several other selections were made from the US national collection including ‘Washi-no-o’, ‘Yoshino Pink’, and ‘Shell Pink’ – all strictly America in origin. This form can be easily bought in Japan, Europe, or America today.
‘Ivensii’ – another white flowered weeping form developed by Hillier Nurseries in Hampshire, England and introduced into the USA in 1937 by the Arnold Arboretum. It is relatively small, typically not more than 5 meters tall (16 feet), and has weeping branches with a broad spreading habit, creating an umbrella-like crown. No doubt this is another out-crossing of the original P. x yedoensis, but certainly a lovely one. Flower color is white. Though not as well known as ‘Shidare Yoshino’, this tree is available from a number of nurseries world-wide.
Within Japan there are a staggering array of cherry varieties that fall under the name P. x yedoensis including ‘Candida’ (a supposed natural hybrid crossed back onto P. speciosa), ‘Kichijouji’ (another P. speciosa outcross from Oshima Island), ‘Morioka-Pendula’ (another weeping tree), ‘Sotorihime’ (a selection from Dr. Takenaka’s hybrids), ‘Amagi-Yoshino’ (yet another Takenaka creation developed to determine the origin of P. x yedoensis), ‘Mikado-Yoshino’ (a remake of the original hybrid also from Takenaka’s work), and on and on! All are the result of either crossing the original Yoshino cherry back to the parent trees, or to other cherry forms. More recently an early flowering deep pink hybrid known as youkouzakura has become popular in Japan. It is the result of crossing P. ‘Amagi-Yoshino’ with P. campanulata, the Taiwan cherry. The rich colored flowers have given it the nickname beni-yoshino, which means “red Yoshino”. It flowers about a week ahead of the Yoshino cherry.
This is a fairly straight-forward tree in cultivation, demanding little more than even moisture throughout the year, and plenty of sunshine. It is said to do well in clay, sand, or loam based soils provided they are well drained and on the acidic side. It is listed as cold hardy from USDA zones 5b though 8a, though it grows and flowers well in Japan in equivalent zone 9 conditions. The rub is that winters in southern Japan are consistently cool, below 8 C on average, giving the flower buds adequate chilling for them to flower correctly. In cool summer climates with relatively cold winters this tree can be grown even to zone 10 (for example coastal Ireland), and in hot summer climates it can withstand winters that average around 10 C or so, but not warmer (such as southern Georgia and northern Louisiana). Most likely it is best suited to USDA zone 7 in the eastern USA.
Given its relatively contained stature, and lovely inverted vase shape, it makes a great lawn specimen. In Japan it is planted along rivers, in parks, and on both sides of relatively narrow streets, creating a “cherry tunnel” with interlocking branches overhead. It does fairly well under urban conditions, but suffers from too much compaction of soils (for example near walking paths and parking lots). Like many Prunus, it responds well to pruning and can even be made into large bonsai.
Its drawbacks are the many pests and diseases it is susceptible to, and its reputation for being short lived. In my opinion, the latter issue is overblown unless you are planning to live more than another 60 years yourself! Common pests include sooty molds due to aphid infestations, various scales (easily controlled with horticultural oil), spider mite damage of the leaves, and caterpillar infestations defoliating trees, especially in late summer. I’ve watched defoliated trees for a number of years and they don’t seem to miss a beat as long as leaf loss is late in the growing season.
Diseases seem to focus particularly on the twigs and branches – cankers and galls caused by bacteria or viruses. Diseased wood should be removed and the tree fertilized to promote growth. Various bacterial and fungal rots and mildews can afflict the leaves, but again these tend to not do serious damage to trees long-term. A condition seen in some trees is witches broom, an atypical dense mass of growth shoots, resulting in a structure like a broom or bird’s nest. Causes for these are wide ranging from fungal and bacteria infections, insect damage, viruses, nematodes, mechanical damage, or even invading parasitic plants like mistletoe. Trees can be treated by the removal of the brooms once they are detected, and again by applying fertilizer. A general rule of thumb is that weak trees are susceptible to both diseases and pests, so protect your trees by keeping good cultural practices such as proper fertilization and maintaining good soil quality, and by avoiding mechanical damage to the tree and its roots.
The Yoshino cherry is a tree with both positive and negative aspects – it is somewhat prone to diseases and pests, and is relatively short lived. On the other hand it has a lovely form, is fast growing as a young tree, is fairly compact growing, has mounds of gorgeous flowers in early spring or late winter, and can withstand a wide range temperatures. On balance, I’d say this tree is a winner for temperate gardens around the world.