The Sakura Obsession

[The Sakura Obsession] cover

In Japan, “the sakura, or cherry-blossom, culture of the twentieth and twenty-first centuries revolved around the flower’s short life and swift, predictable death. The cherry blossom was ephemeral, like life itself.”

Naoko Abe wrote about this tradition in her native Japanese in a book published in 2016. It was very well received and there was immediate interest in an English translation. She decided instead to do further research, especially on the British roots of her story. In 2019 she published the largely newly-written Sakura Obsession, the source of the quotation above, in English. For this more global audience, she included the history of many societal practices likely unknown outside of Japan.

She also describes the wild species and the many cultivars and selections of Prunus made over the centuries in Japan. By the late 1800s, these had largely been pushed aside from gardens by Prunus x yedoensis ‘Somei-yoshino’ that as a clone, provided the uniformity desired for Japanese ceremonies. This is the cherry tree of the University of Washington Quad and the dominant variety planted at the Washington, D.C. Tidal Basin.

In a parallel storyline, Abe writes the biography of Collingwood ‘Cherry’ Ingram (1880-1981), who rescued many out-of-favor cherry selections by bringing them from Japan to his English garden, later reintroducing them to their home country. It is also the study of the close relationship between two island nations and colonizing powers, Japan and Britain, and how horticulture was a common language.

There is a somber side to this history. As is possible in any culture, the symbolism of the flowers changed, especially for Japanese children, including Abe’s father, in the 1930s. “Rather than focusing on cherry blossom as a symbol of life, the songs, plays and school textbooks now focused more on death.” During World War II, branches of cherry blossoms were used to wave farewell to kamikaze pilots as they took off in their planes, going to their deaths.

On the whole, however, this is a book of hope and international goodwill. I didn’t expect to get hooked by this story but I did, and recommend it for the engaging narrative of intellectual exchange and horticultural history.

Published in the Leaflet for Scholars, February 2021, Volume 8, Issue 2.

Treating peach leaf curl

Have you any advice about how to combat peachtree leaf curl using
natural methods at this stage in the season? I’ve just read about the
use of thyme or oregano oil, but no advice on amount used. I would be
glad of any help!

The information I was able to find about thyme oil as a treatment for
Taphrina came from an application to the U.S. Patents Office, so I cannot
speak for its efficacy.

The U.S. Department of Agriculture’s Agricultural Research Service offers
research on the use of plant essential oils in postharvest disease control, too. My impression is that the efficacy of these plant-based oils is still being studied and evaluated.

I also found information on managing peach leaf curl (Taphrina deformans)[formerly available online] from
the National Sustainable Agriculture Information Service which suggests
using lime sulfur, acceptable by U.S. organic standards, though European
standards may differ. Below is a more substantial excerpt:

The life-cycle diagram above in Figure 2 shows that the infection period
for leaf curl is when new leaves start emerging from buds in the spring.
Spraying after the buds have opened is ineffective, because infection
takes place as the young leaves emerge, and the fungus develops inside
the leaf.

Accordingly, sprays must be applied during the trees’ dormant
period after the leaves have fallen and before the first budswell in the
spring. Many orchardists spray just prior to budswell during the months
of February and March. Orchards with a history of severe peach leaf curl
benefit from a double application: in the autumn at leaf fall and again
in late winter or early spring just before budswell.

Fortunately for the organic grower, lime sulfur is one of the most effective
fungicides for control of peach leaf curl and is allowed in certified organic
production . Bordeaux and copper fungicides are also approved for certified
organic programs and are effective as well, but not as effective as
lime-sulfur.

Pscheidt and Wittig (6), performed trials comparing Kocide, lime-sulfur,
several synthetic fungicides, and Maxi-Crop seaweed for leaf curl
control. Lime-sulfur and one of the synthetics (ziram) were best, roughly
twice as effective as Kocide. Seaweed sprays, despite positive anecdotal
reports, were completely ineffective.

Severe leaf curl infection can cause the tree to shed many of its leaves
and to replace them with a second flush of growth. At this time the tree
will benefit from a light feeding with a quickly-available soluble
fertilizer such as compost tea or fish emulsion to help it recover.

There are various levels of resistance to leaf curl among varieties;
however, because of the relative ease of controlling the disease,
breeding for resistance has not been a priority. Redhaven, Candor,
Clayton, and Frost are some of the cultivars with resistance to leaf
curl, though none is immune. In contrast, Redskin and cultivars derived
from it are susceptible.

____________________

The City of Seattle’s Integrated Pest Management Solutions pages for
landscaping professionals also suggests methods of prevention and
control. Damage may be reduced by sheltering the tree from winter and
early spring wet. If only a few leaves are affected, they may be removed
by hand. Peach leaf curl does not usually kill the tree, though fruit
yield will be reduced. This resource also mentions using copper
fungicides and lime sulfur when the tree is dormant.

Fruit–Diseases and pests, Plant diseases–Control, Prunus

UW cherry tree blossoms

I would like to know when most of the beautiful flowering trees will be in bloom on the University of Washington campus this spring? I would like to bring a tour group to see them.

Typical bloom time for the Yoshino cherry trees (Prunus x yedoensis) in the Quad is mid- to late-March, but timing is weather-dependent. You can check the UW Cherry Cam, which they update each spring: https://www.washington.edu/video/campus-webcams/

This article shows the stages of flower development and provides additional detail about the factors affecting bloom time. Here is another article about research into predicting bloom time.

Excerpt:

“The timing for peak bloom — meaning 70% of buds have emerged — varies each year based on weather conditions that the developing buds are exposed to in January, February and March.

“”‘In order to reach peak bloom, buds need to accumulate a certain number of both cold and warm days, known as ‘growing degree days,’ said Marlee Theil, a UW graduate student in the School of Environmental and Forest Sciences.”

Flowering cherries, Flowering trees, Garden tours, Prunus, University of Washington

Dwarf flowering cherry

I have an area in my garden where I would like to plant a cherry blossom (Prunus). However there are telephone and power wires above so I would like the tree to reach no more than 15 feet in maturity. Are there any dwarf or smaller growing varieties?

Here are two suggestions for smaller flowering cherry trees, from a list in Trees & Shrubs for Pacific Northwest Gardens (2nd ed.) by John A. Grant and Carol L. Grant (Timber Press, 1990):

Prunus serrulata ‘Shogetsu’ reaches 15 feet tall, by 22 feet wide.
Prunus x ‘Hally Jolivette’ reaches about 15 feet.

Here is an article by Wayne Winterrowd in Horticulture Magazine (May 1, 2007) with additional information about this tree, which he refers to as the “loveliest of trees,” and the best of the flowering cherries.

Flowering cherries, Prunus

cherry tree blossoms in February?

Is it possible that I’m seeing cherry trees flowering this early (mid-February)? Some have white flowers, and some are pink.

It is certainly true that things may be flowering early when we have a mild winter. In 2014, the famous cherry blossoms in the University of Washington’s Quad began opening on March 13, and the winter of 2015 was warm, so they may be opening earlier than that. While it is possible you are seeing flowering ornamental cherries (Prunus species), they are easily confused with their cousins in the same genus, flowering ornamental plums–extremely common street trees in Seattle–most of which are definitely flowering now. Ornamental pears (Pyrus) are also flowering now. They have white petals, and might be mistaken for cherry trees as well but the distinctive odor of pear blossoms is a big clue to their true identity: acrid, astringent, and just plain stinky!

The Vancouver Cherry Blossom Festival offers some pointers on how to tell the difference between cherry and plum blossoms. Most cherry blossoms aren’t noticeably fragrant, while plum blossoms are fragrant. Cherry blossoms usually have small splits or indentations at the ends of their petals. Note, however, that the book Japanese Flowering Cherries by Wybe Kuitert (Timber Press, 1999) says cherry “petals are mostly [emphasis mine] retuse,” that is, not all of them have a shallow notch or split on the ends of the petals.

Project BudBurst, a citizen-science phenology project, offers this distinction: apple blossoms have 3 to 5 styles whereas cherries have one. And what is a style? It is the part of the pistil between the stigma and the ovary. Brooklyn Botanic Garden also has a helpful guide to flowering trees that are not cherries.

According to the British Natural History Museum, one unifying characteristic of cherries is “flowers in clusters with stalks all arising from a central point, or arranged along a short stem, or in spikes.”

blueberry bushes lack of blooming and fruiting

We have three blueberry bushes of different varieties that have been bearing just fine over the last several years. This year one of them bloomed heavily and looks like it’s generating a good crop. The other two only had a few flowers. What could account for this? Is there anything we should be doing to encourage blooming and fruiting?

I am also wondering when we will ever see fruit on the Italian Prune tree I planted several years ago. It was already pretty big when we bought it, and now it is about 2 inches caliper near the base and is about 12 feet tall. Is there anything we can do to encourage some fruit on this? I do not even remember seeing it bloom this year. Could it have something to do with the weather patterns?

One problem might be a lack of bees. There could also be other reasons, such as Botrytis blossom blight, and blueberry shock virus.

Here is a page from Oregon State University which has some good general information on growing blueberries .

Is it possible that the blueberries have become dense and twiggy? If they are not pruned, they may become unproductive. The information below is from University of Florida Cooperative Extension:

Pruning mature blueberry plants is largely a matter of cane removal or cane thinning. The objective of pruning mature bushes is to stimulate the proper balance of vegetative and reproductive growth, and limit plant size. Pruning stimulates the development of new canes which are more productive than older canes. A general rule is to remove about 1/4 to 1/5 of the oldest canes each year (usually one to three of the oldest canes). This will result in continuous cane renewal so that no cane is more than three or four years old. Pruning to reduce the number of flower buds may also be required on some southern highbush cultivars which set heavy crops such as ‘Misty’. Flowers should always be removed from one and two-year-old plants by pruning or rubbing them off before fruit set occurs. Most pruning is usually done immediately after harvest during the early summer. Removal of some of the flowers buds to adjust the crop load is usually done during the late winter just before growth begins.

As for the Italian prune, a plum tree may not begin to bear until it is 3 to 6 years old.

You may also want to visit a Master Gardener Clinic with your questions. You can locate a Master Gardener Clinic within King County on this website.

the fruit infesting Spotted Wing Drosophila

Could you tell me more about a new type of fruit fly that is supposedly infesting fruit here in the Pacific Northwest? Which fruit are affected?

The fruit fly is called the Spotted Wing Drosophila. It is known to affect strawberry, raspberry, blueberry, plum, peach, cherry, and grape. Oregon State University has created an information clearinghouse about this pest. Here is their information for home fruit growers. Washington State University has also devoted several web pages to this fly. Here is their Integrated Pest Management information, excerpted below (SWD stands for Spotted Wing Drosophila):
“Monitor for SWD using traps. […] These vinegar traps are for monitoring purposes only and will not provide control of SWD. Remember, chemical control is not necessary if SWD is not present.
Composting fruit will likely not be effective at destroying maggots and pupae.
Remove infested and fallen fruit. Destroy or dispose of infested fruit in a sealed container.
Management recommendations are currently being developed for this pest. For the time being, good sanitation practices should be used.”

Whatcom County Extension has clear, basic information for home gardeners as well. Since this insect is a relatively recent invader in the Northwest, information is constantly being adjusted and research is ongoing.

fungal growth on trees

I have a 50-year-old Italian plum tree. The limbs have oyster-shaped growths on them. These growths will not come off–they are hard. Is it a fungus or disease? Or is the tree just getting old?

Hard fungal growths on trees are called conks, a type of bracket fungus, and they are not a good sign. According to The Sunset Western Garden Problem Solver, these growths “indicate a hazardous condition from decay inside.” Usually by the time they are seen, decay inside the tree is substantial and you may need to get an arborist’s help to keep the tree from breaking and dropping branches, and to assess whether it is a danger to structures or people. The Pacific Northwest Chapter of the International Society of Arboriculture provides a listing of local certified arborists. You can also get an arborist referral from Plant Amnesty.

Peach leaf curl and plum pockets

For three years, my plum tree has had leaves that curl and shrivel somewhat. I have heard of aphids causing leaf
curl in plums, but I don’t see many aphids.

I also have a peach tree that has “Peach Leaf Curl” or Taphrina
deformans and the symptoms on the plum leaves look similar to that.
Here is what I wonder:

The peach and plum are at least 100 yards apart. Is it really possible that the peach infected the plum?

With the peach tree the fruits are also affected but with the plum
fruits do not appear to be affected.

Are peach and plum affected by the same diseases?

Both peach and plum trees are in the genus Prunus. Your plum tree’s problem sounds like plum pockets and peach leaf curl, which are caused
by fungus (usually Taphrina).

From Iowa State University Plant Pathology:

Have you noticed lately that your peach leaves appear curled or puckered?
Do leaves appear to be lighter than normal, flushed with red, blistered,
distorted, and curled? Chances are your tree has peach leaf curl, a
fungal disease caused by Taphrina deformans. Although peach leaf curl is
primarily a disease of peach, nectarines are also affected. Peach leaf
curl is first noticed in spring when young leaves start to emerge. The
entire leaf or a portion of it may appear crinkled and curled with
flushes of red or purple . Later on in the season, the fungus begins to
produce spores and leaves appear silvery or powdery gray. Infected leaves
turn yellow and brown and fall off the tree and are replaced by a new set
of foliage. Flowers, young fruits and stems may also be infected.
Affected fruits are distorted with wrinkled, discolored areas on the
surface. Extensive defoliation may affect fruit yield the following year
and may also predispose the tree to winter injury and other diseases.

Plum pocket is a disease in plums caused by Taphrina communis. Leaf
symptoms are similar with peach leaf curl and the plums appear to be
distorted, wrinkled, and puffy. This disease is not considered a serious
problem in most commercially cultivated plum varieties.

Here is Oregon State University’s online guide to plant diseases (aimed at professional gardeners) This is Washington State University’s site intended for home gardeners.

I don’t know if your plum could have gotten the same species of Taphrina fungus
that is affecting your peach (i.e., Taphrina deformans), but the conditions in our climate are probably ideal for this type of fungal disease.
University of California, Davis says that the pathogen which causes peach
leaf curl survives on tree surfaces and buds, and is enhanced by wet
spring weather.

From University of Nebraska Plant Pathology:

Plum Pockets is very similar to the well-known disease peach leaf curl.
It reached epidemic proportions on plum in the 1880’s and sand cherry in
the 1940’s. The disease is still common today but rarely has an economic
impact on stone fruit production. However, its unique symptoms always
seem to peak the interest of individuals who are seeing it for the first
time. The disease is caused by two species of Taphrina. Taphrina communis
(Sadelbeck) Giesenh. has a worldwide distribution. Its hosts include plum
(Prunus angustifolia) and several wild Prunus spp. found in America.
Taphrina pruni primarily infects European plums and is rarely found in
America. The disease cycle of Taphrina communis is similar to that of
Taphrina deformans (peach leaf curl). The fungus overwinters as conidia
on twigs and bud scales. Infection generally begins at bud break when
these spores are rain splashed to susceptible green tissue. Leaves,
shoots, and fruit are all susceptible but symptom development is most
common on fruit. The fungus invades host tissue directly through
epidermal cells. Once the fungus is established, a specialized mat of
fungal cells (hymeneal layer) containing asci and ascospores forms. The
asci are not protected by a specialized ascocarp. Ascospores are
released, germinate and begin budding, much as a yeast does. Conidia (bud
conidia) serve as secondary inoculum in the spread of the disease.
Initiation of the disease cycle is favored by cool wet weather.

You might consider bringing in samples of the affected leaves to a Master
Gardener Clinic for a definitive diagnosis. They may also have more information on whether the disease can pass from peach to plum, or whether your two types of trees simply have two different strains of the pathogen.

Chipped laurel as mulch

I have a laurel hedge that I am taking down. Can I use the chips as
mulch or will the mulch kill things as I’ve heard that laurel is
poisonous?

Is your laurel an English laurel? If so, it is the plant Prunus laurocerasus which does have toxic properties (cyanogenic glycoside and amygdalin, according to the information here from North Carolina State University Extension) but I think that the toxicity mainly affects people and other creatures if they eat its leaves, twigs or seeds. My guess is that the wood chips should be safe to use, but what you could do is use the mulch on a path or other area where you do not want plants to grow and it will not touch anything you will eat.

University of Georgia School of Forest Resources has a list of potentially allelopathic tree species and Prunus laurocerasus is not among them.