Arbutus unedo, the strawberry tree, is an evergreen shrub that gained popularity in the bonsai world due to its beautiful fruits. It got the Latin name from the term ”unem edo,” which means “I eat only one.” The popular name of this shrub is Cain-apple, Killarney strawberry tree, and Cane-apple. It got the name cane apple from the Irish name for the tree, caithne. Hence, this tree is also known as the ‘’Irish Strawberry tree’’. Due to the dark red- and yellow-colored fruits, there is a legend associated with this fruit. The berries are considered as the clots of Abel’s blood.
The fruits look like strawberries (Latin name- Fragaria X ananassa- the ones used in making ice-creams and eaten with cream), however, these fruits are extremely sour. This tree belongs to the plant family Ericaceae and grows up to fifteen feet in height. The growth rate of this tree is extremely slow. Some trees grow up to twenty-five feet in height, however, are found rarely.
The bark is reddish-brown and looks flaky. The flowers look like inverted ivory pots and the gardeners love this tree for its beautiful flowers. The flowers are pollinated by bees and they are hermaphrodites. The red-stemmed leaves are dark green and have a leathery texture.
Origin and Availability
It is presumed that this tree was brought by the Romans from the Mediterranean to England. Arbutus Marina, a close cousin of Arbutus Unedo is also known as a strawberry tree. It can grow up to fifty feet and is a hybrid tree that was first discovered in 1917 in Marina, San Francisco.
Arbutus Unedo is native to the Mediterranean region and western Europe. Various varieties of the strawberry tree are found in South-Eastern France, Portugal, Bulgaria, Italy, Croatia, Greece, Slovenia, Albania, Turkey, Lebanon, and Ireland. Apart from Europe, this tree is found in middle east regions too- Libya, Algeria, Morocco, and Tunisia. The widespread of this tree talks about its hardiness and its capability to withstand various types of climatic conditions. Hence this plant is easy to cultivate.
Since strawberry trees are fairly drought resistant, they grow well in regions that have lesser rainfall. They are frost-resistant and grow well in colder climates that receive snowfall. Since they are shade tolerant, they grow in regions that receive lesser sunlight. And due to their salt tolerance, they grow in soils closer to seacoasts.
Arbutus unedo belongs to the kingdom of Plantae, and the genus of Arbutus. In 1753 AD, Carl Linnaeus, the famous botanist, and zoologist wrote about Arbutus unedo in his famous book Species Plantarum.
Scottish Botanist William Aiton discovered the red-flowered variant, named Arbutus Unedo Rubra in 1785. It was growing wild in Ireland.
How Long Does It Take to Grow Arbutus Unedo (Strawberry tree) Bonsai Tree?
Arbutus Unedo has a slow growth factor, and even the normal tree grows between twelve to twenty-four inches per year. So, it takes any time between ten to fifteen years for a full-grown tree to mature up and reach a height of about fifteen feet. Since the growth of bonsai is slower as it is a potted plant, you will have to wait for a minimum of fifteen years to see the complete growth. However, strawberry plants do take about a year to start bearing fruits. Hence you can enjoy the beauty of the potted plant in your garden or home.
The tree is capable of carrying both mature fruit and flowers at the same time. This aspect of Arbutus Unedo makes it extremely popular with horticulturalists.
Arbutus Marina being a hybrid grows faster, just about twelve inches in a year. The young trees have faster growth and almost after ten years, the growth rate reduces. Since this variety can grow up to fifty feet tall, you will observe some growth even after thirty or forty years of growing the tree. However, the bonsai of Arbutus Marina grows a little faster than the bonsai of Arbutus Unedo.
Position and Lighting
It is advisable to grow Arbutus Unedo in USDA plant hardiness zones seven through ten. For you to understand easily, grow the bonsai in a sunny area. Since it does not need much water, it can be grown in a region which receives less rainfall.
There are multiple close cousins of Arbutus Unedo like madrone (Latin name Arbutus menziesii), common heather (Latin name Calluna vulgaris), blueberries (Latin name Vaccinium spp.), bearberries (Latin name Arctostaphylos uva-ursi) rhododendrons and azaleas. All of them have slower growth compared to many other types of trees. However, plant lovers prefer Arbutus Unedo and Arbutus Marina the most for creating bonsai plants.
The tree is hardy in zones eight B through eleven, which means it can grow in regions between −6.7 °C and 10 °C. The Arbutus Unedo bonsai should not be exposed to temperatures below freezing however, since they are frost-proof, they can bear colder temperatures. This quality is unique to the bonsais of this genus and unlike many other bonsai which will die if placed in places with temperatures below 0 degrees centigrade.
Arbutus Unedo and more than that Arbutus Marina is a very popular ornamental plant in California. Even in other parts of the west coast of North America, these trees are very popular cultivars.
Strawberry trees also grow well in the cool and wet summers of many European counties as you read earlier. They also grow well in temperate regions of Europe and Asia.
Arbutus unedo grows well in soils that are basic (limy) in nature. They grow better in acidic soils. While preparing the soil for strawberry trees, check if it is acidic in nature. Your bonsai will grow well in such soils.
Bonsai soil requirement is the most crucial part of bonsai cultivation. The soil should be capable of providing excellent drainage and should allow good nutrient binding. The soils should be able to help to split the roots without impacting the health of the plant. The moisture content of the soil should be ample, but the soil should not be watery. There should be a good amount of air circulation in the soil.
There are premixed soil components available in the nurseries if you are not familiar with the process of making your own soil mix.
While preparing the soil, ensure that you plant a fine mesh along the bottom of your pot. This will stop the nutrients from the soil from washing out of the pot easily.
Being tolerant to drought-prone regions, these trees do not need much water. Light to moderate is the water requirement and you need not water the plant daily. If you live in tropical or hot areas, increase the frequency of watering during the summer months. It will be ideal if you do not let the soil grow dry. However, if you miss watering the bonsai once in a while, it still will live.
During the months when the tree is flowering, you need to feed it properly. So, during the early spring months from February till mid-autumn in October, feed the tree once a month. During mid-summer, you can give a break for a month and not fertilize the tree. Water-soluble Miracid is the ideal plant food for the strawberry tree. Since it is acid-loving plant food, it will mix well in the acidic soil and give the right nutrients to the tree.
How to Plant and Grow Arbutus Unedo (Strawberry tree) Bonsai Tree?
Propagation can be done by germinating seeds, or by grafting a strong branch. Layering or cutting is the most commonly used method for propagation for reducing the lead time for plant growth. So healthy plants are used for grafting the branch and using it for growing new trees. It also ensures the quality of the new plant.
If you are planning to use the seed for growing a new tree, then ensure that the seed has undergone a one-month cold stratification period. If you are not aware, then stratification is a period that breaks the dormancy of the seed.
Then the seeds need to be soaked for five to six days in warm water. This will improve germination success. Once the seedlings germinate, for the first year you need to be careful. They are prone to damp and pests attack them a lot in the first year. The germination rate for Arbutus Unedo seeds is low, around twenty percent.
Air layering can take up to two years. It is a method of propagating new trees from stems that are wrapped with damp moss. The stem will be still attached to the parent plant, and later it will be cut and planted in the pot. It has a good success rate, and most bonsai enthusiasts prefer this method of propagation for strawberry trees.
Cutting is done with a fifteen-centimeter-long mature wood, however since the success rate is not very high, it is not a preferred method for propagating bonsais.
Pruning and Wiring
After two pairs of leaves have appeared, you need to start with wiring first. Visualize, watch videos, discuss with other bonsai lovers, and create your own intricate designs. Before the blooms break (spring season commences), wire your plant. Use a soft copper, iron, or stainless wire to direct the branches in the route you want them to grow in. The branches of Arbutus Unedo are flexible which will make the task of wiring easy for you.
Prune new shoots of the strawberry shrub back to two leaves between the spring and autumn season.
Repot once in every two to three years in early spring. Change the soil and ensure that the soil has seventy to eighty percent organic matter. It can have the rest as an inorganic matter like sand and grit. Also, the soil should be fast draining in nature.
How to Care for Your Arbutus Unedo (Strawberry tree) Bonsai?
Saving from Pests and Diseases
Arbutus Unedo can be affected by several common diseases and pests. Annosus root disease (Latin name- Heterobasidion Annosum / Fomes Annosus), Leaf galls (Latin name- Exobasidium vaccinii) are the common diseases that attack Arbutus Unedo easily.
Anthracnose, Arbutus leaf spots (Latin name- Septoria unedonis / Elsinoë mattirolianum), Phytophthora, Twig dieback are some other diseases that attack especially in the initial years after planting the bonsai.
Sudden oak death is a plant disease caused by a fungus-like plant pathogen. It impacts many types of plants including the strawberry tree and it is caused by a pathogen named Phytophthora ramorum.
Safeguard your bonsai from pests like Aphids (Latin name- Aphidoidea Superfamily), Flatheaded borers, Leafminers, Scales, Thrips, and Western tent caterpillar (Latin name -Malacosoma californicum).
So, take good care of your bonsai and enjoy the journey of its growth and vitality.