Caring for Outdoor Bonsai

Nancy Helms, Extension Master Gardener in Anoka County

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This Christmas I received the gift of a bonsai tree, a rather daunting gift as I had no idea how to care for it. My only experience with bonsai was from watching the movie The Karate Kid where Mr. Miyagi uses caring for bonsai to teach life lessons to the Kid. When you're a gardener others believe you to have a natural green thumb: "She can grow anything." Rather than prove them wrong, I decided I needed to learn how to care for my new charge.

The word bonsai, literally translated, means 'a tree planted in a shallow container'. The art of bonsai originated in China and was later refined in Japan. There are indoor bonsai and outdoor bonsai. My tree is an outdoor tree so I will be challenged to keep it alive until spring when I can find a sunny south location for it. It is recommended to move the tree outside in the spring when night time temperatures remain above 40 degrees. Likewise, it will need to be brought inside in the fall when night time temperatures fall below 40 degrees. While outdoor bonsai need some protection from Minnesota elements, they are trees and their natural element is in the open.

I was surprised to learn how much care these little trees need.  Watering is by far the most important task. Because they are planted in small containers, they require frequent watering.  Water when the soil gets slightly dry; the soil should never be allowed to completely dry out. Keep watering until water runs out of the drainage holes as the roots need to be thoroughly soaked. In full sun, they may require daily watering. I can already see that I will be looking for a tree sitter for my new bonsai whenever I travel.

During the growing season these miniature trees require fertilizing even more than other container grown plants, due to the limited amount of soil they grow in. Solid or liquid fertilizers high in nitrogen and applied at half strength are fine as long as they are the correct amount for the size of the container.

Pruning and pinching new shoots during the growing season is essential to keeping the plant small size. Be certain to always leave some new growth to sustain the health of the tree. Some trees require wrapping the branches with wire to achieve an artistic form. Before attempting wiring it should be thoroughly understood and researched. Many factors come into play including the size and type of wire used and the best time of year for different varieties.

Bonsai need to be repotted when the roots circle around the root system. Lift your tree out of the pot and check the roots to see if they are still contained in soil; if they are, wait another year before checking again.

Bonsai gardening is recognized as an international art form. It is said to emote a sense of calm inner peace. Who couldn't use some inner peace as winter drags on?

Anoka Master Gardeners welcome you to visit our website: for information on many gardening topics, including: Home Landscape and Garden Fair, April 8; Plant Sale, May 16-17; Diagnostic Clinics, starting May 17; Landscape for Life classes, May 17-June 21; Walks in the Garden, starting June 14.