One of the first things to research when entering the world of Bonsai is which trees are best suited for your area. Not all bonsai will thrive, or even survive in every part of the United States. As the health of your tree is the #1 concern, it's important to be familiar with the plant hardiness zones, the special needs of bonsai trees in pots, and what is and isn't possible.
The story has played out many a time; a young beginning bonsai student is eager to find a particular variety of tree; say a Yoshino Cherry, or shishigashira maple. They visit local bonsai nurseries and find none. They ask around, and are told "those really don't do well here." Determined, they go online and find one, buy it, ship it, and proudly add it to their growing collection.
A few months later, the tree has died.
It's often hard to accept that every bonsai practitioner cannot own every type of tree.
All trees--indeed all plants--have been categorized in three classifications depending upon origin and growth habits:
Temperate Zone: Require a significant dormancy period. Think of deciduous trees that drop their leaves, or conifers that drop brown needles. These trees set buds for the spring. Pines, elms, maples.
Subtropical Zone: Have a shorter dormancy, and cease to grow around January to February. They don't have a winter silhouette (drop leaves) and can be damaged by extreme cold.
Tropical Zone Trees: Grow year round. These trees come from the tropics, and have very little temperature variation between summer and winter. These trees will begin to die if exposed to winter temperatures.
Horticulturalists have mapped out the world into hardiness zones defined by temperature and identified by number. The lower the number, the colder the zone will get. Every plant and tree has a correlating zone or zones, allowing gardeners, agriculturalists and plant keepers to easily see where their plants can survive and thrive. Some plants can survive in several zones; many conifers have a wide range. Some plants are restricted to a single zone. Here is the USDA's Plant Hardiness Zone map, updated in 2023. If you follow the link, you can enter your zip code and find your zone.
-Source: U.S. Dept. of Agriculture https://planthardiness.ars.usda.gov/
Additionally, which particular zone an individual tree was grown or propagated plays a role; a tree from a Florida nursery may require a bit of adaptation when it arrives in Maine.
Furthermore, some trees will require winter and summer protection due to the fact that all bonsai are kept in pots, and the difference between what happens to roots in a pot and roots in the ground is vast. Less soil around the roots, surrounded by a clay pot means that extreme temperatures can quickly freeze or cook the root ball. Therefore, more advanced keepers adapt their collection to extreme temperatures; putting up shade cloth in summer and, in some parts of the nation, bringing trees into an unheated garage, greenhouse, or under plastic covered benches in the winter.
Here is a list of minimum temperatures tolerated by popular species of bonsai, from Bonsai Journal -Fall 1981. Comparing them to the USDA Hardiness zone map, it's a little easier to choose the right trees for your climate, and to weed out the ones that will struggle or die:
Bonsai is a fun, rewarding hobby! Remember to always put your trees's health as a priority, and ensure they have the best conditions possible to thrive!
For hands-on learning, don't forget to check out our workshops and events!
-information from this blog came from the USDA website, Bonsai Journal, the Prairie State Bonsai Society , and Bonsai Tonight.
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