As I travel around teaching workshops, I often receive questions about how to care for kusamono during the winter months. The care of these plants can be challenging as species have different requirements for temperature, light, and water. In addition, unlike trees planted in the ground, bonsai trees and other plants are in containers so their roots are not as well insulated.

Most species of plants used for kusamono require a cold period. As daylight hours shorten and temperatures drop in the fall season, the plants need their immature growth to harden off. By the time frosts first arrive, it’s time to bring them in. Their growth will stop for 4-5months.

The following tips can help your kusamono plants survive the long winter months.

1. Separate kusamono into two groups. The first group will consist of tropical and subtropical species. The second group are plants that require exposure to cold temperatures. The second group should be separated further; large containers and small containers. Small pots and moss balls require more monitoring of moisture levels.

2. Place the tropical and subtropical plants indoors or in a heated greenhouse. For all other kusamono place them in an unheated greenhouse, shed, or garage. The location should not be too hot (> 50 F) or too cold (< 40 F). Any higher temperature could allow the plant to come out of its winter dormancy.

3. Check containers about once a week for to water. For plants inside the unheated area, the roots should be kept more dry than wet. The plants will not need much water during dormancy. My method is to touch the soil surface and if dry, then spot water the plant.

4. When spring arrives and temperatures rise, you may wish to remove your plants from their winter home. However, beware of late frosts. Plants should be protected when forecasts call for frost by covering with cloth or plastic. A blanket works well for this.

Preparing Tray

Your plants can be stored for easier moving by placing several in a tray. Below, I show how to prepare a tray for your plants.

Use a tray with holes in the bottom for drainage.

Line the bottom of the try with the screen.

Place the crushed granite over the screen.

This is an example of the granite that I use.

This type of the crushed stone keeps the container moist.

Here is an example of kusamono in an unheated greenhouse.

Larger containers are arranged and stored in between bonsai.