Last fall I wrote a post outlining my plans for two serissas (Serissa foetida) for the winter that's just ended. Briefly, both trees would be exposed to subfreezing temperatures, but not equally: one would be protected below 28° F (roughly -2° C,) the other below 24° F (-4-1/2° C.) Both are species trees, not members of a named cultivar. (To see that earlier post, click here.)
Overnite low temperatures in the mudroom stay quite consistently about 10° F warmer than the outside, and that's what I go by. However, there is a bit of variation from the expected, from time to time. Consequently, the second tree passed one nite when the temperature got down to 23° F (-5° C,) one degree lower than planned.
Winter is over. Both trees survived, and are happily pushing their spring growth. But there are visible differences between them.
Both these pictures were taken yesterday, March 22nd. You can see that foliage started coming in earlier on the tree that took less cold, than on the other. In addition, while the first tree lost no foliage, the second did lose a little, far from the roots (arrows.) Two thin twigs -- pencil-lead thickness -- may have died as well; it's too early to be sure yet.
(I know you're wondering. I assign ID numbers to my bonsai and bonsai-to-be for record-keeping purposes.)
Results so far: somewhere between 28° F and 23° F is the temperature at which serissa foliage starts to suffer injury. Next winter I will attempt to refine that observation. Eventually I want to determine just how cold serissas can get before they start to suffer cosmetic damage.
I also plan to experiment with a couple of other (expendable) trees, to find out just how cold serissas can get and still survive, period. Knowledge of both limits will be useful to temperate-zone bonsai growers, obviously.
Meanwhile, expect pictures of these tree's flowers in the near future. Isn't bonsai fun? :-)
Overnite low temperatures in the mudroom stay quite consistently about 10° F warmer than the outside, and that's what I go by. However, there is a bit of variation from the expected, from time to time. Consequently, the second tree passed one nite when the temperature got down to 23° F (-5° C,) one degree lower than planned.
Winter is over. Both trees survived, and are happily pushing their spring growth. But there are visible differences between them.
 | |||
| B135. Protected below 28° F. |
(I know you're wondering. I assign ID numbers to my bonsai and bonsai-to-be for record-keeping purposes.)
 |
| B134. Lowest temperature last winter, 23° F. |
I also plan to experiment with a couple of other (expendable) trees, to find out just how cold serissas can get and still survive, period. Knowledge of both limits will be useful to temperate-zone bonsai growers, obviously.
Meanwhile, expect pictures of these tree's flowers in the near future. Isn't bonsai fun? :-)
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