Summer dormancy?

Three years ago I moved from the pleasant climate of Eugene, Oregon, Sunset Zone 6, to Sweet Home, Oregon, Zone 1. My Siberian Larch has given me fits. Three straight days of 100 degrees F. in the summer and it looks dead. Regardless of water. Dead. All three years it starts to grow again in the Fall, in fact it looks healthier than ever! I presume this is a survival thing in Siberia? Has anyone experienced this in their bonsai? It's pretty scary!
Herb.

Hey Herb,

Alot of my trees go into a 'dormancy' ie stop growing over summer, some loosing the majority of there leaves, only to put on a fresh flush come autumn. This is mainly with the cooler climate deciduous species that are so hard to keep looking green & healthy over our summers no matter what your watering & microclimate.

Many of our natives are also dormant at this time of year and some like the brachychiton's are usually leafless for some of the season too. It is a natural suvival mechanism of our natives so I see no reason why it wouldnt also apply to the siberian elm which would have to endure some pretty extreme temperature variations in its natural environ.

Matt

Hello Herb,
I was looking at a Plant Zone map of Oregon and they list the coldest zone in Oregon as a "4", the warmest was an 8 or 9. You shared that you moved from zone 6 to zone 1, within Oregon? Were you joking or serious? Would you explain?
Thank you for your help.
Todd

I believe Herb was referring to Sunset zones--a different system from the USDA zones. Sunset zone 1 (coldest temperatures in the West) probably corresponds to USDA zone 3 or 4.
Oliver

Thank you for explaining that! I need to read about Sunset Zones!
Todd

The Sunset zones take into account summer temperatures, growing season length, humidity, etc., not just winter low temperatures.

However, using 97386 as the zip code for Sweet Home, Oregon, I get a USDA zone of 7b (zone 8 from the Arbor Day Foundation site). Herb?

Oliver

Yes, Sunset Zone 1. As far as the Zip code of Sweet Home is 97386, that is true, but that is the climate at the Post Office! I use that Post Office rarely, as I am on a Rural Mail Route 1000 ft. higher in elevation. I look out my front window and see Mt. Jefferson.
Herb.

Yes, 1000 ft higher elevation CAN make a bit of difference!

I must say, that with all the larch yamadori being shown here lately, I am starting to get larch envy. I tried growing seedlings in the ground here a long while ago, but the hot, humid summers here (USDA zone 6b-7), perhaps combined with inadequate care, did them in the first summer.
Oliver