Are all outdoor mushroom cultures started in spring?

Are all outdoor mushroom cultures started in spring? We live in cool temperate climate were the winter is usually sunny
and days are usually around +10C nights sometimes -5C for short periods.

No. Some people start outdoor beds because they find some mushrooms and grind them up in a blender and put them in wood chips or some other substrate. Mycelium is generally more comfortable in a cool wet climate than in a dry sunny one. So I think that it depends on the preferred climate of that species of fungi and your climate. I do think that spring is the most frequent time to start them, because many climates have harsh winters that can harm baby fungi.
John S
PDX OR

Thanks! Good time to start a shiitake culture?
I get gum (eucalypt) or pine woodchips easily maybe I can get some thicker gum branches. There are guys in TAS who sell
plug spawn, expensive, but for a first go maybe.

We plug shiitakes here the first week in march although others in this area sometimes plug in the fall. We have never tried any wood other than a variety of oak logs, cut within two weeks of plugging. There are a few other woods that could work but we stick with what is reliable for us and that we have on our land. I don't think pine would work. If the gum you mention is sweet gum i think I have heard it will work.
Hopefully you will get some more folks answering your question but in the meantime check out 'field and forest' for some more info on what wood to use...their catalog has a bit of basic information and they have been very helpful when we have called with a question. and 'fungiperfecti' is another catalog folks mention a lot here.

Page 16 of this PDF covers inoculating logs.

Research at Cornell’s Arnot Forest has shown that winter and spring inoculations are ideal;
however, summer and fall inoculations also produce sizable harvests.

I will be inoculating throughout the late spring/summer/fall.

The danger in felling a tree outside of winter is that the bark is more likely to fall over, injuring the log.

Angelika Maier wrote:
I get gum (eucalypt) or pine woodchips easily maybe I can get some thicker gum branches. There are guys in TAS who sell
plug spawn, expensive, but for a first go maybe.

Page 9 covers tree species. This booklet is for NE US but I don't think Eucalypt or Pine will work.

I agree. All my sources say pine and eucalyptus, redwood, and cedar Thuja are not to be used for mycology.
John S
PDX OR

That means I must talk to the tree guys. We are in half-suburbia and there are plenty of blokes who fell trees for other people. What most comes is
gum.

Angelika Maier wrote:That means I must talk to the tree guys. We are in half-suburbia and there are plenty of blokes who fell trees for other people. What most comes is
gum.

Eucalyptus can be used. I thin these guys might be in your hemisphere, inspiring stuff.
http://milkwood.net/2011/07/20/making-a-shiitake-mushroom-log/

I am going to question the idea of removing the bark from a tree to grow shiitake. Stamets urges people to only grow shiitake on thick barked logs. People in my mushroom club insist that if the bark is removed, shiitake wont' produce mushrooms. Stamets urges against thin barks like birch and alder, and for oak, BECAUSE the bark stays on. I've heard this in seminars too.
John S
PDX OR

John Saltveit wrote:I am going to question the idea of removing the bark from a tree to grow shiitake. Stamets urges people to only grow shiitake on thick barked logs. People in my mushroom club insist that if the bark is removed, shiitake wont' produce mushrooms. Stamets urges against thin barks like birch and alder, and for oak, BECAUSE the bark stays on. I've heard this in seminars too.
John S
PDX OR

I agree, unless there is something in the bark which inhibits fungi, like maybe, camphor in eucalyptus? I'm just guessing though, I have no experience with using eucalyptus.

Eucalyptus is often used for shiitake cultivation. Stamets has a few examples in Growing Gourmet & Medicinal Mushrooms.

http://www.fungi.com/shop/grow-mushrooms-on-logs-and-stumps.html

http://www.fungifun.org/mushworld/Shiitake-Mushroom-Cultivation/mushroom-growers-handbook-2-mushworld-com-chapter03-02_p.61.pdf

Taking off the bark helps with drying out a log. Growing shitake requires keeping moisture at about thirty percent. I think the magic number where the mycelium dies is twenty percent.

They gave no reason for taking off the bark and seem unaware that it impacts the moisture levels in the log. And it might be worth noting, the fungus only colonizes the outer layer of the log, the part that will most readily dry with the bark removed. They're waxing the ends to keep in moisture, but taking off the bark....