In anticipation that Tree Jacket would be the next KAL I contacted the Zephyr gals and asked if they could give us some specific yarn suggestions. The pattern calls for a worsted weight wool blend.
Here's their reply: "... the red photographed sweater was knit with Knit Picks Andean Silk, which was lovely. Both of us Zephyr gals have also knit it with Lion Brand Cotton Ease, which you can get for a great price from (Discount Yarn Sale) I think we both prefer this yarn over the other... it's just so soft and wonderful! Rowan Cashsoft is another that would just be dreamy to work with and machine washable too!!!" Thanks Zephyr gals!
A Knitters Review of RYC Cashsoft is here. According to the KR review Cashsoft is similar to Debbie Bliss Cashmerino Aran .
I'd love to see other yarns suggestions posted.