Sorry for not responding I've been busy this week.Do the Trees need to be pure bred to crossbreed?
No they don't need to be pure bred but I believe just like bees they also have a chance of using both the species when mutating so you may not get the mutation you want.
For anyone who has successfully bred a Willow tree, what biome were you located in? I never got one in Plains or Woodlands despite tons of bees & trees interacting and was only finally able to get one when I setup a pair of Marshy bees surrounded by the appropriate trees in a Swamp.
And also, I love the grafter. That one simple device has made tree breeding about 10,000 times less tedious and annoying. In the two days since our server upgraded to Forestry 2 as part of Mindcrack 8 I have gotten more new tree species than in the previous couple of weeks under the old version of Forestry. Yeah, I may have burned through most of a stack of bronze, but the only trees I have left to "discover" are the Yellow Meranti and the three whose breeding is bugged in version 2.0.0.2 (Wenge, Baobob, & Sipiri).
Glad you confirmed this for me as I also got a willow by breeding in a swamp. I'm not sure if its impossible to get in other biomes, but I got one very fast before 2.0 and the grafter in a swamp and never have gotten one in the plains biome my other trees are in.
 
				
		
 due to a severe lack of information i will post this here. As i have no idea how to do a spoiler tab, i will just come right out and confirm that Sipiri Saplings will only grow in warm/humid biomes. I still have no idea the breeding combination yet (its completely left out of the chart) but i would suggest a tropical location to attempt breeding them. They give out greenheart logs, and look somewhat similar to a cross between balsa and yellow meranti (my starting point for trying to breed them naturally) but they also have similarities to the kapok (ive only ever bred one of those, so i dont have the material to research that link yet). They only require one sapling to grow.
 due to a severe lack of information i will post this here. As i have no idea how to do a spoiler tab, i will just come right out and confirm that Sipiri Saplings will only grow in warm/humid biomes. I still have no idea the breeding combination yet (its completely left out of the chart) but i would suggest a tropical location to attempt breeding them. They give out greenheart logs, and look somewhat similar to a cross between balsa and yellow meranti (my starting point for trying to breed them naturally) but they also have similarities to the kapok (ive only ever bred one of those, so i dont have the material to research that link yet). They only require one sapling to grow.