diff --git a/rose-trees.cabal b/rose-trees.cabal
--- a/rose-trees.cabal
+++ b/rose-trees.cabal
@@ -1,5 +1,5 @@
 Name:                   rose-trees
-Version:                0.0.1
+Version:                0.0.1.1
 Author:                 Athan Clark <athan.clark@gmail.com>
 Maintainer:             Athan Clark <athan.clark@gmail.com>
 License:                BSD3
@@ -14,6 +14,7 @@
   HS-Source-Dirs:       src
   GHC-Options:          -Wall
   Exposed-Modules:      Data.Tree.Rose
+                        Data.Tree.Knuth
   Other-Modules:        Data.Tree.Rose.Internal
   Build-Depends:        base >= 4 && < 5
                       , containers
diff --git a/src/Data/Tree/Knuth.hs b/src/Data/Tree/Knuth.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Tree/Knuth.hs
@@ -0,0 +1,36 @@
+{-# LANGUAGE KindSignatures #-}
+{-# LANGUAGE DeriveFunctor #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+
+module Data.Tree.Knuth where
+
+import Prelude hiding (foldr)
+import Data.Monoid
+import Data.Foldable
+
+data KnuthForest a = Fork { node :: a
+                          , children :: (KnuthForest a)
+                          , siblings :: (KnuthForest a) }
+                   | Nil
+  deriving (Show, Eq, Functor)
+
+appendSibling :: KnuthForest a -> KnuthForest a -> KnuthForest a
+appendSibling Nil _ = Nil
+appendSibling (Fork x xc Nil) y = Fork x xc y
+appendSibling (Fork x xc xs) y = Fork x xc $ appendSibling xs y
+
+instance Monoid (KnuthForest a) where
+  mempty = Nil
+  mappend = appendSibling
+
+instance Foldable KnuthForest where
+  foldr f acc Nil = acc
+  foldr f acc (Fork x xc xs) =
+    foldr f (foldr f (f x acc) xs) xc
+
+newtype KnuthTree a = KnuthTree { unKnuthTree :: (a, KnuthForest a) }
+  deriving (Show, Eq, Functor)
+
+-- | Breadth-first
+instance Foldable KnuthTree where
+  foldr f acc (KnuthTree (x, xs)) = foldr f (f x acc) xs