diff --git a/lib/sapling/greenhouse.rb b/lib/sapling/greenhouse.rb
new file mode 100644
index 0000000..cf88e19
--- /dev/null
+++ b/lib/sapling/greenhouse.rb
@@ -0,0 +1,15 @@
+require 'erb'
+
+# The rack application
+class Greenhouse
+  attr_reader :tree
+
+  def initialize(file)
+    @tree = file
+    @response = ERB.new(File.read('lib/sapling/index.erb')).result(binding)
+  end
+
+  def call(_env)
+    ['200', { 'Content-Type' => 'text/html' }, [@response]]
+  end
+end