--> tree
If 'tree' is not a typo you can use command-not-found to lookup the package that contains it, like this:
    cnf tree
------------------------------------------------
--> cnf tree
The program 'tree' can be found in the following package:
  * tree [ path: /usr/bin/tree, repository: zypp (repo-oss) ]

Try installing with:
    sudo zypper install tree
------------------------------------------------
--> sudo zypper install tree
Retrieving repository 'openSUSE-13.1-Update' metadata ...................................................................................................................................[done]
Building repository 'openSUSE-13.1-Update' cache ........................................................................................................................................[done]
Loading repository data...
Reading installed packages...
Resolving package dependencies...

The following NEW package is going to be installed:
  tree 

1 new package to install.
Overall download size: 43.7 KiB. After the operation, additional 94.9 KiB will be used.
Continue? [y/n/? shows all options] (y): y
Retrieving package tree-1.6.0-7.1.2.x86_64                                                                                                                (1/1),  43.7 KiB ( 94.9 KiB unpacked)
Retrieving: tree-1.6.0-7.1.2.x86_64.rpm .................................................................................................................................................[done]
(1/1) Installing: tree-1.6.0-7.1.2 ......................................................................................................................................................[done]
------------------------------------------------
--> which tree
/usr/bin/tree
------------------------------------------------
usage: tree [-acdfghilnpqrstuvxACDFQNSUX] [-H baseHREF] [-T title ] [-L level [-R]]
	[-P pattern] [-I pattern] [-o filename] [--version] [--help] [--inodes]
	[--device] [--noreport] [--nolinks] [--dirsfirst] [--charset charset]
	[--filelimit[=]#] [--si] [--timefmt[=]] []
  ------- Listing options -------
  -a            All files are listed.
  -d            List directories only.
  -l            Follow symbolic links like directories.
  -f            Print the full path prefix for each file.
  -x            Stay on current filesystem only.
  -L level      Descend only level directories deep.
  -R            Rerun tree when max dir level reached.
  -P pattern    List only those files that match the pattern given.
  -I pattern    Do not list files that match the given pattern.
  --noreport    Turn off file/directory count at end of tree listing.
  --charset X   Use charset X for terminal/HTML and indentation line output.
  --filelimit # Do not descend dirs with more than # files in them.
  --timefmt  Print and format time according to the format .
  -o filename   Output to file instead of stdout.
  -------- File options ---------
  -q            Print non-printable characters as '?'.
  -N            Print non-printable characters as is.
  -Q            Quote filenames with double quotes.
  -p            Print the protections for each file.
  -u            Displays file owner or UID number.
  -g            Displays file group owner or GID number.
  -s            Print the size in bytes of each file.
  -h            Print the size in a more human readable way.
  --si          Like -h, but use in SI units (powers of 1000).
  -D            Print the date of last modification or (-c) status change.
  -F            Appends '/', '=', '*', '@', '|' or '>' as per ls -F.
  --inodes      Print inode number of each file.
  --device      Print device ID number to which each file belongs.
  ------- Sorting options -------
  -v            Sort files alphanumerically by version.
  -r            Sort files in reverse alphanumeric order.
  -t            Sort files by last modification time.
  -c            Sort files by last status change time.
  -U            Leave files unsorted.
  --dirsfirst   List directories before files (-U disables).
  ------- Graphics options ------
  -i            Don't print indentation lines.
  -A            Print ANSI lines graphic indentation lines.
  -S            Print with ASCII graphics indentation lines.
  -n            Turn colorization off always (-C overrides).
  -C            Turn colorization on always.
  ------- XML/HTML options -------
  -X            Prints out an XML representation of the tree.
  -H baseHREF   Prints out HTML format with baseHREF as top directory.
  -T string     Replace the default HTML title and H1 header with string.
  --nolinks     Turn off hyperlinks in HTML output.
  ---- Miscellaneous options ----
  --version     Print version and exit.
  --help        Print usage and this help message and exit.
------------------------------------------------