Sure (it's limited on the number of glyphs, but it seems your locale is using UTF-8 encoding).

I use this for testing:

 #!/bin/sh
 # send character-string to enable UTF-8 mode
 if test ".$1" = ".off" ; then
 printf '\033%%@'
 else
 printf '\033%%G'
 fi

and (calling it "utf8"), "utf8 on" turns the encoding on.

Using the example given with `pstree`, here is an example *after* running the script (before, the same sort of output as in the question):

[![screenshot after "utf8 on"][1]][1]

As noted in a comment, there's a script `unicode_start` which does *more*, but all that is needed to address the question posed is the small script used as an example.

Addressing a different comment: At least on my system (and in the screenshot shown in the question), all of the characters used by `pstree` are supplied in the 512-glyph font used by default for Unicode support in the Linux console.

Further reading:

 - [console_codes - Linux console escape and control sequences][2]
 - [Into the Mist: How Linux Console Fonts Work][3]


 [1]: https://i.sstatic.net/nZNW2.png
 [2]: http://man7.org/linux/man-pages/man4/console_codes.4.html
 [3]: http://www.tldp.org/LDP/LG/issue91/loozzr.html