Kain didn't actually start planting any of the spiritual plants because they'd be completely vulnerable to being damaged or taken away by any passing human or spiritual creatures.
What Kain needed for his future base of operations were wards.
Unfortunately, the cheapest wards that the college had to offer with no defensive abilities and only served as an alarm notification of invasion for Kain, was 1000 credits. Not to mention that it would be easily bypassed by any orange-grade spiritual creature or 3-star beast-tamer.
Now with 5360 credits to use, Kain could purchase a much more powerful ward to protect his plants.
He filtered the wards to limit them to ones that would be effective against yellow-grade spiritual creatures.
