Plantastic is designed to be easily concealed in the foliage of most plants, so you can even use it all the time, not just while you are on vacation.  Just replace the Flo-Disks when the water level stops dropping after a week.  Most water qualities will allow the Flo-Disk to be reused for 2-3 refillings of the bottle.  If your water has a lot of impurites (very hard well water) then consider bottled water, although for vacation watering, this is rarely necessary.  Includes Plantastic 40 oz, Cap Spike, Top Dust Cap, 3 Flo-Disks.