This schematic is used for sapling-grown large cacti, so should not
destroy the sand node below, as sand nodes are in short supply in
some situations.
Like trees, only force-place the node that replaces the sapling.
Alter 'large cactus' schematic to place another force-placed cactus node,
to replace the cactus seedling on growth.
Make schematic 5x7x5 to solve rotation, placement and protection check
issues.
Add a y-slice probability for height variation.
Growth time is tuned to not make this a faster way to obtain cactus nodes
compared to normal cactus farming.
Seedling texture by Extex101.
Use sapling/seedling description in protection intersection message in
'sapling_on_place' function.
