Rose beds were grown in mid-evil times to detour people from approaching homes.
Roses from that period were large, thorn covered thickets, and others were climbing, and if you know what 'Old Fashioned' or 'Multi-Floral' roses are, you get an idea of what they looked like.
Dense hedges and rose 'Mazes' were made into 'Garden' features in the beginning of the industrial revolution, but in mid-evil times they were very carefully designed to confuse aggressors and assassins around area & regional castles and homes.
Anyway, there are several bushing and climbing plants that will cover your 'Castle Keep' with spines and toxins!
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Time for a side tangent about flowers...
In Mid-evil times it was believed that sweet smelling flowers could ward off disease...
Plague, TB, Small Pox, ect.
("Ring around the
Rosie, Pocket full of
Posy".... Ever wonder what those lyrics were about? .... Warding off Bubonic Plague!)
When the troops came back from WW II they started building 'Housing Subdivisions' were before WW II many homes in cities actually touched each other...
Called 'Row Houses'.
When the subdivisions as we know them came along, many people saw WW II vets with 'Post Traumatic Stress Disorder' (PTSD) out walking the neighborhoods after dark as a precaution from window 'Peeping' many people started planting roses under windows...
Remember, this was just after WW II, and there weren't central air-conditioning yet, so most people had their windows open day and night during the warm months...
These guys weren't 'Peeping',
They were taking their demons, acquired during the war, for a walk since the demons wouldn't let them sleep...
But there was no such thing as a 'PTSD' diagnosis then, and church going housewives didn't understand the problem, and their imaginations ran away with them....
Today, things like Coy ponds, rock gardens, and decorative fencing can make the terrain uneven and hard to navigate,
And can also camouflage things like motion sensors, lights, alarms (silent and neighbor annoying), along with bushes that will detour any aggressor to a particular path of travel...
If you make a shrub 'Wall', the aggressor will simply pick a random place to cut through...
If you leave a gap in the bushes, an *UNTRAINED aggressor will take the path of least resistance and come through the gap...
At which time you can have anything from a dog stationed there (you want an Quiet dog for that post!

) or you can have something as benign as a motion sensor light aimed at that 'Gap'...
(Or, in the event of serious aggression, a trip wire!)
*A trained aggressor will NOT take the gap and will make his own ingress point so he can control the situation...
But what is the chance you will be stalked by a 'SeAL' Team?
Anyway, just a little strategy and history...