Physical Danger
Literally everything you work with has a sharp edge on it. Some of them are attached to combustion engines. Much of the time you'll be using them while standing on top of a ladder bent over a bush full of sticks and thorns. What about this sounds safe to you?
Lawnmowers, edgers, power hedge shears, and even blowers are nothing to mess around with. Pruning shears, machetes, and other blades are dangerously sharp even without a motor to back them up. This is a dangerous job, and since you need all of your limbs attached to perform it, we'll just stress this once, here: be careful.