Definition of PLACOID. : of, relating to, or being a scale of dermal origin with an enamel-tipped spine characteristic of the elasmobranchs. ADVERTISEMENT.Greek plak-, plax flat surface.First Known Use: 1842.efinition of PLACOID. : of, relating to, or being a scale of dermal origin with an enamel-tipped spine characteristic of the elasmobranchs. ADVERTISEMENT. Greek plak-, plax flat surface. First Known Use: 1842.
A tree pruner is a class 1 lever. The fulcrum is where the two blades cross, and the load is what you are cutting. The effort is applied to the two handles.
Test Garden Tip: Trees that produce a heavy sap flow when pruned in winter -- maples, birches, elms, and dogwoods -- are known as bleeders.. The sap flow may be unsightly, but it doesn't harm the tree. To avoid the bleeding, you can wait until the leaves have fully expanded in summer to prune these species.