Should leggy seedlings be planted deeper so they don't flop over?
Only as a last resort. Sometimes you can prop the seedlings up against a clod of soil, but best to avoid buying lanky seedlings in the first place as it usually means that the plants have been in their nursery pots too long. If you grow your own seeds, give them good light once sprouted and don't over-fertilise the starting soil. And note that some seeds need light to sprout, while others are best kept in the dark.
Do I need to seal pruning cuts?
Not necessarily. In the past, gardeners have been advised to seal cuts with pruning pastes and paints. But current advice more often suggests that if you prune correctly, especially in early spring, the plant or tree should be able to heal itself. In fact by covering the wound with a sealant, you may be encouraging harmful bacteria to grow.
Note that trees, vines, roses and perennials all have different pruning requirements and timing, so do some homework before attempting drastic action.
If you have a gardening question, email Glenys at firstname.lastname@example.org