Right now, you have with you a most useful pruning tool — two different kinds of pruning tools, in fact: your hands, and your thumbnail.
Let’s start with the first.
Use your hands to rip unwanted stems from plants. Yes, it seems brutal, but this method of pruning can sometimes do a better job and leave the plant healthier than can a precision cut with fancy pruning shears. Hand pruning — by ripping off stems — is the best way to get rid of suckers, which are vigorous, usually vertical, stems.
On apple trees, suckers often pop up from the upper sides of limbs. The problem with apple suckers is they’re usually not fruitful, they shade the rest of the tree and they rob other branches of nutrients.
On tomato plants, suckers grow wherever a leaf meets the main stem. Sucker growth causes tomato plants trained to grow up stakes or inside cages to become congested with stems. That makes it harder to find fruits and the resulting dankness promotes diseases. Just rip those suckers off.
So what’s wrong with using pruning shears on suckers? Pruning shears can infect a healthy plant with diseased sap picked up from a sick plant. Your hand, grabbing only the outside of a stem, is unlikely to transmit disease from one plant to the next.
Also, suckers cut back with pruning shears often rebel with one to four vigorous, new suckers poking up right where you cut. Such regrowth is rare when you grab a sucker in your hand, then give it a quick downward jerk, because then buds hidden at the base of a shoot come off also. Hand pruning is most effective with suckers still young and succulent.
Now for the thumbnail. This tool has a different use than your whole hand.
Your thumbnail is ideal for pinching out just the tips of shoots. Why would you want to do that? For one thing, to promote bushiness. Of your zinnia plant, for example. Or your cushion ’mums. Or your potted avocado, which thus far is perhaps nothing more than a single, gawky stalk.
Pinching out the tip of a shoot with your thumbnail is also useful for temporarily checking the shoot’s growth. Do this when more than one stem is trying to become the main trunk of a young tree. Too many “top dogs” leads to weak limbs, so pinch out the tips of all but the best shoot to give that shoot the opportunity to jump ahead of the pack and become the future tree trunk.