Let's Talk Pruning!

Pruning has to be one of the weirdest things we do for plants. It makes sense that a plant needs food, water, sunlight, and an appropriate temperature to be happy and healthy, but cutting a plant's extremities off in order to make it healthier?! That seems like madness! 

The tomato plants were being smashed up under
the porch railing containers, so they got pruned!

The truth is, plants (especially plants grown in pots) need pruning in order to stay healthy. It keeps them from turning "leggy," where the bottom foliage dies off and only the tips are left. It makes them squat and compact to keep the wind and rain from breaking the stems off haphazardly or knocking the pot over. Pruning flowers off after they've passed peak bloom can help a plant conserve energy if you don't want it growing too many seeds. It can also be used to save a plant that has diseased or insect-infested leaves and force the plant to grow new, healthy leaves instead!

Before trimming mint: Leggy and bare.

A week or so after trimming mint: New growth!

To prune plants you can either use your fingers or preferably some sort of shears or scissors. The sharper the cutting tool the better the plant will heal over, especially if it's a particularly large stem. Stems can get infected from bacteria or fungus in the environment, so a clean cut is going to produce the least amount of surface area for gross stuff to get into the nooks and crannies. To keep diseases from spreading, dip your shears in isopropyl (rubbing alcohol) after cutting from a plant that's been infected with something. (Generally the advice is to dip it between cuttings from EVERY plant, but I'm lazy and unless I spent a crap-ton of money on a plant or am really in love with it I'll take the risk of sharing shears between healthy plants.)

Shears for trimming tiny stems. For larger stems I use kitchen shears.

When making a cut, try your best to always trim from the top of the plant, getting rid of the newest leaves first. The exception in this case is if the leaves lower down are infected or dead already, in which case you can cut off those individual leaves further down. Cut the stem between two leaf layers, just above the leaf level where you want new leaves to grow. This will encourage the leaf layer below to bush out and make more foliage. Sometimes you'll get new leaves all the way down the stem once you cut the top leaves off. There's more sunlight getting to the stem area below, and the plant also sends out signals: "Grow more leaves! We're being eaten!" Leaving a bit of stem above the leaf layer you want will allow you some room to cut it back further if the stem gets infected. If you have an infected stem it'll start getting mushy and brown, spreading down the stem. Cut it below where it's mushy and dab some isopropyl on the cut. It'll help it dry out faster and kill the nasty germs!

Pruning the catnip between leaf layers

For a diseased or leggy plant it depends on the type of plant how much you can trim off. If you know from prior trimmings that the plant rapidly bounces back from trimming (like my Columbine and mint plants), go ahead and trim off as much as you need to. For plants that you're unsure about the general rule is to only cut off a max of 1/3 of the leaves at a time. Let the plant start new growth before cutting off more leaves.

Diseased leaves all over the Columbine plant, pre-trim
(I trimmed these back to the ground)

Columbine plant post-trim, about a month later.
New leaves don't have any mildew, leaf miners, or mites!

For flower blooms, it's best to "deadhead" the flowers before they start forming seeds. That way the plant conserves energy and flowers more. Seed-making is hard work! It's also good to take the flowers off of plants even if they're the "non-seeding" hybrid varieties because a) it looks prettier not to have dead flowers all over the plant and b) dead flowers can rot and lay on the leaves, causing molds, fungi, and gnats to colonize the plant. To deadhead a flower, pinch or cut the stem just below where the flower was.

Deadheading the begonia flowers after the bloom has wilted.

I hope this has been useful! It's hard at first to know when and how much to prune, but try looking online for pruning advice for the plant you have. The internet has helped my plants a lot, especially looking up plant diseases and tips for getting rid of them! Everything else I'm learning the hard way. Haha.