I bought new shoes this weekend! They’re nothing special, just a pair of cheap lightly-antiqued brogues from Aldo that I’ll wear with what’s becoming my typical work outfit of straight-leg raw jeans and a slim button-up shirt with the sleeves rolled way up.

You can see how the thin leather’s already starting to crease a bit. That’s fine for these guys, they’re meant to be a bit beat up. But you can also see that I’m fighting the creases with shoe trees!

If you’re a typical guy, you probably have at least one or two pairs of shoes with leather uppers and sole like these. (Or maybe with leather uppers and a rubber sole made to look like a leather sole. Those probably count too, although it’s not as urgent.) If you do, you should have at least one pair of shoe trees.

Shoe trees are cedar (or plastic, but you want cedar) forms which wedge into your shoes to restore their condition after you’re done wearing them. Here’s what the sort you’d pick up for $20-$30 at a typical mall shoe store look like:

There’s a few moving parts: the bar between the toe and heel parts is hinged vertically at the toe and spring-loaded for length, and there’s an expander wedge between the two toe parts which pushes them outwards to fill the toe box when the heel is pushed down into the shoe.

Two particular elements of daily wear greatly accelerate the wearing out of leather shoes. First,when you walk around, you roll on the ball of your foot, and that curves the sole upwards. That creases the upper and slowly bends the sole up at the toe. Second, you sweat, which means the shoe goes through moist-then-dry cycles with every wearing. That’s hard on the leather to begin with, but it magnifies the potential damage of the sole-bending: moistening stiff leather is how cobblers intentionally bend it!

Shoe trees address both of those problems. The unfinished cedar slowly absorbs the moisture from the leather, and the spring between the toe and heel stretches the sole out flat so that it dries in that position.

Because shoe trees work on moist leather, it’s important to get them in the shoes as soon as they come off your feet, and then leave them in for a day or two. (You can leave them in longer if you want; some people buy a couple pair of trees for all their shoes, and others buy one pair of trees for each pair of shoes.) Note that that means that you need at least two pairs of shoes for daily wear. The easiest way to destroy a pair of leather shoes is to regularly wear them two or more days in a row without letting them recover for a day.

Shoe trees can easily double the lifespan of a pair of inexpensive (sub-$300) leather shoes. I recommend considering them a necessity, just like a hanger is a necessity for a suit jacket. Shoe trees come in sizes, so be sure to find the size that matches the shoes they’re going in. (Don’t confuse them with shoe stretchers, which are of a similar shape but which apply much more pressure between the heel and toe and across the toe box, intended to stretch the leather instead of maintain it!)

(Leather dress boots like Chelsea boots also benefit from trees and can often get by with shoe trees, but it’s worth looking for boot trees that also shape the ankle of the boot. Expensive shoes often include their own shoe trees, carved to match the last on which the shoe was formed!)