Quick Answer: Wet weather damages flare hems in three ways — the trailing edge frays on wet pavement, absorbed water stretches the hem out of shape while it dries under its own weight, and grit embedded in the fibres accelerates abrasion. Drying flat rather than hanging, and rinsing the hem after wet wear, prevents most of it. A hem already stretched can usually be partially recovered with steam.

This is the maintenance article nobody writes, and it is the difference between two seasons and five out of a good pair.

What is actually happening to the hem?

Abrasion, and it is concentrated in a very small area. The back of a flare hem contacts the ground on roughly every step at heel strike. On dry pavement that is manageable. Wet pavement adds grit that embeds in the knit and turns the fabric into a mild abrasive against itself.

Water adds weight where the garment is weakest. A wet flare hem can hold a surprising amount of water, and a hem that is stretched downward by that weight while drying sets slightly longer and looser than it started. Do this ten times and the hem opening is visibly wider and floppier than the day you bought them.

Elastane recovery is temperature and moisture dependent. Fibres that dry under tension recover less completely than fibres that dry relaxed. This is the single mechanism behind most permanently stretched hems.

The damage is invisible for weeks. By the time you see fraying, the structural stretching has usually been happening for a month.

How should you dry them after wet wear?

Flat, always, on a towel. Hanging a wet flare puts the entire weight of the absorbed water through the hem, which is precisely the area you are trying to protect.

Reshape the hem while damp. Lay the leg flat and smooth the hem opening back to its original width with your hands. Two minutes of this at the damp stage does more than any amount of care later.

Never over a radiator. Direct heat is the fastest way to relax elastane permanently, and the first autumn radiator is where a lot of good activewear dies.

Rinse the hem if you walked through grit or leaves. A quick rinse under a cold tap removes embedded particles before they cut fibres in the wash drum.

Do not wring the hem. Press water out between towel layers. Twisting the hem is a reliable way to distort the opening.

What nobody tells you about flare hem recovery

Steam recovers more than you would think. A stretched hem held over steam for thirty seconds and then reshaped flat while cooling will often regain a good portion of its original width. Elastane responds to heat and then sets as it cools — which is both how it gets damaged and how it can partly be repaired.

Do it once and then leave it. Repeated steaming degrades the fibre further. This is a rescue, not a routine.

Cold wash does more for elastane than any detergent claim. Warm water is the primary cause of elastane relaxation in domestic washing.

Fabric softener actively harms technical fabrics. It coats the fibres, reduces wicking, and does nothing for stretch recovery.

Turning them inside out protects the hem’s outer face from the abrasion of the wash drum, which matters more once the fibres are already slightly compromised.

And the one that surprises people: the hem fails faster on a pair you love. Wear frequency is the dominant variable, and rotating two pairs roughly doubles the life of each — not because of rest, but because the abrasion is halved.

How do you protect them going into winter?

Get them hemmed a centimetre shorter for the wet months. The most effective preventative measure available, and reversible in the sense that you can simply buy the next pair longer.

Consider a cropped flare as the winter pair. Ending above the ankle removes ground contact entirely, and it works better with boots anyway.

Add a hem tape or overlock finish before the fraying starts. An alteration shop will do it inexpensively, and once fraying has begun the repair is much less tidy.

Check the hem monthly on dark pairs. Fraying on black fabric is genuinely invisible until it is severe.

Keep one pair out of the rain entirely. The pair you wear to things where you want them to look right should not be the pair you walk the dog in. This is an obvious thing that almost nobody actually does, and it is why most people’s best flares look worn out by February.

TL;DR:

• Wet pavement grit abrades the back hem, and absorbed water stretches it while it dries.
• Dry flat on a towel and reshape the hem while damp — never hang wet, never near a radiator.
• Steam can partially recover a stretched hem, once. Cold wash, inside out, no fabric softener.
• Hem a centimetre shorter for winter or switch to a cropped flare for the wet months.
• Rotating two pairs roughly doubles the life of each by halving the abrasion.

The flare is the part of the garment doing the most work and getting the least care. Ten minutes of attention through autumn buys entire seasons.