Stay Cozy on the Peak: My Top 7 Merino Base Layers from Alpinetrek for Winter 2025/26

Written by Sophie Gent in T-shirts and tops

Merino base layers
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There is nothing quite like a crisp, misty morning at the trailhead. You know the feeling—the air is so sharp it stings your nose, the ground is crunchy with frost, and the peaks are calling your name. But let’s be real: if you’re shivering before you’ve even strapped on your gaiters, it’s going to be a long, miserable day.

I’ve spent more winters on the trail than I can count, and if there’s one thing I’ve learned the hard way (hello, teeth-chattering lunch breaks on a windy summit!), it’s that your hike is only as good as your base layer. For me, Merino wool is the undisputed queen of the mountains. Unlike synthetics, it keeps you warm even if it gets damp, it regulates your temperature so you don’t overheat on the inclines, and – best of all – it doesn’t hold onto that “hiker funk” after a long day.

I’ve been scouring the current collection at Alpinetrek to find the absolute best merino tops for this season. Whether you’re a “fast and light” hiker or someone who just wants to feel like they’re wearing a warm hug, here are my top picks.

Note: I’ve curated these from Alpinetrek because they carry the brands I trust. If you shop through my links, I may earn a small commission at no extra cost to you – it helps keep me out on the trails!

The “Heavy Hitters” (For the Deep Freeze)

1. Stoic – Women’s MerinoSoft245 TuleboSt. Half Zip

The Vibe: The ultimate “mid-winter” layer for when the frost doesn’t melt all day.

  • The Benefit: This is a substantial piece of kit. At 245g, it’s thick and plush. The half-zip is a lifesaver; I love being able to zip it all the way up to protect my neck, then vent it wide open when I’m working hard on a steep ascent.
  • The Downfall: It’s heavy. If you’re a fast-paced hiker or it’s a milder spring day, this might feel too bulky. It also takes a bit longer to dry out than thinner layers.
  • Check Price on Alpinetrek (Currently over 50% off!)

2. Heber Peak – Women’s Merino250 RootHe. L/S

The Vibe: Your “Old Reliable” for sub-zero days.

  • The Benefit: If you want maximum warmth for your money, this is it. It’s 250g of pure merino goodness. It feels incredibly sturdy and durable – the kind of top you aren’t afraid to actually live in.
  • The Downfall: It’s a very basic, functional design. If you’re looking for high-fashion patterns, this isn’t it – it’s built for the job, not the photo op.
  • Check Price on Alpinetrek (A total bargain at under £45)

The “Style Meets Substance” (The Alpine Aesthetic)

3. Kari Traa – Women’s Smekker Half-Zip

The Vibe: For the lady who wants to look as good as the view at the summit.

  • The Benefit: Kari Traa is famous for their gorgeous Nordic patterns, and the Smekker is no exception. It’s 100% merino and has a slim, flattering fit that looks just as good in the post-hike pub as it does on the ridge.
  • The Downfall: This brand runs quite snug. If you don’t like a “second skin” feeling, or if you have a larger bust, I highly recommend sizing up.
  • Check Price on Alpinetrek

4. Kari Traa – Women’s Rose Half-Zip

The Vibe: The gold standard of merino base layers.

  • The Benefit: This is a cult classic for a reason. The 100% merino wool is exceptionally soft (no itch here!) and it has a fantastic warmth-to-weight ratio. It’s breathable but surprisingly cozy.
  • The Downfall: It’s one of the pricier options on the list. While the quality justifies the cost, it’s definitely an investment piece.
  • Check Price on Alpinetrek

The “Technical & Versatile” (For High-Intensity Hiking)

5. Stoic – Women’s MerinoMesh150 SadjemSt. L/S

The Vibe: For “Fast-Packers” or hikers who tend to run hot.

  • The Benefit: The mesh panels on this top are genius. They are placed exactly where you need them to prevent that “soggy back” feeling you get under a heavy backpack. It’s lightweight (150g) and moves beautifully with your body.
  • The Downfall: Because it’s mesh-hybrid and thinner, it won’t keep you warm on its own if you’re standing still in a gale. You’ll need a solid mid-layer to trap the heat.
  • Check Price on Alpinetrek

6. Patagonia – Women’s L/S Cap Cool Merino Shirt

The Vibe: The eco-conscious, multi-sport choice.

  • The Benefit: This is a merino/polyester blend. The benefit of the blend is that it’s way more durable than pure wool and it dries lightning-fast. If you’re doing a multi-day trek and need to wash your gear in a stream, this is the one.
  • The Downfall: It doesn’t have that “luxurious” woolly feel. It feels more like a technical gym shirt than a cozy mountain layer.
  • Check Price on Alpinetrek

7. Aclima – Women’s WW Crew Neck

The Vibe: No-nonsense, professional-grade gear.

  • The Benefit: Aclima is what the pros wear. Their “WarmWool” (WW) is incredibly resilient. This top is reinforced in the right places and is built to last for years of abuse.
  • The Downfall: It has a very functional, utilitarian look. You won’t win any style awards, but you will stay warm and dry when the weather turns nasty.
  • Check Price on Alpinetrek

Buyer’s Guide: Tips from the Trail

What do the numbers mean? When you see numbers like 150, 200, or 250, that refers to the weight of the wool in grams per square meter.

  • 150: Lightweight/Summer or high-intensity.
  • 200: The “Goldilocks” weight – perfect for most UK winter hikes.
  • 250+: Heavyweight – for sub-zero temps or if you really feel the cold.

Don’t ruin your wool! Merino is a miracle fibre, but it hates the tumble dryer. Always wash your base layers on a cool, wool-specific cycle and air dry them flat. They’ll last for years if you treat them right!

Final Thoughts: Which one should you pick?

If you’re only buying one top this year and you want the best “bang for your buck,” I’d go for the Heber Peak 250 – the warmth is unbeatable for the price. If you want something that makes you feel amazing for those summit photos, you can’t go wrong with the Kari Traa Smekker.

Alpinetrek is currently running some massive sales (up to 55% off some of these!), so it’s the perfect time to stock up before the snow really starts to fall.

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