Cleaning a Bee Hotel Once a Year Without Killing Guests

By Austin Little

Clean a bee hotel at the wrong time and you throw away next year's bees. Clean it at the right time, with the right setup, and you cut mites, mold, and parasites without losing a single cocoon.

AI disclosure. This page was drafted with AI assistance and edited for Apiary. We don't invent quotes, stats, people, or events. If something looks off, tell Austin — that's the point of a living hive.

The short version: you clean a bee hotel once a year, after the bees inside have finished developing and before the next generation needs the space, and you never just scrub out filled tunnels. For spring mason bees, that usually means opening nests in fall, once the young have spun cocoons and turned into adults inside them. You remove the cocoons, clean or replace the nesting material, store the cocoons somewhere cool and protected over winter, and put them back out in spring. For summer leafcutter bees, timing is different, so you handle their nests separately.

If your bee hotel is a block of wood with drilled holes that can't be opened, you can't really clean it. Your safe options are to leave filled holes alone until the bees emerge, then retire the block or switch to a setup that opens. Most of the trouble with bee hotels comes from that one design problem.

This guide covers why cleaning matters, what's actually living in your bee hotel, when to clean for each kind of bee, step-by-step cocoon harvesting, how to clean different hotel types, what to do about mites and mold, and how to store cocoons so they make it to spring.

Why clean a bee hotel at all

In nature, solitary bees nest in scattered stems, beetle holes, and cavities. If one nest gets infested with mites or fungus, the problem stays small. A bee hotel packs dozens of nests side by side, year after year, in the same tubes. That's convenient for bees, and also for their pests.

Over a few seasons, an uncleaned hotel can build up:

• Chalkbrood and other fungal problems, which can kill larvae and leave spores in tunnels.
• Mold in damp tunnels, especially in hotels without a roof overhang.
• Old debris: mud partitions, frass (larval droppings), dead larvae, and leftover pollen.

Who's inside your bee hotel

You need to know who you're hosting, because each group runs on a different calendar.

**Mason bees (Osmia)**

• Active in spring, often around fruit tree bloom.
• Seal nest cells with mud. A mud-capped tube is the giveaway.
• Young develop through summer and, in many species, become adults inside their cocoons by fall.

**Leafcutter bees (Megachile)**

• Active in summer.
• Line and seal cells with cut leaf pieces. A leafy plug is the giveaway.

Other tenants

• Resin bees and other small bees may seal tubes with resin or chewed plant material.
• Solitary wasps often use bee hotels too, plugging tubes with mud or debris and stocking them with caterpillars, aphids, or spiders. They're usually beneficial predators.
• Grass-carrying wasps may stuff tubes with dry grass.

Because mason bees and leafcutter bees overlap in the same hotel, a single "clean everything in October" plan can destroy leafcutter nests that aren't ready to be opened. If you see leaf plugs, read the leafcutter section before you touch anything.

The golden rule of timing

Don't open or clean a tube that's still in use or still holds developing young that can't survive outside it.

In practice:

• Spring and summer: hands off. Bees are building, provisioning, and developing. Don't remove tubes, don't scrub, don't move the hotel unless you absolutely must.
• Fall (for mason bees): often the right time to harvest cocoons, once they've finished developing.
• Winter: cocoons in cool storage; the empty hotel gets cleaned or new nesting material goes in.
• Early spring: cocoons go back out near the hotel as temperatures warm and flowers start blooming.

If you don't want to harvest cocoons, there's a simpler middle path covered below: move filled tubes into an emergence box in spring and put fresh tubes in the hotel. That also keeps reused material from piling up pests.

Step 1: Figure out what kind of hotel you have

Cleaning depends on the design.

Opens easily (best):

• Stackable wooden trays that come apart into halves, exposing every tunnel.
• Paper tubes with removable liners or paper inserts.
• Reeds or cardboard tubes you can split or unroll.

Hard to clean:

• Bamboo: tough to split cleanly, and nodes can make tunnels uneven.
• Drilled solid blocks: can't be opened without destroying them.
• Decorative "insect hotels" with pine cones, mixed holes, and glued parts: mostly impossible to clean, and many holes are the wrong size anyway.

If your hotel is hard to clean, that's not a reason to feel bad. It's a reason to plan a switch. Apiary has a separate guide on building a mason bee house that actually works if you want the full design rundown.

Step 2: Harvest mason bee cocoons in fall

This is the main event for most backyard bee hotels.

What you need:

• Gloves (optional, but helpful with mud).
• A tray or shallow box to catch debris.
• A soft brush or a blunt tool like a popsicle stick or plastic spoon.
• A container for clean cocoons with some airflow (a small cardboard box or a container with a few small holes).
• Paper towels.
• A notebook or phone for counting.

Before you start: Bring the nesting material indoors to a cool room, or work outdoors on a mild day. Don't leave cocoons in direct sun or near heat.

For wooden trays:

1. Gently separate the trays.
2. You'll see rows of cells: mud walls separating cocoons, with pollen remains and frass.
3. Use a blunt tool to lift out each cocoon. Mason bee cocoons are typically small, oval, and brownish-gray.
4. Set aside anything that doesn't look like a healthy cocoon: dried, chalky larvae, cells full of dusty mites, or cocoons with small exit holes (which may mean a parasite emerged).

For paper tubes or liners:

1. Unroll or tear open the paper gently.
2. Lift out the cocoons as above.
3. Throw away the used paper. Don't reuse it.

For reeds:

1. Split the reed lengthwise with a knife or by hand along the grain. Go slowly and away from your body.
2. Remove cocoons.
3. Compost or bin the old reeds.

Count cocoons and note any problems you saw. Over a few years, these notes tell you more about your hotel than anything else.

Step 3: Clean the cocoons (optional but common)

Many mason bee keepers do a gentle cleaning of cocoons to remove pollen mites and debris. Methods vary.

Dry cleaning (gentlest):

• Sift out the sand.

Rinse cleaning (more thorough):

• If you try this, follow a reputable source's exact instructions, work quickly, and make sure cocoons are completely dry before storage. Wet cocoons can mold.

If you're unsure, skip washing. Just removing cocoons from old, dirty material and starting over with clean nesting material already does much of the good.

Step 4: Store cocoons over winter

The idea is to keep cocoons cool and stable so the bees stay dormant until spring, without letting them dry out or get eaten.

Common approaches:

• A cool, unheated, protected space such as a garage or shed, in a box that keeps out rodents and birds. Works in some climates but temperature swings can trigger early emergence.
• A refrigerator with a dedicated container for cocoons, plus a small source of humidity like a damp (not wet) paper towel nearby but not touching the cocoons.

Storage rules:

• Keep them away from fruit in the fridge.
• Label the container so nobody in the house throws it out.
• Check monthly for mold or drying.
• Don't store them for too long. Holding them far past natural emergence can weaken bees.

Step 5: Put cocoons back out in spring

When temperatures are warming and early flowers like fruit trees are starting to bloom, put the cocoons back outside.

How to do it safely:

• Use a small emergence box or shelter: a little box with a small exit hole, mounted next to or on top of the bee hotel, protected from rain and birds.
• Place cocoons inside on a dry surface.
• Make sure there's fresh nesting material in the hotel and a mud source nearby. Mason bees need damp, clay-rich soil to build their walls.
• Watch for emergence over the next few weeks. Males usually emerge first.

Don't: Toss cocoons into the open where birds can eat them, or put them out weeks before flowers bloom.

Step 6: Clean or replace the nesting material

While cocoons are in storage, deal with the hotel itself.

Wooden trays:

• Scrape out mud, pollen, and frass with a blunt tool.
• Inspect for cracks or gaps where parasites can get in.
• Let trays dry fully, ideally in sun, before reassembling.

Paper tubes or liners:

• Replace with new ones every year. Don't try to clean paper.

Reeds:

• Replace with fresh reeds every year or every other year. Old reeds harbor mites and fungus. Apiary's guide to reusing mason bee tubes gets into the details.

Bamboo:

• Hard to clean well. Many keepers replace it rather than reuse.

Drilled blocks:

• If you can't open them, you can't clean them. Options are below.

The housing (roof and frame):

• Brush out spiderwebs and debris.
• Check that the roof still overhangs enough to keep rain off the tubes.
• Tighten mounting so it doesn't swing in wind.

Leafcutter bees: a different schedule

If you see tubes plugged with leaf pieces, those are likely leafcutter bees, and they need different handling.

• Don't harvest them with mason bees in fall unless you know what you're doing.
• A common, simpler approach for backyard keepers: leave leafcutter-filled tubes intact over winter in a sheltered, protected spot outdoors or in an unheated space, and move them into an emergence box in late spring, with fresh tubes nearby for the next generation.
• Some advanced keepers harvest and store leafcutter cocoons for controlled emergence. If you want to try that, follow a detailed, reputable guide written for leafcutters specifically.

The main safety point: don't scrape out leafy tubes in fall assuming they're empty. They often aren't.

Mason bees, the "no harvest" method

Not everyone wants to open nests and handle cocoons. This simpler approach still reduces pest buildup.

1. Spring: Leave the hotel alone while bees work.
2. Fall or winter: Remove the filled tubes, reeds, or trays and store them in a protected emergence box or ventilated container in an unheated, sheltered spot. Protect them from birds, rodents, and rain.
3. Same time: Put fresh, clean nesting material in the hotel.
4. Spring: Put the old filled tubes in an emergence box near the hotel. Bees emerge and nest in the fresh tubes.
5. Summer: Once bees have emerged and the old tubes are empty, throw the old material away.

This keeps bees from emerging into, and immediately nesting back in, dirty tubes.

What to do with drilled blocks

Solid drilled blocks are popular and almost impossible to clean. Here's how to handle one humanely.

• Leave filled holes until bees emerge. Don't drill, scrape, or poke into sealed holes.
• Retire the block after a season or two. Once bees have emerged in spring, you can stop using that block. Some keepers set it inside an emergence box with fresh nesting material nearby so bees have a clean option next door.
• Switch to an openable design. Wooden trays or paper liners in the same frame are easy upgrades.
• Don't burn or bin a block with sealed holes in it. If you need to remove it, wait for emergence.

Spotting common problems while cleaning

Pollen mites

• Look like fine dust, sometimes orange or tan, packed into cells.
• Cells may contain no healthy cocoon, just a mass of mites and pollen.
• Cleaning cocoons and replacing nesting material each year helps keep them under control.

Chalkbrood

• Larvae look hard, chalky, white to gray or black.
• Remove and discard affected cells. Clean or replace the material they came from.

Parasitic wasps

• Cocoons with tiny holes, or cells with many tiny wasp pupae instead of one bee.
• Discard affected cocoons.

Mold

• Fuzzy, damp growth in tunnels.
• Usually a sign the hotel gets wet. Improve the roof overhang, avoid placing tubes where rain blows in, and make sure stored cocoons are dry.

Bird damage

• Pecked-out tube ends.
• Add a wire mesh guard in front of the hotel, set an inch or two away from the face.

Safety for you while cleaning

• Wear gloves if you're handling old material, since mold and debris can irritate skin.
• If you're cleaning with any chemical, including diluted bleach, use it in a ventilated area, follow product label directions, and keep it away from kids and pets.
• If you're allergic to insect stings, take extra care and follow your doctor's advice.
• Work on a table, not your lap. Split reeds and blunt tools slip.

A once-a-year calendar

Here's a simple version for a typical mason bee hotel in a temperate area.

Once a year really is enough. The work concentrates in one or two sessions in fall, and it's mostly patient, fiddly, and kind of satisfying.

Common mistakes

Cleaning in spring or summer. That's when bees are building and developing. Wait.

Scrubbing out sealed tubes. Sealed means occupied. Leave them.

Treating leafcutter nests like mason bee nests. Different schedule. Check the plugs.

Reusing old reeds and paper tubes. That's how mites build up. Replace them.

Storing cocoons somewhere warm. Bees may emerge in winter with nothing to eat.

Putting cocoons out with no protection. Birds will eat them.

Never cleaning at all. Over a few years, pest buildup can undo the good the hotel does.

FAQ

How often should I clean a bee hotel? Once a year, after the bees inside have finished developing. For mason bees, that's often fall. For leafcutter bees, it's usually later.

Can I clean a bee hotel in spring? It's not recommended to open sealed tubes in spring or summer. Bees may still be developing or actively nesting.

Do I have to harvest cocoons? No. You can use the simpler method of moving filled tubes to an emergence box and putting fresh material in the hotel. Harvesting gives more control over pests.

What if I have a drilled wood block? Leave filled holes until bees emerge, then retire it or move it to an emergence box and add an openable nesting setup.

What's that dusty orange stuff in my tubes? It may be pollen mites. Cleaning cocoons and replacing nesting material helps keep them down.

Can I wash cocoons with bleach? Some keepers use a very dilute bleach rinse, but methods vary. If you try it, follow a reputable source's exact instructions and dry the cocoons thoroughly.

The bottom line

A bee hotel isn't set-and-forget. Without yearly cleaning, it can turn into a mite and fungus farm. With one careful session a year, it stays a nursery.

Clean at the right time: fall for mason bees, later for leafcutters, never during active nesting. Use nesting material you can open. Harvest or relocate cocoons, store them cool and protected, replace or clean the tubes, and put the bees back out when flowers bloom. Your guests will check out healthy and come back next spring.