Opening the Sides of the Broodnest - OSBN

Main points:

During Swarm Season:

  • Place empty/undrawn frames on the outer edges of the Brood Nest.
  • Trigger wax making with a Partial Foundation/Foundationless Frame (OSBN Frame).
  • Maintain at least 2 empty/undrawn frames in every box throughout Swarm Season.
  • Move honey frames up and out of the Brood Box(es).
  • Can start as soon as Drones are being raised.

(This assumes that the hive is looking nearly full, healthy and has a few frames of honey stores.)

During the Main Flow:

  • Maintain at least 2 empty/undrawn frames in each of the Supers only.


  • Develops comb building before Swarm Season, which helps to reduce swarming. Due to extra comb for nectar storage and using up of nectar to make wax.
  • Enlarges the size of the Broodnest when the bees would usually be reducing it (by backfilling), because the Queen lays in empty comb as it is being built.
  • Can be done at colder temperatures than inserting empty Frames inside the Broodnest, "Opening the Broodnest".
  • Does not touch the Broodnest, so it doesn't force bees to heat a larger volume than they are used to heating. (Which can lead to chilled brood.)
  • Does not split the Broodnest, so if cold weather sets in there is no possibility of having the cluster split.
  • The bees still have direct access to the frames that were beside the Broodnest as they are now they are above it instead. Not a problem, when heat rises.
  • The bees can build the comb in their own time, but an empty space (Hole) gives them an incentive to build comb.
  • Causes Wax Makers to move out of the Broodnest so it becomes less crowded.
  • Maintaining at least 2 Undrawn Frames in each Box throughout Swarm Season helps to keep Wax Makers occupied during Swarm Season.

What you will need:

  • At least 1 box of mostly New Undrawn Frames, which are the same size frames as your Brood Box. (If a few frames are partially drawn, this also helps.)
  • At least 1 or 2 sheets of Foundation cut in order to make a couple of Partial Foundation Frames. This is so that there is a large enough Hole to trigger Wax Making. (For example: cutting the Foundation to make a Wedge shape. See photo below.)


  • Frames are all the same size
  • Start at least 3-4 weeks before you usual Swarm Season (or from when you see Drone Brood).
  • Do at least every 2 weeks until bees are drawing out multiple combs in the New Box.
  • New frames have a Hole large enough for the bees to want to fill it with comb.
  • Hive is healthy, has a few frames with capped honey and bees covering over 90% of the frames in the hive.


OSBN is a Swarm Prevention method for Beekeepers who don't have enough spare, empty comb coming into spring.
OR for those who have enough Bee Hives (ie. don't want to do Splits or make more Bee Hives).


To get the bees building comb in a New Box/Super before Swarm Season starts, and to have at least a full Box drawn out by the end of Swarm Season, to help reduce swarming and to get a honey crop.


1. Develop Wax Makers well before Swarm Season.

2. Maintain Wax Making throughout Swarm Season and into the Main Flow.

3. Encourage enlargement of the Broodnest until the Main Flow.



Start 3-4 weeks before your usual Swarm Season (or when Drone Brood is being raised):

  1. Move each outermost frame from a Brood Box up into the middle of a New Box (of Undrawn Frames), placed directly above the Broodnest. (So that 2 Old Frames have moved up.)
  2. Insert a New Frame (Partial Foundation or Full sheet of Foundation) on each outside edge of the Broodnest of the Brood Box. So that Brood frames are only on one side of each New Frame. (2 New Frames inserted, at least one Partial Foundation initially, the other can be a Full sheet of Foundation.)
  3. Check the Hive in 2 weeks and repeat steps 1-2 if comb has been at least partially drawn on the New Frames in the Brood Box. (So that 2 Old Frames are moved up, 2 New Frames inserted into the Brood Box.) You will now have 4 Old Drawn Frames that have been moved up into the New Box.
  4. Check again in 2 weeks. The New Box should now have comb getting drawn out. Repeat steps 1-2 if needed.
  5. Throughout Swarm Season ensure that there is at least 2 Undrawn Frames in each Box. This is to maintain Wax Making by getting the young bees to draw out new comb. (These Frames can now all be full sheets of Foundation.)

During the Main Flow:

  • Maintain at least 2 undrawn frames in each of the Supers only.


  • It helps to scrape the capping of any capped honey on the frames that are moved up to the New Box.
  • The New Frame can be Empty Drawn Comb or a sheet of Foundation, but (at least one frame should) have a large "hole" that is equivalent to no less than 1/4 of the frame. You can cut off the bottom corners off the comb or Foundation to make a Wedge shape.
  • When adding 2 New Frames at once, one can be a Partial Frame of Foundation and the other a Full Frame of Foundation.
  • Place the 2nd OSBN Frame beside the 2 Honey Frames in the New (Top) Box.
  • The Hole(s) will often be filled with Drone Comb.
  • If concerned that adding a New Box will be too much space for the bees to heat when temperatures are low, the Inner Cover/Crown Board can be placed in-between the Brood Box and the New Box. This helps to maintain the Temperature in the Brood Box, but the bees still have access to the frames in the New Box through the hole in the Inner Cover/Crown Board. It can be moved up to the top once temperatures are warmer.
  • If the outermost Brood Box frames are moldy, you may wish to remove them completely and not put on a New Box until the third step.
  • If you still want to use slightly moldy frames, then cut the cappings off any capped honey. Move them up to the New Box, but have at least a couple of frames of foundation between them. These frames will usually get emptied out.
  • You can start doing this method as soon as Drones are starting to be raised and the weather forecast for the next week is warm.
  • With Partially Drawn New Frames where the comb that is rounded off around the edges, it may help to cut off the rounded edge so that it is rough and damaged. This helps with the bees wanting to repair it.
  • For the bees to move into a box, I have found it best to have at least 3 or 4 drawn combs together, in the middle of the new box. When there is less than 3 frames in a box and not together, they usually get emptied out. So if you have a spare drawn comb, the more the better.
  • If you have to move up a Frame with eggs or brood, place it in the middle of the New Box, directly above the Broodnest.
  • After the 4th Step, you may be able to repeat the steps again with a second New Box on top.
  • The timing of 2 weeks is for deep frames. If you use mediums, the times will be shorter and can be more like 1 week.
  • Best to use all the same size frames.
  • It is harder to get bees to draw out Plastic Foundation. Make sure to coat the Plastic Foundation well with wax!
  • Do not allow the bees to complete a Honey Dome around the Broodnest. Throughout Swarm Season ensure there is at least 2 Undrawn Frames in the Brood Boxes for the bees to work on drawing out comb.
  • Also, remove any burr comb from the bottom of frames.
  • It is recommended to have 2 Deeps (or 3 Mediums) for the Brood Boxes during Swarm Season. Once the Main Flow has started the Broodnest can be reduced to 1 Deep (or 2 Mediums) for the rest of the year.

Timing on when to Start

Based on what I see when I start Opening the Sides of the Broodnest, here is a guide for the Timing on when to start:

Start at least 3-4 weeks before you usual Swarm Season or when Drone Brood is being raised.

Night time: 40°F / 5°C or above
Day time: 55°F / 13°C or above

Brood - Capped and Open Brood (50% of the main Brood Box)
10 Frame Deep: 5 or more Deep Frames
2 x 10 Frame Mediums: 5 or more Medium Frames in the main Brood Box

Frames of Bees (90% of the main Brood Box)
10 Frame Deep: 9 or more Deep Frames
2 x 10 Frame Mediums: 9 or more Medium Frames in the main Brood Box

Pear Trees in blossom.


  • 3 Weeks before Swarm Season is the most important point related to Timing.
  • If the hive is not as strong as 50% Brood and 90% Frames of Bees (in the main Brood Box), then Open up 1 (ONE) Side of the Broodnest with a Frame of Partial Foundation.
  • If the hive is very weak, IE. 30% Brood or less and 50% Frames of Bees or less, then check if there is a Honey Dome around the Broodnest. There should not be frames of Capped Honey on both sides of the Broodnest. If there is, swap the positions of those frames with mostly empty comb if possible. Then check again in a week or two.


  • Make at least 2 Partial Frames for OSBN per Hive.
  • Cut Foundation or Comb into the Wedge shape.
  • Mark the top of the Partial Foiundation Frame so it can be easily identified.
  • Later in the season the Partial Frames can be moved out to the edges so that they are filled with honey.
  • Then cut the Comb off the bottom corners, so that the Partial Frames can be used again the next season.

Ways to cut foundation:

Best result for comb:


Most efficient use of Foundation:


Other Two Pieces:


With the Wedge shape, 2 Frames can be made with 1 Sheet of Foundation.

It is would also be worth gluing the Foundation in the groove of the Top Bar, especially with making a Wedge shape with the 2 Off-Cuts.

Turn the Frame upside down, put a line of Wood Glue (PVA) in the groove of the Top Bar, then place the Foundation in position. Wait until it is dry.

Label the OSBN Frames so that it makes it easier to identify them when in the hive.

Remember to coat Plastic Foundation with wax!


This is a close-up of the right side of the above Partial Foundation Frame after it has been drawn on the Wedge Shape Foundation (and then extracted).

Notice that the foundation-less part has been drawn as Drone Comb and the plastic foundation drawn as Worker Comb.
Also, note the darker area where brood has been raised. The amount of area used for Drone Brood is not large.

Here is the recommended configuration for placing new OSBN Frames:


YELLOW - Frame of Honey/Nectar/Pollen
BROWN - Frame with Brood

More details:

"Opening the Sides of the Broodnest - OSBN" is all about triggering Wax Production before Swarm Season and then maintaining Wax Production into the Main Flow. So the bees build more comb for raising brood and storing nectar and also use up incoming nectar to make the wax.

This method is for beekeepers who do not have enough Drawn Comb OR do not want to Split because they have enough Hives.

The new frames to trigger wax making can be partially drawn or foundation. If using foundation use no less than half a sheet of foundation. Cut to a Wedge shape works well as the middle is then worker comb and the holes will be filled with Drone Comb. There must be a HOLE close to the Broodnest. The Hole beside the Broodnest is what triggers comb building, (the bees want to fill the hole and complete the Broodnest before they can swarm).

The "Sides" of the Broodnest/Cluster are opened up, rather than inserting frames into the middle of Broodnest. At this stage of the Season when temperatures can drop suddenly it is important that the bees are not forced to heat a larger volume than what they are used to. It also doesn't split the Broodnest which could cause issues if very cold weather sets in. Inserting frames into the Broodnest can set back brood rearing and also cause issues such as chilled brood if cold weather sets in, especially earlier in the season.

Bees will usually build mostly Drone Comb before Swarm Season. If the frame is completely Foundationless it will likely be drawn mostly Drone Comb.

The hive should have a few frames with a band of capped honey across the top of the frame. I prefer not to feed, but if they haven't got enough stores you may need to, as they will use up all their stores trying to fill the hole(s) with comb. Make sure you leave them some stores close to the Broodnest in case bad weather sets in. This is why the frames that are moved up are put directly above the Broodnest. As long as daytime temperatures are above 55°F / 13°C the bees can break cluster and fill up on honey.

The bees having to store honey in their stomach and having to cling onto each other in the area of the "Hole" simulates a Swarm like condition. This triggers Wax Making.

Once Wax Making has started, the bees will drawn out Foundation.

Only the first couple of manipulations need to have a "Hole" to trigger Wax Making. Once excess nectar starts coming in during Swarm Season then Foundation is readily drawn out.

As a guide, I would start Opening the Sides of the Broodnest around half way through the period between Cherry blossoms and Apple blossoms. The period between these blossoms for me is quite long, around 2.5 months. If it is around 1 month for you then you initially may need to use drawn comb. So when daily maximum temperatures start getting over 15°C /59°F, go into the hive and move the two outside frames up into a new box and place them together in the center (try to make sure there are no eggs in these frames.) Then find the outside edge of the Broodnest. Insert a New Frame on each side the outer edge of the Broodnest (one being a Partial Foundation Frame.)

The temperature is a guide to when you can go into the hive. It's when the bees are able to forage every day and fruit trees are flowering. But it's also the stage that the hive is at, that is just as important. With a 10 frame deep box, I'm looking for at least 5-6 frames of brood and at least 3 frames with a decent amount of capped honey. If they don't have a good amount of stores, you are just going to stress them and if bad weather sets in, even cause starvation because they will use up the honey making wax. If they don't have that you should wait. Also, the hive should look full, with bees covering all frames. Look at the weather forecast for the next week. A few days of good weather will enable them to forage or move stores, whilst the Wax Makers get busy. Start at least 3-4 weeks before Swarm Season.

With different overwintering configurations you have different conditions to look for. In general I would say 2/3 brood, 1/3 honey.

5 frame Nuc - 3 frames with brood, 2 with honey
8 frame (double) Nuc - 5 frames with brood, 3 with honey
10 frame deep - 6 frames with brood, 3-4 with honey
Double deep - several frames with brood, 4 or more with honey

I believe this could be applied in many environments, that have winter temperatures below 13°C/55°F (this or below bees will cluster.)

If you see only 2-3 queen cells, DO NOT WORRY. This means the bees are superseding. As with Walt Wright's Checkerboarding, the Broodnest can fill up to 3 brood boxes. The queen may be running out of stored sperm and needs to be replaced. (Obviously if you see more than 3 Queen Cells then they are likely in Swarm mode. Try removing all but 2 Queen Cells and do OSBN again.)

I only need to do OSBN 2 or 3 times in Swarm Season. From then maintain 2 frames of Foundation in each box and the bees just continue to draw out comb in the supers. Do not allow the bees to complete a Honey Dome around the Broodnest. Think of the Broodnest like a watermelon shape. Where the Red part is Brood and the White part is Honey. You want to maintain a Hole in the Honey part. Throughout Swarm Season ensure there is always at least 2 Undrawn Frames in the Brood Box for the bees to work on drawing out comb. Keep them working on building new comb until well into the Main Flow.

After a number of discussions with people who have tried Opening the Sides of the Broodnest, it looks like a modification needs to be made if there is a fast and heavy flow in your area when Spring starts (like the Maple flow). This seems to be in places that have snow, and the transition between Winter and Spring is quite quick. I too would be reluctant to add frames of foundation while there is still snow around. So better to use empty Drawn Comb with the corners cut off. A Cover Board or Cloak Board can be used between the Brood Box and the New Box if night time temperatures get below freezing.

Apparently in these areas, with a New Frame of Foundation there is just too much nectar coming in and the Wax Makers either don't start or can't make enough new comb in time to keep up with the amount of nectar coming in.

Beekeekers in this situation are using empty DRAWN comb to Open the Sides of the Broodnest until this initial flow is over. This enables the Broodnest to be able to expand out sideways, without getting backfilled.

After this initial period has passed, then frames of Partial Drawn or Half sheet foundation can be used as per the method.

New Frames are added on the outer edge of the Broodnest because temperatures can drop too low and quickly in Spring. Once you are into the Main Flow and temperatures are higher and more stable, then inserting New Frames into the Broodnest is no longer an issue.

Throughout Swarm Season ensure that there is at least 2 Undrawn Frames in each Box. Place these frames close to the Broodnest. These Frames can be full sheets of Foundation. This is to maintain Wax Making by getting the young bees to draw out new comb. It also means there is more comb to store incoming Nectar.

Example of the OSBN Method:

So let's look at an example using the following notation:

P = Partial Frame of Foundation (OSBN Frame)
N = New Frame with Foundation.
D = Frame of older Drawn Comb with some honey, nectar or pollen.
B = A frame with some Brood on it.

Frames that have been moved are in Bold.


NNNPPPPNNN (New Box, 4 Partial Frames)

DDBBBBBDDD (Single Brood Box, 5 Frames with Brood)



Expecting the bees to work on at least the 2 New Partial Frames in the Brood Box, as these are the Holes in the Broodnest. Drawn Frames that are moved up may be emptied out.



Partial Frames have been mostly drawn and have Brood. Brood on the bottom inbetween the Old Drawn Frames in the New Box, bees have expanded into the New Box.



Expecting the bees to work on at least the 2 New Frames in the Brood Box, as these are the Holes in the Broodnest, and also start drawing out New Foundation Frames.



Partial Frames have been mostly drawn and have some Brood. Brood on the bottom of the Old Drawn Frames in the New Box, bees have become established into the New Box and drawing out New Frames of Foundation.

It is now Swarm Season



In order to keep 2 Undrawn frames in the Bottom Box, the first Brood Frame was moved up beside other Brood Frames. Then 3 Drawn Frames are moved up into a New Box on Top.

A new Box is added because of the amount of Brood. The population is increasing rapidly at this stage and needs the space to expand into. For example, 6 frames of Capped Brood will emerge after 2 weeks and occupy at least 12 or more Frames. Some say even more, more like 3 Frames of Bees for every Frame of Capped Brood.

Depending on the amount of Nectar and Pollen coming in will depend on how many frames get drawn out in the next 2 weeks.

What I do:

  • Pull out 2 New Partial Frames from the middle of the New Box before opening the hive.
  • Take out the Outermost Frame from each side of the Brood Box, check them for eggs or brood. If none, scrape or cut off any honey cappings and put the Old Frames straight into the middle of the New Box
  • In the Brood Box look for capped brood on the next outer frames. If none, pull out the frame and look for eggs.
  • If no eggs or brood, slide the frame over and look for eggs or brood on the next frame.
  • Once you see eggs or brood, you now know where the edge of the Broodnest is (and you've usually only had to look at 1 or 2 frames).
  • These are the only brood frames that I look at. No need to look for the queen or queen cells. If there are eggs you have a queen. If she has space to lay, it is unlikely there will be any swarm cells. (Because if they are making wax and building comb they are unlikely to want to swarm.)
  • Do this in both sides to give them at least 2 new Frames in each Brood Box to work on. This helps to decrease the frequency that you need to go into the hive (compared to just adding 1 Frame.)

Have fun!

For more details and discussions on this method, also see:

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