Vertical splits and making increase

A vertical split describes the division of a colony into two – one queenright, the other queenless – on the same floor and under the same roof, with the intention of allowing the queenless colony to raise a new queen. If successful, you end up with two colonies from the original one. This approach can be used as a means of swarm prevention, as a way to requeen a colony, as a way to generate two colonies from one, or – to be covered in another post – the starting point to generate a number of nucleus colonies. It’s a hands-off way of queen rearing … without the need to graft, to prepare cell raising colonies or to manage mating nucs.

Wally Shaw has written an excellent guide to simple ways of making increase (PDF) which includes a number of variants of the straightforward vertical split described here. There are additional instructions available on the Kent beekeepers website by Nick Withers (Swarm Management – Under One Roof … in which the ‘split board’ described below is termed a swarm board). Wally’s article is particularly good, but includes complications like brood and a half colonies and a host of further embellishments. For simplicity I’ve restricted my description to a situation when you have one colony – on single or double brood boxes, possibly with supers on top – and want to divide it into two.

The split board

Split board

Split board …

You need a way to divide the colony in two and provide an upper entrance. There are many ways of doing this, including the multi-entrance Snelgrove board (PDF) and the increasingly popular Horsley board, but one of the most straightforward is a simple split board as shown in the picture. A single sheet of 9-12mm plywood forms the basis for the board, with a ‘beespace’ rim on both faces. On one side (the ‘upper’ side when in use) make a simple hinged door as shown. In the middle of the board cover a 100mm square hole with a single sheet of Varroa mesh – this allows the odour of the colonies to merge and for warmth to spread from the lower box to the upper one.

Vertical split – in principle

The general idea is to divide a strong, healthy colony into two. The colony is arranged so that the queenright side of the split gets depleted of bees which boost the queenless side, so providing ideal conditions for making emergency queen cells. After the cells are sealed the colony is manipulated to deplete the queenless side of bees, and strengthen the queenright side. This prevents swarming. Nectar collection continues without too much interruption if there is a flow on. All of this is achieved by straightforward manipulations of the colony on day one and day 7. You should have a mated, laying queen (in the originally queenless side of the split) about 3 weeks later.

Vertical split – in practice

It’s only worth rearing queens from colonies that exhibit desirable qualities – healthy, docile, a good laying pattern, steady on the comb etc. Of these, I’d argue that health and temper are two critical characteristics. You need to make these judgements over an extended period – I’ve briefly discussed the basics of good record keeping when selecting larvae for grafting, and the same principles apply here. Like computing – rubbish in, rubbish out. If your colony doesn’t have the necessary desirable characteristics there are ways of modifying the method described below to raise queens from better stock … but lets deal with the basics first.

Day 1

  1. Gently smoke the colony and remove the lid and crownboard. You need to find the queen so don’t gas them. If the colony is already on double brood move the top box – which probably contains the queen – off to the side. If the colony is on a single brood box you’ll need a second brood box and 11 frames of drawn comb (ideally) or foundation.
  2. Having checked carefully that the queen isn’t present on them remove a couple of outside frames to allow you space to manipulate the remainder. Go through the boxes carefully and find the frame with the queen on it. Either put this somewhere safe, like a two-frame nuc box, or leave it well separated from the other frames so that the queen stays put on it.
  3. Rearrange frames between the two brood boxes so that the queen, older larvae and some sealed brood is present in what will become the upper box, together with a frame or two of stores. Eggs and young larvae should predominantly be in the bottom box. This isn’t a precise science, you need sufficient brood with the queen to build up a new colony and sufficient eggs and very young larvae for the queenless side to have a good choice of young larvae from which to raise a new queen.
  4. Reassemble the boxes with the brood in the centre, flanked by either stores and/or the new frames. The idea is to create two brood nests, one above the other, roughly centred on the mesh-covered hole in the split board.
  5. Place the queenless box on the original floor. Put the split board on top with the entrance open and facing in the opposite direction to the original entrance. Put the queenright box on top of the split board, then replace the crownboard and the roof (see the note about supers below).
  6. Leave the colony for a week.

What’s happening … During this week foragers leaving the top box will mainly re-enter via the entrance at the front of the colony, so significantly boosting the numbers of bees in the bottom box. This box will rapidly realise it is queenless and will raise new queen cells. The concentration of bees in the bottom box will ensure that the developing queen larvae are well fed. If there were queen cells in the top box (with the queen) the depleted bee numbers will mean they will soon get torn down. The queen will continue laying uninterrupted.

The Vertical Split in pictures

The Vertical Split in pictures

Day 7

  1. You don’t need to inspect the colony at all, but you do need to rearrange it. If there are no supers on the colony and you’re feeling very strong you can simply reverse the entire colony on the stand. The original bottom entrance is now at the ‘back’ and the upper entrance is at the ‘front’. That’s it … leave them to it. There should be a new queen, mated and laying, in the bottom box in about 3 weeks.
Charles Atlas

Charles Atlas …

However, remember that this is a double brood box at the height of the season. There is likely to be a good nectar flow on and there should be some reasonably fragile queen cells in the bottom box – dropping the hive when reversing it could be catastrophic, and not just for anyone standing nearby (as an aside, the mushroom-like cloud of bees that erupt from a dropped brood box is one of the most spectacular sights in beekeeping … probably the ultimate test of how impenetrable your beesuit is and how steady your nerves are). Far better than Charles Atlas-like heroics it’s probably better to separate the colony below the split board, put the upper box aside, reverse the lower box and floor, then replace the upper with the entrance now facing in the opposite direction (see the figure above).

If you do inspect the colony at this stage you’ll find a happily laying queen in the top box. There will be no queen cells in the top box unless there is something wrong with the queen. There should be relatively fewer bees in the top box – thousands not hundreds. In contrast, the bottom box will be very crowded with bees and there will be multiple queen cells present, both sealed and unsealed. Leave them … the bees will choose a good one in due course.

What’s happening … During the next few days the bottom box will get depleted of bees as they leave by the lower entrance and return to the ‘front’ of the hive, eventually finding the upper entrance and strengthening the upper box containing the laying queen. Initially there will be considerable confusion, with hundreds of bees milling around at the site of the original entrance. For this reason it’s best not to rearrange the colony late in the evening … do it earlier in the day to allow them ample time to reorientate to the upper entrance. This reorientation takes a couple of days – don’t worry about it, there will be a lot more activity around the entrances (and positions of previous entrances) during this period.

A limited number of virgin queens should emerge about 16 days after the initial manipulation and the depleted bee numbers in the bottom box will ensure that the colony shouldn’t throw off casts. If multiple virgins emerge at the same time they’ll probably fight it out to leave just one. In due course, usually about 5-6 days after emerging, the virgin will go on one or more mating flights and return to the lower box and start laying.

Vertical split

Vertical split – day 7 …


If there are supers on the original colony, or the nectar flow is strong during the month-long process and you need to add supers, then there is a simple rule about where they should be placed – above the strongest of the two brood boxes, separated by a queen excluder. This means that during the first week they will be on top of the lower brood box, below the split board, and in subsequent weeks they will be above the upper brood box, underneath the crown board. Because the split board has a mesh screen the colony odours are mixed and the bees should not fight during these rearrangements. There’s no need to empty the bees from supers when moving them.

Making things easier …

Any enthusiastic DIY beekeeper will realise that the entire process can be made much easier by creating both a split board and floor with two opposing entrances. Using these there would be no need to reverse the colony on day 7. The split board might be a sensible modification – something to build during the winter. However, the Kewl floors I favour don’t readily lend themselves to this type of design and – although having a physique more like Charles Hawtrey than Charles Atlas – I find it easy enough to manhandle the colony as needed. A floor with opposing entrances would also benefit queen rearing using a Cloake board which has some similarities to the principles of the vertical split.

And finally …

At the end of this vertical split you will have two queenright colonies under a single roof. You can either move one or other away (remembering the 3 feet and 3 miles rule or the box that remains on the original site will collect all the returning foragers) thereby doubling your colony number. Alternatively, you can inspect the upper box and sacrifice the old queen (of course, if she’s simply surplus to requirements but still performing OK you could offer her to another beekeeper … these little acts of kindness are appreciated both by the recipient and the queen), remove the split board and thereby unite the two colonies into one strong colony. And, of course, if something goes wrong – the new queen doesn’t get mated or the old queen fails during the process – you can simply merge the colonies back down to one.

Advantages and disadvantages

I see the main advantages (in no particular order) as:

  • limited horizontal space required.
  • almost no additional equipment needed.
  • colony ‘smell’ retained making uniting or exchanging supers easier.
  • swarming and controlled increase are possible with little intervention.

… and the disadvantages:

  • vertical lifting required and boxes may be heavy.
  • inspections of the bottom box are complicated (not least by the mass of bees trying to return to the upper entrance).
  • supers need to be moved during the procedure and add to the weight (but think of all that lovely honey 😉 ).
  • some smaller colonies may not raise a new queen in the bottom box – I don’t know why this is, but suspect it’s due to the amount of queen pheromone, particularly from a young, strong queen in the top box. I intend to investigate whether a super separating the boxes might help prevent this.

2 thoughts on “Vertical splits and making increase

  1. Brian

    Excellent post, really interesting. Need to get my act together as to what methodology I will employ to increase my stocks, as I plan to. Keep em coming ! 🙂

    1. David Post author

      This sort of split works well to double your stocks, or simply requeen in due course. There are also ways of modifying a vertical split to generate several nucs from the queenless side. I think Wally Shaw describes this in more detail in his linked article. I’ve not done this as I would generally prefer to graft and use the Ben Harden system or a Cloake board.


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