Why 2:1, and why it changes in autumn

Autumn syrup is mixed two parts sugar to one part water by weight. Spring syrup is usually 1:1. The difference is not tradition: thinner syrup resembles a nectar flow and tends to stimulate laying, while thick syrup is closer to something the colony can simply store.

The other half is work. Bees cap stores at roughly the moisture content of honey, in the region of 17 to 18 percent water. Starting from 1:1 they have far more water to remove than from 2:1, and every gram of that water has to be fanned out of the hive. In August that is easy. In October it is the whole problem.

The real cutoff is evaporation, not the calendar

Two things stop happening as autumn cools. Bees become reluctant to take syrup at all, and the colony loses the warmth and airflow it needs to concentrate what it has taken. The commonly used rule of thumb is that syrup around 50°F (10°C) stops being readily taken, and that once daytime highs sit below that the liquid season is over.

Treat that as a rule of thumb rather than a hard threshold, because it is exactly that in the sources it comes from. It is also worth noting that the temperature that matters is the syrup's, not the forecast's. A feeder that chills overnight may never warm enough during a short autumn day to be worth visiting, which is why feeding often slows before the air temperature suggests it should.

The practical version: start early enough that you are finishing in good weather rather than chasing the last few pounds into the cold.

The second reason to stop: late brood

This is the part that gets left out of most feeding advice, and it matters more than the fermentation risk.

The bees that carry a colony through winter are physiologically different from summer bees. They carry enlarged fat bodies and high levels of the storage protein vitellogenin, and they live for months rather than weeks. Randy Oliver's Fat Bees series is the most accessible account of what that means in practice and is worth reading in full.

Feeding is a signal. Keep feeding hard into late autumn and you encourage the colony to keep laying, which does two unhelpful things at once: it spends the fat reserves of the bees you are relying on to survive, and it keeps capped brood available for varroa to reproduce in during the weeks you most want the colony broodless. Feed to fill the box, then let them wind down.

What too-late feeding actually does

  • It may ferment. Syrup stored without being concentrated and capped is a sugar solution in a warm, humid box. Fermented stores are not what you want a cluster eating in February.
  • It adds water to the hive. Every gram of water the colony evaporates has to leave through the hive. Doing that in October adds to the moisture load in the season where shedding moisture is already the hard part.
  • It can arrive as unusable weight. A hive that hefts heavy in November because it is full of uncapped syrup is not as well provisioned as it feels.

Once the window closes: solid feed

After liquid feeding ends, the options are all solid sugar placed directly above the cluster: fondant, a poured candy board, or dry granulated sugar on newspaper in what is usually called the mountain camp method.

All three are emergency feed rather than a way to build stores. Bees take solid sugar slowly and need moisture to use it at all, which in practice means the hive's own condensation. If a colony needs fondant in January it will probably survive on it, but the reason it needed it was a decision made in September.

Things worth getting right while you are feeding

  • Never feed honey you did not produce. American foulbrood spores remain viable in honey for decades, and feeding bought honey is a well-documented way to introduce them to a clean colony. Honey from your own healthy hives is fine.
  • Do not feed with harvest supers on. Anything they store from a feeder can end up in supers you intend to extract, and that is no longer honey.
  • Do not boil the syrup. Heat, especially with anything acidic added, encourages the formation of hydroxymethylfurfural, which is harmful to bees at sufficient concentration. Warm water to dissolve the sugar and stop there.
  • Feed inside the hive during dearth. Autumn feeding coincides with the worst robbing pressure of the year. An internal feeder and a reduced entrance give a small colony a chance.
  • Plain white granulated sugar only. Not raw, brown or unrefined sugars, whose solids bees cannot digest well and which are associated with dysentery over winter.

How to tell when you are done

Stop when the hive is at target weight for your climate, not when the calendar says so. The target itself varies enormously, and the winter stores guide and the overwinter feed calculator exist to work that out for where you are.

The field test is hefting: lift the back of the hive an inch off the stand and learn what a ready colony feels like. Do it each time you visit through autumn. The change from week to week tells you whether they are still taking feed down far more reliably than looking in the feeder.

Sources and further reading

Bloom timing, dearth and first frost all move with latitude, so treat any month named here as a starting point and calibrate against your own season and your local association.