September is an important transition month for beekeepers in the San Francisco Bay Area. Summer is coming to an end, natural forage is becoming more limited, and colonies need to prepare for fall and winter.
Our winters are relatively mild compared with many other parts of the United States, but that does not mean we can ignore winter preparation. What we do in September can have a major impact on colony strength during the coming months.
Here are the main things I focus on in my apiaries during September.
1. Check Colony Strength
The first priority is to evaluate each colony.
Open the hive and look at the population, brood pattern, food reserves, and overall condition of the colony.
At this time of year, I want to see a healthy queen with a consistent brood pattern and enough bees to maintain the colony through fall.
Weak colonies deserve particular attention. September is a good time to decide whether a colony has enough strength to continue on its own or whether it should be combined with another colony.
There is little benefit in carrying a very weak colony into winter.
2. Make Sure the Queen Is Still Performing
September is also an important month to evaluate the queen.
The amount of brood naturally begins to decrease as the days become shorter and forage becomes less abundant. However, the colony should still maintain a healthy brood nest.
I look for eggs, young larvae, and a reasonably compact brood pattern.
A failing queen in September can create serious problems later in the fall, when replacing her becomes much more difficult.
3. Pay Close Attention to Varroa
Varroa mites remain one of the biggest threats to honey bee colonies in California.
After the summer season, mite populations can be high just when the bee population begins to decrease. This means the number of mites relative to the number of bees can increase rapidly.
This is why monitoring Varroa in late summer and early fall is so important.
Do not assume that a colony is healthy simply because it has a large population of bees. A strong-looking colony can still have a serious Varroa problem.
The objective is to enter fall with healthy bees and a mite population under control.
Always follow the label instructions of any approved Varroa treatment and pay particular attention to temperature restrictions.
4. Monitor Food Reserves
September can be a difficult month for forage in the Bay Area.
The spring bloom is long gone, summer vegetation is drying, and rainfall usually has not yet returned.
Check the amount of honey stored in each colony.
If a colony is light, supplemental feeding may be necessary. I prefer to make that decision based on the actual condition of each hive rather than automatically feeding every colony.
The objective is simple: colonies should enter fall with enough reserves to remain healthy even if natural forage becomes scarce.
5. Support Brood Production When Necessary
September bees are important because they will help carry the colony into fall.
When natural pollen becomes scarce, brood production can decrease significantly.
Depending on colony strength and local forage conditions, a pollen patty can help support brood production. The goal is not to force the colony to grow indefinitely, but to help maintain a healthy population as summer forage disappears.
Every apiary is different, so observe what the bees are bringing into the hive before deciding whether supplementation is necessary.
6. Watch for Robbing
As nectar becomes scarce, robbing pressure increases.
Strong colonies may begin attacking weaker colonies, particularly when syrup, exposed honey, or open combs are present around the apiary.
Avoid leaving honey or syrup exposed during inspections. Work efficiently and do not leave colonies open longer than necessary.
Reducing entrances on weaker colonies can also make them easier to defend.
7. Start Thinking About Fall — Not Winter
In Northern California, September is not winter preparation in the traditional sense.
We still have many warm days ahead of us.
But September is the month when I start positioning colonies for the next phase of the season: healthy queens, sufficient food reserves, controlled Varroa levels, and colonies strong enough to move into fall.
The goal is not simply to keep bees alive through winter.
The goal is to have healthy colonies capable of building rapidly when the next season begins.
Final Thoughts
Beekeeping in the San Francisco Bay Area is very different from beekeeping in colder parts of the country.
Our Mediterranean climate gives us a long season, but late summer and early fall can still be challenging because forage becomes scarce while temperatures remain relatively high.
September is therefore a month of observation and preparation.
Check your queens. Evaluate colony strength. Monitor Varroa. Watch food reserves. Prevent robbing.
The decisions made now will influence how your colonies perform during the fall — and how strong they will be when the next beekeeping season begins.