The first, is that it takes 21 days for a worker bee to be born. Honeybees don't take any of the old nest with them, but rather have to build new comb wherever they decide to settle down. That's 21 days where the population is getting lower and lower. So the sooner swarming can occur the sooner they can start becoming productive. The saying around here is "swarm after July, let it fly." This is true enough, but of course all they really need is lots of help. Boosting with frames of brood or already drawn frames of comb, as well as maybe extra feeding, should help any hive along.
The second reason is likely the ever prevalent sources of nectar available to the bees. As early as February all the trees start blooming here. Willows, Maples, Hazelnut, quickly turn into Dogwood, Redbud, Poplar, Oak, Magnolia, Cherry, Basswood/Linden, Birch, and assorted Fruit Trees, such as Apple, Plum, Pear, Peach and so on. Before the end of spring, Honey Locust Trees, and White Dutch Clover will bloom, which are two of the most abundant sources of nectar locally here in NJ.
The abundance of food available makes spring time the easiest for bee swarms. Even before they've found a place to live, hanging swarms send out foragers.
Here Chip Taylor (Chuck?) over at Monarch Watch has caught a swarm using a chemical swarm lore.
I often hear beekeepers proclaim that they're hives are good for the environment. In truth, Apis millifera, is a nonnative species that was imported to aid with mono-cultural farming. Their native range is most of Africa, Europe, and about the western third of Asia. A food crop in their own right, Honeybees have become something of a backyard hobby for community gardens, people with to much land, and even city residents.
So their nectar needs are pretty much filled in the spring time. This leaves people wondering what bees work, or more precisely, what they can plant to help their honey yields.
Asking your local beekeeping association and they'll likely recommend: Purple Loosestrife, Japanese Knotweed, Kudzu, Catmint, Chinese Popcorn Trees. Generally the more of a noxious weed and invasive it is the more honeybees love it. Ask anyone who is environmentally conscious and they'll tell you NOT to plant any of these!
Why Do Honeybees Love Invasive Plants?
This has to do with the way Honeybees communicate to one another.
Minus a strange comment about "if the bee doesn't stop dancing immediately she will be stung to death" this is fairly accurate.
So we have an entire society of around 60,000 bees with many of them acting as foragers. As they find abundant sources of food up to 6 miles away from the hive, they have to return and tell the other foragers what and where they found. Invasive plants tend to take over or be very abundant where they occur. So naturally when they discover such a food source they take full advantage of it, passing over other, less abundant sources in the process. In essence they get distracted. As mentioned before they are used to pollinate farms which are typically monoculars. Despite blueberry plants having flowers that honeybees have trouble with, the bees still manage to persevere and pollinate the plants. In fact honeybees love just about everything that flowers in a vegetable and herb garden.
Understanding these habits is the key to getting honeybees into your garden.
Native Plants Honeybees Love
When planting for Honeybees the 3 to 5 plant rule most certainly applies, more would be better! But all flowers are not created equally.
Liatris, Shooting Star, is a great option. Don't restrict yourself to the mass marketed one sold by the bag in garden centers though. There's nothing wrong with that species but it only flowers in June.
Much taller and later flowering species such as Liatris ligulistylis, are a magnet for Monarch butterflies.
Dalea purpurea, Purple Prairie Clover. There is also a White Prairie Clover that I imagen gets the same amount of attention. I think this is a clump of several plants in this video as I've never known them to get that tall or big.
Tick Seed, Coreopsis sp. Ones that reproduce slowly by seed are best, not only for free plant, but they help compete with grass that is otherwise taking up space.
Rudbeckia sp. These are hit or miss. Some years I see bees going nuts over the Black-Eyed Susans and on other years they could care less.
Anis Hyssop, Agastache foeniculum.
Hypericum sp. has wonderful puffy yellow flowers that produce rich amounts of pollen bees can’t resist. H. punctatum and H. pyramidatum are herbaceous perennials. H. prolificumis a deciduous shrub that gets to be about 4’ by 5’in diameter. Be afraid of H. perforatum,which is an imported noxious weed!
Eupatorium coelestinum, Blue Mist Flower, is a smaller species that blooms towards the end of summer. I haven't had it for very long but I've found honeybees enjoy it. I've read however that it's a tad aggressive.
As we move into fall Asters become a main source of nectar. Something to note though is that Aster was recently divided into 7 genera, that are all now Asters in common name only. The genus Symphyotrichum is the main one you want to pay attention to I've found, S. novi-belgii, New York Aster, is one I like but can't seem to come back year after year.
Aster oblongifolius is one I'm trying this year. It blooms in November, very late in the year! But it has a natural domed habit so no falling over.
Goldenrods are the second big plant now, if not the biggest plant! Beekeepers are on the fence with these as they're great nectar sources, but also make a honeybee hive smell like a gym sock, which the bees don't mind. The honey tastes good, but has a tangy fragrance. Typically the bees will have eaten these stores over the winter if left alone.
The other thing about goldenrods is the majority of species are aggressive. Often they'll spread by root suckers. People who restore and maintain prairies for a living often shun Canadian Goldenrod for this reason. And honestly there's enough of it colonizing roadsides and areas around major power lines that it's not essential to anyone's garden. Still though I've added a few good choices that are at least easy to control.
Solidago altissima, Tall Goldenrod, is NOT one I recommend for the garden. I have it in my own garden but only because it blooms in October through November when almost nothing else is in flower. Naturally it gets covered in bees and I even see queen bumblebees working it in preparation for next year.
This plant started as just one cane coming from the ground. Year two that turned into about 7, and it's been sending up 7 to 12 more canes every year now. Despite being aggressive though I've found the root suckers are simple to weed. Cutting them off at the tip causes them to grow out from the sides of where you just cut, so you can sort of herd it to grow like a box and pull up what you don't need.
Another honorable mention should go to Vernonia sp., Ironweed, which I don't have a picture of so here's a google image search. They're also a hit with butterflies as well as bees.
Thistle is also good for bees but sadly I've found all species to be aggressive spreading, covered in thorns, and the very definition of what a weed is.