Tuesday, October 30, 2018

Leaf Cutter Bees

A week or so back I was delighted to see the chewed margins of this pipevine (Aristolochia sp) leaf. Chewing is usually cause for alarm in the garden, but in this case it is evidence of leaf cutter bee activity, something to be welcomed.


A Leaf Cutter Bee Was Here!


The species I see could well be native to Florida. It also could be Megachile rotunda, the "alfalfa bee," imported into the U. S. after the 1930's to: you guessed it! pollinate alfalfa fields. Honeybees are not efficient pollinators of alfalfa. This useful little critter has spread since then to much of the U.S.

The family of leaf cutter bees, Megachilidae, contains at least 2,000 species, and occurs virtually worldwide. Around 63 -75 species can be found in Florida alone. Another common leaf cutter bee, the "mason bee," Osmia sp., constructs its egg chambers with leaves and mud. Osmia bees are produced commercially and can be ordered over the Internet.

The Megachile bee is about the size of a honeybee. It does not sting unless provoked, and the sting is said to be less painful than that of a honeybee. It is somewhat chunky, with black and white bands on the abdomen and black on the upper thorax. Both sexes are generalist pollinators - they like just about everything. Only the female nests. Instead of packing pollen into leg pouches like honeybees, she carries it on the underside of her abdomen.




Megachile on Heliotropium polyphyllum 


She will nest in just about anything the right size and shape - oarlocks, unused hoses, rotten wood, hollow twigs, burrows, or manmade nesting boxes. In Florida the bees also like holes drilled in stucco for fastening hurricane shutters! Nests in underground burrows don't seem to be affected by short-term inundation, or by getting gradually filled in.

Once she has found a suitable nesting place, the female cuts a round bottom plug, and then builds up the chamber with overlapping oval pieces of leaf. She cuts  these sections out of leaf margins one at the time. She works smoothly and precisely, taking only a few seconds. She's so fast that you're lucky to catch her in action. She carries the leaf section slightly curved, under her abdomen, to her nest. I've timed a bee in action, from entrance to exit from burrow.  She takes 60 to 90 seconds to get the new leaf section in place.


Megachile Carrying Oval Leaf Section


When the chamber is complete she packs it with a mixture of nectar and chewed pollen, lays a single egg, and departs to cut the circular seal, or plug. This is when the closely related cuckoo bee. Coelioxys sp., may make her move. She crawls into the nest, and lays her egg, which will hatch and eat both pollen and competing larva.

The  Megachile bee makes a series of chambers, one atop the other. The resulting cylinder is said to resemble a cigar somewhat. It would have to be a cigar no bigger in diameter than a straw. I extracted one from an oarlock one year and kept it in a dish. After a month or so, a faint, persistent buzzing told me that something was happening, and sure enough, one bee, followed quickly by another, emerged. At this point I took the bees and the rest of the cylinder outside where they belonged.

Leaf cutter bees live only a few months. The female dies after she completes her egg-laying. The larva pupates and overwinters in the nest as an adult until it emerges in the spring.



Megachile on Goldenrod


If you're trying to grow a prize rose or dahlia for exhibition, the leaf cutter bee could be a nuisance. Otherwise, since they are solitary, not part of a colony, the damage they do is minimal, and I think just adds interest.

There is a wealth of information on the Internet about leaf cutter bees. The Honeybee Conservancy site has great info, pictures and video. Click the following link to get to the site. leaf cutter bee. The University of Florida also has a good article. Go to edis.ifas.ufl.edu/in619. Another of my favorite sites is from the BeeInformed organization. https://beeinformed.org/2014/07/30/alfalfa-leafcutter-bee-.


Megachile Work on Gopher Apple, Licania michauxii


Honeybees  have the reputation of being the best crop pollinators, but that is not necessarily the case. Our native bees are vital in the pollination of crops, ornamentals and our native flora. I don't know whether the one in my yard is a native or the imported alfalfa bee, but either way it is more than welcome.


Tuesday, October 9, 2018

Sedges and Swales


I have been weeding in the swale - a 12-15-foot wide area between the property line and the street. It is county right-of-way, but the homeowner has to "maintain" it, i.e. nothing over 18 inches tall. People with lawns generally just let the grass grow to the street, but there was no lawn when we bought the house - just rocks - and there's no lawn now because we went with mulch instead of grass. The swale itself is covered with coarse drainfield rock, and, lamentably, many weeds.

Swales are designed to collect and hold rainwater so it filters down through layers of sand and soil to the groundwater below instead of running directly into a body of water or open land. The  middle of the swale, the lowest point connected to our lot, retains some soil moisture even in the dry season. The rock also helps keep the underlying soil relatively cool and moist.

It's no accident that a lot of things want to grow here, especially since the swale is located under the utility lines and gets daily contributions from the birds. Years ago I planted the iris relative blue-eyed grass (Sisyrinchium angustifolium) along the property line, but it migrated to the swale, which it liked much better, and has flourished and multiplied ever since.



Blue-eyed Grass, Sisyrinchium angustifolium


But so have the weeds. In theory you should not pull weeds, because that further disperses their seeds. Cutting them back before they bloom or killing them with herbicide aren't always options for me here, because the grasses and grass-like weeds grow right next to, or even within clumps of the blue-eyed grass, so I end up teasing them out, one by one. It sometimes feels like weeding with tweezers. I just hope that by persevering I eventually will have a blue-eyed grass meadow.

The grasses and sedges are the most troublesome weeds in the swale. They often superficially resemble the blue-eyed grass, and as I mentioned, are competing for the same turf. I really have to pay attention so that I don't inadvertently yank out clumps of the good stuff.

 I decided to draw a few of them, and then id them - fat chance! The sedge family, Cyperaceae, contains at least 5,000 species, and the genus Carex, the "true" sedges, has over 2000 species. The study of sedges is so complex and specialized that it even has its own name - caricology.

With botanical drawing you sort of have to know what you are looking for before you go looking for it, and I didn't read anything on the sedges until after I had drawn them, so I didn't collect enough detail for anything certain. About all I knew was the mnemonic, "Sedges have edges." Members of the genera Carex and Cyperus both have 3-angled stems.

As far as I can tell, I didn't find any Carex species on this first go-round.

The plant below might be Cyperus surinamensis,  and then again, it might not be. If I've identified it correctly, it's native to Florida.



Cyperus surinamensis ? - Flatsedge



The same goes for the sketch below. I simply didn't collect enough information for an id. Just going by superficial resemblance the closest candidate so far would be Cyperus croceus, "Baldwin Flat Sedge." This species is also native to Florida, but whether it's the one below is an open question.



Cyprus croceus? - Baldwin Flat Sedge?






The black-and-white drawing below is a species of Kyllinga, an exotic weed. Due to close similarities, botanists have folded this genus into Cyperus, so newer descriptions would list it as Cyperus brevifolius. This paraticular species  grows in mats in the wettest part of the swale. It stays short, definitely under 6 inches tall, and usually much shorter.


Yellow Nut Sedge? and Green Kyllinga




I am most confident about my last sedge. I'm pretty sure it is Cyperus rotundus, "purple nut sedge,"  or "purple nut grass."This species is sometimes called the "worst weed in the world," because it is so hard to eradicate. Though it's not my most troublesome weed, I have to patrol for it least weekly, or it would take over. You have to pull it low to the ground, or else the top just breaks off, and the plant regenerates from the rhizome.  Sometimes, if the soil is loose enough I get a long piece of the rhizome, and as I pull out one plant, another, a few inches away, disappears underground and comes up with the first one - really cool when it happens. Kind of like a botanical magic trick. Plants that haven't bloomed yet make good compost.



Cyperus rotundus - "Purple  Nut Sedge"


Last but not least, in my first foray, is Fimbristylis, another genus in Cyperaceae. It sometimes is called "fimbry" or "fringe rush." I have several species in the yard. I don't know what the one below is. The Fimbrystilis in our yard are rather attractive. They grow in tidy, basal clumps, and their small, pale brown "heads," with a bluish fringe between scales are pretty. I tried leaving some in the swale, but it quickly got out of hand. I may pot some and place them in one of my bog gardens to see if they can be controlled.



Fimbristylis Species





I have yet another sedge in a vase, waiting for me to draw it. I don't know whether it is another species, or just an immature specimen. It's quite ornamental, actually. I have a sneaking suspicion that I am getting slightly hooked on the Cyperaceae family. There are many sedges available in the nursery trade, but mine are scarcely likely to be among them.