It's that tree again

In a previous blog I mused on the tree species Acer negundo or box elder. It cropped up again (my friend Serendipity at work again) in another context, that of pollination. But let me, as always, digress. My earliest proper beekeeping was at the college of agriculture in Aberdeen, where the biggest challenge was getting the bees in good condition through winter. We fed generously in autumn, we insulated the hives, we provided a microclimate kinder than conditions even a few metres away, and made sure that the colonies went into winter strong, heathy and queen-right. And as spring started to appear, we beekeepers were probably as excited as the bees. We concentrated on growing plants that would give early sources of pollen - crocus, snowdrop, hellebores and especially willows. (Now there's an interesting topic, willows, which I will certainly come back to.) The willows, several species chosen to give a sequence of flowering, were by far the most copious yielders, and really kick-started the spring build-up. I spent many happy hours watching bees on willows...

...and recently someone asked me why bees work wind-pollinated flowers, such as willow. That had me stumped, but I think the argument goes as follows. Wind-pollinated trees typically have catkin-shape male flowers which produce enormous amounts of light and dry pollen that is not particularly nutritious as far as bees are concerned. The female flowers carry sticky stigmas which catch pollen grains which are blown in their direction. It's a bit hit-and-miss, but nobody could deny that it has been a successful strategy for millions of years (billions even? - I need to check). The willow family changed over to partial insect-pollination by investing energy in creating attractive pollen (sweet, protein-packed, colourful and aromatic) while retaining the typical wind-pollinated flower shape.

It's not only the willows that have adopted this tactic, the Acers have as well, such as our sycamore and plane. So far so good. Now, let's go back to our cryptic box elder. According to D. M. van Gelderen (Maples Of The World), Acer negundo is in the process of changing its mind anthropomorphically speaking. Having started out as wind-pollinated plant, it changed to insect-pollination and now seems to be going back to wind. How strange is that? What environmental pressures is the species responding to?

Bee hotel

But let's get back on track. I really should be talking about bees. What I would like to do is share some of the fun of a year of looking after solitary bees, and this is a good point to start. I have a nest provided by Robin Dean of the Red Beehive Co. as shown in the photo. It contains tubes of several different sizes and has been well-occupied by several species of cavity-nesting solitary bee.

Mason bee and leaf cutter cocoons

I could just leave the nest in the garden all winter, but it is instructive to open the tubes and identify the contents. That also gives me the chance to remove any parasites and pests. When I have done that, I identify the individual cocoons by placing them in marked tubes and place them in the fridge until spring, as in the second photo.

Cocoons in tubes for over winter storage in fridge

In my next blog I will show the results of opening this nest and discuss winter management.