July 2018

In a recent ‘Nature Notes’ I talked about seed dormancy and rattled on about tough seed cases and scarification.  It turns out that I was completely wrong – or at least that wasn’t the whole story.  Listening to ‘The Life Scientific’ on Radio 4 recently, I heard Professor Caroline Dean explain the genetic and molecular basis of vernalization, the process that tells the seed when it is spring.  It turns out that seeds have a gene that codes for a protein that keeps the seed in a dormant state.  Cold weather turns the expression of that gene off.  However, it turns the gene off only one cell at a time so that it takes several weeks to turn all the genes off and stop the production of the protein.  This explains why seeds don’t suddenly start to sprout when we get a warm spell in mid-December.  Once all the genes are turned off, then the seed has to wait for all the other conditions to be right – temperature, moisture, day length, etc. – before growing into what should then be spring.  Interestingly, plants grown in colder climates take longer for this process than warmer countries with shorter winters.  So if you take seeds from Sweden and plant them in Spain, they will still need  say 10 weeks of cold weather when the native Spanish plants of the same species need only four weeks.

In last month’s Nature Notes I spoke about how interesting it was watching the solitary bees nesting in our solitary bee hotels.  It turns out that we weren’t the only ones interested in them.  One day we went out to find short bamboo tubes all over the patio, emptied of their content, with a corresponding huge hole in the bee hotel above.  We suspected that a woodpecker had learnt that it wasn’t only crevices in trees that contained juicy snacks, but we were open to other possibilities until further evidence presented itself. 

Note that the box on the right is unoccupied, mainly because the tubes are too big.

We didn’t have long to wait.  A few days later we were rudely awakened at 5 in the morning by a loud hammering on the back wall.  Opening the back door scared the great spotted woodpecker away and saved the bees from further carnage.  We still have two more bee hotels that are so far unscathed but we are seriously considering building some sort of woodpecker-proof cage round them.

While I was looking up woodpecker damage on the internet (of course it has happened to others), I found another interesting fact about solitary bee hotels.  The majority of bees in our bee hotels were red mason bees.  These emerge in spring and will have laid their eggs and died long before the end of June.  However, another group of solitary bees – the leaf-cutters, which are summer nesters – have now emerged and are looking for nesting sites.  If a red mason bee has run out of eggs or energy or life before completely filling the nest hole, then the rest of that hole may be used by a leaf-cutter bee.  (If you find almost circular holes in the edges of your lily leaves, it will be leaf-cutter bees that have taken the bits of leaf to seal up their nest cells.)  The problem with this is that the red mason bees will emerge first and will have to eat their way through the leaf-cutter cells thereby killing their occupants.  Life is tough at the bottom of the food chain!