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Pithy Stems

LoxleyLoxley Posts: 5,698
edited August 2020 in Plants
Sharing a post from a Facebook Page I found interesting:

https://www.facebook.com/beeactivenow



PITHY STEMS

The survival of wild bees depends, among other things, on finding a suitable nesting site as quickly as possible. To achieve this goal, a wild bee constantly scans its surroundings during flight. In doing so, it falls back on its genetically fixed search grid.

For wild bees, which gnaw their nest tunnels into the marrow of plant stems, the key stimuli are single, vertical structures, which then are examined more closely for their suitability as nesting sites.

Then they gnaw into the soft plant marrow a passage for the nest. The fracture or interface allows the bees access.

Only Osmia tridentata is able to gnaw a hole in the side of the woody stem wall.
The natural orientation of the stems is without exception vertical or oblique.
Those who do not leave their garden "broom-clean" for winter in autumn can leave an important habitat for some wild bee species.

The first and most important protective measure is to simply leave the dry tendrils and stems of blackberry (Rubus fruticosus), dog rose (Rosa canina), mullein (Verbascum), etc. and break off or cut off their ends to allow the bees to enter.

If you still want to cut them off completely, you can collect the stems and tie them vertically or slightly diagonally to a pole or garden fence in a sunny spot in spring.
You can also tie them to a rod driven into the ground with wire. Individually standing stems are better accepted than bundled ones.

If the stems are driven directly into the ground, they rot very quickly in the soil moisture and break off easily at the transition point between soil and air.
Cut off blossoming mullein or other pith-containing plants with garden scissors to expose the pith. However, the wild bee offspring will not hatch until the following spring, so the stalks must remain in place at least until then.

Whether they have been colonized can then be easily recognized by the drill holes, either directly at the top of the cut edge or at lateral fractures.
Many thanks for the photos to Nestor Gomez (Huixtan, Mexico)


"What is hateful to you, do not do to your neighbour". 

Posts

  • BobTheGardenerBobTheGardener Posts: 11,385
    Elder (Sambucus niger) is an easy way to source pithy stems in the UK and would seem perfect for this.  :)
    A trowel in the hand is worth a thousand lost under a bush.
  • B3B3 Posts: 27,505
    I throw the long branches on the log pile at the side of the garage. I never thought to look to see if anything had moved in. They're all horizontal, though.
    In London. Keen but lazy.
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