Looking out my window, I can see many dozens of mature Douglas-firs. By this time of year, I expect to see green cones developing. But I haven't seen a single one!
Where are they? Please send your own observations and comments.
Maybe the green cones are late this year. Maybe I'm overlooking them. Maybe there aren't any. Other possibilities?
If there are no green cones in an entire area, why would this be? One reason could be this:
Conifers generally produce a heavy crop of cones only once every several years (sometimes called a mast year).
In between, the trees produce moderate or light crops or even no cones. The number of years in a cycle depends on the species.
A cycle for Douglas-fir is typically 5 to 7 years long.
Some scientists believe one reason for these cycles is to keep the rodent population in check.
A series of years with low-or-no seeds sustains a small, stable population of rodents.
Then, a heavy-seed year overwhelms those rodents with more seeds than they can possibly eat, ensuring that some new seeds can germinate.
There is no complete agreement yet on how trees coordinate their plans.
The methods may include release of scents or pheromones in the air and/or through roots, including through mycorrhizae.
Could this be a no-seed year for Douglas-firs in my area? Only further investigation will tell ...