Timing of Bloom in Bulbs
Mary Sue Ittner (Sat, 17 Jun 2006 09:22:05 PDT)

Dear Judy,

Observing the California bulbs, most bloom in spring or early summer. If
they started into growth in fall rainfall is hit or miss so even if this
was a good time to bloom it's not really a good time to start growing. In
South Africa many of the winter rainfall amaryllids bloom in fall since
they have seeds that germinate very soon and they will need a nice wet spot
in the ground for awhile to grow or otherwise the seed will die and there
would be no new plants. This isn't going to happen in spring or summer in
those areas. Some of the other families that have seed that isn't
recalcitrant bloom in spring or summer. Even some of the fall bloomers from
South Africa in other families like the Hyacinth family don't have ripe
seed until later, but many of them are from very dry areas so rainfall to
destroy seeds isn't as much a factor.

Where I live the wet humid weather often causes disease in the flowers in
winter and early spring of the bulbs and the seed pods I grow that are not
native so blooming in late spring or early summer as most of them do not
only assures that pollinators will be out as you don't see many pollinators
when it is raining, but also assures that the seeds won't rot. Many of the
flowers in the Brodiaea complex (Dichelostemma, Brodiaea, Triteleia) and
even the Calochortus bloom as their leaves have withered, especially in a
dry year.

I added a picture my husband took of a field of Brodiaea elegans he came
across near Auburn, California, in June. You can see it on the wiki
Brodiaea page:
http://pacificbulbsociety.org/pbswiki/index.php/…
The grass it was growing in had already turned brown. Seed is yet to come
but pollinators are plentiful.

So I think it has to do with survival techniques. They bloom when they have
the best chance to have seed be pollinated and survive to grow new plants
in the future. There will always be exceptions that don't make a lot of
sense, but I suspect generally this will explain the majority of cases.
This fits with what John wrote too.

Mary Sue