What's Blooming in February?

For a few months this year, we’re taking a look at what is blooming, month-by-month here in the San Francisco Bay Area. These are not necessarily native plants, but plants or trees that are at home in our Mediterranean climate. They enliven the landscape with their early blooms.

Because of El Niño, we are having a wet and warm winter. After a long stretch of rain, followed by several weeks of warm, balmy weather, many trees and plants are starting to bloom. Some specimens may be blossoming a little ahead of their usual schedules, and some may be putting on an extravagant show to ensure reproduction after a four-year drought.

Prunus spp. in Oakland, CA

Rosmarinus officinalis in Dublin, CA

Along Highway 13, the Acacia are in full golden bloom; and along Interstate 580, through San Leandro, the naturalized Prunus are starting to bloom. I think I even spotted a Ceanothus with an early wash of blue flowers emerging. In Dublin, the Prunus are surprisingly late, but the Rosmarinus that is used for street planting is awash in indigo blooms. Closer to home in Oakland, the Helleborus is still producing flowers; the Camellias are going strong; and the Muscari are starting to amass. What a show!

Helleborus spp. in Oakland, CA (can you name those flower parts?)

Birds and Bees – Flower Parts

If you’re going to study something, it is a good idea to learn its terminology. Terminology gives you a common language for talking with others; searching for information; and understanding new concepts. Before we delve into plant propagation this year, let's learn the names of key plant reproductive parts, and what they do. I’m turning to one of my favorite references, How to Identify Plants, written by H.D. Harrington, and illustrated by L.W. Durrell; and using this diagram by Maria Ruiz.

Mature flower parts (by Maria Ruiz, public domain)

Plant reproductive morphology—the study of the physical form and structure of plant parts that are related to sexual reproduction—is complex and varied and fascinating. To narrow our scope, let’s start with basic flower parts for a complete (has sepals, petals, stamens, and pistils present) and perfect (has both stamens and pistils) flower. See, it is already complex!

Structure	Description
PISTIL	The seed-producing organ, or female reproductive parts (think, “pistil-packing mama”), consisting of: Stigma – the part of the pistil that receives pollen, typically near the apex. The stigma may be hairy, protruding, or sticky. Style – the stalk-like part of a pistil connecting the ovary and stigma. In summary, the pollen grows through intercellular spaces in the pistil to create a tube, through which fertilizing sperm cells can travel to reach the eggs, or ovules. Ovary – the part of the pistil that contains the ovule. The ovary may have a single chamber, or locule, or many. Walls, called septum, separate locules. Each locule contains one or more ovules, connected to the placentae in various configurations (such as parietal, axile, basal, or free-central). The diagram shows an axile placentae. Ovule – the structure that develops into a seed.
STAMEN	One of the pollen-bearing organs of a flower, or male reproductive parts, consisting of: Anther – the pollen-bearing part of the stamen. Filament – the thread-like body that supports the anther. Microsporangium – the container structure that holds small spores or microspores.
PERIANTH	The flower envelope, or “bling” that lures pollinators, consisting of: Corolla – the inner series of the floral envelope; a collective name for petals. Calyx – the outer series of the floral envelope, especially when it differs from the corolla in size, color, or shape. Sepal – part of the outer whorl of the flower envelope, or calyx, which is usually green.
PLUS	Plus a few more terms: Floral axis – a modified stem which bears the essential reproductive organs (like stamens and pistils), and supportive organs (like sepals and petals). Nectary – a gland or tissue that secretes nectar. Nectar attracts pollinators, and provides them with nutrients (in a mutually beneficial exchange). Articulation – a joint or node between two separable parts, like the pedicel and the flower. Pedicel (Peduncle) – these terms are sometimes used interchangeable for the stalk to a flower, but Harrington uses this distinction: (1) Pedicel – a stalk to a single flower of an inflorescence (a complex flower configuration); and (2) Peduncle – a stalk to a solitary flower or an inflorescence).

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Well, that is a great start on terminology for complete and perfect flowers (those that come fully loaded with all reproductive flower parts), versus other interesting configurations. Once we master these terms, we can tackle terms for some of these fascinating variations.

Discriminating Squirrels

Last fall, I noticed the squirrels were leaving many acorns from our Quercus agrifolia on the ground, rather than stashing them. Typically they grab nuts as soon as they fall, scamper to a hiding place, glance around, and then quickly bury the nut. Sometimes they double-back, dig up the nut, and rebury it somewhere else. Instead, they were ignoring many nuts, and burying only a few.

Acorns from Quercus agrifolia in the Bay Area.

Naturally, this behavior change caught my attention. My folks were visiting from Alaska, so we launched an investigation. The first thing we noticed is that almost all of the ignored nuts had a bore hole in them. My dad split open a healthy nut, and several nuts with bore holes. The unhealthy nuts were filled with frass, but no inhabitants.

Acorn with a bore hole.

Two insects that target acorns in the San Francisco Bay Area, are filbert worms (Cydialatiferreana) and several species of filbert weevils (Curculio spp.). After mating in spring, the female filbert weevil drills a small hole in an immature acorn, and inserts her eggs; the female filbert worm lays her eggs on the outside of an acorn, and the larvae bore into the nut. In both cases, the larvae develops and feeds in the acorn, leaving its frass; and then bores out in the fall, moving to the soil until spring. The number of infected acorns varies by year, environmental conditions, and the individual tree. The infestation does not harm the tree, but the acorns are infertile.

Left: healthy acorn. Middle and right: infested acorns.

Interestingly, birds and squirrels can discriminate between the healthy and infected acorns. Much like humans, they separate the infested nuts, and preserve the healthy!

Learn More:

• Filbert Pests in Live Oaks (prepared and edited by John M. Harper, Richard B. Standiford, and John W. LeBlanc)
• Pests of Acorns (prepared and edited by Richard B. Standiford and Pamela Tinnin)

Sex in the Garden

As mentioned in an earlier post, I plan to learn about plant propagation this year. I don’t have a specific course of study in mind, but want to learn more about plant reproductive morphology; how plants reproduce, both sexually and asexually; about their pollinators (that’s where the birds and the bees come in); and how to take advantage of this knowledge to grow plants. Basically - sex in the garden!

Digital microscope with azalea images displayed on a computer monitor

For Christmas, my husband gave me a digital microscope with 250x magnification from Plugable. Using the microscope, a USB connection, and a viewer running on my computer, I can zoom in on minuscule flower parts to see incredible detail, and then take pictures, movies, or time lapse sequences. For very little money, I can explore the micro world from the comfort of my own home and garden!

Azalea leaf and bud	Cutaway of an azalea flower bud
Developing petals and reproductive organs	The stigma, the tip of the pistil that receives pollen

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Above are some of the close up shots I took of an azalea leaf and bud in January. I still need to hone my skills, like focusing and lighting the subject, but you can see the potential. This digital microscope will definitely be in my toolkit as I take on plant propagation this year!