Author Archives: John Chau

About John Chau

John studies plant evolution at the University of Washington and is excited to explore the diversity of botanical phenomena in the city and in the field.

Pikes/Pines | Beautiful monsters

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A double rose (Images: John Chau)

A double rose (Images: Jon Chau)

Since ancient times, people have cultivated plants not just for simple utility as sources of food, medicine, fiber, dyes, and other materials, but also for their beauty and the pleasure it brings into our lives. In the course of selecting for plants that are ever more attractive in their growers’ eyes, people have promoted plants with bigger flowers, brighter colors, exaggerated patterns, and larger displays.

Although these changes arose naturally by genetic mutations, such oddities likely would not have persisted for long in the wild since the ability of the plants to survive and reproduce may be compromised. Fortunately for these mutants, humans and human-dominated environments have become an important part of the earth’s ecosystem, and organisms that are able to catch human fancy can increase in abundance and become successful through their human benefactors.

A prime example of a plant favored and propagated by humans can be seen on practically every block of Capitol Hill at this time of year: the rose. Continue reading →

Pikes/Pines | A surge of spurge in Capitol Hill gardens

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Mediterranean spurge (Euphorbia characias)
(Images: John Chau)

Popping up here and there in gardens around Capitol Hill are the flowers of a plant that seems to have come from a Seussian landscape. With beautiful evergreen blue-green leaves and now topped with large clusters of striking chartreuse disks, these spurges (Euphorbia) are popular shrubs for adding a bit of dramatic flair to yards and planters.

The most commonly planted species is the Mediterranean spurge (Euphorbia characias), native to southern Europe, but several other species in the genus, including wood spurge (Euphorbia amygdaloides) are occasionally seen.

(Image: John Chau)

(Image: John Chau)

So what exactly are those chartreuse disks? Flowers would be the obvious answer, but take a closer look and they don’t appear quite like what one would expect.

A typical flower has petals, stamens (the male parts producing pollen), and a pistil (the female part producing seeds) inside. The spurge has something that looks similar, but each disk actually holds a collection of multiple flowers. The disk is a bract, or modified leaf, and above the bract are very small flowers and oftentimes a pair of additional bracts, each with its own cluster of tiny flowers. Each flower is highly reduced and consists of just a single small yellow stamen or a single green 3-lobed pistil. The unisexual flowers are surrounded by brown or yellow glands which produce nectar. This very unique arrangement of flowers is called a cyathium and is found throughout the genus Euphorbia.

You have almost certainly seen a cyathium before. The genus Euphorbia is among the largest in the plant kingdom with about 2000 species, and one of those is that favorite Christmas plant, the poinsettia (Euphorbia pulcherrima), which has cyathia above bright red bracts.

Each bract may hold its own pair of bracts in addition to a cyathium (Image: John Chau)
Cyathia of poinsettia (Euphorbia pulcherrima). The female flower is green and 3-lobed. (Image: Wikimedia)
Torn leaf oozes milky-white sap (Image: John Chau)

Another interesting feature of the spurge is found in the leaves and stems. When they are broken or damaged, they exude a milky-white and sticky sap that offers the plant protection against herbivores. The sap is toxic and irritating, and gardeners working with the plant should take care to avoid prolonged exposure on the skin. Milky sap, or latex, is common throughout the relatives of Euphorbia.

The latex of another species in the Euphorbia family, the rubber tree (Hevea brasiliensis), is tapped to make natural rubber.

 

Pikes/Pines | Queens of spring: flowering trees around Capitol Hill

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An ornamental pear in bloom (Images: John Chau)

This week we welcome new CHS contributor John Chau to join Brendan McGarry in bringing you Pikes/Pines, our semi-regular look into the nature of Capitol Hill.

Spring has bloomed. With the mild winter this year, the gardens, parks, and parking strips around Capitol Hill have been filled with life and color again for several weeks already by plants in full flower.

Among the most spectacular and noticeable of these early spring bloomers are the trees. The most common and showy ones are generally either magnolias, which have large flowers with many petals, or members of the rose family. The rose family is a large and important one that can be easy to recognize if you remember that their flowers typically have five petals and many stamens. Three popular trees in this family in bloom now are the ornamental pears, flowering plums, and flowering cherries.

Ornamental pears
Ornamental pears, seen above, are among the first to flower. They generally have white flowers and green leaves that appear when the flowers start to fade. Most ornamental pears belong to one species, Pyrus calleryana, which is originally from Asia. They are commonly called Callery or Bradford pears. Continue reading →