Another breakfast at the Gamble

Yesterday, another breakfast picnic at the Gamble Garden in Palo Alto (report on last week’s event is here). Plants not previously posted on on this blog: one edible, rhubarb, and one ornamental, dahlia. Plus re-visits to pelargoniums (for their scent) and tropical hibiscus (for their showy flowers).

Rhubarb. In its vegetable garden, GG has some truly enormous rhubarb plants. I remembered that they presented an oxalic acid danger, but didn’t quite get all the details right. From Wikipedia:

Rhubarb (Rheum rhabarbarum) is a species of plant in the family Polygonaceae. It is a herbaceous perennial growing from short, thick rhizomes. It produces large leaves that are somewhat triangular, with long fleshy petioles. and small flowers grouped in large compound leafy greenish-white to rose-red inflorescences.

In culinary use, fresh raw petioles (leaf stalks) are crisp (similar to celery) with a strong, tart taste. Most commonly, the plant’s leaf stalks are cooked with sugar and used in pies and other desserts.

… The colour of rhubarb stalks can vary from the commonly associated crimson red, through speckled light pink, to simply light green. [The GG stalks are light green with a dusting of pink.] Rhubarb stalks are poetically described as “crimson stalks”. The colour results from the presence of anthocyanins, and varies according to both rhubarb variety and production technique. The colour is not related to its suitability for cooking: The green-stalked rhubarb is more robust and has a higher yield, but the red-coloured stalks are much more popular with consumers.

… Rhubarb leaves contain poisonous substances, including oxalic acid, which is a nephrotoxic and corrosive acid that is present in many plants. Humans have been poisoned after ingesting the leaves. Such poisoning was a particular problem in World War I, when the leaves were recommended as a food source in Britain.

… In the petioles (stalks), the amount of oxalic acid is much lower, only about 2–2.5% of the total acidity [this is the important fact that I had forgotten], which is dominated by malic acid.


Dahlias. A favorite of serious perennial gardeners, with an interesting genetic twist to them. From Wikipedia:

Dahlia [BrE pronunciation with /e/, AmE with /a/] is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae (or Compositae), dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 2 in (5.1 cm) diameter or up to 1 ft (30 cm) (“dinner plate”). This great variety results from dahlias being octoploids — that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons — genetic pieces that move from place to place upon an allele — which contributes to their manifesting such great diversity.

(Many sources say the plant was named by Linnaeus after his student, the Swedish botanist Andreas Dahl (1751–89), but Wikipedia disputes that.)

The original plants were single-flowered, like daisies or anemones, and these are still widely cultivated. But now there are plenty of dramatically double-flowered cultivars, like this red one, much like some flowers we admired at GG:


Scented Pelargoniums. See my 6/24/13 posting on nasturtiums (Tropaeolum) vs. Nasturtium (to which watercress belongs) – they share a similar spicy oil — and geraniums (Pelargonium, or storksbills) vs. Geranium (the cranesbills), which are related genera in the same family.

Pelargoniums have been bred to mimic hundreds of scents in their leaves — different types of roses and other flowers, all sorts of fruits, spices, etc. A nice sampling of these at GG. All quite intoxicating to touch one plant after another (until sensory overload sets in).

Tropical hibiscus. See my 3/27/13 posting on Abutilon and its relatives, including photo #5 there of a Chinese or tropical Hibiscus, H. rosa-sinensis. GG has quite a few big, stunning pure white Hibiscus (of what species I couldn’t determine). There are a fair number of photos on Google that look very close to the ones we saw — but, annoyingly they all seem to have been taken by photographers anxious to show off their photographic expertise, with no visible interest in the botany of the plants. Here’s one:


(Taken in Key West FL in 2006 by Kent Croy.)

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