Friday, July 18, 2014

Survival of the Fittest Onion

Onions are biennial plants. This is how they work:

Life Cycle of an Onion Plant
Year 1, Spring:Seeds germinate and start to grow.
Year 1, Summer:First the leaves sprout, then the bulb at the base of the plant begins to swell.
Year 1, Autumn:The bulb, where the plant stores food reserves for the winter, reaches maturity, but the foliage dries up and dies. This is when the onion bulb is usually harvested.
Year 1, Winter:If left undisturbed, the bulb lies dormant all through the cold months.
Year 2, Spring:Answering the call of the springtime sun, the bulb sends forth a shoot which initially feeds on the food stored in the bulb, then sprouts leaves which aid in photosynthesis.
Year 2, Summer:The stem "bolts" (begins to elongate rapidly) and produces a bud. The bud blooms into a flower, which eventually "goes to seed".
Year 2, Autumn:The plant dies, but next spring the seeds can grow into new plants.

Last spring I bought some onions from the supermarket and stored them in my kitchen cupboard. The cupboard is a dark, airless place, but even in such harsh conditions, life prevails. A few days later I discovered that one of the onions had begun to sprout.

Impressed by its will to live, I decided not to chop it up, and instead planted it in a pot.

The plant was undemanding – I just watered it every other day and fertilised it with coffee grounds. Still it grew steadily, putting forth leaves and in May, a pair of buds. But its tribulations were not yet over.

While I was on holiday in the USA, the pot was blown over by the wind. The plant lay ignominiously on its side, but undeterred by this misfortune, it bent upwards at a right angle and continued to grow. When I righted it, the stems – always reaching for the light – again bent upwards at a slightly higher point, giving the plant an interesting shape, a bit like a modernist sculpture. Here are some photos of the flowers in various stages of development.


At the time of writing, the flower petals are drying up. If the flowers have successfully self-pollinated, they may soon produce seeds. I think it's pretty cool that an onion bulb can flourish and reproduce even after being uprooted, sold in a supermarket and lying neglected in a kitchen cupboard.

Thursday, July 3, 2014

Lone Fox Dancing

I have previously posted about foxes in winter and foxes at night. In the interests of more well-rounded fox coverage, I now present a photo of a fox in summer, and in the daytime.


I took the photo inside our housing development, where red foxes have burrowed into the earth to make a den whose entrance is concealed by bushes.

The titles of my first two fox posts referenced a song (Fox in the Snow) and a book (The Foxes Come at Night). Last week at an outdoor cafĂ© in London I saw a notice which would have gone really well with the second post:


In case you were wondering, the title of the post you are reading now references a poem: a reader suggestion.

Monday, June 30, 2014

Flagging Demand


England car flags being sold for a discount at a supermarket in London, after England's first-round exit from the Football World Cup.

If I had any sense I would buy the lot, and sell them before Euro 2016 at a 700% profit.

Saturday, June 21, 2014

Seasons: Island Gardens, London

Move your cursor over the image below, and it should change to another image of the same scene in a different season. (If it doesn't work, check that your browser has JavaScript enabled.)


Base photo:31 May 2014
Mouseover photo:13 November 2011
Approx. coordinates:51.487°N, 0.008°W

One day in the autumn of 2011, I mentioned to my cousin that lots of people walk their dogs in my neighbourhood park. She likes dogs, so she asked for photos. The mouseover photo in this post is one of the few photos I took that day which does not have a dog in it. Summer is my favourite season in London, but there's no denying that the sugar maple trees in the park are at their best in autumn.

The base photo was taken last month, but I thought summer solstice is as good a day as any for a Seasons post.

Happy solstice, everyone!

Friday, June 20, 2014

The Roti Algorithm

Rotis (by which I mean the thin, circular rotis cooked without oil, called ruti in Bangla) are made by rolling atta (unleavened wholegrain wheat) dough into thin circular disks, which are then cooked over a dry tawa.

Cooking one roti at a time is inefficient because firstly, you waste time placing each roti on the tawa and then taking it off, and secondly, by the time the last roti is cooked, the first one is no longer warm. It is possible to cook several rotis on the tawa simultaneously, but to be properly cooked, each side of each roti must be in contact with the tawa for roughly the same period of time. Like most experienced roti-makers, my mother achieves this by flipping the rotis in a complex sequence. But when I asked her, she could not tell me what exact sequence she follows, because the technique, born of long experience, comes naturally to her.

So I gave some thought to the problem, and came up with an algorithm for cooking any number of rotis on the tawa at the same time, thus bringing advanced techniques within the grasp of even the most hapless roti-noob.

The algorithm is best illustrated by a flowchart:


A couple of definitions which are used in the flowchart or later in this post:
"Lowest Side" means the lower side of the bottom roti in the stack (i.e. the side in contact with the tawa).
"T" means the time taken to cook the Lowest Side, and is counted from the instant of completion of the most recent flip of all the rotis in the stack.

Some notes on the algorithm:
As it is inconvenient to flip or remove rotis which are in the middle or bottom of the stack, I designed the algorithm so that (a) the flip operation only involves flipping either the top roti or the whole stack, and (b) once a roti cooked on both sides, the next action always brings it to the top of the stack whence it can easily be removed.
On high heat, the Lowest Side gets cooked before it can conduct much heat to the roti above it. So while the Lowest Side is being cooked, the states of any rotis above the bottom roti are not significantly affected.
To make multiple rotis at once, the dough has to be fairly dry so that the rotis in the stack do not stick to each other. If they're still sticky, it helps to spread a thin film of dry atta on each roti.
It is rarely necessary and never practical to cook more than 5-6 rotis at a time, because the time thereby saved is offset by the difficulty of flipping several rotis at once. But the algorithm works for any number of rotis.

The algorithm is actually easier to master than the flowchart might suggest. Once you get the hang of it, the next step is obvious even without referring to the flowchart.

To give you an idea of how the algorithm works, I made a short animated video for 6 rotis. Each side of each roti is represented by a black rectangle, which turns red when it is cooked. T in the video is 1.5 seconds, which is shorter than the actual time it takes to cook one side of a roti in real life. Click on the image below to see the video (0:36).