Some areas of eastern England get about what parts of Southern California get for annual rainfall: 15 inches (38 cm). But rainfall isn't everything--there is the number of sunny days, and there are winter temperatures, summer heat, and relative humidity to consider as well, along with the distribution of the rain over the year, pH, soil composition, drainage, prevailing wind, and on and on.
How dry is dry enough? I found out with my tiny Echeveria plants. I put them on a highly visible sloped spot by the stairway where I could dote upon them every time I went up and down the stairs. Afternoon shade; perfect drainage, what could be better?
There are Echeverias in there somewhere. My doting opportunity became instead guilt-inducing every trip past this spot:
They didn't grow at all, remaining about 1 inch (2.5 cm) wide. At first I thought it was my fault for having left them in a pot for too long, until one day I left a slightly leaky hose dripping slowly at the top of the slope, The soil became thoroughly moist down to a depth of about 2" (~5 cm). Within just a few days they were double the size. Instant growth. The poor long-suffering baby Echeverias had only been waiting for water--enough water.
The light sprinkling they were getting from the irrigation system wasn't doing it. I checked the average annual rainfall of Oaxaca State, Mexico. Oaxaca, besides being fun to figure out how to pronounce, (Wa-ha'-ka) is pure paradise for Echeverias. Oaxaca is home to more Echeveria species than just about anywhere else on earth (including the shelves on my patio). It has an average annual rainfall of 750-800 mm (29.5"-31.5") or about double of what we get, and about triple of what I thought Echeverias get.
Now I know.
A plant that wanted water:
As to tomatoes, this is still August, therefore they continue. Another day, another round of picking. This 'Mortgage Lifter' weighs 25 ounces (700 mg).
Crude (very crude) calculations lead me to believe that one tomato contains about a pint and a half of water. I'm impressed. Somehow or other the tomato plant managed to suck at least a pint and a half of water out of fairly dry ground to produced that fruit, and the plant had many fruits. Where did all that water come from? I'm giving six tomato plants combined a couple of gallons of water a week; not more than that. Are they stealing it from the Echeverias or something? Killing and sucking the blood of gophers? (Now that's a good idea. Tomato plants that did that would sell like crazy! )
Different day, different tomatoes:
The lovely thing about plants is that the more you learn about them, the more impressive and amazing they become. Plant lovers are generally level-headed and modest people. Must be the plants that make us so. I know in my case, those are virtues I would have been unable to come up with on my own.
The Plumeria don't get much water either. Is that why it's stingy with flowers? A new mystery to investigate.
Anyway, sorry about the crappy photos. They just were not turning out yesterday. It was too hot to take more than one quick shot of anything. Is this any better?