#61 - Aug 2022 - Garden Stuff with - © Sandy Lang - slang@xtra.co.nz
GREENHOUSESAugust/September: Almost spring. Days lengthening. Temperatures rising. •Pruning late, beats not pruning at all – clean, sharp tools, dry weather (disease). •Trees/shrubs. Leaky water pipes, so severe water restrictions this summer, so mulch well now to conserve water. Feed with slow-release fertiliser. •Repot pot plants in new potting mix, in slightly larger pots. Feed with slow-release fertiliser. Greenhouse: A greenhouse (expensive) or a plastic grow tunnel (cheap) - Google grow tunnel - will let you raise young plants weeks earlier in winter/spring. Why? It’s warm inside. Why? Sunlight enters a greenhouse or grow tunnel (or car) through the plastic/glass. It warms the inside surfaces, which warm the inside air. Ventilate, or it’s too hot. Confusion: Oddly, a greenhouse is not warmed by the ‘greenhouse effect’ but our planet is… Sunlight: There’s lots of energy in sunlight. About 1400 W/m² at the Earth's surface. Sunlight is a mix of three sorts of light: •visible (600 W/m²), •infrared (IR) (750 W/m²) and •ultraviolet (UV) (50 W/m²). Your eyes sense only visible light, but your skin senses all three sorts as warmth, and it senses UV as sunburn (next day). Greenhouse effect:. Only a small amount of the sunlight reaching the Earth’s surface is reflected back to space (e.g., by snow). Most is absorbed, warming up the oceans, forests and land. Warmed up, they emit IR light back up. But some components of the atmosphere (greenhouse gasses) are opaque to IR. So, much of this IR light energy is trapped within the atmosphere and reflected/emitted back down again. So, with its greenhouse-gas ‘blanket’, Earth’s average surface temperature is a cosy +13.9°C. With no greenhouse gasses it would be a chilly -18°C. So, greenhouse gasses are good. They stop us freezing solid. But… Greenhouse gasses: There are three main greenhouse gasses: •water (vapour + droplets), •carbon dioxide and •methane. There are many minor ones. These three contribute about 50% (water), 20% (carbon dioxide) and 5% (methane) to our atmosphere’s total greenhouse effect. Global warming (climate change) is mainly due to increased carbon dioxide. It was 310 ppm (parts per million) when I was born, it’s now 420 ppm, and it’s rising fast. Some industrial pollutants also increase the greenhouse effect. The net result is Earth’s average temperature has risen by 0.08°C /decade since 1880 and by 0.18°C /decade since 1980. Scary… ___________________________________
GREENHOUSESAugust/September: Almost spring. Days lengthening. Temperatures rising. •Pruning late, beats not pruning at all – clean, sharp tools, dry weather (disease). •Trees/shrubs. Leaky water pipes, so severe water restrictions this summer, so mulch well now to conserve water. Feed with slow-release fertiliser. •Repot pot plants in new potting mix, in slightly larger pots. Feed with slow-release fertiliser. Greenhouse: A greenhouse (expensive) or a plastic grow tunnel (cheap) - Google grow tunnel - will let you raise young plants weeks earlier in winter/spring. Why? It’s warm inside. Why? Sunlight enters a greenhouse or grow tunnel (or car) through the plastic/glass. It warms the inside surfaces, which warm the inside air. Ventilate, or it’s too hot. Confusion: Oddly, a greenhouse is not warmed by the ‘greenhouse effect’ but our planet is… Sunlight: There’s lots of energy in sunlight. About 1400 W/m² at the Earth's surface. Sunlight is a mix of three sorts of light: •visible (600 W/m²), •infrared (IR) (750 W/m²) and •ultraviolet (UV) (50 W/m²). Your eyes sense only visible light, but your skin senses all three sorts as warmth, and it senses UV as sunburn (next day). Greenhouse effect:. Only a small amount of the sunlight reaching the Earth’s surface is reflected back to space (e.g., by snow). Most is absorbed, warming up the oceans, forests and land. Warmed up, they emit IR light back up. But some components of the atmosphere (greenhouse gasses) are opaque to IR. So, much of this IR light energy is trapped within the atmosphere and reflected/emitted back down again. So, with its greenhouse-gas ‘blanket’, Earth’s average surface temperature is a cosy +13.9°C. With no greenhouse gasses it would be a chilly -18°C. So, greenhouse gasses are good. They stop us freezing solid. But… Greenhouse gasses: There are three main greenhouse gasses: •water (vapour + droplets), •carbon dioxide and •methane. There are many minor ones. These three contribute about 50% (water), 20% (carbon dioxide) and 5% (methane) to our atmosphere’s total greenhouse effect. Global warming (climate change) is mainly due to increased carbon dioxide. It was 310 ppm (parts per million) when I was born, it’s now 420 ppm, and it’s rising fast. Some industrial pollutants also increase the greenhouse effect. The net result is Earth’s average temperature has risen by 0.08°C /decade since 1880 and by 0.18°C /decade since 1980. Scary… ___________________________________