What does Full Sun actually mean?? A common problem is knowing what to plant where. The main issue is that we get plant labels telling us a plant needs part shade or full sun or whatever, and we merrily pop our plant into what we naively think is a suitable position, only to realize months later that it either isnt getting enough sun to flower and fruit, or, more commonly, that it is getting TOO much!!! Full Sun is not a fixed quantity. Technically, the base definition is 6 or more hours of direct sun, with four of those hours occurring between 10:00AM and 2:00PM (strongest sun of the day). But its not that simple.. the sunlight (heat and intensity) is stronger the closer to the equator you get, so those farther south get more energy from the sun in the same time as those of us farther north. At the same time the atmosphere closer to the Poles is thinner and there is less protection from certain wavelengths of the damaging UV rays. A plant that needs full sun in a Cool Temperate latitude may need protection in a Warm Temperate area. A plant that is happy in six hours of sun in a Warm Temperate area will need more direct sunlight in a cooler area in order to flower and fruit... A tropical plant will need as much warmth as it can get when grown further south, but will also need added humidity to protect it. The amount of usable energy from the direct sunlight a plant receives is mitigated by the other climactic conditions such as temperature, rainfall, humidity, and hours of daylight.... So, full sun in Broome is not the same as full sun in Perth is not the same as full sun in Albany.... In order to figure out how much your planting location receives, do the following: Classify the sunlight received before 10AM at 1/2 strength, and the sun after 5PM at 1/2, so every hour before 10 or after 5 counts as 1/2 hour of full sun. Dont count anything within two hours of sunset/sunrise toward the total. Also take into account seasonal variation. An area on the South side of a West facing building can get full sun in summer and none in winter... An area on the East side of a fence or building will be protected from the fiercest afternoon heat while a West facing location will get hammered... Then you need to factor in temperature. Plants in general stop actively growing once the temperature is over 30C. Some actually suffer physiological damage if heat is prolonged. The heat tolerance depends on where the plant originated and what its natural climate is. Many plants that are classed as full sun in their country of origin do perfectly well with only 4-5 hours of sun from 11AM until 4PM in our climate. If they get more than that they may mature prematurely, such as many vegetables do when they bolt to seed.. And some plants that only get to a certain size in their native countries will absolutely love the extra warmth and get a lot bigger and more vigorous here (roses are a perfect example). It comes down to trial and error to really know what works. Labels often try and quantify things like 6+ hours=full sun, 3-4 hours=part sun etc., but really it isnt that simple. It does depend on your particular plant. Another thing to consider is when the area gets the sun. A plant that is dormant in winter wont mind shade all winter but a perennial will. A plant that needs to put on active growth for early flowering needs a certain number of daylight hours, the correct warmth, and amount of sun in Spring.... you have to evaluate the exposure then (when it needs the energy) and not in high summer when it may get more sun but it will be too late for proper development.
Posted on: Thu, 01 Jan 2015 04:10:25 +0000
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