All plants require sunlight to grow, but differ in the amount and intensity of light needed to prosper. Plant labels identify the amount of sun a plant requires as full sun, part sun, part shade or full shade as defined: Full sun – Plants need at least 6 hours of direct sun daily.
Generally, sunlight is best for plant growth but artificial lighting can improve the quality of light plants receive, improving plant growth. When artificial light is needed to supplement natural light, the spectrum (colors the lamp produces) is important.
Direct sunlight and high temperatures should be avoided as much as possible. This may sound contradictory, because light and heat are essential for the growth of plants, so-called photosynthesis. For an optimal growth there should be a good balance in climate between temperature, light and humidity.
Intensity matters
Sunlight reaches its highest intensity between 10 a.m. and 4 p.m. Morning sun is the least intense. A few hours of morning sun isn't as intense as a few hours of mid-day and afternoon sun, realizing the hot afternoon sun can burn the leaves of some plants, even those of certain sun-loving varieties.
Any amount of sun greater than six hours is considered full sun. What is Part Sun? Part sun is defined as four to six hours of direct sun per day. Not all those hours need to be accrued consecutively—it could mean a few hours of morning sun plus a few more in the afternoon.
If the soil feels dry three or four inches below the surface, water. A common rule of thumb is that most plants need the equivalent of one inch of rainfall a week, on average—enough to soak into the soil about six inches. However, in hot weather, plants may need more.
“Partial sun” or “partial shade” means that the plant needs 3-6 hours of direct sun per day.
The best time to water outdoor plants is in the morning when temperatures are usually cooler. This gives the plants time to absorb the water so they can get through a long, hot day. The second-best time is late in the afternoon or early in the evening. Try not to water at night.
Morning watering is actually preferable to evening watering as the plant has time to dry before the sun goes down. At night, water tends to rest in the soil, around the roots, and on the foliage, which encourages rot, fungal growth, and insects.
The general consensus among experts is that watering plants is best done in the mornings if you can. As the temperature rises and the sun comes out, plants start to transpire and lose water through evaporation. So if you don't give them a morning shower it can lead to parched plants with shrivelled leaves.
The light that passes through a window is considered indirect, as the rays will be diffused and won't have the same intensity. However, it depends on the window. If your window is south facing and there are no obstructions, it can be considered direct light.
Pale green and yellow leaves that drop off are a sure sign of inadequate sunlight. Also, with variegated plants, the leaves will revert to a solid green color so the chlorophyll within can do its job. If your typically colorful plant has lost its color, move it to a sunnier place and see its color return.
Most plants need some light in order to grow, but shade-loving plants can easily get by with indirect light, or even artificial light from regular light bulbs.
What makes the shady side grow faster? It can work two ways. In grasses and similar plants, a growth hormone becomes more concentrated on the shady side, speeding up the growth there. In plants like sunflowers and radishes, on the other hand, a natural chemical slows growth on the sunny side.
In fact, your plant palette isn't limited if your garden is mostly shaded. Many pretty annuals, perennials, and even a few shrubs thrive in shady locations.
Most plants shut down during extreme heat, so if it is over 100 degrees, it may be best to wait to water even if your plant is stressed. Throw a damp sheet over it, or mist it lightly to bring the temperature down.
Rather than misting your plants at night, a morning mist is the perfect way to start your plant's day. Misting in the morning allows plants time to dry off throughout the day. This is important to prevent mildew and other diseases.
If the soil feels dry, it's time to water. In the spring and fall and in cooler climates, it might be sufficient to water container plants every two to three days. In the summer and in warm climates, container plants usually require daily watering, unless they are succulents or other drought-tolerant xeriscape plants.
During really hot weather, water your vegetables at least two to three times a week. Watering the garden deeply is critical. The water must go down, down, down to encourage deep roots and get away from the hot soil surface.
Hands down, the best time of day to water is early in the morning. Watering during the day can increase risk of disease. If you can't water early in the morning, water late in the evening, especially before days forecasted to have dangerously high temps.
In hot weather you need to water in the mornings when it is cooler. This will allow more water to reach the root system before it evaporates in the heat. There may be times when you cannot schedule watering in the morning. In this case, water the plants in the late evening before bed.
When you sit in the shade, your skin is exposed to scattered UVB rays. These rays aren't as strong as they would be in direct sunlight, but they still allow the body to produce some vitamin D over time.
While seeking shade is an effective way to prevent sunburn, it does not entirely block the sun's rays. So if you're wondering whether you can still get sunburned under an umbrella or awning, the answer is yes.
Partial sun and partial shade usually mean 3-6 hours of sun/shade each day, preferably morning and early afternoon sun. Full shade is bright light but little or no direct sun; what we often refer to as dappled light.