The Garden Guru: Longer nights and the lower angle of the sun can spur the growth of seasonal plants and bathe your landscape in autumn warmth

Any photographer will tell you that the most dramatic outdoor photos are taken early and late in the day, when the sun is low. Now, as our seasons are changing, the sun is spending much of its day lower in the sky, which makes for some really strong natural garden lighting.

Have you noticed how the color of daylight changes gradually during the fall? The clear blue-white light of the summer gradually gives way to shades of orange-yellow as autumn moves in. You’ll see it in the color cast on plants’ leaves, and you’ll notice it as the morning or evening sunlight shines on their trunks. The entire outdoors takes on an amber glow for several hours daily — until the middle of the morning and after midafternoon. It’s a beautiful season to be outside.

Put that strong, angular lighting to work for you. Allow it to shine onto a stone wall or through an arbor or pergola. The visual "warmth" of its rays will highlight rust, orange and yellow leaves and flowers. Reds and pinks, by comparison, may actually be muted.

However, the best way to capitalize on the angle and color of the natural autumn lighting is to let it shine through wispy plumes of flowers, seeds and foliage. Ornamental grasses are the epitome. Gulf muhly grass with its rosy-pink flower heads comes alive when it’s hit by the late-afternoon sunlight, as are any other grasses that hit their peak in the fall.

There’s another aspect of the sunlight that comes into play each autumn. It’s the "day length," a term used to describe the number of hours of natural sunlight. As our days shorten, we see many plants come into bloom. Mums are the prototypes, but fall asters, Maximillian sunflowers and Mexican bush salvias all measure the length of the days to determine when the proper flowering season has arrived.

Actually, these plants meter the number of hours of total darkness they get each night. The growth hormone that stimulates flower-bud formation is destroyed by light. The plants coast along without setting buds in June, July and August, even into September. Then, almost magically, enough of the hormone begins to accumulate during the lengthening nights to send the plants into the reproductive phase.

The reaction to the longer dark period is exactly why you see mums, poinsettias and Christmas cacti blooming naturally in mid- to late fall. It’s a trick that greenhouse growers use to bring their plants into bloom at will. They can light the plants if they’re not mature enough to bloom during the winter, or they can pull shade fabric over them from late afternoon until morning if they want them to flower in the summer. That’s not especially appealing for holiday crops, but it’s how chrysanthemums can be grown all year long.

If you have showy tropical plants growing on your patio or deck and are hoping to bring them into the house for the winter, you need to begin acclimating them to the lower light intensities. Move them gradually to darker surroundings outdoors over the next three to four weeks.

Cut back on the plant food you give them, and let their growth slow considerably. It’s amazing how dark our homes really are. Even the brightest spot near a window will equate to a really shady spot in the garden. Light-loving houseplants like ficuses, ferns and crotons that have done well in the shadows outdoors will need absolutely the brightest place in your house. If you have to trim a plant back somewhat so that it will fit into the space, do so — just don’t stick it into the garage and expect it to be happy over the winter.

Finally, fall is a great time to supplement natural sunlight. Extend your evenings by having landscape lighting installed. Positioned high in your trees, lights will create a second look to your landscape with almost no additional work on your part. It will highlight the beauty spots and leave less attractive spaces in the shadows.

Lighting plays an important part in the lives of our landscapes, and it is never more evident than now. It’s part of fine-tuning great gardening, and you’ll amaze yourself with what you observe.