Don’t Be Afraid Of The Dark

In about four weeks we will have reached the time of the year when the sun is depressingly low and gives us the least amount of its light, creating days that are stingily short. This seems to have a physiological effect on humans as well as plants but for those of us with poor daylight exposures in our homes, it represents an added challenge—growing plants indoors in low light conditions.

What exactly is low light?

Let’s first assume that we have a window that is at least 3 feet wide and 5 feet tall. If at least half of that window is obstructed by trees, buildings, curtains or anything else where you will be placing the plants, that could qualify as being in low light.

This being the case, the following should describe exactly what would be a low light condition:

It’s 4 feet back from an obstructed north window.

It’s 6 feet back from or at the edge of an unobstructed north window.

It’s 6 feet back from or at the edge of an obstructed eastern- or western-facing window.

It’s 8 feet back from or 1 foot to the side of an unobstructed east- or west-facing window.

It’s 8 feet back from or 1 feet to the side of an obstructed south-facing window.

It’s 10 feet back from or 2 feet to the side of an unobstructed south-facing window.

You can be more precise in your measurements of light if you use a light meter or if you use the light meter in a camera with a manual setting.

First, using a digital camera, set the ISO “film” speed to 200. Next, set the shutter speed to 1/125 of a second.

Use a white piece of paper about 24 inches square and place it where the top third of the foliage of the plant will be located and face the flat surface of the paper toward your maximum light source. Now aim the camera at the paper.

If you were taking a picture of the piece of paper, the light meter would tell you at what F-stop (lens opening) to set your camera. If it tells you to use an F-stop of 5.6 with a shutter speed of 1/125 of a second, you’ve got low light. Additionally, an F8 will indicate medium light and F11 will indicate good to high light.

Growing plants in low-light range can be risky business. If you are expecting geraniums to bloom, or cherry tomatoes, or an amaryllis in full glory, then dream on. On the other hand, there is a nursery industry called the “foliage trade” that to some degree caters to this market.

There are nurseries all through Florida, Texas and Puerto Rico where foliage houseplants are grown specifically for low-light situations. The plants are grown outdoors, but under huge areas covered with black saran shading that simulates our northern growing conditions.

Plants may not thrive, indeed they may not even grow at all, or they will grow imperceptibly. However, if the plants are chosen wisely, you can have a wide range that will exist in low light for many months or years before they need to be replaced or rejuvenated.

Since there is added risk in putting plants in this situation, it is extremely important that the plants be properly acclimatized. You don’t want to buy a plant that has been growing in a warm, sunny greenhouse and then put it 4 feet from a northern-facing window.

Many of the better plant shops and garden centers sell plants that are preconditioned for low light situations. These are the ones to seek. Otherwise you can tempt fate at the supermarket or discount store and play the odds.

There is a large variety of good plants for low-light situations. Here are a few.

Aglaonema, or the Chinese evergreens, are plants of tropical origin grown for their variegated foliage and they are somewhat indestructible. The dark green, waxy, oblong leaves splashed with white are thick and fleshy and the plant should not be expected to bloom.

You may be able to find a number of cultivars and virtually all will do fine in low light and they will even tolerate dry air. They prefer night temperatures of around 60 degrees and daytime temps between 70 and 75.

If the plants become too tall, over time they can be headed back. The tips that are cut off can be rooted in moist perlite or sand in spring or early summer.

Aglaonema modestum is an erect plant about 2 or 3 feet tall. It has pointed, oval leaves that are about 12 inches long and up to 5 inches wide.

A. commutatum is the variegated form. It is similar to the green except that the leaves are smaller and blotched white or light green.

A. pseudobracteatum grows only to 2 feet. It has bright variegated leaves splashed with creamy white to yellow.

Alocasia has large, heart-shaped or arrow-shaped leaves with showy veins, making it a worthy and somewhat exotic houseplant. Tropical in origin, it thrives at between 70 and 80 degrees, 50-percent humidity and on the bright side of the low-light situation.

These plants can make striking indoor specimens. An older clump can fill a 24-inch clay pot with a foliage spread another 2 feet tall and 2 feet wide.

You may already be familiar with these plants as some gardeners use them outdoors where they thrive in the hot summer shade and are known as “elephant ears.” They are grown from large tubers similar to cannas and the tubers can be divided every few years or suckers can be separated from the parent plant.

Alocasia cuprea, an even more exotic plant, is only a foot tall. It has heavy, wavy, prominently veined leaves that are dark metallic green above and maroon to purple beneath. A. amazonica has large, glossy, arrow-shaped leaves that are showily veined.

Aphelandra is one of only a few plants that will flower in low-light conditions, though it needs the greatest amount of light possible. It has waxy, bracted flowers in terminal spikes and shiny, emerald-green leaves with white veins. 
The blooms consist of 1-inch long, two-lipped flowers colored orange or red with overlapping yellow bracts. The plants rarely mature in the home, but in the right conditions they may grow to 2 feet tall. They bloom in late summer and become somewhat dormant in the winter, though the foliage remains attractive.

These plants are native to tropical Brazil and they thrive in moist soil and humid air so a humidifier in the area will be helpful. During the summer months, if you want them to flower, move them to an area that is brightly lit but never put them in direct sunlight.

Once the flower starts to fade, remove it promptly or the plant may deteriorate. The variety that you are probably most familiar with is the zebra plant, or A. squarrosa.

The variety Louisae is very showy with green-tipped yellow flowers and golden bracts. The one thing this plant will not tolerate though is overwatering.

Other low-light plants to consider are some of the palms: Kentia, Parlor, Bamboo and Lady. In Dracaenas, there are corn plants, warneckii, Janet Craig, godseffiana, sanderiana, borinquensis and compacta. In the philodendron group there are: finger leaf, split leaf, Swiss cheese, horsehead, golden pothos, marble queen, satin pothos, and bronze and green philodendron.

Prayer plants and calatheas have red and pink lines in their foliage that add interest. At night, the foliage can curl or arch upward.

Also consider nerve plants and sansevierias. Peperomia obtusifolia is virtually carefree and has a waxy but white and green marbleized foliage.

The Boston fern can also do well in low light if that’s where it has been started. But if you take one of these ferns from a high-light situation and move it to low light, it gets sloppy and defoliates quickly.

There is a large number of dieffenbachias (dumb canes) on the market that will tolerate low light and these can grow to be fairly substantial plants. Solid green types do best in lower light while those with variegation do better in moderate light.

When they get too tall the canes can be cut back and this forces new shoots to develop from dormant buds above and below the soil. If these plants are grown in enough light, they will flower when mature, some with a surprisingly sweet fragrance.

Keep in mind that plants growing in reduced light need reduced care. Don’t overwater them and feed sparingly

Don’t stay in the dark. Keep growing.