What does 'medium light' mean?

As the weather grows cooler, more and more of us pay attention to those displays of houseplants in supermarkets, home stores, and garden centers. Which ones will do well in your house?

The best thing to do is to match the preferences of the plants with the conditions in your home. So if the label indicates that it prefers evenly moist soil and you know you're erratic about watering, you probably want to pass on that plant, no matter how much you're drawn to its appearance.

But what does it mean when a label says that a plant needs medium or high light levels? And how do you know if that's what's available in the spot you want to place the plants?

Here's a quick guide:

On a sunny day, get a piece of white printer paper and place it where you want to put a new houseplant. Then hold your hand 12 inches above the paper. Can you see an indistinct shadow? If so, that's low light.

If the shadow is a  bit fuzzy but mostly looks like a hand, that's medium light. A clear hand shadow indicates a high level of light.

Although light is always going to be brighter near a window than in the middle of a room, some windows allow more light through than others. Big ones more than smaller ones, for instance.

And a south-facing window will provide more sunshine than one on the north side of the house -- provided that the light isn't blocked by a tree, a building, or other obstruction.

Clean windows let in more light than dirty ones (and you may not have known that clean leaves absorb more light than dusty ones). Watch out for screens and sheer draperies, which do lower light levels a bit.

Because light levels are naturally lower in winter than in summer,  a plant that was perfectly happy on an east-facing windowsill in summer may need to be moved to one with a western exposure after cold weather arrives.

Since more of us have low light in our homes than sunny areas, I'll provide a list on Monday of plants that grow nicely in these ordinary household conditions.