Lately I've had numerous requests for plants that transition well from outside in the summer to inside when the days turn chilly.  And why not?  If you have the space and the right conditions indoors, there's no sense in tossing out a perfectly healthy plant at the end of the season. 

Many plants will not only survive indoors during the winter, they will grow and bloom, lifting your spirits on those cold, gray days.  Most important is choosing the right plant for the right place, and then transitioning the plants properly.
In choosing your plants, you must first consider the light they will receive.

Choosing your plants

Full sun plants (6 hours or more of direct sun) kept outside in summer will require lots of light inside to thrive, so plan on placing them within 1-2 feet of a south or southwest window over winter.  Even at that, the light they will receive at that time of year is about 10% of the intensity to which they have been accustomed, so some blooming plants may require additional lighting to provide a good display.  

Plants that have been kept in a shaded location outside will normally adapt to lower light conditions inside--close to an east window or in a north window during winter.  Some will also be perfectly happy in a south or west window this time of year, since the light is less intense.

Location, location, location

Don't forget to check your chosen location for any cold drafts or dry air coming from heat vents, both of which can be damaging to indoor plants.  Remember that since plants will be receiving less light over winter they will require less water, and in most cases should not be fertilized.  

Ok, so think about what it's like when you walk outside into glaring sunshine from a dark room.  You usually cover your eyes because it's difficult to see, right?  Well, that's sort of what it's like when you take a plant that's been growing outside all summer and then suddenly move it inside.  Just like your eyes need to acclimate to the bright day, plants need time to acclimate themselves to the vastly different cultural conditions of the indoor environment.
 
If this is not done, many plants will partially or completely defoliate in an attempt to rescue themselves.  Leaves grown under high light will not function properly in a low light environment, and vice versa.  Therefore, the plant has no choice but to shed those leaves and try to produce new leaves that match their current conditions.  The leaves of plants grown in sun are usually smaller, thicker, and lighter green than those of the same plant grown in shadier situations.

Acclimation

It's pretty easy to acclimate your outdoor plants before you move them inside. Simply place them in a progressively shadier condition over the course of at least a week--ideally two weeks.  The longer you give them, the better they'll fare in the long run.  Even if you're bringing the plant into a sunroom or atrium, they will benefit from this treatment, since the sunlight will be lessened somewhat as it passes through the glass.  Be sure to get this accomplished before temperatures drop too low--most tropical plants will suffer some damage below 50 degrees F.

Keep the bugs out!

In addition, don't forget to thoroughly wash your plants before you bring them in--a strong spray of water from the hose will remove most pests.  This is especially important if you are placing the plants in a room with existing plants.  If you do find insects, you can treat with a granular systemic houseplant insecticide that is sprinkled onto the soil and watered in.  Or, if you prefer the strict organic route, a summer weight horticultural oil or neem oil will do the trick.

Some plants to consider...

What plants are best for indoor-outdoor transitioning? In general, the less humidity a plant requires, the easier it will be to winter indoors, so you might want to research that fact before you buy.   Good blooming plants that are commonly found are zonal geraniums and their scented cousins, lantana, new guinea impatiens and begonias. 

Some lesser knowns are streptocarpella, a blue-flowering relative of the African violet that thrives in shade outside and bright light inside, and pentas, or Egyptian star flower, with round clusters of blooms on a bushy plant that will thrive in a sunny window. 

Of course, tropical bloomers like hibiscus and citrus are often overwintered inside, and do well if given sufficient light.  More unusual tropicals to look for are ixora, or jungle geranium, and crossandra. 

Ornamental peppers, with green, black, purple, or purple variegated leaves and variously colored fruits are readily available in the fall, and will continue to bloom and produce fruit through the winter in a sunny window. 

Typical foliage plants would include wandering Jew, spider plant, and snake plants. The old-fashioned piggy-back plant makes a fabulous hanging basket for shade outside and medium to bright light inside--and has low humidity needs to boot.  For something fun and different, try coleus--with so many varied leaf shapes, colors, and habits, you could have a whole house full with no two plants alike.  Keep these in bright light inside, even though they may do fine in shade outside! 

There are also many new Swedish ivy varieties available--they may be masquerading under their real name of Plectranthus, however. These have thick, fuzzy leaves that may be green, gold, grey, or purple--some also have showy spikes of pink or purple flowers.   Blood leaf (Iresine), Joseph's coat (Alternanthera), hawaiian ti (Cordyline) and croton are foliage plants that beg to be noticed, with leaves in various shades of purple, red, orange, pink, yellow, and green--often in the same plant--think a spilled box of Crayolas!

So, as the sun dips lower in the sky and temperatures begin to cool this fall, take a look at your outdoor garden and see what might come inside to cheer you out of your winter blues. 

One added benefit--those daylight spectrum lights are as good for you as they are for the plants, so you might as well share!