Last year’s poinsettia has spent the summer outdoors.

If it was set in a semi-shaded garden bed, it must have flourished through last summer’s benign climate. Its lush foliage would have added an exotic note to its surroundings. Its role as a two-season plant has been a success. Let it go.

Another poinsettia, still in its pot, is ready for more. By now, it’s back indoors. Did it grow broad or gangly? Quickly, shape it lightly. Continue to water it.

Now for the challenge: with proper care, it should bloom again at Christmas.

Poinsettias are programmed to flower during the season of short days and long nights. In New England, they need human help to do so.

First, look for a dark closet that won’t be opened on any night. Now, get out a calendar, one in plain, every-day sight.

Mark the nights from Sept. 21 (give or take a night) to mid-December.

Each day, continue to care for the plant as usual. Each evening before supper, stand the pot in that dark closet. Remind everyone in the household to leave that closet shut.

Next morning at breakfast time, remove the poinsettia from the closet and return it to its place on the windowsill. That should give it 12-14 solid hours of darkness, mimicking the natural hours as they would be in the semi-tropics.

Going away? Don’t turn the heat off — just cooled down. Ask the plant-minder to follow this routine, including watering time. (Don’t overwater!)

Explain to everyone what’s happening and why. Figure out how to keep the cat from having her kittens in that special closet (one never knows).

At the end of that time, terminal leaves should be turning red and the “flowers” should be on their way to Christmas.

The red leaves are really the bracts around the flowers, which are the little gold nubs in the center of each rosette. One can’t have the flowers without those showy bracts.

Save these directions, for this fall or one in the future. Why not let me know how the project ends?