Flowering plants are always welcome gifts that make the holiday season more festive and meaningful.

Deciding whether to keep a flowering houseplant after it finishes blooming depends on the species.

Most plants will grow better and give more satisfactory results if they can be planted outdoors during the summer. The outdoor environment more closely matches the plant’s natural habitat.

Select a lightly-shaded area in the garden, protected from strong winds, where the containers can be plunged into the soil up to their rims. If possible, put stones or gravel in the bottom of the hole before sinking the containers. This will ensure good drainage.

Twist the containers every two weeks to discourage roots from growing through the drainage hole and becoming established in the soil. Water the plants when needed and increase the frequency with which the plants are fertilized when they are actively growing. If night temperatures cool enough to where there is a threat of frost, bring the plants back inside.

Easter lilies (Lilium longiflorum) will bloom as an outdoor plant or can be forced again indoors, though they are not as easy to force as other spring bulbs. While the plant is displayed indoors in a bright location away from direct sunlight, remove flowers from the plant as soon as they die. After the plant stops blooming it will require much less water.

When the plant turns brown, cut it off at the soil line. For outdoor culture, plant it in the garden in May after the last spring frost. Plant the bulbs four to six inches deep in a sunny, warm location. After the ground freezes in the fall, mulch the area until you see new growth in the spring; then remove the mulch a little bit at a time.

For indoor culture, remove the bulb from the container after the plant has turned brown. Store it in a cool, moist place, such as a basement. Repot it in a six-inch container in new potting mix a few weeks before Christmas. Then place it in a cool, sunny window until it blooms.

Hydrangeas (H. macrophylla) need a cold period in the fall to develop flower buds and should be well-watered when actively growing, especially when flowering. Prune them back to about three inches in height just before you set them outdoors after the last frost date. To prevent the new growth from becoming unsightly, fertilize once a month with a general garden fertilizer, such as 5-10-5 or 5-10-10.

Leave the plant outside as long as possible in the fall and cover it at night to protect it from early light frosts. When frosts become more regular, bring the plant into a very cool (40 degrees), dark place and leave it there until Jan. 1. Be careful to prevent the plant from freezing.

The leaves will drop off during this period, so it will be necessary to keep them picked up to prevent any diseases from starting. About Jan. 1, place the plant in bright light in a warmer room with a temperature between 55 and 60 degrees. It should now bloom for Easter.

Hydrangea blooms can be blue or pink, depending on the acidity of the potting mix.

To get blue blooms, apply aluminum sulfate at the rate of 3/4 of an ounce to 1/4 of water. Apply this every two month after you prune the plant. Do not use a complete fertilizer after you start the forcing period (after Jan. 1). The phosphorous in the fertilizer will make the aluminum available to the plant.

To get pink blooms, add a teaspoon of limestone to the container in August; and during the forcing period (after Jan. 1). Water the plant with a solution of 1/4 teaspoon of general garden fertilizer every 10 days.

It may take several weeks or months for the color of your hydrangea to change. When the color change does occur, the resulting color may not be as you expected. This is because certain varieties develop better blue flowers than pink, and vice versa. It is not possible to change the color of white hydrangea varieties.

“Growing Green” is contributed by Diane Dorn, Lehigh County Extension Office Staff, and Master Gardeners. Information: Lehigh County Extension Office, 610-391-9840; Northampton County Extension Office, 610-813-6613