Italian stone pine (Pinus pinea), true to its roots, is "molto contento," that is very contented, in Mediterranean-like climates, and it is cold-hardy in U.S. Department of Agriculture plant hardiness zones 7 to 11. Also known as umbrella pine for the rounded shape it eventually achieves, it can reach 100 feet outdoors. However, Italian stone pine is often sold as a miniature Christmas tree in far-from-fitting climates. Although it tolerates dry air better than most pines, it still isn’t likely to be a happy houseplant for longer than 6 weeks. After that, if not given extra attention, your Italian stone pine may end up stone dead.
Move your Italian stone pine to the brightest window you have if the plant is green on top but shedding needles underneath. Either indoors or out, if the tree isn’t receiving the full sunlight it prefers, the most shaded part is likely to die first. For an outdoor specimen, cut back any other nearby trees that could be blocking its light.
Grasp your indoor plant by the base of its trunk and ease it gently out of its pot, if it appears to be drooping and discolored even though it is well-watered. Then check the hue of its roots. If they look dark brown rather than tan, they have probably been too well watered and are rotting.
Clean off the roots of the Italian stone pine by swishing them in a container of water, and prune out all of the dark and mushy ones, leaving only the firm and lighter-colored. As you are working, dip the shears after each cut in a mixture of 1 part bleach to 9 parts of water, wearing plastic gloves to protect keep your hands from the harsh bleach. Once you have finished, plunge the pine’s surviving roots quickly into and out of that solution as well. Repot the plant in a fresh quick-draining medium, such as a mix of half peat moss and half fir bark. Water that medium only enough to keep it lightly moist.
Look for fungi around the base of a discolored outdoor tree, as that is a frequent indicator of root rot. If you see signs of it, rake away any mulch to help the soil dry out a bit and refrain from watering the tree except during drought. The Italian stone pine should be planted in well-drained soil that includes a good amount of sand or gravel. If your ground is soppier, drill a few 2-inch-wide drainage holes 18 inches deep in the soil at intervals around the pine’s drip line, and fill the holes with a mix of peat and pumice.
Give an indoor tree some air, even if only from a slowly rotating overhead fan. Move it outdoors in midspring. The Italian stone pine will tolerate temperatures down to at least 20 degrees Fahrenheit when in the ground, but you probably shouldn't risk more than light freezes with a young potted plant. Place it in a shaded and protected spot first -- such as on a cement stoop that soaks up heat -- gradually adjusting it to more light and more cold. Leave it out as late as possible in the fall as well.