|Temperature||In its growing state or while blooming, prefers 55°-75° but will tolerate 38°-90° F. While dormant, if well mulched and well established in the ground, will tolerate down to 0° F.|
|Light||Prefers medium light indoors but in the yard, morning sun and afternoon shade.|
|Water||Keep soil always moist. Drench thoroughly when watering, then remove excess.|
|Fertilizer||None required while in bloom. Use acidic fertilizer during growth phase.|
|Soil||Peat moss, topsoil (2:1 ratio.)|
|USDA Zone(s)||Zones 7 - 9. For best results in zone 7, mulch dormant cane well in the winter or cover with poly or blanket. Click here for a zone map.|
After the plant has bloomed out, it can be planted outdoors. Plant it where it gets morning sun or dappled shade, away from harsh winds. As flowers age, some may just wither but others will turn a darkish color. To get them to rebloom, you deadhead them, or just remove the dried up flowers in the late fall or winter. In that way, you do not cut off flowering buds. The buds low on the plant will in most varieties be vegetative buds without flower buds in them.
It is better to plant your hydrangeas outdoors well before winter so it can develop a good root system and get acclimated before it turns cold. Water and mulch well or protect with cloth or plastic when weather turns cold. In the spring, new leaves and buds should appear and reward you with blossoms. A mature hydrangea bush can become quite large if left untrimmed (5-7 ft. in diameter) so prune it back in early fall if you want to keep it compact.
An amazing feature of hydrangeas is that a plant that displays pink or red blooms can be changed the following season to produce blue or a lavender shade and vice versa. The reason is that the availability of aluminum to the plant alters flower color. With the presence of aluminum, flowers turn blue to lavender. Without aluminum, flowers are pink or red. Aluminum availability is dependent upon the pH of the soil. With pH less than 5.5, aluminum is readily available and flowers will turn blue. With pH greater than 6.5, aluminum is tied up in the soil, thus the flowers will be pink. Most growers recommend the use of aluminum sulphate or potassium aluminum sulphate (follow instructions on label) as well as addition of peat in the soil to make it more acidic. Sometimes, if the soil is naturally alkaline (chalky or limestone), it is very difficult to get it acid enough to get blue flowers. Whites will not change color regardless of soil conditions.
Hydrangea is difficult to grow indoors for prolonged periods although while in bloom, the product is intended to be kept indoors. Cut off spent flowers. When all the flowers are gone, take it outdoors and place in an area where it gets morning or partly shaded sun. In early fall, cut the plant back rather severely so that only 2-3 pairs of leaves remain on each branch. Keep the soil moist at all times. During the winter when the plant goes dormant, all the leaves will drop. As the weather turns cold, protect the plant well or bring indoors so it will not freeze. Take it outdoors as soon as it gets warmer. In the spring, new leaves will appear and then buds. When the plant begins to bloom, if you prefer, bring it indoors to enjoy.