Growing Guide Hydrangea (HousePlant)
LIGHT: When you receive your new Hydrangea, we recommend that you set it in a window where it will receive 6-8 hours of direct sun. A south-facing window is ideal.
WATERING: It is important to keep the soil mix evenly moist. The simplest technique is to water thoroughly (until the excess drains from the bottom of the pot) when the top 1/2 inch of the potting mix is dry to the touch. Do not allow the soil mix to dry out or let the pot sit in water for an extended period of time (more than 1 hour).
TEMPERATURE: A cool room temperature (60-65°F) will suit your plant just fine.
FERTILIZER: Do not fertilize while your plant is in bloom. Fertilize during the growing season (generally April into September) with a balanced water-soluble fertilizer according to the manufacturer's instructions.
FLOWERING: When the flower heads turn dark green, carefully snip them off.
AFTER CARE: Once the danger of frost has passed in spring, we suggest that you move your Hydrangea outdoors. If winter temperatures in your area do not drop below -10°F (USDA Zone 6), you may plant your Hydrangea in the ground. If you live in a colder climate, you can continue to grow your plant in a container. After several months, the plant may benefit from being repotted into a larger container. If you live in the north, set the pot in a sunny location; if you live in a hot-summer climate, set the pot in partial shade. After the leaves drop in fall but before the soil in the pot freezes solid (which usually occurs sometime in November here in Litchfield), move the pot to a cold (30-40°F) dark place indoors, such as an unheated basement or garage. Water sparingly. In mid-January, bring the plant into a cool (about 50°F) room where it will receive bright light but no direct sun. After 2-3 weeks, move it to a sunny window where the temperature runs about 60-65°F, and begin normal watering. New leaves will sprout and the plant should bloom soon thereafter.
Outdoor Care: Where winter temperatures do not dip below -10°F (except southern Florida and the desert Southwest, where Hydrangeas are not well adapted), Hydrangeas can be grown in the ground outdoors. They prefer partial shade and evenly moist but well-drained soil with an acid pH (a pH of 5.5 to 6.2 is ideal). If your soil is alkaline, you must either grow your plant in a container as described above or adjust the pH by amending the soil with peat moss or an acidifying agent such as aluminum sulfate or sulfur. In alkaline soil, the foliage will yellow and growth will be stunted.