Hydrangeas grow well if you plant them in the fall so that they have time to establish themselves in the garden before spring growing and flowering. If you are planting new shrubs, follow the spacing and planting method recommendations provided by the grower for best results. Hydrangeas slowly establish their roots after planting; however, the grow speeds quickly after the root system is in place. Ideally, choose a shady location for hydrangea bushes. If you cannot avoid sun, choose a spot that has morning sun and afternoon shade.
Hydrangeas benefit from regular watering and feeding. You can use commercially purchased fertilizers, such as a complete 10-10-10 or use an organic fertilizer such as manure. Yellow leaves on the plant indicate that the hydrangea is low in nutrients and will benefit from an application of fertilizer.
If you have Bigleaf hydrangeas, keep in mind that fertilizers that are low in phosphorous will allow the hydrangea to absorb aluminum and produce blue flowers. Ideally, applications in May and July will help your hydrangeas produce the showiest flowers throughout the season. Place the fertilizer along the drip line around the circumference of the shrub. Water the hydrangea shrubs after you apply the fertilizer and every week during the summer if your area does not received at least one inch of water routinely. Older hydrangea bushes may become moderately drought tolerant, however, you should continue water the plants for maximum growth and flower production. Beginning in August, hydrangeas begin to prepare for the fall and winter months. Therefore, do not apply fertilizer to the shrubs after the fall preparation begins.
Image courtesy of USDA.gov