Hydrangeas produce pink, blue or white flowers that can grow more than 10 inches in diameter and blooms from late spring through the summer. Although a hardy plant, care must be taken to prevent root rot in hydrangeas, one of the main killers of this shrub. Avoid poorly draining soils and fertilize to help the plant develop a strong root system.
Prepare a planting site for your hydrangea shrub that has well-draining soil. Amend your soil with 2 to 4 inches of compost before planting the shrub. Plant the shrub so the top of the root ball sits about 1 inch higher than the ground level. Pack the dirt down around the root ball as you fill in the hole to eliminate air pockets, which can lead to root rot by allowing water to stand around the roots.
Water the hydrangea consistently so the soil stays moist, but does not get soggy. Use a drip irrigation system to allow for deep, slow watering and water your shrub every three to four days or when the top 2 inches of soil has dried out. During the summer months, water every other day if necessary to keep the soil from drying out completely and the hydrangea shrub from wilting.
Feed your hydrangea with a good balanced fertilizer, such as 10-10-10. This will help the plant develop a strong root system, which is less likely to develop root rot. A balanced fertilizer has equal amounts of nutrients needed for healthy growth. Stay away from fertilizers high in nitrogen, the first number on the package. Nitrogen promotes more foliage production and less blooms. Fertilize twice a year, once in early spring before new growth develops and again in early fall after flowering is done.
Apply a fungicide to prevent an outbreak of fungi that commonly causes root rot in hydrangeas. Fungicides can be applied to the hole before planting the shrub or to an already established shrub by sprinkling it around the base of the plant and watering in well.