Hydrangeas are popular garden shrubs. Nurseries and garden centres sell a wide variety of hydrangeas species. These plants can vary from small shrubs to tall trees. Hydrangeas produce large groups of flowers, which are most often cream, white, purple, mauve, pink or blue. Some of the pink and blue varieties will change their colour based on the amount of aluminium in the soil. Gardeners find caring for hydrangeas relatively simple due to their low pruning and fertilising regimens.
Choose a fertiliser for your hydrangea plants. A general fertiliser, such as 10-10-10, is appropriate for all hydrangea plants. Organic fertilisers, such as manure, are also suitable. Fertiliser that is low in phosphorous will help the hydrangea absorb aluminium, which will cause colour-changing species to produce blue flowers.
Apply the fertiliser twice in the spring and summer months, such as May and July, around the drip line of the shrub. The drip line is the edge of the branches around the plant. Follow the directions on the fertiliser container for proper application rates. In general, apply approximately 1/4 cup of fertiliser to small plants and up to 3 cups of fertiliser to large plants. Do not fertilise hydrangeas after August 1, because the plant is then preparing for winter. New growth will inhibit the shrub.
Water the hydrangea after you spread the fertiliser. If your climate is dry, water your hydrangeas at least once per week.
Apply additional fertiliser if your hydrangea plants have yellow leaves, which is an indicator of low nutrient levels. Apply aluminium sulphate to the soil to help colour-changing plants produce blue flowers.
Do not use both granular and liquid fertilisers at the same time on your hydrangea plants. Apply liquid fertilisers more often, such as every other week. Do not apply too much fertiliser to your hydrangeas.