Hydrangea bushes have long been favourites of gardeners in mild climates, but with the introduction of hardier hydrangea varieties, northern gardeners can include the bush in their landscapes. Because there are many hydrangea varieties, select a variety that is suitable for your region and garden environment. Even with an appropriate hydrangea for your location, it may not bloom. If you have pruned the hydrangea at the correct time, immediately after it is finished blooming, and there has not been a late frost to damage the flower buds, you may still be able to make the hydrangea bloom.
Analyse the landscape location where the hydrangea is planted. Hydrangeas require six to eight hours of sun daily, preferably morning sunlight. If the hydrangea is in a shaded location and not receiving enough daily sun, it will not produce flower buds. Depending on the location and surrounding plants, you may be able to trim overhead branches to allow in the sun. Alternatively, replant the hydrangea to a more appropriate location.
Amend the soil around the base of the hydrangea with 2 to 3 inches of organic compost or decayed organic material, such as leaves or grass clippings, to add nutrients and improve water drainage. Hydrangeas require consistently moist soil but never soggy soil, which may cause root rot.
Fertilise the non-blooming hydrangea two to three months before bloom time with a high phosphorus fertiliser, often called super phosphorus or triple phosphorus, or a fertiliser with nitrogen and potassium. A higher phosphorus number such as 10-30-10 will suffice. Phosphorus is the nutrient that promotes flower bud development in a plant. After the hydrangea has completed blooming, fertilise it with an balanced, time-release fertiliser such as 10-10-10.
Stop pruning the hydrangea except for removal of dead or damaged branches. Though there are hydrangea varieties that form flower buds on new growth, many hydrangeas bloom only on old wood. Old wood is growth or branches that grew the previous year. If this growth is removed at the wrong time of year, you will be cutting off the potential flower buds of your hydrangea and no blooms will be produced.
Be patient. After transplanting a hydrangea, it may take one to two years before the plant begins to bloom.
Feeding with a fertiliser containing high nitrogen will promote lush green leaves and a full bush but not flowers. The energy of the hydrangea will be going to developing foliage instead of developing flower buds.