A potted hydrangea can be planted in the ground at any time of the year. However, spring or fall are the best times. Wait until the frosts are over in spring, or plant in early fall when the soil will still be warm and before the frosts.
Plants usually require at least six weeks of good weather to set up the establishment of their root systems. And there is no guarantee that the year you plant will be like the prior few years. To avoid a bigger risk of frost during establishment, get those hydrangeas in the ground by early October.
In the spring, I suggest getting them in the ground before the end of June. In the fall I suggest planting in September or October. Once the frost begins to set in your hydrangea will not have ample time to take up water and get comfortable in its new home before going dormant.
In Ground: Hydrangea are easy to grow in most any moist but well-drained soil of average fertility.
Fall is the best season to plant hydrangeas, followed by early spring. The idea is to give the shrub plenty of time to establish a healthy root system before blooming. The best time of day to plant is early morning or late afternoon.
To loosen the soil, mix dehydrated cow manure, garden compost or peat moss (up to 1/3 concentration) into your pile of topsoil. Make sure the peat moss you get is either baled sphagnum or granular peat.
Most common hydrangeas prefer a partial sun location - ideally receiving sun in the morning hours and shade in the afternoon. The reblooming Endless Summer® Hydrangea series prefers part shade. These include BloomStruck®, Endless Summer®, Blushing Bride®, and Twist-n-Shout®.
East Side. The east side of the house is the best planting location, as it gets the morning and afternoon sun. This is the best side of the house for your hydrangeas, traditionally.
However, stop deadheading hydrangea shrubs in mid to late fall, leaving any spent blooms in place. This not only provides winter interest, but also ensures you don't remove the buds that will become flowers next spring.
Best Time To Plant Hydrangeas
They can be planted at any time of the year. However, to get good results, keep these considerations in mind: Whenever possible, plant in early summer or fall. Don't plant in early spring when frosts are still possible.
To prepare hydrangeas for winter in colder areas, add a thick layer of mulch around the base of the plants to protect the crown and roots from freezing temperatures.
Miracle-Gro Performance Organics Blooms Nutrition
This is an all-purpose blossom booster that's suitable for use on a wide variety of perennial and annual blooming plants, including hydrangeas.
Most hydrangeas prefer partial sun with full sun in the morning, followed by some afternoon shade. This is especially true for the Bigleaf hydrangea (H. macrophylla). Some varieties are more tolerant of full sun. Most hydrangeas will thrive in fertile, well-draining soils that receive plenty of moisture.
Hydrangeas grow best in well-drained soil, in a protected, dappled shady spot. They prefer sun in the morning with some shade in the afternoon. South-facing positions are best avoided, and protect young growth from spring frosts.
Some gardeners report success in turning their hydrangeas blue by applying coffee grounds to the soil. The coffee grounds make the soil more acidic, allowing the hydrangea to more easily absorb aluminum. In addition, fruit peels, lawn clippings, peat moss and pine needles, are thought to have a similar effect.
Hydrangeas grow best in full sun (more than 6 hours sun) to part sun (4-6 hours sun). With that being said, all hydrangeas can handle some shade, but the timing and type of shade are important to consider. They can be in full shade during the hottest part of the day, as long as they are getting some morning sun.
They don't form a central taproot like rhododendrons and shrubs. Instead, they grow in a loose, spreading mass of fibers often referred to as a root ball. The vast majority of a Hydrangea's roots will stay within the top six inches or so of soil. However, they do tend to spread quite a bit in the horizontal direction.
Start fertilizing the year after planting.
There are several different types of hydrangeas—bigleaf, panicle, smooth, oakleaf, mountain. All these types should be fertilized at least once a season in late winter or early spring, certainly by the time new growth begins to show around the base of the plant.
To give hydrangeas their best chance at success, apply a layer of chunky mulch around the base of the plant. Decorative mulch is helpful but we recommend straw, marsh hay, or fallen leaves.
Grow hydrangea plants in any rich fertile, moist soil. It's a good idea to work in some well rotted manure or compost prior to planting Hydrangeas, and they will always appreciate a mulch of organic matter in spring to help conserve moisture at their roots and feed them up for them for the coming growing season.