Hydrangeas are almost impossible to keep pruned to a smaller size than they ultimately wish to grow. Plant in well-drained soil! If soil is heavy, add roughage such as pine bark mulch (Make sure it's ground BARK not ground WOOD).
*We don't recommend oakleaf hydrangeas because they don't often look their best when grown in a container. They flourish when planted in the ground. But if you enjoy the look, go for it!
In Ground: Hydrangea are easy to grow in most any moist but well-drained soil of average fertility.
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.
It is always best to plant the potted hydrangea outdoors whenever possible. It should only be planted outdoors in early to mid summer as it needs time to acclimate to outdoor conditions before winter arrives.
Hydrangeas are hardy, but if left in a pot over winter, it will be much colder than if left in the ground. The roots are much more vulnerable to freeze-thaw cycles if the hydrangea is planted in a pot. Pots can be brought inside during the winter, and then brought back outside in the spring and summer.
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.
Miracle-Gro Potting Mix
It is suitable for most types of plants but is best for vibrant hydrangea species since it will enhance the beauty of the flowers. While it may look like a simple mix, it's actually made to meet the needs of hydrangea plants. It contains perlite, peat moss, vermiculite, and fir bark.
Because these hydrangeas are not planted in the nutrient-rich ground, it is important to plant them in good commercial potting soil that has peat moss and organic material. We used Miracle Grow Moisture Control Potting Soil because hydrangeas like to be well-hydrated. But any good quality potting soil will do.
You may consider sprinkling some organic starter fertilizer in and around the edges of the hole to help stimulate root growth and give your hydrangea shrub the best start. Remove the hydrangea plant from the planting container. Use your fingers to gently manipulate the roots at the bottom of the root ball.
As rapid growers—averaging about 2 feet of growth per year—larger varieties of hydrangeas can reach up to 15 feet tall. Applicable in growing zones 3 to 9, hydrangeas are a low maintenance plant that will return year after year with proper care.
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.
The hydrangea should be watered thoroughly at least 3 times a week. Always water the plant all the way around the container, not just in one place. Water should come out the bottom of the pot. Never let it sit in water which will cause the roots to rot away.
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.
Space hydrangeas anywhere from 3 to 10 feet apart, depending on the type. Always space plants based on their expected size at maturity! Gently remove the hydrangea from its container and inspect the root ball, snipping off any dead or rotting parts and teasing free the roots if the plant is especially root bound.
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.
A newly planted bush may bloom the first year if it set flower buds while it was confined to a pot, and then not bloom again for a year or two as it settles into the soil in its new location. Instead it is busy growing new roots and branches, instead of flower buds.
Hydrangeas Are Great Container Plants
Potted hydrangeas are great alternatives if you only have areas where they are unlikely to grow well in the garden due to extreme cold or heat. Hydrangeas generally grow in USDA Zones 3-9, but in either extreme, they are unlikely to do very well. That's where containers come in.
Flower-bud protection is the goal of caring for hydrangeas in winter. The simplest method is to mound shredded leaves or bark mulch around the base of the plant to about 12 inches or so.
If you don't prune hydrangeas then they can eventually resemble a tangled mass of woody stems, and the flowers will become smaller and less showy.