Hydrangea Grow Guide
Hydrangeas are easy shrubs to maintain and they reward the gardener with huge, eye catching flowerheads that can last for weeks. Not only that, after they bloom, the flowerheads are beautiful and long lasting in dried arrangements. Perfect Plants offers three different kinds of hydrangeas for different uses in the home landscape.
The classic bigleaf hydrangeas produce spherical flower clusters that are blue when grown in acid soil and pink in alkaline soil. For blue flowers, the soil pH should be lower than 5.5. For pink flowers, it should be 6.5 or higher. A soil pH between 5.5 and 6.5 will lead to purple flowers or a combination of blue and pink blooms on the same plant. ‘Penny Mac’ is great in shrub borders, behind shorter flowers in beds, and is especially eye-catching in a specimen grouping of three.
This hydrangea has huge cone shaped flowers. It gets up to 8’ tall, and is more drought tolerant than the others. Soil pH does not affect the flower color. Most adaptable hydrangea to soil types. The panicle hydrangeas are well suited for the corners of a landscape or in mixed shrub borders. With thoughtful pruning ‘Limelight’ can be an attractive shrub, or trained to be a small tree.
This hydrangea is an American native that pretty much takes care of itself. It can get over 10’ tall, is rather rangy in appearance, and is best suited for a woodsy or naturalistic garden. Flower color is not affected by soil pH.
Most hydrangeas do best with full sun for 2-4 hours in the morning, and partial shade or dappled sun in the afternoons. Avoid locations with full-on sun all day, unless you are in zones 4 or 5, where full sun is recommended. The further south you are, the more your hydrangeas need afternoon shade. Oakleaf hydrangea tolerates more shade than the others, and Limelight hydrangea likes a bit more sun.
Choose a site where drainage is good, but not extreme. A rich, fertile, sandy loam is best; avoid distinctly sandy locations where roots can dry out quickly, and avoid soils that stay wet where roots can rot. Oakleaf hydrangea thrives in limey soils with a pH around 7.0 or above. The other hydrangeas like an acidic soil, and do best with pH values between 4.0 and 6.5.
If you’re planting more than one hydrangea, position them at least 3-6 feet apart. Try to plant new shrubs in spring or fall, rather than the dead of winter or the heat of summer.
Planting your Hydrangea
Before beginning, thoroughly water the shrub in its original container. Place the pot on its side and slide the root ball out. If the plant is stuck, you can slip a long-bladed knife around the inside edge to loosen it. Gently loosen some of the roots along the sides and bottom of the root mass, and pull them outward so they are not encircling the root mass. It shouldn’t be necessary to prune any of the roots unless they are wound around the circumference of the pot. In that case the offending roots should be shortened so that when they are in the ground they will grow outward and not continue growing in a circle.
Dig a hole twice as wide as the container the hydrangea came in and about the same depth. Mound up some soil on the bottom in the middle of the hole and place the center of the hydrangea’s root mass on top of the mound, spreading the roots out all around the center. Backfill the hole about half way, then water thoroughly. After the water drains, continue backfilling until the top of the root crown is at the same level it was in the original pot, never lower. You may have to pull the plant up a bit as you backfill. Gently tamp the soil down.
Build a 3-6 inch high levee of soil on the surface around the outside of the root zone. This will impound water and allow it to sink into the soil directly over the roots. Water thoroughly. Spread an organic mulch 3-6 inches deep over the root zone and beyond to help hold in soil moisture. You can use hay, straw, leaves, pine needles, bark or wood chips, grass clippings or compost. Do not fertilize at this time.
Caring for a New Hydrangea
Keep your hydrangea well watered during its first growing season. If planted in the fall or winter, you can water once every week or two. If planted during the growing season, it should get watered every day or two for three or four months. If you’re having a dry spell, or your soil is very sandy, you should water every day for the first three or four months. The most common reason for any newly planted shrub to die is lack of enough water.
Once established (after a year of growth), hydrangeas can tolerate moderate dry spells and should not need any supplemental watering unless it hasn’t rained in four weeks or more.
Feed hydrangeas once a year in late winter or early spring with a balanced fertilizer, or one high in phosphorus, which promotes flowering. Too much nitrogen fertilizer encourages leafy growth at the expense of blooms.
Hydrangeas generally do not need any pruning. Prune them only if necessary to maintain size or a desired shape. The bigleaf hydrangeas (such as ‘Penny Mac’) and the panicle hydrangeas (including ‘Limelight’) form their flower buds on new wood, so any pruning should be done in winter or early spring before the new growth begins. Oakleaf hydrangea blooms on old wood, so if you prune in winter or spring you will be cutting off the current season’s flower buds. Instead, prune oakleaf hydrangea (although it’s almost never called for) soon after flowering, before next year’s buds form. To rejuvenate a senescent or leggy hydrangea, cut it back almost to the ground. You may not get any flowers the first season after that, but you will be amply rewarded in subsequent years.