Hydrangea in Minnesota

Master Gardener

Beautiful hydrangea bushes reward you each year with magnificent blooms that will instantly take you back to those fond childhood days. Who can forget the white hydrangeas, with blooms resembling large snowballs. As children we would be amazed by the size. As adults, hydrangeas still amaze and amuse us, which is why growing hydrangeas is so much fun. They are also quite hardy and resistant to most pests and diseases, making it even easier to care for hydrangeas. There are numerous varieties, so you are certain to find one that is right for you.

Spring and fall are the best times to plant. In spring plant after the threat of frost has passed. Put your hydrangea where you won’t have to prune it. These shrubs grow vigorously, and they are big and beautiful by nature. Don’t plant your hydrangea any deeper than it was growing in the pot. Avoid planting under trees, where the roots will compete for moisture and nutrients. Keep your hydrangea watered for the first couple of years, to help develop strong roots, but don’t let water stand around your plants. Fertilize once a year with a balanced, slow-release fertilizer, or fertilize twice a year with 10-10-10. Commercial manure or compost is an organic alternative. Stop fertilizing by August to let your hydrangea get ready to go dormant.

Although there are many types of hydrangeas, most can be grown in partial shade. They do require approximately 4 hours of sun a day. However, many hydrangeas do not like extremely hot conditions, so try to locate them in an area where they can enjoy some afternoon shade. While they can be grown in a wide range of soils, hydrangeas typically prefer rich, moist soil that drains easily. Amending the soil with compost prior to planting will help loosen the soil. You can also add a layer of mulch following hydrangea planting.

Water is an important factor when you care for hydrangeas. They enjoy deep watering at least once a week, especially in dry weather. Hydrangeas can also be transplanted easily, but this should only be done during dormancy in fall or early spring. Be sure to dig up the entire rootball and replant immediately.

There are many types of hydrangeas, pruning and care may differ slightly with each. Before you purchase, check the plant tag carefully for information, zone hardiness, when to prune and to see if it requires sun or shade, so you can plant in the right spot.

Hydrangea macrophylla types, or Hydrangeas:Mophead have rounded, globe-like flower heads. Most prefer morning sun and afternoon shade, but avoid heavy shade which can cause poor flowering. They come in blue and pink, as well as white, lavender, and lilac. H. macrophylla normalis, they have the same basic growing requirements as mopheads and are often called lace cap hydrangea, have flower heads composed of tiny disk shaped fertile flowers in the center surrounded by much larger sterile male flowers in the outer ring. Lacecaps have flattened, loosely arranged flower heads. This creates quite a different look out in the garden. These hydrangeas were often difficult to get to re-bloom in cold climates because they produced flower buds on last year’s stems or the old stems. If they experienced severe winter injury and were killed to the ground, the new stems produced during the season were unable to produce flowers. That has since changed with new introductions of macrophylla types that bloom on both old and new stems. This now gives gardeners a chance of bloom even if stems get killed to the ground. Check label for growing zone (some zone 4, but most are zone 5).

H. serratas are a subspecies of the macrophyllas, and they are smaller shrubs. Give them part shade. H. arborescens is sometimes called smooth or wild hydrangea are good garden hydrangeas. The best-known variety is ‘Annabelle’, which bears big, white blooms and flowers dependably. One of the most adaptable and urban tolerant hydrangeas are the Hydrangea paniculata types. These plants prefer a well prepared, moist soil in either full sun or partial shade.

Here are some varieties listed by the University of Minnesota as hardy to grow in Minnesota. While the University does not promote specific varieties, it does list these varieties to consider for your garden:

Annabelle, this is one of the most recognizable names for hydrangea. Also known as a Snowball hydrangea (or smooth hydrangea), Annabelles have huge, symmetrical blooms in June and July. Hardy to Zone 3, it can grow 4-5 feet tall and 3-5 feet wide. It is probably the showiest hydrangea in the garden with creamy white blooms that are often more than 8 inches across. Annabelle prefers rich, well-drained soil that stays consistently moist. It is tolerant of a wide range of soil pH and does best in partial shade. If it is planted in full sun, be sure to provide adequate moisture or the leaves will droop. Annabelle blooms on new wood and needs to be pruned back to within a foot or two of the ground each spring just as the new buds begin to emerge on the lower stems.

‘Invincibelle Spirit’ is the first pink flowering ‘Annabelle’ hydrangea. This plant produces loads of hot pink flowers from summer to fall and the color is not affected by the pH of the soil. It grows to about four to five feet.

‘Incrediball’ is an improved version of an old reliable, ‘Annabelle’. As its name implies the flowers are very large, up to 12 inches in diameter. In addition the stems are much sturdier than ‘Annabelle’ and are able to hold the large flower heads up and keep them from flopping. ‘Incrediball’ grows to four to five feet.

Hydrangea paniculata ‘Grandiflora’, is also known as a panicle hydrangea. PeeGee is a vigorous variety that is hardy to Zone 3. It has large, showy conical-shaped blooms in August and September. They open a creamy white and, in a few weeks, fade to an attractive bronze-pink that holds well into the fall. In our climate, the shrub will grow 8-10 feet in height and width. PeeGee hydrangeas prefer loamy, evenly-moist, well-drained soil. They are adaptable when it comes to pH and do well in full sun to partial shade. They bloom on new wood so any pruning should be done in spring. Because PeeGee hydrangeas are so hardy, there usually isn’t much dieback.

Hydrangea paniculata ‘Limelight’ While it is closely related to PeeGee hydrangea, Limelight is hardy to Zone 4. It differs from PeeGee by blooming later and having bright lime-green flowers. It forms a rounded shrub that will grow 6-8 feet tall and 6 feet wide. Be sure to give it plenty of space to grow. Limelight grows well in partial shade to full sun. It will provide late summer and early fall bloom. ‘Limelight’ flowers form on new wood and should be pruned in early spring. It thrives in a well-drained loamy soil and tolerates a wide range of pH.

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