All About Hydrangeas
Hydrangeas are a staple in any Zone 4 garden. We love them and can't ever get enough. Their glorious blooms are the sweet reward at summer's end. Hydrangea season is here, and since Minnetonka is the Hydrangea capital of the world, because we said so, you can never have too many. Here is what you need to know to choose and care for the right Hydrange for your location, lifestyle, and garden goals.
Hydrangea arborescens (Smooth Hydrangea)
Hydrangea arborescens are part to full shade hydrangeas, moderately sized shrubs with large spherical flowers that bloom only on new wood.
Hydrangea arborescens varieties that we love:
- Invincibelle® 'Mini Mauvette®'
- Seaside Serenade® 'Bar Harbor'
Hydrangea paniculata (Panicle Hydrangea)
Hydrangea paniculata are part to full sun Hydrangeas, often larger shrubs that bloom with large, long-lasting, conical or lacecap panicles of flowers on new wood (the current season’s growth).
Hydrangea paniculata varieties that we love:
- 'Early Evolution™'
- 'Fire Light®'
- 'Diamond Rouge®'
- 'Little Hottie®'
- 'Limelight Prime®'
- 'Little Lime®'
- 'Quick Fire®'
- 'Little Quick Fire®'
- 'Strawberry Shake™'
Hydrangea macrophylla (Smooth/Bigleaf Hydrangea)
Hydrangea macrophylla are compact hydrangeas for part-shade with colorful, spherical or lacecap blooms, including some cultivars whose color varies with soil pH. Color-changing cultivars, including the Endless Summer® series, will have blue-tinted flowers with more acidic soils, and pink-tinted flowers with more alkaline soils. Garden amendments can further influence bloom color in these cultivars, blooms turning bluer in color with the addition of soil acidifier, and pinker in color with the addition of garden lime to increase soil alkalinity.
Hydrangea macrophylla varieties that we love:
- Blue Enchantress®
- Endless Summer® 'BloomStruck®'
- Endless Summer® 'Summer Crush®'
- Endless Summer® 'Pop Star®'
- Seaside Serenade® 'Cape Cod'
- Seaside Serenade® 'Cape Lookout'
- Seaside Serenade® 'Cape May'
- Seaside Serenade® 'Fire Island'
- Seaside Serenade® 'Hamptons'
- Seaside Serenade® 'Newport'
- Seaside Serenade® 'Crystal Cove'
Hydrangea anomola (Climbing Hydrangea)
Hydrangea anomola are climbing Hydrangea vines providing stunning blooms on an adaptable woody deciduous vine. Preferring full or part sun yet tolerating shade, climbing Hydrangea are excellent for covering walls, fences, and large arbors, reaching a mature size of upwards of six feet wide and 30+ feet tall. A rugged vine for a variety of conditions, climbing Hydrangea are also resistant to deer and rabbit feeding.
Spring and summer, into early fall are all suitable times to plant Hydrangeas. Best practice is always best to avoid planting during the heat of the day or during times of drought. Most hydrangeas love part sun to part shade with Conical Hydrangeas tolerating the most sun and smooth Hydrangeas tolerating the most shade. Morning sun is ideal for most varieties allowing a reprieve from the host afternoon sun. Hydrangeas prefer well-draining soil rich in organic matter.
Follow these simple steps when planting:
- Dig a hole 2 x the diameter of the pot it is growing in
- Break up the root ball
- Plant so that the top of the root ball is even with the soil level, not above or below
- Back-fill hole with 1/2 native soil and 1/2 Planting Mix or Premium Compost
- Water in well
- After planting, apply a thick of layer of mulch using the 3-3-3 rule - 3 inches of mulch, 3 inches away from the base of the plant, 3 feet in diameter.
Smooth hydrangea (H. arborescens) varieties only need one fertilizer application in late winter or early spring.
Panicle (H. paniculata) hydrangeas like to be fed twice per season - once in spring, and once in early summer.
Bigleaf hydrangeas (H. macrophylla) like to be fertilized little and often. Fertilize three times throughout your growing season - early spring, summer, and late summer.
We recommend a well-balanced fertilizer such as Espoma's Organic Plant Tone, which encourages dark, green growth and large, bountiful blooms. For garden beds, mix 4 lbs. per 100 square feet of soil into the top 4 inches of soil. For new planting, use 1 cup per plant and mix into planting hole. For established plants, use cup per foot of drip line diameter.
As their name implies, Hydrangea or Hydra means water. Make sure to water new plantings, long and deep, about 1" of water per week, to establish a vigorous root system. Water more frequently if you see signs of wilt or during periods of drought. Water in the morning before the heat of the day to allow water to soak avoiding evaporation allowing plants to dry through the day hastening favorable disease conditions.
How to Change Flower Color, Endless Summer Series
In the case of the Endless Summer type Hydrangeas, the pH of your soil can influence the color of Hydrangea flowers. 5.0-5.5 (acidic soil) will turn your Hydrangea blooms blue while 6.0-6.5+ (neutral to alkaline soil) will turn your hydrangea blooms purple to pink. Add Espoma's Soil Acidifier for blue, and Espoma's Garden Lime for pink.
Prepare for Winter
Here in Minnesota, unpredictable winter weather extremes, snow totals, and freeze/thaw cycles swing wildly. Although many hydrangeas are considered hardy in our area, all of this can throw them for a loop. They do need some attention in order to survive the winter and come back bigger and better next year. Implement these steps to maximize your hydrangea potential so you will be the giver of this time next season!
Don't stop watering!
Take the pledge! Raise your right hand and say, “I will water my hydrangeas until the ground freezes solid.” Cool, drying winter winds suck the moisture right out of the plants – and hydrangeas don’t use lip balm. Doesn’t have to be hot to be dry!
Give your hydrangeas a boost for next season by adding compost to your beds in the fall. The same is true for hydrangeas. They’ll be hungry for some good compost after a long winter’s nap. After a good night’s sleep, everybody feels better with a good breakfast in their belly. Applied in the fall, compost can break down overwinter, making nutrients readily available in spring.
Mulching protects and insulates the crown and roots of your hydrangeas from extreme winter temperatures. If all goes as it should, snow acts as a natural insulator. However, weird winters with little snowfall and drastic temperature swings are detrimental to plants. 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.
After the ground has frozen, and you've top-dressed with compost. apply a 6"-8" layer of mulch. This insulates plants and protects plants from the heave-ho of spring freeze/thaw cycles which in extreme cases can push them right out of the soil. Mulching too early invites rodents to make this their cozy winter dwelling thus causing rotting and disease and can also trick the plant into thinking it's time to wake up.
Wrap it Ip
Wrap or completely cover marginally hardy hydrangeas. This is especially important for those that bloom on old wood, such as bigleaf hydrangeas (H. macrophylla). However, note that newer varieties of big leaf hydrangeas bloom on both new and old wood. Good for them, good for us! Generally, hardier hydrangeas such as the H. paniculata and H. arborescens don't need extra winter protection. However, extreme cold can cause die-back of their branches. If a colder than normal winter is predicted, consider covering.
Loosely wrap plants with a couple layers of burlap, making sure to secure it with sturdy twine. Another option is to make a mulch mountain, covering the majority of the plant. This method works best for newly planted, smaller specimens.
Pruning Hydrangeas is important to overall plant health, appearance, and maintenance of their natural shape. Pruning also promotes fresh growth and encourages flowering. With regular pruning, the risk of disease and decline is greatly reduced as an open, healthy plant promotes good air flow.
Prune shrubs that bloom on new wood (buds are formed on new growth during the current growing season), in late winter or early spring. In our area, this is late March or early April. You may also prune this type of shrub in the fall, but most gardeners like to leave dried blooms for winter interest. This includes panicle and smooth Hydrangeas. Prune panicle (H. paniculata) Hydrangeas in the late winter or early spring before they begin to leaf out, pruning back each stem by up to 30-50%. Prune smooth (H. arborescens) hydrangeas back to one to two feet above ground in late winter or early spring to encourage abundant new growth.
Modern bigleaf (H. macrophylla) hydrangea cultivars flower on new and old growth, so pruning can be done anytime but is usually best performed in the spring. Extensive pruning beyond basic shaping and removing broken or damaged branches is not usually necessary.
If desired, prune climbing hydrangeas back after blooming.
- Dead, damaged, and diseased branches
- Unwanted branches (top 1/3, old blooms, duplicate/parallel, sprouts, rubbing branches)
- Overgrown smaller twigs and branches
- Thick old growth, to the ground, when renovating or refreshing.
- Once established, it is okay to remove 30% - 50% of your shrub with each pruning.
- At a 45-degree angle
- Just above a bud or set of leaves
- Just above a side branch
- At the node, where one branch or twig attaches to another being careful not to cut into the branch collar which functions to close off the wound at the cut.
- All the way to the ground; a well-established shrub (one that is a few years old) will benefit from removing the oldest wood down to the ground, about 1/3 each year. This is called renewal pruning.