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The Ultimate Guide to Panicle Hydrangeas

The Ultimate Guide to Panicle Hydrangeas

By Stacey Hirvela, Proven Winners® ColorChoice®
Photographs courtesy of Proven Winners® ColorChoice®

Panicle hydrangeas, also known as peegee hydrangeas, hardy hydrangeas, and ‘Limelight’ hydrangeas, are the easiest to grow, most adaptable of all hydrangeas. We like to call them the “black thumb hydrangea” because they are so easy and reliable, they make even people who have no experience (or claim to have a black thumb, which we don’t believe even exists, frankly) look like garden rock stars. Even so, people always have lots of questions about growing panicle hydrangeas, so here are some answers to the myriad questions we get on these popular plants.

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Hydrangea paniculata

Where Can You Grow Panicle Hydrangeas?

One of the things that makes them so popular – besides their undeniable good looks – is that they grow over so much of North America, from chilly USDA Zone 3 through balmy USDA Zone 8 (even USDA Zone 9 in the case of ‘Limelight’). That means they can be planted everywhere from Manitoba to Mobile, and in every area you can count on big, beautiful blooms in summer. Panicle hydrangeas offer the best cold and heat tolerance of all the types of hydrangeas.

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‘Fire Light’ Hydrangea

Picking A Perfect Spot For Panicle Hydrangeas

Light

Panicle hydrangeas are the most sun-tolerant of all hydrangeas, and in colder climates (say, USDA Zones 3-6), we recommend at least four hours of bright sun each day; six or more is preferable, as it encourages the strongest stems and the most flowers. In hotter climates (USDA Zone 7 and warmer), afternoon shade is beneficial, but the plants should get at least some sun each day.

Soil

Overall, panicle hydrangeas aren’t finicky about soil, but good drainage is a must. Soils that are too wet lead to root rot, so avoid planting them in any area that stays wet for any length of time. Aside from that, any average soil in your landscape will do. They can even grow in clay soil, provided it is well-drained. They are tolerant of a range of pH levels, from acidic to alkaline, so unless you live in an area of extreme soil pH, you should not need to make any changes to successfully grow panicle hydrangeas.

Planting

Do not amend the soil when you plant panicle hydrangeas. Do not add any kind of compost, potting mix, topsoil, etc. to the hole when you plant in the ground. This leads to something called the “bathtub effect,” wherein water infiltrates very rapidly into the amendment you added, but as it drains and hits your natural soil surrounding the hole, it slows to a halt. During this time, it sits around the roots, leaving them susceptible to rot. This is our recommendation for planting all of our shrubs, however, it bears repeating here, as this is the number one reason we’ve seen that recently planted panicle hydrangeas might struggle. Make your life – and your new plant’s life – easy: Plant directly into your natural soil only, water after planting, and apply a 2-3”/5-7 cm layer of shredded bark mulch.

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‘Zinfin Doll’ Hydrangea

Water

Like any newly planted shrub or tree, panicle hydrangeas need regular water during their first year or two. Once they are established, they can survive dry conditions, however, too much hot, dry weather can compromise blooming, so regular watering is recommended for the most and best-looking flowers.

Fertilizing

In most areas, it is not necessary to fertilize panicle hydrangeas regularly. If you want them to grow more quickly, an application of a granular fertilizer formulated for shrubs (like a rose fertilizer) in early spring is sufficient. Avoid fertilizing panicle hydrangeas excessively, as this can lead to weak stems. Be particularly aware of incidental fertilizing, such as that applied to a nearby lawn or flower bed, as these tend to be high in nitrogen and more likely to push soft, rapid growth that causes weak stems.

Flowering

“Panicle” describes the shape and arrangement of the blooms of the plant, but it’s easiest to think of them as essentially football-shaped (and sized!). They bloom in summer (mid-late spring in Zones 8/9). The flowers start out white, but as summer stretches on and days start to get shorter and nights cooler, they start to take on pink to red tones. Exact color depends on the variety, and some varieties like Fire Light® or the new Limelight Prime® hydrangea turn a new color entirely, while some, like Zinfin Doll® or the new Quick Fire Fab® hydrangea, will do so gradually, producing a multi-color shaded effect. If the color the flowers turn is muddy, that typically indicates the plant is in too much shade and/or that temperatures, and particularly nighttime temperatures, have been too high.

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‘Limelight Prime’ Hydrangea

The color the blooms turn is a genetic trait that develops with the natural aging of the cells in the florets, and is not influenced by any condition in the soil, like pH level. You can’t change panicle hydrangeas’ color by treating with aluminum sulfate or planting in acidic soil– they will always stay in the pink/red range.

Winter

Because panicle hydrangeas are so tolerant of cold climates, they need little to no special treatment for winter. As long as a good 2-3”/5-7 cm layer of mulch is over the roots, it’s prepared to soldier through the impending cold, ice, snow, and wind.

Pruning

Panicle hydrangeas bloom on new wood – in other words, they create their flower buds for the year only after they’ve begun to leaf out in spring. This means that they can be pruned without negatively impacting their bloom. Though pruning is not strictly necessary, it encourages stronger stems, better blooming, and an overall more attractive shape. If you are starting with a very small plant such as one purchased online, keep pruning to minimum until it has had the chance to develop some good body.

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‘Quick Fire Fab’

When To Prune

Panicle hydrangeas can be pruned in late fall, once the plant has gone completely dormant (i.e., has lost all of its leaves and has been bare for at least two weeks), or in early spring, just as the new growth begins to emerge. Aim to cut the plant back by about one-third its total height; in other words, if it is 6’ tall, cut off about 2’. You should also cut off any thin, spindly stems and side branches.

This is just the tip of the iceberg when it comes to questions about hydrangea care. But rest assured, panicle hydrangeas are easy to grow and maintain using just the information provided in this guide. But if you’re looking for more advice, including a Q & A about panicle hydrangeas, visit the full article on the Proven Winners website.


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