CORVALLIS, Ore. — When botanist John Bartram first identified a hydrangea native to the United States in the 1730s, little did he know it would become a mainstay of gardens, its iconic flowers implying romance with their blustery beauty.
Hydrangeas populate millions of gardens, and with good reason. They can be used as specimens in a place of honor, as partners in mixed beds, in containers and even as hedges, said Heather Stoven, a horticulturist with the Oregon State University Extension Service.
With ongoing breeding, new cultivars continue to appear each year. With species ranging from mophead to oakleaf, panicle, smooth and H. serrata, there’s a hydrangea suited to nearly every garden in Oregon.
Types of hydrangeas
The famous mophead hydrangea (H. macrophylla) is the plant most people imagine when they think of hydrangeas. The big, bouncy blossoms give this species its common name and make it the showiest of the genus. Flowers appear in shades of pink, purple, blue and white. Native to coastal Japan, mopheads — also known as bigleaf hydrangeas — are less cold hardy than other species. They’re suited to Zones 5 through 10, and some tolerate Zone 4.
Though known for their mophead blooms, some H. macrophylla plants produce lacecap flowers — flatter clusters with sepals circling smaller florets. The blooms may be subtler, but a plant full of lacecaps is still striking.
Mophead hydrangeas typically reach 3 to 5 feet tall. Like all hydrangeas, they need consistent moisture. Plant them where they’ll receive afternoon shade to prevent leaf scorch in summer heat.
About 20 years ago, breeders introduced remontant varieties that bloom on both old and new wood, extending the flowering season. The first, ‘Endless Summer,’ sparked renewed enthusiasm for hydrangeas. Other remontant types include ‘Bloomstruck’ (Endless Summer series), ‘Starlight’ (Let’s Dance series), ‘Revolution’ (Everlasting series), and ‘Fire Island’ (Seaside Serenade series).
Similar to H. macrophylla is H. serrata, a smaller, more compact shrub with mostly lacecap flowers. It’s a bit more sensitive to sun and wind, preferring partial to full shade, and is hardy to Zone 6.
If you admired a hydrangea in your grandmother’s garden, it was probably H. arborescens, or smooth hydrangea, with huge mophead blossoms in pink or white. Native to the eastern United States, smooth hydrangeas grow 5 to 7 feet tall, though dwarf varieties are becoming popular. The classic ‘Annabelle’ is well known for its large white flowers. Newer cultivars like ‘Incrediball’ (white) and ‘Invincibelle Spirit’ (pink) offer sturdier stems and larger blooms.
H. paniculata, commonly called panicle or PeeGee hydrangea, produces elongated white, pink or greenish-white blooms that gradually turn shades of pink as they age. The hardiest of the hydrangeas, H. paniculata grows well down to Zone 3. Earlier cultivars reached 10 feet, but newer varieties stay closer to 3 to 5 feet. Popular cultivars include ‘Limelight,’ ‘Pinky Winky,’ and ‘Vanilla Strawberry.’ Panicle hydrangeas thrive in full sun if soil is kept moist, and they can even be trained into single-trunk tree forms or grown in containers.
H. quercifolia, or oakleaf hydrangea, tolerates hot weather and sun better than other species. Its foliage resembles oak leaves and turns rich shades of orange, red and burgundy in fall. Flowers, usually pink or white, are smaller and elongated like panicles. Oakleaf hydrangeas range from 3 to 7 feet tall and are hardy in Zones 6 through 10. Compact cultivars include ‘Munchkin,’ ‘Ruby Slippers,’ ‘Queen of Hearts,’ and ‘Jetstream.’
Regional tips for growing hydrangeas across Oregon
Western Oregon (Willamette Valley and North Coast)
Best fits: H. macrophylla (mophead/bigleaf) and H. serrata.
Light: Morning sun with afternoon shade; avoid reflected heat.
Soils: Often acidic enough for blue tones; still test pH before “bluing.”
Moisture: Even moisture year-round; mulch 2–3 inches to buffer summer dry spells.
Southern Oregon (Rogue and Umpqua valleys, South Coast)
Heat: Hot summers can scorch bigleaf leaves and buds. Prioritize afternoon shade and deep mulch.
Best fits: Heat-tolerant oakleaf (H. quercifolia) and panicle (H. paniculata). Use bigleaf in protected, part-shade sites.
Irrigation: Deep, infrequent soaks; avoid wetting foliage during peak heat.
Central Oregon (High Desert)
Cold and aridity: Late frosts, low humidity, alkaline irrigation water.
Best fits: Smooth (H. arborescens) and panicle hydrangeas (both bloom on new wood and are hardier).
Placement: Morning sun/afternoon shade; shelter from prevailing winds.
Soil/pH: Consider raised beds with amended, well-drained soil; test pH. Bluing bigleaf types is difficult in alkaline soils.
Winter protection: Mulch crowns 3–4 inches after soil cools; wrap young plants with burlap windbreaks where exposure is high.
Eastern Oregon (Columbia Plateau, Blue Mountains, Basin)
Cold winters and big temperature swings.
Best fits: Panicle and smooth hydrangeas for cold hardiness and reliable flowering.
Site: South or east exposure with wind protection; ensure excellent drainage to avoid winter crown rot.
Water quality: High-alkalinity water can raise soil pH; monitor pH if color is important.
Oregon Coast (North and South Coast)
Mild, windy, and often foggy.
Best fits: Bigleaf and serrata thrive in coastal humidity with dappled light; panicle tolerates more sun if soils stay moist.
Salt/wind: Use windbreaks; rinse salt spray after storms. Avoid full, unprotected ocean-facing exposures for bigleaf types.
General microclimate tips
Containers: In colder interiors, grow bigleaf/serrata in large containers; overwinter in an unheated garage to protect buds.
Snow/ice: In snow zones, gently tie stems to reduce breakage; prune damaged wood in spring.
Pruning by type: Bigleaf/serrata/oakleaf bloom on old wood (prune right after bloom); smooth/panicle on new wood (late winter/early spring).
Mulch: Maintain 2–3 inches of organic mulch statewide for moisture and root insulation — keep it an inch off stems.
Planting tips
Choose a site suited to the species’ light requirements — many hydrangeas prefer morning sun and afternoon shade. Avoid planting during hot weather; spring through early fall is ideal.
If flower color matters, test your soil’s pH before planting (see “Bluing” below). Adjusting pH is easiest when planting. Dig a hole twice the width of the root ball, loosen or trim circling roots, and backfill with native soil mixed with organic matter. Mulch well and water thoroughly.
Fertilizing and watering
Apply a slow-release, balanced fertilizer in spring. Excess nitrogen encourages foliage at the expense of flowers, while high phosphorus can inhibit blue blooms.
Hydrangeas need consistent moisture. The name itself derives from Greek: hydro (water) and angeion (vessel). Keep soil evenly moist but well drained—hydrangeas dislike soggy roots.
Pruning
Pruning depends on whether your hydrangea blooms on new or old wood. Prune species that bloom on new wood (H. arborescens, H. paniculata) in late winter or early spring. For old-wood bloomers (H. macrophylla, H. serrata, H. quercifolia), prune in late summer after flowering.
Remove only dead, damaged or weak stems unless reshaping is needed—avoid removing more than one-third of the plant at a time. Deadhead spent blooms as desired, taking care not to remove developing buds.
Bluing hydrangeas
The question gardeners ask most often: “How do I get my hydrangeas to turn blue?”
Only certain H. macrophylla and H. serrata varieties can change color. Blue hues develop in acidic soil (pH 5.5 or lower), purple in slightly acidic (pH 5.5–6.5), and pink in neutral to alkaline soils (pH 6.5 or higher).
To lower pH and encourage blue blooms, apply garden sulfur to the soil (or aluminum sulfate for potted plants in soilless mix). To raise pH for pink flowers, use lime. Amendments are best added in fall, and color changes may take several years.
For more guidance, consult Acidifying Soil for Blueberries and Ornamental Plants in the Yard and Garden: West of the Cascade Mountain Range in Oregon and Washington.
Previously titled Hydrangeas play a pretty role in the garden
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