Newsletter Articles
Hydrangea Care: How to Grow Hydrangeas in SoCal
By Richard Flowers, ACCNP, Green Thumb Nursery Ventura
To care for hydrangeas in Southern California, give them morning sun with afternoon shade, keep the soil consistently moist, and plant in rich, well-drained ground. These are thirsty, heat-sensitive shrubs, so in our climate the afternoon shade and steady water matter most. And the famous blue-or-pink flower color comes down to your soil pH.[1]
Quick answer: Hydrangeas want morning sun and afternoon shade in hot SoCal, rich well-drained soil, and about one inch of water a week (two in heat). For bigleaf types, acidic soil turns flowers blue and alkaline soil turns them pink. Prune old-wood types right after they bloom and new-wood types in late winter.
How to Care for Hydrangeas
Hydrangeas grow well in full sun but need partial shade in very hot climates, along with rich, porous soil and regular water.[1] In Southern California that means siting them for morning sun with afternoon shade and giving them moist, well-drained soil rich in organic matter; hot, exposed spots lead to wilting and scorched leaves.[2] One nuance worth knowing: while hydrangeas are often planted in shade, most actually grow larger and bloom better with more light, as long as the soil stays consistently moist, so aim for bright morning light rather than deep shade.[3]
How Often to Water Hydrangeas
Hydrangeas like steady moisture. Plan on about one inch of water per week in normal weather and closer to two inches per week during hot, dry spells, delivered as one or two long, deep soaks with a soaker or drip hose rather than frequent splashes.[4] A two to three inch layer of mulch keeps the roots cool and holds moisture, and consistent watering is the key to preventing leaf scorch.[2] Bigleaf hydrangeas, with their large leaves, may wilt in afternoon heat even when the soil is moist, which is exactly why afternoon shade helps so much here. For shadier spots, see our guide to shade plants for Southern California.
Blue vs. Pink: Hydrangea Color and Soil pH
The color trick works on bigleaf hydrangea (Hydrangea macrophylla) and its cousin mountain hydrangea (Hydrangea serrata); panicle, smooth, and oakleaf hydrangeas do not change color this way, and white-flowered varieties stay white regardless of pH.[5][2] In acidic soil (roughly pH 5.5 or lower), aluminum becomes available to the roots and the flowers turn blue; in alkaline soil (about pH 6.0 and up), aluminum is less available and the flowers turn pink.[6] To push blooms bluer, lower the pH with soil sulfur or a diluted aluminum sulfate drench; to push them pinker, raise the pH with dolomitic lime.[7] Because much of Southern California has alkaline soil and water, local gardeners usually have to acidify the soil to get and keep that coveted blue.
Fertilizing Hydrangeas
Feed hydrangeas lightly. A soil test first is ideal, followed by a modest balanced or slow-release feeding during the growing season (for example, a 5-10-10 in late spring and again in midsummer, but not after late summer).[4] Skip the high-phosphorus “bloom booster” products: extension research finds that high phosphorus does not increase the number of flowers, and excess phosphorus can actually tie up iron and zinc (causing yellowing) and pollute waterways.[8] If the fertilizer label numbers are a mystery, our guide to what the numbers on fertilizer mean breaks them down.
Types of Hydrangeas for Southern California
Four types cover most gardens, and the differences matter for both heat tolerance and pruning:
| Type | Flowers | Blooms on |
|---|---|---|
| Bigleaf (H. macrophylla, incl. Endless Summer) | Blue/pink mophead or lacecap; color shifts with pH | Old wood (Endless Summer: old and new) |
| Panicle (H. paniculata) | White cone-shaped, aging pink; most sun and heat tolerant | New wood |
| Smooth (H. arborescens, incl. Annabelle) | Large white rounded clusters | New wood |
| Oakleaf (H. quercifolia) | White clusters, oak-shaped leaves, fall color | Old wood |
For our hot, dry climate, the more sun- and heat-tolerant types are the safer bets: oakleaf is a strong choice for hot conditions, and panicle handles sun and tougher sites well.[4] Classic bigleaf hydrangeas, including the popular reblooming Endless Summer, are the ones that change color, but they are the thirstiest and most heat-sensitive, so give them the best afternoon shade and most consistent water.[2] Browse the hydrangeas available at Green Thumb Nursery to see what is in stock.
When to Prune Hydrangeas
Prune based on whether your hydrangea blooms on old wood or new wood, or you risk cutting off next year’s flowers.[5] Old-wood bloomers, such as bigleaf and oakleaf, set their buds the previous season, so prune them right after they finish flowering.[9] New-wood bloomers, such as panicle and smooth (Annabelle), flower on the current season’s growth, so you can prune them in late winter or early spring while dormant.[9] Reblooming Endless Summer flowers on both, so do any needed pruning right after the first flush and let it rebloom through the season.[9]
Ready to add hydrangeas to your garden? Visit any Green Thumb Nursery location and our team will help you choose a type suited to your light, soil, and the color you want.
Hydrangea Care FAQ
How do you care for hydrangeas?
Plant them in rich, well-drained soil with morning sun and afternoon shade, water consistently (about an inch a week, more in heat), mulch to hold moisture, feed lightly in the growing season, and prune according to type.[1]
How often should you water hydrangeas?
Give hydrangeas about one inch of water per week in normal weather and about two inches per week in hot, dry weather, as one or two deep soaks rather than frequent light watering.[4]
Can hydrangeas grow in full shade?
They tolerate shade, but most hydrangeas grow larger and bloom better with some sun. In hot SoCal the ideal is morning sun with afternoon shade, not deep full shade, which reduces flowering.[3]
How do you make hydrangeas blue?
Only bigleaf and mountain hydrangeas change color. Lower the soil pH to about 5.5 or below (with soil sulfur or aluminum sulfate) so aluminum becomes available to the roots, which turns the flowers blue. Since SoCal soils are often alkaline, you usually need to acidify.[6]
What are the best hydrangeas for Southern California?
For heat and sun, oakleaf and panicle hydrangeas are the most forgiving. Bigleaf types (including Endless Summer) are beloved for their color-changing blooms but need afternoon shade and steady water in our climate.[4]
Sources
- [1] UC IPM, Hydrangea: ipm.ucanr.edu
- [2] Clemson HGIC, Hydrangea Care: hgic.clemson.edu
- [3] Chicago Botanic Garden, Hydrangeas: chicagobotanic.org
- [4] UConn Home and Garden, Hydrangea: homegarden.cahnr.uconn.edu
- [5] UMD Extension, Pruning Hydrangeas: extension.umd.edu
- [6] UGA Extension, Hydrangea Blooms and Soil pH: fieldreport.caes.uga.edu
- [7] UGA Extension, Aluminum Is the Key to Hydrangea Color: fieldreport.caes.uga.edu
- [8] NDSU Extension, The Myth of High-Phosphorus Fertilizers: ag.ndsu.edu
- [9] Clemson HGIC, Pruning Hydrangeas: hgic.clemson.edu
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