Hydrangea
Hydrangea
Thirsty and sun-shy: morning light, deep water, and the faded heads left standing to shield next year's buds.
- Type
- Shrub · Perennial
- Botanical family
- Mixed / other
- Foliage color
- Green
- Flower color
- Blue
- Sunlight
- Morning sun with afternoon shade — keep it off a hot south wall.
- Watering
- Water deeply and often, and mulch to hold the moisture in.
- Feeding
- A balanced feed in spring; ericaceous feed for blue flowers.
- Frost tolerant
- Yes
- Flowering
- June
- Pruning
- Prune according to type, and leave the old heads on over winter for protection.
- Mar–Jun Bud Break
- Jun–Aug Flowering
- Aug–Oct Growing
- Oct–Dec Leaf Fall
- Jan–Mar Leaf Fall
- Plant spacing
- 6 ft 7 in
- In-row spacing
- 6 ft 7 in
- Between rows
- 8 ft 2 in
- Square-foot density
- Not suited to SFG
- Root system
- A fine surface mat, and nothing below it
- Working depth
- 4–12 in
- Can reach
- 18 in down where the soil allows
- Spread
- 6.5–10 ft across, about 1–1.5× the width of the plant
- Shallowest pot
- 16 in of soil
Hair-fine roots in a shallow felt, with no deep anchor to fall back on. It cannot chase water, so it is the first casualty of a drought and the first thing killed by a hoe. Mulch it, never cultivate around it, and never let it go dry in its first two summers.
Shallow, fine and very thirsty, which is the whole explanation for the midday wilt: the roots simply cannot keep up. Mulch it thickly, water it in dry spells, and never plant it where it must compete with a tree.
The habit is Hydrangea’s own; the figures are what that habit usually comes to at this size, not a measurement of this species. Roots follow the soil either way: a compacted pan, a high water table or heavy clay stops them well short of any of it, and deep open ground lets them go further.
- Cats and dogs
- Recorded toxic
Recorded as toxic to cats and dogs by ASPCA.
The source pins one species where our catalog holds the genus. Read as covering the entry we file, not as narrowing it to that species.
- Scale insects Hydrangea scale
- Vine weevil Adults notch leaf edges at night; their plump C-shaped grubs devour roots, especially in containers. Hand-pick adults after dark and water in biological nematodes in late summer.
- Honey fungus A fatal root disease of woody plants: white fungal sheets under the bark and honey-colored toadstools at the base. Remove the plant with as much root and stump as possible.
- Powdery mildew A white dusty coating over leaves and shoots when roots are dry but the air is humid. Keep plants watered and mulched, prune for airflow, and remove the worst leaves.
- Frost damage Frost damage to the flower buds
Beneficial predators that hunt this plant's pests — grow their favourite flowers nearby to recruit them. companion plant
- Beneficial nematodes Steinernema & Heterorhabditis spp.Hunts Vine weevil
Microscopic worms watered onto damp soil that hunt down soil-dwelling grubs and release a bacterium that kills them within days. Timing is the whole thing: warm, damp soil and a small target grub, which means late summer for most of what they are used against.
- Frogs & toads AnuraHunts Vine weevil
A resident toad works the beds every night for slugs, cutworms, and weevils. Recruit them with water — even a sunken basin pond — plus damp shade and an upturned-pot toad house; skip the slug pellets that poison their prey.
- Ground beetle CarabidaeHunts Vine weevil
Fast, glossy night hunters that patrol the soil surface for slugs, cutworms, and root-fly larvae. Give them daytime cover — thick perennial edges, stepping stones, a log — and skip the tillage that wrecks their burrows.
- Hedgehog Erinaceus europaeusHunts Vine weevil
A European animal, and worth saying so plainly: there are no hedgehogs in North America, and the ally that does the same night shift here is the toad, the opossum or the ground beetle. Where they do occur, cut a gap in the fence and skip the pellets.
- Hoverfly SyrphidaeHunts Scale insects
Bee-mimicking flies whose legless larvae graze aphid colonies clean while the adults pollinate. A ribbon of shallow, nectar-rich flowers kept in bloom all season recruits wave after wave of them.
- Ladybird (lady beetle) CoccinellidaeHunts Scale insects
The gardener’s favorite ally: adults and their alligator-shaped larvae each eat thousands of aphids, plus scale, mealybugs, and other soft-bodied sap-suckers. Grow flat, open flowers for the adults and never spray a colony that ladybird larvae are already working.
Hostas, Ferns, Astilbe, Heuchera
Green-leaved shrubs, like this one.
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com