Hardy hibiscus
Hibiscus moscheutos
also called rose mallow, swamp rose mallow, dinner plate hibiscus
Dinner-plate flowers, honestly measured: 25 cm blooms in white, pink and red on a die-back native perennial that shrugs off zone 4 winters and blooms through the worst of August.
- Type
- Flower · Perennial
- Botanical family
- Mixed / other
- Foliage color
- Green
- Flower color
- Pink
- Sunlight
- Full sun
- Watering
- High; the rose mallow of native marshes never wants for a drink
- Soil
- Rich, moist to wet; a marsh native that loves the low spot
- Feeding
- Rose & flower
- USDA zones
- 4b–9b
- Frost tolerant
- Yes
- Sow indoors
- 56 days before the last spring frost
- Plant out
- 7 days after the last spring frost
- Plant spacing
- 2 ft 11 in
- In-row spacing
- 2 ft 6 in
- Between rows
- 3 ft 11 in
- Square-foot density
- Not suited to SFG
- Sow depth
- 0 in
- Root system
- A fleshy crown with thick perennial roots
- Working depth
- 12 in–3 ft
- Can reach
- 5 ft down where the soil allows
- Spread
- 4–6 ft across, about 1–1.5× the width of the plant
- Shallowest pot
- 18 in of soil
The crown is the plant’s bank account and it is slow to rebuild, which is why a new planting is left unpicked for a season or two. Plant it at the depth it asks for and no deeper; these rot from being buried far more often than they suffer from being shallow.
A thick perennial crown that wakes very late, often not until early summer, so the gap is easily mistaken for a dead plant. Mark it in autumn and be patient in spring.
The habit is Hardy hibiscus’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.
- When
- Not harvested. Cut the dead stalks in late fall or early spring; each flower lasts one day and self-cleans.
- What to look for
- Stalks frost-killed and hollow. In spring: nothing, silence, bare ground, well past when everything else is up. This is normal.
- How to harvest
- Cut the dead canes to 15 cm whenever they annoy you between November and April; the stubs mark the crown so the June-emerging shoots do not get dug up in error. No deadheading is needed in season.
- How often
- One cutdown a year, and one act of faith every spring.
- Storing the crop
- Nothing to store. The seed pods that follow are handsome dried, and self-sown seedlings come mixed but vigorous if you leave a few.
Beneficial predators that hunt this plant's pests — grow their favourite flowers nearby to recruit them. companion plant
- Assassin bug Reduviidae
A patient ambusher with a curved beak it drives into whatever it catches — caterpillars, beetles, bugs, and the occasional bee, so count it a generalist rather than a specialist. It will jab a careless finger too, so admire it and leave it be.
- Garden birds Passeriformes
Both things are true: birds strip your currants and a brood of blue tits takes several thousand caterpillars out of one fruit tree in a fortnight. Net what you must and welcome them everywhere else — a nest box near the apples is worth more than a spray.
- Parasitic wasps Braconidae & Trichogramma
Tiny, stingless wasps that lay eggs in or on caterpillars, aphids, and moth eggs — the white cocoons riding a hornworm are their calling card, so leave that caterpillar be. Umbel flowers with shallow nectar keep the adults fuelled.
- Praying mantis Mantidae
A sit-and-wait ambusher that snatches caterpillars, beetles, and anything else that wanders close — friend and foe alike, so count it a mixed blessing. Tall, structured plantings give it perches and egg-case anchors.
- Spined soldier bug Podisus maculiventris
A predatory stink bug — same shield outline as the pest, but with a sharp spine at each shoulder and a beak it uses to spear caterpillars and beetle grubs. Learn the spines before you squash a shield bug, because this one is on your side.
- Tachinid fly Tachinidae
Bristly, house-fly-lookalike parasitoids that lay eggs on caterpillars, beetle grubs, and earwigs — the maggot consumes the host from within. Adults sip nectar from shallow umbels and daisies.
- Aphid midge Aphidoletes aphidimyzaHunts Aphids
A tiny midge whose orange maggots paralyze aphids and drink them dry, twenty or more each. Sold as a greenhouse biological control and resident outdoors wherever there are small nectar flowers and an unsprayed aphid colony to find.
- Beneficial nematodes Steinernema & Heterorhabditis spp.Hunts Japanese beetle
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.
- Big-eyed bug Geocoris spp.Hunts Aphids
A stubby 3 mm bug with enormous wrap-around eyes, working the soil surface and the low foliage for aphids, mites, thrips and insect eggs. It is the main natural check on chinch bugs in a lawn and it is killed outright by insecticide.
- Damsel bug NabidaeHunts Aphids
A slender, mantis-armed bug that grabs aphids, small caterpillars, and thrips in low crops and meadowy edges. Leave a strip of unmown grasses and flowers for it to overwinter in.
- Dragonflies & damselflies OdonataHunts Aphids
Aerial hunters that take mosquitoes, midges and small flies on the wing all day, and whose larvae spend a year or more clearing the same insects from the water. A pond with planted margins and no fish is the way to have them.
- Green lacewing Chrysoperla carneaHunts Aphids
Its bristly larvae — "aphid lions" — impale aphids, mealybugs, thrips, and mite colonies, eating hundreds a week. Adults feed on nectar and pollen from small open flowers and overwinter in hollow stems left standing.
- Hoverfly SyrphidaeHunts Aphids
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 Aphids
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.
- Minute pirate bug Orius spp.Hunts Aphids
A pinhead-sized true bug that is the best natural check on thrips, and happily spears aphids, mites, and insect eggs too. It needs pollen when prey is scarce, so keep something flowering nearby.
- Soldier beetle CantharidaeHunts Aphids
Soft-winged beetles seen mating on flower heads in high summer; adults and larvae both take aphids and soft grubs. Open composite flowers are their landing pads and hunting grounds.
- Spiders AraneaeHunts Aphids
Webs, ambushes, and night patrols make spiders the garden’s steadiest generalist predators, taking whatever flies or crawls past. Mulch, ground cover, and undisturbed corners keep the population dense.
It is the latest perennial in the garden to emerge, often mid-June in the North, and every spring someone replaces a live one. Mark the crown, wait past all reason, and it grows 2 cm a day once the heat arrives. Each flower lasts one day; the plant makes hundreds.
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com