When it arrives
Your plug tray
Plant plugs once nights are warm, or pot into 4–6 in pots in rich mix first. Keep them evenly moist and in full sun; they grow fast in heat. Expect a smaller plant the first year.
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Real dishes from our Field Notes recipes, shared by the people who made them.
Holy Grail grown by our community
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- Mature height
- 54.0 in
- Mature spread
- 60.0 in
- Bloom
- Mid-July – peak Mid-August
- Fragrance
- None
- Deer
- Moderately resistant
Lavender companion · grow guide
How to grow Holy Grail
Hardy Hibiscus · Hibiscus
Hardy hibiscus (rose mallow) needs full sun, rich soil and plenty of water. It dies to the ground each winter and is one of the very last perennials to wake up in spring.
Check my zone & planting dates
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Full sunLight
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High waterWet tolerant drainage
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pH 5.5–7.0Soil
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Zones 4a–9bHardiness
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54″ tall60″ wide
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Some resistanceDeer · rabbits some resistance
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Not known toxicPets
Huckleberry saysTell me where you grow and I’ll check if Holy Grail will thrive there.
Hardy in zones 4a–9b
Late spring once soil has warmed, through early summer.
Your year with Holy Grail
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When to plant
Late spring once soil has warmed, through early summer.
How deep
Set the crown, where old stem stubs meet the roots, just below the soil surface with roots spread out.
Spacing
About 3–4 ft apart; mature plants are shrub-sized.
Soil
Loam or silt rich in organic matter · pH 5.5–7.0
Fix-it tip: Mix generous compost into sandy or poor soils to hold moisture. Slightly acidic soil is ideal. It tolerates wet, boggy soil better than drought.
Sun
Full sun (tolerates part sun).
Full sun gives the most flowers and best disease resistance.
Don’t give up on it
Is it alive? What spring looks like
Very late: new shoots often don't appear until late May or June in Michigan, once soil is warm. Don't dig it up. Mark its spot in fall so you don't damage it while you wait.
Spring
Be patient: shoots come late May–June. Feed as growth starts.
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Summer
Big blooms; water deeply; check for sawflies.
Fall
Cut stems back after frost; mark the spot.
Winter
Dormant; mulch crown the first year.
Watering
First season: Keep soil evenly moist the whole first season; water deeply 2–3 times a week in hot weather.
After that: Still needs regular water; give about an inch or more weekly in dry spells. Mulch to hold moisture.
Feeding
Feed in late spring as growth begins with a balanced slow-release fertilizer or compost; it's a heavy feeder for its size.
Pruning & deadheading
Deadhead spent flowers for tidiness. Cut stems back to 12–24 in after frost, or to the ground in spring; leaving short stubs marks the plant and can shelter native bees.
Dividing
Rarely needed; it forms a woody crown. Leave it in place.
Winter
Hardy to about zone 4. Stems die after frost; mulch the crown in cold areas the first winter.
Summer heat
Loves heat and humidity if it has water. Huge flowers each last about a day.
Leaves full of holes, lacy
Likely cause: Sawfly larvae (small green caterpillar-like) or Japanese beetles
What to do: Check leaf undersides early; pick off or spray insecticidal soap. Plants recover and still bloom.
No growth in May
Likely cause: Normal late emergence
What to do: Wait until late June before worrying; keep the area marked.
Buds drop before opening
Likely cause: Drought stress
What to do: Water deeply and mulch.
Too wet or too dry?
Wilting, crisp brown leaf edges and dropped buds: too dry. Plants rarely show overwatering trouble in the garden.
Watch for
- Hibiscus sawfly larvae (leaves skeletonized)
- Japanese beetles
- Leaf spot, rust; leaf scorch in dry soil
Pets & wildlife
ASPCA lists hibiscus (H. syriacus) as non-toxic to dogs, cats and horses. Hardy hibiscus isn't listed separately.
Deer: somewhat resistant · Rabbits: somewhat resistant
Finnegan saysStill not sure what’s wrong? Ask Plant Health — describe it or add a photo.
In a container
Good in pots · 5 gallon+
Grows well in a large pot with rich mix; water daily in summer heat. Overwinter the pot in an unheated garage.
Indoors
Outdoor plant
Needs full sun and winter dormancy.
Winter chill
No chill needed
Blooms on new growth each summer; no chill needed, though it goes fully dormant in winter.
Growing it on
Plugs from the tray
3–4 inch pots for 3–5 weeks, until roots hold the soil
Garden bed or a 5 gallon pot
Time to move up? Slide the plant out: if white roots wrap the outside of the soil, it’s ready for the next size.
Planting with lavender
Give it its own spot
Same full sun, but it wants rich, moist to wet soil that would rot lavender. Plant it in a moister part of the garden, like a rain garden or low spot, rather than in the lavender bed.
Same bedNearbyIts own area
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