Illustration
Delft Blue
Hyacinthus 'Delft Blue'
Delft Blue blooms from March through April.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Delft Blue
Plant it in full sun. It prefers moderate water. It is hardy in USDA zones 4–8. Expect it to reach about 10 in tall and 8 in wide at maturity, in roughly 1 year (a house reading).
Is Delft Blue toxic to dogs or cats?
- Listed as toxic to dogs and cats by NC State Extension, Pet Poison Helpline and Royal Horticultural Society.
- Listed as poisonous to people by NC State Extension.
Lists differ and none is complete. If a pet eats a plant and seems unwell, call a veterinarian or a pet poison helpline.
What was checked
Nine facts were checked against named botanical sources, each recorded beside the sources that carried it: mature height and spread, hardiness zones, sun, water, bloom months and color, the trait tags, and years to mature size, which rests on a recorded house rule where no publisher states one and is marked so. Soil, diseases, pests, toxicity and the plant's own names have not yet been read for this plant, and its trait tags are the ones a feature uses rather than every word a page prints. Each fact above carries its own mark. The planting, spacing and size sections are derived from these checked facts by a fixed rule, not checked separately, and the plant type is the library's own classification.
When to plant Delft Blue
Delft Blue is a fall-planted bulb: get it in the ground 6 to 8 weeks before the ground freezes, typically September or October in zone 6, the middle of its hardy zones 4 to 8. It pays you back the following March to April.
Month-by-month timing for your zone is on the planting calendar; if you garden near zone 6, the middle of this plant's hardy range, start with zone 6 in September. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Delft Blue get?
10 intall5 ft 7 inan adult8 inwideSee Delft Blue in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.
Where these facts come from
Delft Blue's height, spread, hardiness zones, sun, water, bloom months and color and trait tags were checked against 10 published sources on October 22, 2026. Each one is linked below with every fact it carried, which can include a fact this page still marks as not yet checked, because a source carrying a value is not the same as the value being held to the standard. Facts not in that list, and the planting, spacing and size sections, are not covered by these sources.
- Chicago Botanic Gardenhardiness zones, sun, bloom months and color and trait tags
- dutchbulbs.comK. van Bourgondienheight, hardiness zones, sun and bloom months and color
- BBC Gardeners' WorldMagazineheight, spread and bloom months and color
- fedcoseeds.comFedco Seedsheight, hardiness zones and bloom months and color
- adrbulbs.comA.D.R. Bulbsheight, spread and hardiness zones
- NC State Extensionsun, water and trait tags
- RHSRoyal Horticultural Societyheight and bloom months and color
- Missouri Botanical Gardensun and water
- jandewitenzonen.comJan de Wit en Zonenheight
- vannoortbulb.comVan Noort Bulbheight
How the checking works, and what each standard covers, is on the verified plants page.
Good to know about Delft Blue
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note.
Safety
Toxic to dogs, cats and horses; all parts, and the bulb most of all. Eating it causes drooling, intense vomiting and diarrhea. per ASPCA
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Design a garden with this
Drop this plant onto a 3D plan, see how it fills in, and watch your whole garden bloom across the year.