The RHS says prepared hyacinth bulbs, which are heat-treated for an earlier display, should be planted in September because they need 10 to 12 weeks for good root and shoot development. Pot them in peat-free multipurpose compost, or bulb fibre if the pot has no drainage holes, keep the room cool enough for the flower stalk to emerge, and note that the ASPCA lists hyacinth as toxic to dogs and cats.
Choosing and potting the bulbs
The RHS hyacinth growing guide says to use peat-free multipurpose compost in pots with drainage holes, and bulb fibre in pots without them, because bulb fibre holds water without becoming soggy. For indoor displays of prepared bulbs it says to arrange them closer than 7.5 cm (3 in) together, but without letting them touch. The 10 cm (4 in) planting depth and 7.5 cm spacing it gives apply to outdoor containers.
What the RHS page does not say
The page does not give a chilling length or temperature for forcing, an indoor planting depth for prepared bulbs, or room temperatures for the indoor display. If you buy prepared bulbs, follow the pack for the dark, cool stage.
Why the flower stalk does not emerge
The RHS says if the room is too warm the flower stalk may fail to emerge from the leaves before the flowers open, and a weak stalk also means the room is too warm. The fix it gives is to move the container to a cooler room until the stalk is taller than the leaves.
Watering and feeding
Keep bulbs moist while growing and flowering, add water only if the compost feels dry, and reduce water once the leaves begin to die off naturally. For water-grown bulbs, keep the water just below the bulb without touching it. Water-grown bulbs need no feeding. For bulbs that will be kept, the RHS suggests a liquid high-potassium feed, such as tomato fertiliser, from early spring until six weeks after flowering.
After flowering
Cut the stalk at the base when the flowers fade, then move pots to a sheltered spot outdoors or plant the bulbs in a sunny spot. The RHS says water-grown bulbs are usually discarded.
Hyacinths and pets
The ASPCA lists hyacinth, Hyacinthus orientalis, as toxic to dogs, cats and horses. It gives possibly narcissus-like alkaloids as the toxic principle and intense vomiting, diarrhea (occasionally with blood), depression and tremors as signs. See Fragrant Houseplants That Are Toxic to Cats and Dogs and keep bulbs and pots out of reach of pets.
Frequently asked questions
When should I plant prepared hyacinth bulbs?
The RHS says plant in September, because prepared bulbs need 10 to 12 weeks for root and shoot development.
Do hyacinths smell strong?
The RHS describes them as known for highly fragrant blooms.
Can I grow hyacinths in water?
Yes. The RHS says to keep the water just below the bulb without touching it, in a dark, cool place until the vase is full of roots, and that water-grown bulbs are usually discarded afterward.
Are hyacinths toxic to cats and dogs?
The ASPCA lists hyacinth as toxic to dogs, cats and horses.
Sources read for this page
Last reviewed 15 October 2026. Written by Md. Firozur Rahman. This page gives general guidance; see the Disclaimer and contact a veterinarian about any pet health concern. Browse more in Bloom & Fragrance.
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