Reviewed by Sonia Abu Bakar✓, MSc Botany
By Abu Bakar Saadat6 min readPublisher: Saadat Rafiq
Last updated: 1 November 2026References
IllustrationSit a prepared bulb in a hyacinth glass with the water just below its base, then keep it cool and dark for several weeks until the glass fills with roots. Bring it into the light slowly. Wear gloves: the bulb can make skin itch, and it is toxic to pets.
A hyacinth grown in a glass of water is a winter project you can watch from start to finish: first the roots, then the leaves, then a scented flower. The two things that matter most are keeping the water below the bulb and giving it a long, cool, dark start. Below, one example runs from a dry bulb in November to a flower in a glass, with a drawing for every step.
Every step below follows one story, and each drawing shows that exact moment. On 1 November, Amira and her daughter set up one prepared bulb in a hyacinth glass on the kitchen table. They keep it in the cool cupboard under the stairs, check the water every weekend, and bring it into the light once the roots fill the glass.
In our story: Amira and her daughter both put on gloves before they unpack the bulb.
Handling hyacinth bulbs can cause "hyacinth itch": itching, redness and sometimes blisters, and long contact can cause dermatitis (Hong Kong Hospital Authority). The whole plant is poisonous, especially the bulb. If children help, keep gloves on and wash hands afterwards (our advice).
In our story: Amira pours water in slowly and stops when it is a few millimetres below the cup.
Keep the water just below the bottom of the bulb, not touching it (RHS). NYBG says the same: the bulb rests above the water, not in it. A bulb sitting in water can rot (our advice). The RHS says a few pieces of charcoal in the water help stop it going slimy, but you don't need them.
In our story: Her daughter sets the bulb in the cup, flat base down, pointed tip up.
The flat base, where the roots grow from, goes down, close to the water but not in it (RHS, NYBG).
In our story: Amira puts the glass on a shelf in the unheated cupboard under the stairs and closes the door.
Keep it in a dark, cool place until the glass is full of roots and the flower stem is showing (RHS). NYBG says 4 to 8 weeks, and that about 4 to 7 °C is best, between 0 and 10 °C. A bulb that isn't prepared needs much longer, about 10 to 12 weeks of cold (NYBG); WSU Extension gives about 13 weeks at 7 °C. A prepared bulb needs less, so follow the packet (NYBG).
In our story: Every Saturday, Amira opens the cupboard and tops up the water, keeping it just below the bulb.
Check that the water level doesn't drop (NYBG). Once the roots reach the water, they keep the bulb fed; you don't need plant food in water (RHS).
In our story: By early December, white roots fill the glass and a short green shoot pokes out of the top.
That is the sign it's ready to come out: a glass full of roots and the flower stem emerging (RHS), or "a good root system" (NYBG). Started on 1 November, Amira's bulb will most likely flower in January rather than at Christmas; for Christmas, the RHS says to start in September (our estimate from the RHS timing).
In our story: Amira moves the glass to the windowsill in the cool spare room for the first week.
Increase light and warmth gradually (RHS), slowly bringing it into warmth and light (NYBG). Going straight from a dark cupboard to a warm room risks the problem in the next step (our advice).
In our story: When the stem of buds stands taller than the leaves, the glass moves to the kitchen table, away from the radiator.
If the stem hasn't come up before the flowers open, or is weak, the room is too warm: move it somewhere cooler until the stem is taller than the leaves (RHS). Turn the glass every few days so it grows straight towards the light (our advice).
In our story: As the flower opens it starts to lean, so Amira ties it loosely to a thin cane.
Hyacinth stems are hollow and the flowers are heavy, so they may need staking (NYBG).
In our story: In January the flower opens, and the kitchen smells of hyacinth.
Keep the glass topped up while it's in flower. Keep it where cats and dogs can't reach it: hyacinth is toxic to them (ASPCA).
In our story: When the flowers turn brown, Amira cuts the stem off just above the bulb.
Cut the flower stem off at the base once the flowers fade (RHS). Bulbs grown in water are usually thrown away after flowering, but you can try planting them in the garden (RHS). Expect it to take a year or two to flower well again, if it does (our advice).
What if Amira had filled the glass to the top? The base of the bulb would sit in the water and could go soft and rot.
Keep the water below the bulb, not touching it (RHS, NYBG). If the water turns cloudy or smells, tip it out and refill it to just below the bulb (our advice).
| What happens | Likely cause | What to do |
|---|---|---|
| No roots after a few weeks | Water not reaching the base, or too warm (our advice) | Top up to just below the bulb; keep it cool and dark |
| Bulb soft or mouldy at the base | Bulb sitting in water (RHS, NYBG) | Lower the water below the bulb; throw out a rotten bulb |
| Water cloudy or slimy | Old water | Refresh it; charcoal helps (RHS) |
| Flowers open down among the leaves | Too warm too soon (RHS) | Move it somewhere cooler until the stem is taller |
| Stem flops over | Heavy flower on a hollow stem (NYBG) | Tie it loosely to a thin cane |
| Itchy hands after handling | Hyacinth itch (Hong Kong Hospital Authority) | Wear gloves; wash your hands after handling |
Related: Houseplants poisonous to cats, How to get a Christmas cactus to flower and How to repot a houseplant.
No. The RHS says to keep the water just below the bottom of the bulb but not touching it, and NYBG says the bulb should rest above the water, not in it. The roots grow down to reach it.
The RHS says prepared bulbs need about 10 to 12 weeks, and suggests planting in September for flowers at Christmas. NYBG says to keep the glass cool and dark for 4 to 8 weeks first, until there is a good root system.
Cool darkness lets the roots grow before the leaves and flower stem. The RHS says to keep it in a dark, cool place until the glass is full of roots and the flower stem is showing.
Yes. The ASPCA lists hyacinth as toxic to cats, dogs and horses, and the Hong Kong Hospital Authority says the whole plant is poisonous, especially the bulb. Handling bulbs can make skin itch, so wear gloves.
The RHS says bulbs grown in water are usually thrown away after flowering, but you can try planting them in the garden. They may take a year or two to flower again (our advice).
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