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Key takeaways
- Paperwhites and amaryllis need no chilling. Pot them up and they grow straight away, which makes them the easiest holiday bulbs.
- Tulips, hyacinths, daffodils and crocus need a cold period before they'll bloom well. Extension sources give ranges of roughly 11 to 18 weeks depending on the bulb.
- Count back from your target bloom date: chilling weeks plus a few weeks of forcing in warmth and light.
- An unheated greenhouse, cold frame or spare refrigerator can handle chilling. Keep bulbs away from ripening fruit.
- Stagger plantings every couple of weeks for a steady run of flowers through winter.
What forcing means
Forcing is tricking a bulb into flowering earlier than it would outdoors. Spring bulbs like tulips and hyacinths need a period of cold (their "winter") before they'll flower, then warmth and light to trigger growth. Tender bulbs like paperwhites and amaryllis don't need cold at all: they grow as soon as they're potted and watered.
A greenhouse makes forcing easier because it gives you both halves of the process in one place. An unheated greenhouse or cold frame can provide the cold period in many climates, and a heated greenhouse bench or a bright, cool room provides the forcing stage. Outdoor bulb planting is a different job. GardenGear covers it in autumn bulb planting.
Which bulbs need chilling?
Here's the key split, based on published extension guidance.
| Bulb | Needs chilling? | Chilling range (Penn State Extension) | Chilling range (Mississippi State Extension) |
|---|---|---|---|
| Paperwhite narcissus | No | None needed | Not covered (tender bulb) |
| Amaryllis (Hippeastrum) | No | None needed | Not covered (tender bulb) |
| Hyacinth | Yes | 12–15 weeks | 11–14 weeks |
| Tulip | Yes | 15–17 weeks | 14–18 weeks |
| Daffodil | Yes | 15–17 weeks | 14–17 weeks |
| Crocus | Yes | 15–17 weeks | 12–14 weeks |
The two sources don't match exactly, which is normal. Varieties differ, and so do chilling temperatures. Treat these as ranges and check the bulb supplier's instructions for the specific variety you buy. Penn State lists 40–45°F as the optimal chilling temperature for tulips, and Mississippi State gives a wider band of 35–50°F for cold-hardy bulbs in general, with a warning to avoid temperatures below 25°F.
How long until flowers?
Once chilling ends, the bulbs need warmth and light to grow and bloom.
- Penn State Extension: hardy bulbs typically take 2–6 weeks to grow and bloom after chilling ends. Amaryllis flowers in roughly 6–12 weeks after potting, and paperwhites in 4–8 weeks.
- Mississippi State Extension: expect about 3–4 weeks on average from moving chilled bulbs into warmth to flowering.
Worked examples
Paperwhites for Christmas
Paperwhites take roughly 4–8 weeks from potting to bloom (Penn State). For flowers around December 25, pot them from late October through mid-November, and plant a second batch a couple of weeks later in case the first is early.
Amaryllis for the holidays
At 6–12 weeks from potting to bloom, amaryllis needs an earlier start. For December flowers, pot bulbs in September or October. Because the range is wide, many growers pot several bulbs a few weeks apart so something is in bloom for the holidays.
Hyacinths for Valentine's Day
Take a mid-February target. Using Mississippi State's 11–14 week chilling range plus about 3–4 weeks of forcing, that's roughly 14–18 weeks in total. Count back from mid-February and you land in October for potting and the start of chilling.
Tulips for late winter
Tulips need the longest chill. With 14–18 weeks of chilling (Mississippi State) plus a few weeks of forcing, bulbs potted in early October may flower in February or March. If you're starting late, buy pre-chilled tulips.
Step by step: forcing hardy bulbs
- Buy firm, healthy bulbs. Look for varieties the supplier lists as good for forcing. Shorter tulips and hyacinths tend to force best.
- Pot them up. Use a free-draining potting mix and a pot with drainage holes. Set bulbs close together with tips at or just below the surface.
- Water thoroughly once after potting.
- Chill them. Put the pots somewhere consistently cold but not freezing hard: an unheated greenhouse, a cold frame, an unheated garage or a refrigerator. Keep the mix lightly moist.
- Protect from rodents. Mice love bulbs. Cover pots with hardware cloth if you chill in a greenhouse or cold frame. See best greenhouse rodent control.
- Check for roots and shoots. Mississippi State says roots showing at the drainage holes are the main sign bulbs are ready. Shoots are usually starting to emerge too.
- Force. Move the pots into a bright, cool spot. Mississippi State suggests starting around 60–65°F and moving to 65–70°F to speed blooming.
- Turn pots every few days so stems grow straight.
- Move to indirect light once buds show color to make the blooms last longer.
Step by step: paperwhites and amaryllis
These are much simpler because there's no cold stage.
Paperwhites
- Set bulbs on a layer of pebbles or potting mix in a bowl, close together.
- Add water to just below the base of the bulbs so roots reach it but the bulb doesn't sit in water.
- Keep them in a bright, cool spot. Cooler conditions help keep stems shorter.
- Stake or loosely tie stems if they flop.
Amaryllis
- Pot the bulb in a container only slightly wider than the bulb, with the top third of the bulb above the mix.
- Water once and then sparingly until growth starts, then more regularly.
- Give it bright light and turn the pot often.
- Stake tall flower stalks.
Using your greenhouse for each stage
- Unheated greenhouse: Good for chilling in many regions, as long as temperatures stay cold but not deeply freezing. Use a min-max thermometer to check. On sunny days, an unheated greenhouse can get warm, which interrupts chilling, so vent it or keep pots under a bench.
- Cold frame: Often steadier than a greenhouse for chilling, because it's lower and shaded. See best cold frames.
- Heated greenhouse bench: Ideal for the forcing stage. Keep pots in good light and out of direct heater airflow.
- Frost cloth: If a hard freeze threatens pots in an unheated greenhouse, cover them with frost cloth or move them somewhere sheltered.
Hyacinth glasses and other containers
Hyacinths can be forced in special glass vases that hold the bulb just above water. They still need chilling. Chill the bulb first, or set up the vase and keep it in a cold, dark place while roots grow. Crocus can be forced in small crocus vases the same way.
Common problems
- Short, stunted flowers or no flowers: usually too little chilling.
- Tall, floppy stems: often too much warmth or too little light during forcing.
- Rotted bulbs: too wet during chilling or poor drainage.
- Bulbs dug up or chewed: rodents. Cover pots with hardware cloth.
- Buds that dry up: the pot dried out or the bulb was moved into heat too fast.
Planning your winter bloom calendar
Stagger for a long season. Pot a batch of paperwhites every two weeks from late October, pot amaryllis in early fall, and start a round of hyacinths and tulips in October for late-winter flowers. By January, your greenhouse can have something in bloom every week.
Forced hardy bulbs are usually spent after forcing. Many growers compost them or plant them outdoors in spring, where some may recover and bloom in later years. Amaryllis can be kept growing through summer and brought back into bloom. Our bulb and tuber storage guide covers storage gear.
Frequently asked questions
Do paperwhites need to be chilled before forcing?
No. Paperwhites and amaryllis don't need a cold period. You can pot them up and they'll start growing right away, which makes them the easiest bulbs for holiday blooms.
How long do tulips need to be chilled for forcing?
Extension ranges vary. Penn State Extension gives 15–17 weeks and Mississippi State Extension gives 14–18 weeks. Check the supplier's instructions for your variety, and buy pre-chilled bulbs if you're starting late.
Can I chill bulbs in my greenhouse?
An unheated greenhouse can work for chilling in many climates, as long as it stays cold but not deeply frozen and doesn't warm up too much on sunny days. A cold frame or refrigerator is often steadier.
How long do hyacinths need to chill?
Penn State Extension lists 12–15 weeks and Mississippi State Extension lists 11–14 weeks. Pre-chilled hyacinths need less time at home.
When should I plant amaryllis for Christmas?
Penn State Extension says amaryllis typically flowers 6–12 weeks after potting, so pot bulbs in September or October for December bloom. Stagger a few bulbs to improve your odds.
Can I reuse forced bulbs?
Forced hardy bulbs like tulips and hyacinths are usually spent. Some growers plant them outdoors in spring, where they may recover over time. Amaryllis can be grown on and reflowered.