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The working rule for amaryllis is one inch (2.5 cm) of compost all the way round the bulb, and no more. A bulb three inches (8 cm) across goes into a five inch (13 cm) pot. A big bulb four inches (10 cm) across goes into a six inch (15 cm) pot. Hold the bulb over the pot before you fill it: if you can fit two fingers down the side, the pot is too big.
This is not a superstition about the plant liking to be cramped. A large volume of compost around a bulb that has very few roots stays wet for days after watering, and a wet, cold, unused mass of compost sitting against the basal plate is what starts bulb rot. The bulb cannot dry the pot out because it is not yet drawing on most of it. In a snug pot the roots occupy the whole volume within weeks and the compost cycles between wet and just-damp the way the bulb wants.
Depth matters more than width. Amaryllis push thick, fleshy, perennial roots straight down rather than spreading sideways, and a shallow bowl leaves them coiling on the base. Use a pot at least as deep as it is wide, and preferably deeper. A heavy clay or ceramic pot is worth the money here for a second reason: a flowering stalk two feet (60 cm) tall carrying four wide trumpets will tip a light plastic pot over on a windowsill, and the stalk snaps at the neck when it goes.
Drainage holes are not optional. Decorative cachepots with no hole are the single most common way an amaryllis is drowned. If you want to use one, keep the bulb in a plain plastic pot that drops inside it, and lift it out to water.
| Bulb width | Pot diameter | Pot depth | Typical result |
|---|---|---|---|
| 2.5 in (6 cm) | 4 to 4.5 in (10 to 11 cm) | At least 5 in (13 cm) | One stalk, two to three flowers |
| 3 in (8 cm) | 5 in (13 cm) | At least 6 in (15 cm) | One stalk, four flowers |
| 3.5 in (9 cm) | 5.5 in (14 cm) | At least 6 in (15 cm) | One to two stalks |
| 4 in (10 cm) and up | 6 to 7 in (15 to 18 cm) | At least 7 in (18 cm) | Two stalks, sometimes three |
| Any size in a wide pot | More than 2 in (5 cm) of spare compost | Any | Slow rooting, risk of basal rot |
Leave the top third of the bulb above the compost
An amaryllis is planted high. Roughly the top third of the bulb, including the whole shoulder and the neck, stands proud of the surface, and only the bottom two thirds sits in compost. Buried to the neck, the bulb is far more likely to rot at the point where the new leaves and the flower stalk push out, because water collects in that crown and sits there.
There is a second reason for planting high, which is that you can see what is happening. A raised bulb lets you check the neck for softness, spot the flower bud emerging as a blunt gray-green nose rather than the flat pointed tip of a leaf, and catch mealybugs in the scales before there are hundreds of them. A buried bulb hides all three until it is too late.
Set the bulb so it sits squarely on its flat basal plate rather than tipping onto a shoulder. If it already has fleshy white roots, spread them out over the compost you have put in and work compost gently around them rather than jamming the bulb down onto a coiled mass. Those thick roots are perennial and are not replaced each year; break most of them and the bulb spends the whole season recovering instead of flowering.
Firm the compost with your thumbs around the sides but do not compact it hard over the roots. Then water once, thoroughly, until it runs from the base, and do not water again until you see growth. That first watering settles the compost. Everything after it is a judgement call, and until there are roots to drink it the compost should be barely damp.
If the bulb arrived completely dry with brittle, dead-looking roots, soak the base only in tepid water for two hours before planting. Keep the body of the bulb out of the water. This rehydrates the basal plate and starts root growth several weeks earlier.
Compost that drains, and no rich feed at planting
Use a free-draining mix rather than a wet, peaty all-purpose potting mix straight from the bag. Two parts general purpose compost to one part coarse grit, perlite or sharp sand gives roughly the right structure: it holds enough moisture to keep the roots working and lets the excess through in seconds rather than minutes. A commercial bulb or cactus compost also works well.
Do not enrich the compost with manure or a heavy dose of granular fertilizer at planting. The flower for this season is already fully formed inside the bulb and no amount of feed will improve it. Rich, wet compost around a dormant bulb only encourages rot. Feeding matters enormously later, once the leaves are out and the bulb is rebuilding, but not now.
Water quality and temperature are worth a thought at this stage. Use tepid water rather than cold from the tap, because cold water on a bulb that is just starting into growth slows it noticeably. Water around the edge of the pot rather than into the crown of the bulb.
Getting a dry bulb started
A newly bought or newly rested bulb needs a specific sequence to get moving. Rushing the watering is the mistake that costs most bulbs; from planting to the first flower is typically six to eight weeks, and most of the visible progress happens in the last three.
- Check the bulb before it goes anywhere near compost It should be heavy for its size and firm all over, especially at the basal plate. Reject anything soft at the base, weeping, or showing a blue-gray mold in the scales. Red streaks and blotches in the outer scales mean red blotch fungus and are worth peeling off before planting.
- Soak the base for two hours Stand the bulb in tepid water so only the roots and basal plate are wet. Two hours is enough. This is optional for a bulb with plump roots but makes a real difference to one that arrived bone dry.
- Part fill the pot and set the bulb Put in enough gritty potting mix that the bulb will finish with its top third above the rim level. Sit it flat on the compost, spread the roots outward, and hold it in position with one hand.
- Fill around the sides only Work compost down the gap between bulb and pot with your fingers, firming as you go, and stop at the widest part of the bulb. The shoulder and neck stay bare. Tap the pot on the bench to settle it rather than pressing hard on top.
- Water once, then leave it dry Give one thorough watering until it drains, put the pot somewhere warm at 68 to 75F (20 to 24C) and do not water again until a shoot is two inches (5 cm) high. A bulb kept wet with no roots and no leaves will rot within a month.
Note what went in the pot
Write down the potting date, the bulb width, the pot size and whether the bulb was new or one you rested yourself. Then note the date the shoot appeared and the date the first flower opened. The gap between potting and shoot is the number that tells you next year whether your rest period was long enough: a well-rested bulb usually shows a nose within three weeks, while one that was pushed back into growth early can sit doing nothing for six.
Record which end of the bulb the shoot came from too. Amaryllis put the flower stalk out from one side of the neck, and a bulb that has been turned since last year will produce it in the same relative position on the bulb rather than the same position in the pot. That detail is what lets you set the pot down facing the way you want the flowers to face.