Rain Lily

This one is a plant of moist meadows and low woods, so it takes damp ground happily - what it will not take is soil that stays waterlogged right through the dormant season. Improve the drainage in the wettest spots rather than trying to keep it dry.

A planting that fails to reappear at all in its season - the commonest symptom and the last one noticed. Shoots that emerge thin, yellow and stunted, or start up and then collapse. Clumps thinning year on year in the low, wet corner of a bed while the same bulbs thrive on higher ground. Lift a suspect bulb and look: a healthy one is firm and heavy with clean pale scales, a rotting one is soft, brown or blackened, often slimy between the scales, and smells sour. Roots gone brown and stringy rather than firm and pale. Standing water, or a dark permanently damp patch of soil, over the planting after rain.

Nothing brings rotted tissue back, so the work is triage and drainage. Lift the planting, sort the bulbs, and bin every one that is soft, discoloured or foul-smelling rather than composting it. Keep only bulbs that are firm all through, trim any small damaged patch back to clean tissue, let the cut surfaces dry in the air for a day, and replant into free-draining ground or fresh mix somewhere the water moves away. If the same spot rots bulbs every year, do not replant it - raise the bed, open up the soil, or move the planting and grow something else there.

Drainage does nearly all the work. Plant bulbs in ground that drains freely and never stands in water, and where the soil is heavy plant on a raised bed, a berm or a slope, or grow them in containers - a pot needs an open hole and must never be left standing in a full saucer. Set bulbs at the depth the plant actually wants rather than deeper, and keep mulch pulled back from the neck. Water the soil rather than the calendar, and cut watering right back through dormancy when the bulb is not drawing. Never plant a bulb that is already soft, bruised or mouldy, and do not dig or plant in soggy ground.

Bulb rot is not one organism but a group of soil fungi and water molds - Fusarium, Rhizoctonia, Pythium, Phytophthora and others - that live harmlessly in most soils and turn destructive only when the ground stays saturated. A bulb is a swollen food store with no way to shed water, so once the soil around it is airless the scales suffocate, soften and are invaded, and the whole bulb goes brown, mushy and sour-smelling. Dormancy is the dangerous season: a resting bulb draws almost nothing, so it can sit in cold or hot wet ground for weeks with nothing drying it out. The damage is underground and invisible, so the first sign is usually a clump that simply never comes up.

This is a semi-hardy Southeastern bulb, dependable through about zone 7 with a winter mulch over the bulbs. North of that, grow it in containers and overwinter the bulbs frost-free rather than expecting it to hold in open ground.

Bulbs that never reappear after a severe winter, while the same planting under mulch, against a wall, or in a warm corner comes up untouched. Foliage blackened or turned to mush by a hard freeze on evergreen and semi-evergreen types. Containers left outdoors that come up empty in spring. Clumps thinning from the exposed edge inward. A season where the plant sends up leaves late and weakly and never flowers - a bulb that survived but was damaged.

Wait before you dig. A bulb whose leaves were blackened by frost is often alive underground and will send up new growth once the cold passes, so cut off the damaged foliage and give it the rest of the season before writing it off. If nothing appears, lift and check at the end of the season: firm bulbs can be replanted somewhere warmer or potted, soft ones go in the bin. There is no treatment for a bulb that actually froze through - the fix is a different site, a mulch, or a pot that comes indoors, and it has to be in place before the next winter.

Know the actual cold-hardiness of what you planted rather than the range printed for the genus, and match it to your zone. In the ground, plant a little deeper than the minimum and put a loose, airy winter mulch of leaves, straw or pine needles over the bulbs at the cold edge of their range, pulling it back as growth starts. Give borderline plantings a sheltered site - a south wall, a raised sunny bed, ground that drains hard so it is never frozen wet. Beyond their hardiness, grow them in containers moved somewhere frost-free and barely watered for the winter, or lift the bulbs and store them dry.

Cold, not heat or drought or any pest, is what sets the northern limit for a tender or semi-hardy bulb. Hardiness varies by species and even by clone, so a planting can sail through mild winters for years and then be lost to one hard freeze - especially where bulbs sit shallow and unmulched in an exposed bed, or in a container, whose rootball freezes from every side at once and offers none of the buffering that open ground gives. Wet cold is far worse than dry cold: saturated soil carries the freeze down to the bulbs and rots whatever the ice did not kill outright.