How to Grow Ismene in Australia

Ismene (Hymenocallis x festalis), also called Peruvian daffodil or sacred lily of the Incas, is a summer-flowering bulb in the amaryllis family (Amaryllidaceae). It is a garden hybrid of two Peruvian species, grown for its fragrant white flowers with a frilled cup and long, curling petals. It shares its family with the true daffodil but grows in summer and rests in winter. It thrives in warm gardens from Darwin to Sydney and flowers in pots further south. The usual mistake is planting it too early, into soil that is still cold.

Three mistakes that matter

1. Planting into cold soil. Ismene dislikes temperatures below about 15°C, so bulbs planted in early spring sit idle and can rot in cold, wet ground. Wait until frosts have passed and the soil feels warm to the hand.
2. Letting the soil dry as buds form. In a dry spell the flower buds can wither before they open, and the whole summer display is lost. Keep the soil evenly moist from the first leaves until flowering ends.
3. Leaving bulbs in frosty ground, or tearing their roots. Frost can kill the bulbs where winters bite, and badly damaged roots can stop the next summer's flowers. Lift the bulbs before the first frost and keep the roots attached.

When to plant

Plant dormant bulbs in spring, after the last frost, once the soil has warmed. In the cool south, Melbourne Cup weekend in early November is a reliable marker. One planting flowers for years, so there is no need to plant in succession.

Leaves come first and the flowers follow in summer. Bulbs planted late in the window can still flower, later in the season.

Site, soil and setup

Ismene comes from mild, moist country and wants a warm, sheltered spot with rich soil that holds moisture but never lies wet in the cold.

Crop rotation does not apply to a bulb that stays in one place for years. Lift and divide crowded clumps instead, as described under Tips.

What the state weed lists say

No state or territory names ismene as a declared or noxious weed. Western Australia lists it as a permitted organism, not a declared pest.

Container growing

A pot suits ismene where winters are frosty, because the whole pot can move under cover. For two or three bulbs, use a pot at least 30 cm across, about 15 L, with good drainage holes. Fill it with premium potting mix. A plastic pot keeps the mix from drying out as fast as terracotta.

• Planting. Set the bulbs with the neck and shoulder just above the mix.
• Position. Full sun or bright light shade, sheltered from wind.
• Watering. Water every few days in warm weather while the plants are in leaf, so the mix stays moist.
• Feeding. Give fish and seaweed blend at 25 mL per 9 L every fortnight from the first leaves until flowering ends.
• Winter. As the leaves yellow, stop watering and move the pot to a dry, frost-free spot until spring.

Planting Bulbs

Ismene starts from a large bulb with a neck up to about 5 cm long.

Before planting

Choose firm bulbs, and discard any that are soft or mouldy. The bulb is poisonous if eaten, so store it where children and pets cannot reach it, and well away from onions in the kitchen.

Planting in the ground

• Set each bulb upright, neck pointing up.
• Plant with the base about 10 cm deep, so the tip of the neck sits level with or just above the soil.
• Space bulbs about 20 cm apart, in groups of three or more.
• Water in well once, then water lightly until the leaves appear.

Care by growth stage

Ismene wants plenty of water while it grows and flowers, then a dry rest once the leaves die down in autumn.

If growth stalls in poor soil, scratch a light dose of all-purpose controlled release granular (NPK around 14-5-10) into the soil as the leaves appear.

Lifting and storing in frosty areas

Lift the bulbs where frost is regular, such as Canberra, Hobart and the inland, or overwinter them in their pots under cover.

1. Dig the bulbs before the first frost, as the leaves yellow, keeping as many roots as you can.
2. Leave them to dry in the open air, out of rain, then brush off the soil.
3. Dry the bare bulbs for several weeks more, checking that the roots stay plump and pliable.
4. Store them in dry perlite somewhere dry and frost free, between about 12 and 21°C.
5. Replant in spring once the soil warms.

Companion planting

Ismene pairs well with summer plants that like the same rich, moist soil and leave its leaves in the sun.

Grows well with

• Dahlias, which flower alongside it in the same rich soil and are lifted on the same autumn timetable in cold zones.
• Zinnias, sun-loving summer annuals whose bright colours set off the white flowers.
• Alyssum, a low edging that covers bare soil without shading the bulb leaves.

Keep apart

• Crinum, clivia and hippeastrum, because they share the lily caterpillar, which can move from clump to clump.
• Thick plantings of agapanthus and other strappy plants, which shelter snails close to the young ismene shoots.

Harvesting Blooms

Cut a stem for the vase when the first flower in the cluster has opened and the others are swelling.

• Cut in the cool of the morning, with clean secateurs.
• Cut the leafless flower stem low, leaving every leaf on the plant to feed the bulb.
• Stand cut stems in a bucket of water straight away.
• Change the vase water every couple of days.
• On plants left in the garden, cut off each stem once its flowers fade.

Each stem carries two to five flowers, and a planting flowers over about two weeks. The scent is strongest at night, so a vase suits a room used in the evening.

Common problems

Bulbs that do nothing. Cold soil at planting is the usual cause, as described in Three mistakes that matter.

Buds that wither. Dry soil while the stems rise is the cause, as described in Three mistakes that matter. Water deeply before hot days and mulch to hold moisture.

Leaves but no flowers. Crowded clumps and bulbs whose roots were torn at lifting often flower poorly. Divide crowded clumps, and lift stored bulbs with their roots intact.

Weak plants after winter in the ground. In frosty areas, bulbs left in the ground over winter can come back less vigorous and flower less reliably. Lift them, or plant against a warm house wall.

Pests and diseases

Ismene is seldom troubled by disease.

Lily caterpillar (Spodoptera picta). Striped yellow, grey and black caterpillars, up to 5 cm long, attack spider lilies and their amaryllis relatives. They chew the leaves and bore down into the bulb, often killing it. The pest occurs in Queensland, the Northern Territory and New South Wales. In the same states the lily borer (Brithys crini), black with white spots and an orange head, tunnels inside leaves and stems. Search at first light, down into the leaf bases, and pick off egg masses under the leaves. For heavy attacks, use a caterpillar spray registered for the job, repeated as the label directs. Treat the lily borer the same way.

Common garden snail (Cornu aspersum) and slugs. They graze the young shoots and hide among strappy leaves, especially after rain in the cooler months. Hunt for them after rain, and set traps such as saucers of stale beer dug in level with the soil. Read more

Mealybugs (family Pseudococcidae). White, fluffy insects 2 to 5 mm long cluster in the leaf bases and on stored bulbs, leaving sticky honeydew. Dab small colonies with methylated spirits on a cotton bud, and spray horticultural oil on larger ones, but never in hot weather. Read more

Prevention first

• Check new leaves weekly in warm, humid weather, when lily caterpillar is most active.
• Inspect stored bulbs before planting, and discard any carrying mealybugs or soft rot.
• Keep the spacing given under Planting Bulbs, so air moves through the clump.
• Clear dead leaves after dormancy as part of everyday garden hygiene.

Tips

1. Push a label in beside each clump at planting, because nothing shows above ground through winter.
2. Divide clumps once crowding thins the flowers, often after about five years, in late winter before new growth starts. Replant the offsets at once.
3. Pot up the small offsets that come away when you lift or divide, and grow them on until they reach flowering size.

Due to quarantine restrictions and our shipping policy, we cannot send ismene bulbs to Western Australia or Tasmania.