How to Grow Lilies

True lilies (Lilium) are hardy bulbs that come back each summer with tall stems of large, often fragrant flowers, typically 3 to 6 inches across. They are easy if you meet two needs: drainage good enough that the bulbs never sit wet, and roots kept cool. Don’t confuse them with daylilies, which grow from fleshy roots, not bulbs, and belong to a different family.

Lily groups to know

NC State and South Dakota State describe the main garden groups:

• Asiatic hybrids. The earliest and easiest, flowering in early summer, usually under 3 feet, in reds, oranges, yellows, pinks and white. Most have little or no fragrance. Colorado State rates them hardy to zone 3 or 4. Illinois Extension points to dwarf ‘Pixie’ types, 18 inches or less, for edging and pots.
• Oriental hybrids. The showiest and most fragrant, up to 8 feet tall, blooming mid- to late summer. They prefer acidic, humus-rich, moist soil and cool roots. Colorado State says they and trumpet lilies prefer milder winters but are said to survive in zone 4 with heavy mulch.
• Trumpet lilies. Tall, with outward-facing or hanging flowers.
• Orienpets (OT hybrids). Oriental-trumpet crosses: tall, fragrant and large-flowered.
• LA hybrids. Crosses of Easter lily with Asiatic lilies, Illinois Extension says, with large flowers and a slight scent.
• Martagon lilies. Many small, nodding flowers. They tolerate some shade and suit woodland gardens, but NC State notes they do poorly in hot, humid climates.

In much of the South, garden lilies are near the edge of their range; most are rated only to zone 8. In Florida, UF/IFAS suggests planting a potted Easter lily (L. longiflorum) outdoors after the holiday, once frost danger has passed. It will usually bloom naturally in summer.

Where to plant

Give lilies full sun to afternoon sun for the leaves, at least six hours, with the root zone shaded or mulched. NC State’s formula is sun on the leaves, shade for the roots. Interplanting with taller plants, South Dakota State notes, gives lily stems support and wind protection, and other flowers keep the bed interesting after the lilies finish.

Drainage is critical. Wet soil rots lily bulbs, but the soil shouldn’t dry out completely either. Illinois Extension amends beds with peat and compost, up to one-third of each by volume. In heavy soil, South Dakota State plants lilies in raised beds.

How to plant lily bulbs

Lily bulbs are planted in early fall, which Iowa State calls an excellent time, or in spring once frost danger has passed. Maryland Extension prefers late fall. See when to plant lilies and the dates for your zone above. Plant bulbs promptly after buying them. If they must wait, NC State suggests holding them in moist peat at about 35°F.

1. Depth. Three times the bulb’s diameter (Iowa State): about 6 to 8 inches for large bulbs (Illinois). NC State plants 8 inches deep, South Dakota State about 6. Deep planting helps protect bulbs in winter and leaves room for the roots that grow from the buried stem.
2. Spacing. At least 1 foot apart (Illinois).
3. Grouping. Plant in groups of five or more for impact.
4. Spring planting. Handle carefully; South Dakota State notes the developing shoot is fragile and easy to snap.
5. Potted lilies can go in during spring or summer at the depth they grew in the pot.

After fall planting, add a few inches of mulch over the bed for winter protection.

Care through the season

Keep soil evenly moist but never soggy, and maintain mulch to keep roots cool. Stake tall varieties, especially in open, windy sites.

After flowering, snap or cut off the spent flower head just above the top leaves. Leave the stem and leaves until they turn yellow; South Dakota State calls the leaves the most important part of the plant, because they store food for next year.

For cutting, take Asiatic stems as the first buds show color and start to open. Illinois Extension finds they can last up to 10 days in a vase with floral preservative. Remove the pollen-bearing anthers as flowers open, since the pollen stains. Don’t take all the foliage with the cut stem; the plant needs leaves to rebuild the bulb.

Dividing lilies

Lily bulbs multiply, and crowded clumps flower less. South Dakota State divides in early fall, typically early September. Illinois Extension digs Asiatics in August, before the leaves yellow, then replants or stores the bulbs somewhere cool and dry until spring.

Problems

• Lily leaf beetle. A shiny scarlet beetle, about 1/4 to 3/8 inch long, from Eurasia. It was first found in the US in Massachusetts in 1992 and is believed to have arrived with imported bulbs, so be careful not to move it on transplants. Adults and slug-like larvae eat leaves and buds and can defoliate a plant. UConn recommends hand-picking adults and checking leaf undersides for reddish-orange egg masses; neem kills larvae if reapplied every five to seven days after eggs hatch. Lilies grown in containers and moved each year break the beetle’s life cycle.
• Bulb rot. Poorly drained soil. Use a raised bed or better site.
• Botrytis. A fungal blight of leaves and flowers. Improve air circulation and remove infected parts.
• Lily mosaic virus. Spread by aphids and incurable. Pull infected plants and control aphids.
• Rabbits and slugs. Rabbits eat spring shoots; slugs are worst in shady, damp sites.

Lilies are toxic to cats, NC State notes, so keep plants and bouquets out of their reach.