While in the San Diego area about 10 years ago, I purchased a bulb about the size of a softball. It was labeled "white squill."

Over the years, it has produced long strapping leaves like an amaryllis and it is now two bulbs. For the first time, this year the leaves died and two spikes have appeared with tiny flowers with no smell.

Please tell me the correct name and how to care for the plant.

– Betty Knopf, Carmichael

Your mystery plant is a giant white squill (Urginea maritima), known as the world's largest flowering bulb.

Living up to its name, these bulbs are huge. They often weigh 6 to 8 pounds and can reach 12 inches long.

"Each bulb gets the size of a football," said Ellen Zagory, horticulture director of the UC Davis Arboretum. "They multiply into large clumps."

The arboretum has several giant white squills in its all-white Carolee Shields Garden that surrounds its shady gazebo. Also known as "sea squills," these bulbs bloom in August and early September with spectacular spikes 4 to 5 feet tall and covered with little white flowers.

The hotter the temperature, the faster the spike grows – often 3 inches a day.

Giant white squills tend to start blooming when 10 years old, so your bulb appears right on schedule. After that first bloom, squills should consistently flower for years to come.

Like the familiar "naked lady" amaryllis (Amaryllis belladonna), squills sprout 3-foot-long strappy leaves in November and stay in leaf through May. In early summer, the leaves die back in preparation for the flower spike in late summer.

To cue that dieback, cut back irrigation of your squills in May. Leave the bulbs as dry as possible in June and July, then provide shallow irrigation when the spike starts to appear.

A native of the Mediterranean, these bulbs like dry summers such as Sacramento's. The extensive root system demands good drainage; these bulbs don't like heavy clay or soggy soils. Plant in an area that gets little summer irrigation – not on the edge of a lawn.

Squills thrive on neglect. They have few if any pests and serve as a natural rodent repellent in the garden – gophers hate them!

The only way to kill a squill is with kindness. Too much water – particularly in summer – can rot that huge bulb.

A member of the lily family, giant white squills prefer a spot where they can get sun in winter and partial or afternoon shade in summer; placement under a deciduous tree is ideal. The bulbs are hardy down to 28 degrees, but can be protected if there's danger of frost.

A favorite of high-end floral designers, giant white squills make stunning cut flowers that will last at least 10 days in a vase. If harvested when the florets just begin to open, the spikes will continue to grow 6 to 8 inches after they're cut.

GARDEN QUESTIONS?

Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties.

Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to h&g@sacbee.com. Please put "Garden Detective" in the subject field and include your postal address. To contact your UC Extension directly, call:

• Sacramento: (916) 875-6913; 9 a.m.-noon and 1-4 p.m. weekdays

• Amador: (209) 223-6838; 10 a.m.-noon Monday through Thursday; email ceamador.ucdavis.edu

• Butte: (530) 538-7201; 8 a.m.-noon and 1-5 p.m. weekdays

• El Dorado: (530) 621-5512; 9 a.m.-noon weekdays

• Placer: (530) 889-7388; 9 a.m.-noon on Tuesdays, Wednesday and Thursdays or leave a message and calls will be returned

• Nevada: (530) 273-0919; 9 a.m.-noon Tuesdays through Thursday or leave a message

• Shasta, Tehama, Trinity: (530) 225-4605

• Solano: (707) 784-1322; leave a message and calls will be returned

• Sutter, Yuba: (530) 822-7515; 9 a.m.-noon Mondays and Tuesdays and 1-4 p.m. Thursdays

• Yolo: (530) 666-8737; 9-11 a.m. Tuesdays and Fridays, or leave a message and calls will be returned

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