September 2012 Culture

Perennial Solutions: Scilla peruviana ‘Caribbean Jewels Sapphire Blue’ By Paul Pilon

The Peruvian lily is a striking evergreen perennial that has great potential as a spring flowering container crop. This underutilized bulb crop can be grown an marketed alongside other spring flowering bulb crops such as daffodils, hyacinths and tulips.

Several years ago Golden State Bulb Growers introduced Scilla peruviana ‘Caribbean Jewels Sapphire Blue’ to the industry. Sapphire Blue produces large striking blue conical-shaped flowers atop slim, lance-shaped leaves in mid to late spring. The flower stalks produce 50 to 100 deep blue, starry blossoms. These unique flowers have an impressively long bloom time.

In the landscape, mature plantings of Sapphire Blue grow to 18 to 22 inches in height. They should be grown in locations with full sun to light shade. In the northern United States, scilla are can be grown and marketed as potted plants or in combination containers, but they can be sold as perennials in USDA Hardiness Zones 7 to 10. They are relatively cold hardy and can tolerate light frosts down to 28° F without experiencing plant damage.

Perennial growers should consider adding scilla to their tender perennial programs to supplement their current offerings with this novelty plant. Additionally, ‘Caribbean Jewels Sapphire Blue’ is relatively easy to produce, has few cultural problems and can be grown with cool temperatures. These attributes, along with its unique flowers, make scilla a great addition to any perennial program.

Propagation

It is not economical or practical for growers to propagate Peruvian lilies, grow the bulbs to maturity and then produce a finished crop. Commercial growers obtain fully mature, ready-to-plant bulbs of scilla ‘Caribbean Jewels Sapphire Blue’ to pot into their final containers.

Production

There are three bulb sizes available to commercial growers: the medium bulbs measure 11/2 to 13/4 inches and are suitable for production in 41/2- to 5-inch containers, large bulbs are 13/4 to 21/4 inches across and are ideal for gallon-sized containers, and finally jumbo bulbs measure 21/4 inches or more and are commonly used for 6-inch or larger-sized containers.

‘Sapphire Blue’ can be planted from September to February to produce flowering plants to be marketed from February through June. Plant scilla bulbs into a coarse, well-drained growing mix. After planting, there should be approximately 1/2 to 1 inch of growing mix over the nose of the bulbs. Proper planting depth is critical for best plant growth, vigor and performance.

The growing mix should be kept moist, but not overly wet throughout production. Avoid allowing the media to dry down excessively, especially once they begin to flower. Scilla have light fertility requirements and only need to be fertilized sparingly to enhance foliage coloration. Irrigate with a 100 to 200 ppm of a balanced water-soluble fertilizer as needed to maintain plant coloration and growth. Avoid over fertilization or the foliage and blooms will appear loose and may not stand up well. The acceptable pH range is 5.5 to 6.5.

Although proper cultural techniques and growing conditions can produce high-quality plants, it is beneficial to use plant growth regulators to improve plant appearance. Spray applications of 30-ppm paclobutrazol (Bonzi, Paczol or Piccolo) can be applied if toning is necessary. Additionally, plant growth regulators have been proven to provide optimal postharvest performance and customer satisfaction. Apply a paclobutrazol drench late in the production cycle when the buds are almond to walnut sized and still located deep within the leaf rosette. The optimal rate of paclobutrazol varies by growing environment and the type of growing mix used; consider trialing starting rates of 6 ppm for plants grown in peat based growing mixes or 12 ppm when bark-based growing mixes are used.

Insects and Diseases

There are relatively few insects and diseases affecting the production of scilla ‘Caribbean Jewel Sapphire Blue’. Aphids, fungus gnats, mealybugs, shore flies, thrips and whiteflies are the insects observed most frequently when producing scilla; however, these pests rarely become problematic. Several plant pathogens including Dreshlera and/or Helminthosporum leaf spot, Erwinia, Pseudomonas, rust, and Sclerotium may arise on occasion. For the most part, these diseases can be minimized or avoided by keeping the foliage as dry as possible using adequate plant spacing, providing adequate air movement, and watering early in day to avoid extended periods of wet foliage. Insects and diseases can be detected with routine crop monitoring; control strategies may not be necessary unless the scouting activities indicate actions should be taken.

Temperature and Scheduling

‘Caribbean Jewels Sapphire Blue’ prefers to be forced into bloom under bright and cool conditions. This is an ideal crop to be grown bright cold frames or Quonset structures with minimal freeze protection. In certain parts of the country, they can be grown outside as they are somewhat cold hardy and can tolerate light frosts of 28 to 32° F without experiencing frost damage.

The above production scenarios result highest quality plants; the production of scilla inside heated greenhouses often results in plants that are stretched and may appear loose or floppy. The optimal temperatures for production are 50 to 65° F days and 35 to 50° F nights. They prefer bright conditions and grow well with light intensities between 2,500 and 5,000 foot-candles.

Scilla does not require vernalization for flowering; cold treatments can actually damage the bulb and decrease flowering. The main factor influencing the timing of Sapphire Blue is temperature. For early spring sales (February through March) it takes 20 to 24 weeks to finish when they are grown at 50° F 24-hour average temperatures. For mid to late spring sales they can be forced into flower in 17 to 19 weeks at these temperatures. Exact crop timing is greatly influenced by the environment they are being grown in as well as the daily fluctuations in temperature. Avoid high temperatures (over 70° F) as the plants will grow soft and leggy. The main key to success is to keep scilla in cool and bright growing conditions.

Availability
Scilla ‘Caribbean Jewel Sapphire Blue’ is brought to the market by Golden State Bulb Growers (www.goldenstatebulbgrowers.com). All bulb sizes (medium, large and jumbo) are available from a number of reputable plant brokers including ABBOTT IPCO (www.abbott-ipco.com), Fred C. Gloeckner & Company, Inc. (www.fredgloeckner.com), Sheppard West and Syngenta Horticultural Services (www.sg-flowers-us.com).