Lilies are a popular flowering plant and cut flower crop with large, spectacular blooms in a diverse range of colors that often take center stage in bouquets at Easter and Christmas.
True lilies are flowering plants that belong to the genus Lilium. As a commercial crop, they have undergone some extensive breeding programs to produce the impressive hybrids grown hydroponically and in greenhouses.
In a heated indoor area, hydroponic growers can produce lilies year-round with the use of pre-planting bulb chilling followed by flower “forcing” under warm conditions and good light levels.
There are several different lily types suited to hydroponic production. The most well-recognized is the Easter lily (Lilium longiflorum), a white flower native to Japan and Taiwan that is traditionally grown for the Easter market trade. Different varieties of this lily are used as a greenhouse crop for the cut flower trade and as dwarf potted plants.
The second group of lilies are the large-flowered, colored Orientals, which have been bred to produce outward-facing, scented flowers. The flowers are often six to eight inches across with recurved petals, and they come in colors including pure white, purple, pink, dark red, and bi-color.
Oriental lily types tend to be tall growing and are sometimes called “stargazers” as the flowers appear to look upward. Oriental lilies make excellent cut flowers; however, some find the strong scent to be a little overpowering.
Next, Asiatic lily hybrids have upright or outward facing flowers, mostly in white, pink, orange, gold, or yellow. The flowers are smaller in size than the Orientals or Easter lilies, being four to five inches in diameter and unscented.
Different from the tall-growing types often produced as cut flowers, dwarf Asiatic lilies are bred for containers and grow to an average height of 14-23 inches.
Apart from these three main groups of lilies, interbreeding has developed new types and hybrids that are grown commercially and by home gardeners. These include the LA hybrids, which are derived from L. longiflorum and Asiatic hybrids and come in a range of colors, and OT types, which are Oriental and Trumpet lily crosses that have large, heavily scented flowers up to 10 inches across.
There are also LO types, which are L. longiflorum and Oriental hybrids that have six- to 12-inch wide flowers with mainly white trumpets and darker centers. These trumpet-shaped, outward-facing flowers have recurved petals and a mild fragrance.
Forcing Lilies Hydroponically
Commercially, the forcing of lilies for cut flower production is common practice amongst greenhouse growers. The same principals can be applied on a smaller scale in an indoor garden.
“Forcing” refers to the use of environmental control or other techniques to induce plants to flower on schedule, often to target specific markets like Christmas or Easter.
The technique of forcing is now less based on traditional methods of growing plants in soil or potting them into large containers of substrate, and more on the use of bulb crates similar to those used commercially to force tulips and other similar cut flower bulb crops.
Lily forcing crates are sturdy, black, rectangular plastic crates with an open structure into which bulbs are packed densely in a small volume of substrate.
Crates used in greenhouse forcing are typically 24x15x10 inches and hold 10-18 bulbs, depending on cultivar and size. The crates provide a mobile system in which the bulbs can be moved into and out of chillers or cool rooms as part of the treatment process and allow more rapid production of blooms.
On a smaller scale, use of smaller-sized bulb crates allow lily bulbs to be grown separately from the main hydroponic system and shifted around an indoor garden as space permits.
Using pre-chilled lily bulbs, placed into bulb crates, and grown into a warm, well-lit growing area provides a system of rapid production of flowers and, if timed well, can provide blooms ready in time for Easter or Christmas.
Hydroponic Systems for Lily Production
Apart from forcing systems like bulb crates, lilies grow well using several different hydroponic techniques. Research has shown that lily bulbs can be supported in large stone wool cubes using NFT or ebb and flow methods to deliver the nutrient solution intermittently.
For bulbs grown in pots, containers, beds, troughs, or other substrate systems, selection of the right type of hydroponic medium is essential for hydroponic lilies. Coarser grades of composted bark, coconut fiber, sawdust, perlite, and various combinations of these usually gives good results.
On a small scale, standard grow and bloom nutrient products can be applied during the growth phase. Lilies are not initially a high nutrient demanding crop as the bulb remains a reservoir of nutrients during early growth; however, once stem growth and bud development has occurred, calcium and potassium need to be boosted to ensure strong flower formation.
During the bud development stage, a suitable lily hydroponic nutrient formation contains the following levels of elements:
Boron 0.70 ppm Copper 0.07 ppm Molybdenum 0.05ppm
Pre-planting Bulb Treatment for Lilies
When lily bulbs are first harvested, usually outdoors in the late summer, the apical meristem is vegetative. These bulbs need to be “vernalized,” or cold pre-treated, in cool, moist conditions (35-50˚F, depending on cultivar) for a six- to eight-week period.
Asiatic lilies are usually given a chilling period of six weeks and Orientals slightly longer with eight weeks. The vernalization treatment can be carried out artificially under refrigeration or if season and temperatures permit, naturally by placing potted plants outdoors over winter. (Note that bulbs can also be bought pre-chilled.)
The cold treatment provided during vernalization allows the bulbs to rapidly produce a high-quality flowering shoot.
Once chilled, the bulbs can be stored or planted out under warm growing conditions in a moist substrate such as sawdust, peat, or vermiculite. Once planted, lily bulbs begin a rapid growth phase and the central bud contained within the bulb will produce a leafy stem that will eventually terminate in flowers.
Unlike other bulbs such as tulips and hyacinth, a lily’s floral initiation does not occur during the cold treatment, but during this subsequent growth phase. Lilies begin shooting in one to three weeks after planting out, depending on variety and growing conditions. Meanwhile, one of the buds at the base will develop into daughter bulbs, which can later be used to propagate more plants.
Asiatic lilies produce some roots from the stem base and it is these, rather than the basal roots, that provide nutrients for the flower stalk. So, the bulb must be planted at a depth that allows sufficient room for stem roots to develop. Standard spacing of hybrid lily bulbs in hydroponic media beds is usually around 4x4 inches, with a planting depth of two to four inches.
The bulbs need to be watered well and provided with sufficient warmth to promote bud growth and stem development. The ideal temperature range depends on the type of lily being produced. Asiatic lilies produce best within a range of 66-70˚F in the day and 52-55˚F at night, while Oriental hybrids need warmer daytime conditions of 69-78˚F.
Lilies need reasonably high light levels. The use of artificial lighting to provide “night interruption” will increase the rate of flower production and help prevent bud loss due to low light. If provided with sufficient warmth and light, most lilies will rapidly produce flower buds; time to flowering in many hybrids is just 95-120 days.
Lilies grown for cut flowers can be harvested as soon as the most advanced bud has developed color. Blooms should be placed into a solution of flower preservative to maintain vase life as long as possible.
Take note that some varieties of lilies have a tendency to stretch and produce overly long stems during the growth and flowering phase. This is often aggravated by low light, high density, and shaded conditions with warm temperatures and long days.
Ensuring each plant has sufficient space and good light levels is required, and selecting dwarf cultivars is often preferable where excessively tall plants need to be avoided.
While lilies can be propagated from seed, seed-raised plants won’t have the same characteristics as their parents since many of the cultivars grown hydroponically are hybrids.
Plants raised from seed can also take many years to flower, meaning this method is generally only used by plant breeders. Lilies are best propagated vegetatively, which is relatively easy to carry out.
As the plant matures, the lily bulb starts to produce “offsets,” or small bulbs that can be divided away from the main bulb and used as future planting material. Another method is to propagate from bulb “scales,” fleshy sections of the main bulb.
The scales are snapped off as close to the base of the main bulb as possible, then the lower half is placed into a free-draining substrate such as sharp sand. After a few weeks under warm conditions, small bulblets begin to form on the scales. When these have developed roots, they can be gently removed and potted up for growing on.
Lilies are a familiar cut flower or potted plant with a long history of cultivation and appreciation by many cultures. No matter if they are being grown as a crop of cut blooms for a special occasion or just an attractive dwarf potted plant, they are versatile, colorful, and often highly perfumed additions to an indoor garden.
Selecting some of the latest hybrid bulbs, which are widely available in an ever-increasing range of colors and sizes, allows hydroponic growers to experience an amazing indoor grown floral display.