Propagation Of Lilies By Seed

One of the most fundamental ways of propagating plants is through the germination of seed. To lily growers seed germination has several advantages. It allows them to propagate lilies that are difficult to obtain as bulbs; it allows them to produce cheaply more bulbs of the same plant than they could afford to buy if purchased as mature bulbs; and it allows them to raise their own hybrid stock.

However, the most valid reason for raising plants from seed is that bulbs so raised are free of virus infections that can be so easily introduced with purchased material. Once these diseases have been introduced they are difficult to eradicate and can quickly run through the whole stock, distorting or killing all the lily bulbs in the garden. Seed-produced bulbs are virus-free even if the seed comes from plants that are themselves infected.

If the seed comes from a species, particularly one in the wild, where there has been no hybridization then there is a good chance that the ensuing plant will resemble the parent. However, seed from cultivars, hybrids or species that have crossed with nearby plants will not necessarily produce offspring that are identical to their parents, in fact the chances are they will not. Any plants raised from seed of a cultivar must not be given the same name as the parent. Vegetatively propagated bulbs will be a true replica of their parent and can bear the same name.

Producing seeds

Lilies are self-sterile; that is, a plant will not set viable seed if pollinated with its pollen. Both species and hybrids must therefore be cross-pollinated, either by natural pollinators such as bees or by artificial means. Pollination may take place either under protection or outdoors. A greenhouse or protective structure is ideal because of the control over weather. Increased temperature during pollination and fertilization produces superior seed set. Excellent seed can, however, be obtained under various conditions.

The pods, or capsules, are collected just before they turn brown and start to split. If possible, they should be picked only in dry weather, although this may be impossible in some climates; it may also be next to impossible to ripen late-developing lily pods outdoors. If frost is forecast or the weather becomes persistently wet, the entire stem can be cut while the pods are still green. The cut stem is brought indoors and hung upside down in a warm, well-ventilated room to mature the pods.

After harvest, the pods are brought indoors and dried on newspaper lined trays or paper plates in a well-ventilated room. They must be spread thinly. The room should not be too warm because the pods need to dry slowly; a temperature of 15° to 21°C (60° to 70°F) is ideal.

The seeds should be removed from the pods, or "shealed," when dry. If the pods are left until they become brittle, bits of capsule tissue can become mixed with the seed. During this process it is necessary to watch carefully for signs of disease, especially Botrytis; remove infected pods or seed and keep the remainder as clean as possible.

The seed should be left in the trays for a few days after shealing until it becomes completely dry, a process facilitated by daily stirring. Chaff can be removed from small quantities by placing the seed in a shallow pan and gently blowing on it while moving the pan around. The good seed, which is heavier, tends to remain in the pan while the chaff flies up over the side. For the larger quantities produced by commercial growers, there are excellent seed-cleaning machines. Examine seed for the presence of embryos-a sign that the seed can produce a plant-by placing the seed on a white sheet of paper or frosted glass with strong light below it. The embryo appears clearly as a dark line running lengthwise across the flat seed. Occasionally seeds are darkly pigmented, making it difficult to see the embryos; in this case, if the seed is plump and of regular shape, it is safe to assume that an embryo is present. If proper precautions have been taken in pollinating the flowers, species and closely related hybrids yield heavy, plump seed with well-formed embryos embedded in the endosperm.

After drying and cleaning, small quantities of seed are placed in packets such as coin envelopes, and larger quantities in plastic sacks. All must be carefully labeled. It is recommended that all seed be stored at a temperature below freezing following harvest. Under these conditions seed can remain viable for 35 years or more. Home growers who are going to plant the seed the same season can store it in a well-sealed container in the refrigerator.

Germination patterns

There are two types of germination in lilies, epigeal, meaning "above ground," and hypogeal, "below ground". These two categories are again divided into immediate and delayed emergence; the vast majority of epigeal germinators are immediate, and the vast majority of hypogeal germinators are delayed. It is critical to know the germination category to which seed belongs before sowing it. Epigeal germinators are normally sown in early spring, and hypogeal germinators in late summer or fall. Whether germination is epigeal or hypogeal, there are four basic principles in growing lilies from seed:

1. Plant in a well-drained soil mix.
2. Water sparingly at first, never allowing soil to become saturated.
3. Provide shade throughout the hot season; 60 percent shade cloth is ideal in most areas.
4. Spray regularly to control Botrytis and aphids.

EPIGEAL GERMINATION

In this pattern, the seed germinates quite rapidly after it is exposed to moisture and warm temperatures, producing growth above ground in a few weeks. The long, slender green cotyledon pushes up, frequently carrying the seed coat on its tip. This is followed by true leaves produced throughout the growing season. Most lilies with epigeal germination can flower in their second growing season if growing conditions have been favorable. Asiatic and trumpet hybrids belong to this group, as do many Asian species, including Lilium amabile, L. concolor, L.longiflorum, L. pumilum, and L. wallichianum.

Immediate epigeal germination in outdoor beds

Sowing seed in outdoor beds was very successful for many years in the northern Oregon. Millions of trumpet species and hybrids were raised from seed by this method, which was also used to a lesser extent for Asiatics. The keys to success are a good site with excellent drainage and land contours, and high soil fertility.
Seedbeds are usually established following a cover crop of rye. The area is plowed deeply in July and disked to produce good tilth. It is then professionally fumigated with methyl bromide, using a plastic cover after the chemical has been injected; the cover is removed after four weeks. This method effectively kills perennial weeds and weed seeds, essential in reducing the cost of seedling production. Diseases and pests such as nematodes are also controlled.
Seed is planted in outdoor beds when the ground is workable in early spring. The soil is disked and harrowed again before planting and the beds carefully leveled by raking. The seed is sown thinly by hand at a rate of one seed per 12 square centimeters (2 square inches), or 765 seeds per meter (700 seeds per yard) of a 120-centimeter (4-foot) wide bed. The seed is covered lightly, to a depth of approximately 1 centimeter (0.5 inch). An organic mulch is applied soon after planting to conserve moisture and prevent soil cracking.
A good sprinkler system is essential; the seedbed must never be allowed to become dry during the germination stage. Fertilizer is applied according to specific recommendations based on soil analysis. A fertilizer low in nitrogen is recommended. My preference is to incorporate a general fertilizer in the soil before planting and later, in early July when there is a good flush of leaves, to apply a granular slow release fertilizer.
A regular spraying program is essential to control Botrytis blight, using fungicides currently recommended for this disease. The beds must also remain free of weeds always; with fumigation this problem is minimized. Control of insects, particularly aphids, is also crucial on these small, vulnerable plants; a granular systemic insecticide is safest and is effective over a long period, whereas sprays may damage new foliage.
The seedbeds are dug and the young bulbs lifted in late fall or early winter after the tops senesce. The foliage of these young plants may persist later in the season than that of mature plants. The bulblets are graded by size and stored at a cold temperature until they are planted in field rows the following spring.
There is no reason why this method cannot be adapted to a much smaller scale by amateur growers. However, the home gardener may find it more difficult to sterilize the soil and may prefer to grow lily seedlings in containers.
Epigeal germinators can also be planted in greenhouses, either in beds at ground level or in trays of soil or raised benches. The procedure for the former is almost identical to that followed for outdoor beds: fumigation, early spring planting, sowing, mulching, and fungus and aphid control. The one exception is that the soil must be firmed before planting because the rototillers and spading machines used in greenhouse beds loosen and fluff it up excessively.

Immediate epigeal germination in containers

Epigeal germinators can be grown successfully in a wide variety of containers and media. The ideal method is to sow the seed in a soilless mix in February. The flats, trays, or pots can then be placed under protection in a greenhouse or cold frame. Many enthusiasts sow their seeds earlier under artificial lights. Such seedlings can be moved outdoors when the weather permits.
Care is critical for success in seed-sowing. Firm the mix thoroughly after filling the container. Distribute the seed evenly and cover it lightly with about 1 centimeter (0.5 inch) of soil, then firm it gently.
Watering must be done very sparingly at first. The soil must be moist always, but never saturated. It is always best to water in the early morning, so some surface drying can occur before evening. When seedlings are crowded, their leaves may form a thick cover later in the season, becoming matted together and making it difficult for them to dry out. It is very difficult to control Botrytis blight under these conditions. If a trickle irrigation system is installed, wetting the leaves can be avoided.

Delayed epigeal germination

Lilium candidum, however, requires cool temperatures during germination and frequently fails to germinate immediately if the seed is sown late, when soil temperatures are high. Cold storage of the dry seed appears to be necessary for the seed of L. sargentiae and its closely related hybrids; if kept for at least two months in the freezer, the seed germinates perfectly.

HYPOGEAL GERMINATION

In this pattern the seed germinates slowly. The short cotyledon remains below the soil surface, within the seed coat, and its tissue nourishes a tiny bulb which forms at the side of the seed. After this it requires a period of cold storage (or, in natural conditions, a winter season) before above-ground leaves can develop.

In many lilies with this pattern, such as Oriental species and their hybrids, not all the viable seeds germinate the first year. This seems to be a natural protective strategy, holding some seeds in reserve in case weather or predation destroys the first batch of young bulbs. The home grower may wish to sow seeds in a large enough container to keep for two years to permit complete germination of a batch of seed, particularly if it is a rare species.

Immediate hypogeal germination

Lilium brownii var. australe and L. dauricum consistently show this type of germination, producing a large number of leaves in one season. They can thus be sown successfully at the same time as epigeal germinators. Lilium humboldtii has also shown a tendency to this pattern.

Delayed hypogeal germination

The following observations apply primarily to Oriental species and hybrids. The seed is sown in late July or August in plastic bags containing a moist medium, which may consist of vermiculite, sphagnum peat, or a mixture of the two. The degree of moisture is critical. The medium must be moist but not saturated: no water should drip out when it is squeezed in the hand. This permits the aeration essential for good germination and satisfactory root development, which require oxygen.
The bags are placed in perforated trays or boxes and stored in the dark at a temperature of 15° to 21°C (60° to 70°F) for incubation. A period of three or four months is required for bulblets to form, depending on the variety.
Once sound, firm bulblets and roots have formed, the trays are moved to a cooler room (10°C/50°F) for approximately three weeks. They are then placed in cold storage (1°C/34°F) for a minimum of 12 weeks; this is known as the vernalization period.
The "pregerminated" seed is planted the following spring as described above for epigeal germinators, with one exception. Hypogeal bulblets are best sown in April, a month or two later than the seed of epigeal types, when soil temperatures and light conditions are ideal for immediate growth. In good conditions the tiny bulblets produce true leaves one week after sowing.
Western American lily species and hybrids, Lilium martagon and its hybrids, L. monadelphum, and other hypogeal-germinating species and hybrids from Europe can also be germinated in this way. In general, however, they require cooler temperatures; the recommended temperature for the initial stage is 10°C (50°F).
Alternatively, hypogeal germinators can be sown in beds, trays, flats, or pots in late July or August, using a reliable soil mix. The containers are placed in a cold greenhouse, frame, or other protected site. The seed germinates under natural conditions, overwinters, and emerges the following spring. Western American and European species and hybrids respond well to this method.
It is seldom advisable to plant the later-flowering Orientals in outdoor beds, some form of protection being recommended. Nonetheless, outdoor planting can succeed if the seedlings are allowed to remain down for two years.
Harvest the bulblets after the tops are completely senesced and pack them in dry sphagnum peat in cold storage (1°C/34°F) until the next spring planting.