Growing Lilies from Seeds(Published in Pacific Northwest Lily Society Bulletin, Vol 16 Number 2 1997.)
Joseph C. Halinar
Growing lilies from seed is an easy and economical means of acquiring a distinctive collection of lilies, of freeing species of virus, of maintaining genetic diversity and, for the hybridizer, an essential step in creating new cultivars.
The lily genus includes diverse species found growing in the northern hemisphere from the subtropics to the far north. Some are easy to grow and readily available commercially while others are difficult, rewarding and nearly unobtainable. Even though bulbs of the latter type are rarely sold, seeds can frequently be obtained through specialists, correspondence or the NALS seed exchange. Raising lilies from seed is a rewarding experience and the results are especially exciting for the hybridizer waiting for the first bloom from a cross.
The key to growing lilies from seeds successfully are patience, good drainage, disease and weed control and common sense.
Impatience is probably the biggest cause of failure. Prepare first by learning germination requirements and any special treatments needed for the particular lily before beginning. A mistake many novice gardeners make is germinating too many seeds. A packet of 20 or 30 seeds does not look like much, but will require considerable garden space when the bulbs reach blooming size. It is always a good idea to germinate a few more seeds than needed to allow for natural loss and to discard any weak seedlings. Determine the number of mature bulbs needed and plant accordingly. Extra seed can be stored in an airtight container in the freezer for later use.
Lily seeds are classified according to how quickly they germinate and the position of the cotyledon. Germination can be either immediate or delayed. Delayed germination often requires a warm period followed by a cold period. The cotyledons can emerge above ground (epigeal) or remain below (hypogeal). Hypogeal lilies form a hypogeal bulblet that usually requires a cold treatment before sending up a true leaf. Lily seeds that most gardeners encounter are either immediate epigeal or delayed hypogeal. A few species have erratic germination. Hybrids between species with different germination types will usually have one dominate but also may exhibit erratic germination, especially in second generation seedlings
The most important requirement for the planting mix is drainage while retaining moisture. Planting mixes containing a lot of peat moss are poor. They are often too wet and they tend to dry out easily and are difficult to re-moisten. Such mixes also have a tendency to "cake," leaving the top of the pot moist while the bottom is dry. Packaged planting mixes high in peat moss need at least an equal amount of sand, soil, ground bark or perlite added.
Heavy clay soils are also poor for seed germination. They provide poor drainage and the surface too often forms a thick crust when allowed to dry. Clay soils should be mixed with a generous amount of sharp sand and composted organic matter. Sandy soils need compost or a substitute such as vermiculite to improve water retention.
The exact composition of the planting mix isn't particularly critical. Use a combination of sand, soil, vermiculite, perlite and whatever organic matter is at hand to produce a light, airy mix which retains moisture but allows good drainage. Heat sterilize for about an hour at 200-300F to kill disease organisms and weed seeds if you are using soil or reusing planting mix.
Indoor germination: Lily seeds are not difficult to germinate indoors and to grow under lights, although some people may find it easier to just plant the seeds outdoors in the spring. Seeds germinated in the fall may flower the following summer if given adequate growing conditions, but that isn't too common. Planting containers should be at least 4-5 inches deep to allow deep root development. Inexpensive 16-ounce plastic drinking cups are good when four or five 3/8" holes are drilled in the bottom. These are suitable for up to 15 seeds each.
Plant seeds about 1/4 inch deep and keep moist. Check individual type for optimum temperatures. A plastic sandwich bag placed loosely over each pot will keep moisture in and cut down maintenance for a few weeks. However, plastic bags can act as greenhouses and overheat the seeds if placed in direct sunlight or too close to lights. Pots can be covered with cardboard or newspaper to keep the mix from drying out.
Provide seedlings with artificial light as soon as they begin to germinate. Regular fluorescent lights are adequate, but special grow lights are slightly better although more expensive. Halogen lights are expensive to purchase and to operate but the results are rewarding. Feed the germinating seeds with a balanced soluble fertilizer about once a week, half strength for soil, higher for sand or vermiculite mixes. Pot-grown seedlings may need additional nitrogen. A twice-a-month feeding with a teaspoon of ammonium sulfate per gallon of water may be beneficial. One or two treatments with micro-elements or with chelated iron will also help. Indoor grown seedlings may be attacked by sucking insects which can quickly do considerable damage. Use a systemic plant and pot insecticide at the first sign of infestation. Lily seedlings are not immune to damping off disease. A heat-sterilized medium with good drainage should overcome the problem. The planting mix should be kept moist but not overly wet. Threat the planting medium with a fungicide if damping off or bulb rot appears or transplant the seedlings to a clean sterilized medium after washing the seedlings free of old soil.
Outdoor germination: It is usually easier to plant seeds in containers placed outdoors rather than planting directly into the ground. Use clean 6-8" plastic pots, gallon size cans or thoroughly cleaned flats.
Protect the emerging seedlings from heavy rain and hail which can beat down emerging cotyledons and leaves by placing containers in a sheltered location with adequate light. Cold frames and greenhouses are excellent and temporary shelters can be made of discarded windows, fiberglass sheeting or plastic hung over a frame. Prevent overheating of the poting mix by giving containers afternoon shade or partly plunging them in bark or sawdust.
During the spring months keep containers moist but not overly wet. In hot summer weather it is difficult to over-water if drainage is quick. It is best to apply enough water so that excess water comes out of the drainage holes as too little water will cause soil caking. Feed with a balanced soluble fertilizer as soon as the seedlings emerge. There after fertilize about every two weeks. Container-grown plants heavily watered during the summer months will benefit from extra nitrogen. Sprinkle a few ammonium sulfate crystals on the soil or water with a teaspoon of ammonium sulfate per gallon of water. Be careful about applying granular fertilizer to young seedlings as you can end up killing the seedlings if the fertilizer comes in contact with the leaves or is too close to the bulbs.
Gardeners using hard water or water with high salt concentrations should be careful to water thoroughly to prevent a salt buildup. Softened water may have a sodium content high enough to harm plants. Water with high chlorine concentration can be left in an open container for several days before applying to plants. Acidic water can be sweetened with an occasional pinch of hydrated lime. Soil in such areas should be checked with a pH meter.
For direct garden planting, prepare the site well in advance. Build a slightly raised bed and add sand, organic matter, perlite or vermiculite as needed. Acidic soils should have some lime added to bring the pH to about 6, especially if a large amount of organic matter is incorporated. Alkaline soils need acidifying organic matter such as peat moss or pine needles. Dry sulfur is also helpful in lowering soil pH. However, never use aluminum sulfate to reduce soil pH as aluminum ions are highly toxic to plant roots. Weed control is probably the most important factor when planting directly into the garden. Herbicides applied according to directions on the container are effective for perennial weeds. A slow but hot fire of straw or leaves in the fall or early spring before the seeds are planted can be an effective weed control. The ash, lightly worked into the soil, is a rich addition of potash and potassium. Covering the site with clear plastic sheeting all summer will kill weed seeds to a depth of several inches. Herbicide spraying prior to laying the plastic increases the effectiveness. Fall planted seeds should be covered with composted sawdust, ground bark or straw and protected from domestic or wild animals by covering with chicken wire or plastic mesh. A temporary lath frame or screen will provide protection from heavy rains. Spring planted seed can be protected with an elevated board placed above the seed row until the seeds germinate.
Collecting and Storing Seed: Collecting seeds from early flowering lilies usually does not present any problems. However, trumpets, Orientals and late blooming Asiatics do not mature until late fall and are often damaged by inclement weather. Wet and cold weather will often cause soft rot that destroys seeds. One of the easiest methods to protect immature pods in the fall when wet weather may cause soft rot is to loosely cover them with aluminum foil. Spraying the pods with a systemic fungicide prior to covering will be helpful, but the pods need to be dry before applying the aluminum foil and the foil has to be loose and not pressed up against the pod. Plastic or wax paper will not work as either one may overheat and cook the pods. Late maturing pods also need to be protected from frost. The best way to collect seeds from late blooming lilies is to grow the plants in containers that can be moved indoors. Stems of garden-grown lilies can be cut above the bulb but below the stem roots and potted up and brought indoors to finish maturing. Indoors, they should be placed next to a south facing window or given artificial light.
Harvesting the Pods: Lily pods are ready to harvest when they become soft and turn brown. Carefully clip pods from stems and bring indoors to dry slowly for two to three weeks in a place where they will have good air circulation without becoming too hot. Shake seeds from the pods and separate the good seeds from the chaff.
Lily seed viability quickly diminishes after nine to ten months storage at room temperature. For long term storage, store dry seeds in air tight containers in a freezer. Good quality seed stored in a deep freezer will last 40 years or longer.
Germination requirements by type:
Asiatic: Most Asiatic lilies have immediate epigeal germination and are easy to grow in the garden, but may be difficult to grow in pots. For indoor germination, provide a temperature for 60-70 degrees F. Germination will take three to six weeks, although some seeds will still germinate after eight to ten weeks. For outdoor germination, plant anytime from late winter to late spring. Lilium bulbiferum has delayed hypogeal germination. It is probably best germinated by giving seeds a two to three month warm period followed by a two or three month cold treatment. L. dauricum is slow to germinate and generally is best at cool temperatures of 50-60F; allow two to three months for the seeds to germinate. Asiatic seedlings can be transplanted into the garden in the fall, held over in a cold room during the winter months or removed from the soil and stored in almost-dry peat moss in the refrigerator.
Martagons: These lilies have delayed hypogeal germination but are easy to germinate. The seedlings are slow growing and may require five to seven years before blooming. Seedlings do not transplant easily and they are difficult to grow in pots. Growth begins in early spring and seedlings may go dormant by mid-summer. Place seed in a plastic bag with a loose moist medium such as peat moss, composted sawdust or vermiculite. Keep at 70-75F for 10 to 12 weeks until seeds germinate and form small hypogeal bulblets and then follow with a 10-12 week cold treatment. It's best to plant the hypogeal bulbils directly into the garden where you want them to mature, although you can transplant them after a few years when the bulbs get larger. Martagon lily seedlings will do best when given light shade.
Caucasian lilies: The Caucasian group is variable in cultural and germination requirements. Some are reasonably easy while others are difficult but rewarding. Many of this group's rare species require a double cycle of warm-cold treatment.
L. candidum requires cool temperatures for germination. Seed is best planted directly in the garden or containers set outdoors in late fall or early winter. Germination occurs in early spring but seedlings are frost hardy. Seedlings go dormant in late summer. L. pyrenaicum and the L. monadelphum L. szovitsianum complex have delayed hypogeal germination and are best treated with the martagon method. Seedlings are slow growing and don't like to be transplanted.
American species: Eastern and western American species are quite distinctive in their cultural and germination requirements. Both groups have delayed germination but need to be treated differently. Eastern American species and hybrids require a warm-cold cycle to germinate. If planted in the fall, they probably will not germinate until two years later. Seeds planted in pots should be given a three to four month warm period followed by a three to four month cold treatment. Germination may still be erratic. Some people have success using the martagon method in plastic sacks but planting directly in pots is probably the best way. Eastern species and their hybrids are generally easy to grow in containers.
Western American species require a long cool treatment to germinate and do their best in areas with mild winters and dry summers. On the Pacific Coast, the western species are best planted directly into the garden in the early fall. They are susceptible to bulb rot and generally difficult to grow in containers. If they must be grown in containers, use a medium that is very porous with a high bark content and keep the containers as cool as possible during the summer months and treat with a fungicide about every two weeks. The western American lilies are difficult to grow in the Midwest and the northern and eastern states although some people have been suscessful with some of the wet land types. Seedlings transplanted into the garden should be heavily mulched during the winter and should be allowed to dry off in late summer.
Western species seed can also be mixed with moist peat moss or vermiculite in a plastic bag, stored in the refrigerator for four to five months, and then planted into the garden or container in early spring. However, it is very important to plant the cold treated seeds outdoors before they start to germinate. Western American seeds left in a plastic bag in a refrigerator will germinate very quickly once they reach a certain cold requirement and are next to impossible to transplant once that happens.
L. philadeiphicum has immediate epigeal germination under warm temperatures and seedlings are difficult to grow and maintain in a garden. They appear to be reasonably tolerant of wet summers but appear to prefer being dry during the winter months.
Easter Lily group: L. longiflorum and its allies are easy to germinate and grow but are susceptible to frost damage. Plant seeds indoors at 70-75F and allow three to five weeks for germination or plant seeds outdoors in late spring after danger of frost is past.
Trumpets: The trumpet species and hybrids are easy to germinate and grow. Plant seeds indoors under lights at a temperature of 65-70F or outdoors in pots in early spring. Germination will take three to six weeks. Seedling growth is generally rapid, so take care not to overcrowd. The trumpet lilies are generally easy to grow in pots, but some crosses will be difficult in pots and will easily rot.
L. henryi and Aurelians: This group is generally easy but slow to germinate and need a cooler temperature than the trumpets. Germinate indoors under cool temperatures of 50-60F allowing 10 to 12 weeks. Plant seeds outdoors in late winter or early spring.
Orientals: These lilies have delayed hypogeal germination and are best treated with the martagon method. Oriental seedlings do not like hot weather and will benefit from some shade. Keep pots as cool as possible during the hot part of summer.
Doubtful species or hybrids: Rare species, valuable hybrids or wide crosses probably should be planted in pots indoors. If no growth appears after 10 to 12 weeks at room temperature, refrigerate the pots for 10 to 12 weeks. Most seeds should germinate well after a warm-cold cycle but those that do not should be given a second warm-cold treatment before discarding. Some hybrids or wide crosses will produce seeds with embryos that appear to be good but will have poor germination, while others will have poor looking seed but good germination rates. Embryo culture can be used to overcome germination barriers but is probably not feasible for most people. When in doubt, plant! With rare species or valuable hybrids, some extra seed should be stored in a freezer in an air tight container for insurance.