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:

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