Cultivating Humboldt Lily Seeds and Bulbs

By Nancy Gilbert

black and light yellow butterfly on one of many large pendulous orange flowers with brown speckles
Pale swallowtail butterfly feeding on a Humboldt lily (Lilium Humboldtii)

People go nuts over the jaw-dropping beauty of Humboldt lilies (Lilium humboldtii) in bloom! The flowers themselves go nuts, too — in terms of seed production. So you may someday be fortunate enough to receive a batch of Humboldt lily seeds, or even bulbs. Follow along here to learn how to select planting conditions that duplicate the habitats favored by dry-land lily bulb. (These differ from those for riparian-growing lily species.)

Balance Shade and Sun

Most native lilies like their feet in the shade and their heads in full to part sun. Plant or seed out dry land lilies where there is filtered light, such as under native oaks, pines and shrubs rather than full, hot sun or very dense shade. The lilies should not be planted in low spots that have poor drainage or where there will be summer watering, as they prefer well-drained sites. They often are found growing on partially shaded, sloping banks for this and other reasons.

Protect from Deer

Lilies are generally popular with the deer, so plant them where the deer either cannot reach them or are likely to overlook them. Our experience has taught us to help protect them from deer predation by planting them strategically among rock outcrops, on steep banks, or under native shrubs.

We have also had good success with some of the commercial deer repellants on the market such as Ropel, Deer Away, and Repellex. These repellents also protect lily bulbs from voles, gophers and rabbits. There are also home remedies such as liberally applying cayenne pepper, tobacco sauce, coffee grounds, castor oil, or other substances around the problem areas. I have not tried these, so consider using these as trial research projects.

Another way to protect the lilies is to place a metal mesh cage around the bulbs or, even better, construct a deer fence around the areas where you garden near your home. This is what we have done, as individual cages are unsightly and a bit of a nuisance. We love the gardening freedom our fenced garden gives us.

Protect from Gophers and Squirrels

Unfortunately for gardeners, lilies are also a tasty treat for gophers and squirrels. If you have these rodents in your area, it behooves you to protect your bulbs, especially at the time of planting, when they are most vulnerable.

Once the bulbs have been in the ground for a few years, they are less vulnerable to gophers or the digging of squirrels, as the lilies pull themselves deeper using retractile roots.

Tucking lilies into rock outcrops is one way to make them less accessible. The best protection is to construct a subsurface cage of aviary wire or hardware cloth. Dig a hole 12 to 18 inches deep by 10 to 12 inches wide; line this planting hole with the wire. Then return the soil to the hole and plant as detailed following. After covering the bulb with soil, put a mesh top on the cage. If you have an over-abundance of gophers, you may want to consider trapping them.

Prepare Planting Holes for Bulbs

Make the planting hole for a lily bulb deep enough that there is about three inches of soil over the top of the larger bulbs and two inches over the top of the smaller bulbs. If the soil is compacted, dig a hole both wider and deeper than necessary, and loosen this soil. If the soil is very low in organic matter, then you may amend it with compost or humus, but don’t add more than 1 part humus to 3 parts native soil. This allows the roots to penetrate into the soil and provides better drainage. Do not use any compost that contains animal manures, as this promotes soil-borne pathogens.

In general, it is not advisable to add any fertilizer to planting holes except amendments formulated specifically for bulbs. These fertilizers are high in phosphorous and potassium but low in nitrogen. We add only soft rock phosphate to our planting holes and have had good results. Bulb fertilizers containing bone meal can be a problem, as some animals will be attracted to digging for the bone meal.

Plant Your Bulbs

After you have finished planting the bulb, mulch to keep the soil cool and to slow moisture loss. Shredded bark spread one to two inches deep works very well, as do native pine needles or oak leaves. You might want to mark the planting location with a colored flag so you locate it for monitoring.

Direct Seed in Ground

If you are planting Humboldt lily seeds in-ground, choose your location carefully, as discussed earlier. Be sure to remove any weeds that will compete with the lily seedlings. Lily seeds need a period of warm, moist stratification followed by months of cool, moist stratification, which our Sierra climate provides if you seed them in September. Scarify the top layer of soil with a rake or cultivator to create a rough and soft seedbed. Spread the seeds loosely over the bed so they are well spaced out.

Cover them with about one-quarter inch of loamy topsoil. Gently tamp the seedbed to compact it slightly. Mulch the seedbed with a thin layer (about one-half inch thick) of bark fines, pine needles and/or oak leaves to protect the seeds from erosion and reduces intrusions from varmints. Mark your seedbed with flags, rocks or some other method so that you will be able to find your seedlings.

Water as Nature Would

Gently water the seedbed and keep moist throughout the winter months if we have a dry winter. Note that not all seeds will germinate the first year but instead germinate over a two-to-three year period. Lily seedlings are quite small their first year, having one or two small, oval leaves above ground. They are investing most of their energy into forming a bulb to store energy for the next year’s growth. Be patient; a lily needs to grow for four to five years to store enough energy in its bulb to flower. Then, the glory of those huge, pendulous orange and speckled flowers will provide you with great satisfaction and reward for your attention!

Note: For more information, see our Redbud post on propagating California bulbs and corms from seed.

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