This is an article I wrote a few years ago, which was reprinted in the book LILIES, written by Pamela McGeorge (Firefly Books Ltd., 2004 ISBN 1-55297-883-4).
Our climate is quite harsh, as we have experienced many winters without reliable snow for protection in the past 5-10 years. Even a couple inches of snow provides good protection, and a foot of snow is great! We have been having periods of drought for the last 3 years as well, the summer of 2002 was the worst on record in 133 years in Alberta. Our springs are unpredictable - one day +10 Celsius, then next day may be -15! Killing and damaging frosts occur often after the lilies have pushed their noses through the ground. We can still experience killing frosts in mid June in central Alberta.
Our lilies start to push through the ground as early as the beginning of April during a warm spring. The average date for emergence here is the end of April, although in spring of 2002 (very, very cold) they did not emerge until after May 20th. Extreme heat by the end of June allowed them to catch up and bloom only 1-2 weeks off their regular bloom period, but the bulb health suffered as a result of the rapid top growth. Most notably, the root systems on newly planted bulbs (fall 2001 and spring 2002) were underdeveloped or non-existant. It was quite surprising to find inadequate and nonexistent roots during harvest in fall, under bulbs which bloomed beautifully during summer. It was very disheartening to realize that bulbs without adequate roots prior to the onset of winter would likely not survive the winter, or another dry spring.
I have found the established LA hybrids to be virtually unaffected by drought, while young seedlings seem to struggle in early spring without adequate moisture. The LA's appear to be perfectly hardy without any protection here at our zone 3 location, but we have customers in Calgary, AB (chinook zone 3-4) who cannot overwinter them. Zone 2 growers (Vermillion, AB) also have no luck with overwintering them.
Our Asiatic selections have been affected by drought & heat most notably in their height and colors. The colors have shown quite a variance over the past 3 years, depending on the heat factor when they first open. Hot temps wash the colors out, while cool temps make for more vivid colors. Often I have wondered if I had certain varieties tagged incorrectly as the flower colors did not resemble the previous year colors at all. Typically the lilies only achieve 2/3 or ½ their height potential under drought conditions. Hardiness of asiatics does not seem to be affected by drought or lack of snow cover over winter. The asiatics are truly hardy! Only those stressed or affected by disease such as fusarium or basal rot struggle to survive our harsh winters.
All varieties of lilies ability to increase in bulb size has been affected by drought conditions - they do not gain any size from the previous year if they do not receive adequate moisture. They have also started to reproduce themselves much more prolifically these last 2 years in an effort to overcome the stresses Mother Nature inflicts on them. This is a common occurance in many plants - to reproduce themselves when they feel their existence is threatened.
The LA hybrids tend to reproduce prolifically under normal growing conditions, but have kicked into overdrive with the weather patterns the last 2 years! It is not uncommon to find many underground bulbets the size of a nickel or bigger when harvesting mature LA hybrid bulbs. These bulbets try to bloom their second year, but we pinch the buds off as soon as they begin to form, in order to allow the bulb to use the energy to increase in size rather than expending itself in immature blooms. LA's also double their original bulb size under good growing conditions. I have heard some say they are not long lived, but with prolific reproduction the mother bulbs do not need to be. There is one drawback I find with the LA hybrids, and that is their virus resistance, or lack of it. I find that many varieties succumb to TBV over time, usually 3-5 years and it will appear if present. It is worth noting that I have never seen virus in any of the ‘Royal' series of LA hybrids. It is my personal theory that the interdivisional crosses (which the LA's are) are genetically weaker because of the cross, and this makes them more susceptible to virus. Stress triggers the virus, and of course our unpredictable and harsh climate puts them under stress, so we have seen more virus symptoms in the past 2 years than ever before. We promptly remove and burn ALL stock suspected of being virused, so as not to have it spread to other varieties.
What have we done to help them overcome the stresses of weather? Mulch, mulch and more mulch! Mulch is effective in controlling ground temperature, moisture levels, pests and soil born diseases. Mulch spread throughout the beds, to a depth of even 2 inches is very beneficial in keeping moisture in the ground - I cannot stress this enough! I would recommend mulch to a depth of at least 4 inches wherever possible, but any depth is better than none at all! Mulch also provides extra winter protection during years without snow cover. I highly recommend applying mulch over varieties that are under particular stress, less hardy (such as orienpets and orientals) to a depth of 6-8 inches for winter. Mulch also is effective in keeping the ground temp consistant in spring, and slowing the thawing process so that the lilies will emerge a little later than those without mulch, and perhaps escape the late killing frosts as a result. Slow and steady ground temperatures encourage good root systems to develop before top growth begins. We use bark mulch throughout our lily beds, and have used dried grass clippings and sawdust in the past as well. If using a form of wood mulch, extra nitrogen fertilizer may be needed during the growing season as wood mulches tend to deplete the nitrogen content in the soil quicker.
We are fortunate to have a variety of soil conditions throughout our small acreage - we live within ¼ mile of a large river valley, almost pure sand to healthy, rich black soil exists here. The lilies do the best in the sandy areas, providing they receive adequate moisture. If not, the lilies in these areas are the first to suffer under drought. Drainage is key to good lily growing and performance. Many people confuse the statements regarding good drainage and adequate moisture. Lilies do indeed love constant moisture, but only if they have excellent drainage as well. If not, they will rot and/or deteriorate rapidly. We recommend planting in raised beds or amending the soil heavily with sand where heavy clay soils exist. The most common reason for bulb rot in containers is too much moisture and not enough drainage. It is worth noting that heavy additions of sand to the potting mix used in containers makes for much fatter & healthier bulbs by the time fall rolls around. If soil structure contains a high ratio of sand, extra fertilizing will be needed.
We do not grow orientals or trumpets in the ground, here at our location due to their lack of reliable hardiness. We grow them in pots over summer, harvest in fall and store in a ground cold pit at +2 Celsius over winter. We live in the country, where temperatures plunge a little bit further than in the towns or cities. We do have many customers who live within towns or cities who have great success with overwintering their orientals and trumpets in zone 3, when planted against heated foundations or protected sites. The common complaint is that they still do not thrive, bud count decreases each year and they eventually die out, usually within 3 years of planting.
The latest in interdivisional crosses (orienpets, asiapets and asiatic/aurelian crosses) have given us mixed results over the past 4 years. We find those bred on the Prairies grow best on the Prairies, such as Wilbert Ronald & Lynn Collicut's selections (Northern Star, Northern Carillon, Starburst Sensation, Easter Morn, etc.) Scheherazade and Leslie Woodriff (both orienpets bred outside of Canada) have proven reliably hardy here as well, providing they are planted at a minimum depth of 8 inches, and planted in spring so as to allow good root growth over summer and prior to the onset of winter. Most orienpets are doing very well in provinces such as Manitoba where they still get good snow cover over winter, but here in AB mixed results are found when we have no snow cover. Again, we recommend planting these in spring only, to a depth of 8-12 inches, and heavy mulching in fall before snow falls. The mulch must be removed as soon as possible in spring, in order for the bulb to warm up and start growing. Because they are planted deeper, they will take longer to emerge. The alternative is to grow them in pots and overwinter in a protected spot or root cellar. My biggest concern with the hardiness of the orienpets and orientals revolves around their late blooming natures. We experience killing frosts as early as mid August, which is often the time the buds are just maturing on these varieties here. If they freeze hard, too early in their life cycle, the bulb is unable to gather enough energy before winter sets in, and this may very well be the reason they do not survive the winter extremes on the prairies. I believe they have the ability to still collect some energy through the stems even after they are limp after a killing frost, so we leave those ugly frozen stems on them despite their unsightly appearance.
We fertilize by adding a slow release pellet (14-14-14, 3-4 month life) in early spring, as soon as the lilies emerge. This is scratched into the ground just below the surface of each clump or row. We use a water soluble fertilizer of 15-30-15 during irrigation once, just prior to buds opening, and we also use a water soluble fertilizer of 20-18-18 with minor trace elements added once during the growing season, shortly after flowering. It is only the last 2 years we have irrigated our lilies, because of extreme drought conditions. Lilies are very drought tolerant providing they are healthy to begin with.
Disease is almost non-existant here, probably due to the weather extremes. If we experience prolonged periods of cloudy, damp or wet weather, there is usually an outbreak of botrytis to follow, but it is easily controlled with a spray of Benomyl (severe outbreaks) every 2 weeks, or a simple baking soda solution sprayed every 3-4 days as a preventative measure. The recipe for this is on my web site on the feature articles page. It is worth noting that you can virtually guarantee botrytis will appear sooner or later if severe frosts occur during the early development of stems. Generous spacing of the bulbs goes a long way in controlling botrytis symptoms as well, as does good cleanup practices in fall. If we experience heavy botrytis during summer we pull the stems and burn them all in fall, otherwise, we leave them be over winter in order to trap more snow, and pull them in spring before the new shoots emerge.
Lilies are rarely affected by pests here at our location, the only bothersome pest is aphids. I have never seen an outbreak in the lilies grown in the ground, but often they affect the potted lilies and must be controlled because of their ability to spread virus and disease. We control them very effectively with a new organic product called ‘End All', produced by the good people at Safer's. The last 2 years have seen an increase in the grasshopper population, no doubt due to our drought and extreme heat. We expect them to reach epidemic proportions next year as they were near that this year. They have not damaged the lilies yet, I assume because they do not like the rough nature of the bark mulch which surrounds our lilies. Clouds of grasshoppers greeted us as we walked across the lawn in summer this year, but very few were found amongst the lily beds.
We grow a few species here with good success; cernuum, pumilum, citronella, lankongense, henryi, tsingtuaense and of course lancifolium. We are experimenting with a great variety of others, but it is too soon to tell if they are reliably hardy under our conditions yet. We must evaluate their ability to thrive and reproduce, not just their ability to live under our conditions.
Martagons are extremely hardy, but I only grow them in my personal collection, not for commercial use. There are commercial growers already established in this market and I prefer to focus on the hardy asiatics and interdivisional crosses. I am too new to growing Martagons to provide any relevant growing tips.
We split and divide our bulbs every 3 years on average, in order to prevent bulb deterioration due to overcrowding. Experience has shown us that if we leave them one extra year, we will end up digging and moving the entire row completely because the bulbs will deteriorate that quickly. Because we are commercial growers with the intent to ship the largest, healthiest bulbs possible, we snip the buds on immature stems, and cut off spent flowers immediately after blooming, to encourage the bulbs to put their energies into increasing bulb size rather than seed production. It is important to leave at least 2/3 of the stem above ground when cutting the lilies, so that the leaves can collect as much energy as possible for the remainder of the summer, and store it in the bulb for use the next year.
Harvest is begun as soon as the stems begin to yellow and die off in fall, sometimes this is the end of August, sometimes not till the end of September. Stem ripening is greatly affected by the moisture levels in the ground, lots of moisture means they will be slower to ripen, less means they are quicker to ripen. If a stem does not tug out of the bulb easily or cleanly in one quick snap, then it is not ready to be harvested and we put them back in the ground and try again 2 weeks later. If a bulb is harvested too soon, it's ability to survive and thrive the next year is affected. Flower and stems performance is directly linked to the growing conditions and treatment of the bulb the year before. Good growing practices this year result in great performance the next year.