Lilium (the name distinguishes them from daylilies, which are hemerocallis) come in many divisions, or groups, or types. Some require essentially no care, and some are fussier. In zone 5a to 6b, where I have lived for the last 20 years, I have found that the bloom sequence for lilies can be extended over several months, from asiatics in June to formosanum/longiflorums in fall. Best of all, there are lilies that can survive zones 1 through 10.
Here are the classifications of lilies:
Division 1: Hybrids of Asiatic species
Division 2: Hybrids of Martagon lilies
Division 3: Hybrids of L. candidum and L. chalcedonicum
Division 4: Hybrids of American species lilies
Division 5: Hybrids of L. longiflorum and L. formosanum
Division 6: Aurelian hybrids, Trumpet lilies and L. henryi crosses
Division 7: Oriental hybrids
Division 8: All other hybrids
Division 9: All other species and their cultivars
The earliest blooming lilies in my 5a zone garden are the division 2 martagons, which are legendary for the characteristic of such early bloom. Mine typically open in the first week of June (zones 5 to 9). You can adjust these bloom times for your own zone.
This is lilium martagon album:
The most popular lilies sold to gardeners in garden centers are Division 1 asiatics. They are usually potted. (Caution: do not buy lilies that are sold as individual loose bulbs in bins. Lilies never go dormant, and perform poorly if allowed to linger in warm conditions, so those room temperature lilies bloom poorly or not at all). You can remove them from the pots and plant them anywhere in sun. They are tough, healthy, disease resistant, multiply readily, and have an enormous color range. They are upright, outfacing or pendant but, and for some this is important, they have no scent. They don't need mulch. In fact, I find that I can leave them in their pots and put them in the rear of my unheated garage in the winter, under a quilt, and with just a bit of water once a month, they not only survive but multiply!
This is the asiactic lilium 'Royal Sunset'. This is one that has been in a pot for three years, and for which I use, each year, the overwintering technique I described above.
However, there is newer development. There are Asiatics with some longiflorum "blood" that are significantly hardier than longiflorums (which can be temperamental in zones as cold as zone 5) and bloom early, along with typical asiatics. And these have scent and all of the toughness of standard asiatics. One of the best is 'Red Alert'. In my garden it opens, with a blast, in mid-June. These are hardy in zones 3-10, and are great for short seasons such as those in very northern climates.
There are many asiatics that open in mid-June. But there is also a very special lilium that blooms at that time: Lilium candidum, the Madonna lily. This astounding plant has been in cultivation for over 3,000 years. It is unlike typical lilies in that it prefers alkaline soil, is only planted one inch deep, and is planted much later in the year (around September) and forms foliage in the fall.
In July, the trumpet lilies bloom, along with the longiflorum/orientals crosses (LO's) of division 5. They are particularly lovely. While the trumpets are tough as nails, the L/O's are a bit tender, so I mulch them in fall, but it is worth the trouble. The Easter lily is a longiflorum, but blending them with Orientals makes them more cold resistant. The one pictured is 'Prince Promise" which blooms a little earlier than the orientals. The picture shows Prince Promise, an L/O, at the top in full bloom. The bottom lily is the Oriental 'Sorbonne' which is next in the bloom sequence. 'Sorbonne blooms for weeks after 'Prince Promise fades. By combining the lilies from different divisions (Orientals are division 7) you can get many weeks of bloom.
I didn't forget division 6! Those are trumpet lilies. I love them personally, but they are less popular because of a lily I will mention shortly, Orienpets.
Trumpet lilies are highly scented, with large flowers and great refinement. Some are downfacing, and other outfacing. They are my personal favorites. This is Emerald Temple. It is out of commerce, so I am actually growing it from seed! For me, they bloom in July.
Oriental lilies are probably the best known of the older lilies. There are sometimes complaints (I made them in my early years) that they did not return. There is a reason. Some Orientals are very tolerant of alkaline soil, like 'Sorbonne' above, and will bloom, although they will be shorter, but to insure full growth and reliable return, oriental lilies need acid soil. I acidify my soil by using a iron based fertilizer or supplement in the planting hole or on top. Just a bit does the trick. I often wonder why sellers of lilies do not include this vital piece of advice. I will bet that some of the readers of this article planted oriental lilies that never returned. That was certainly my experience. Once I acidified them, I not only reaped a nice harvest but my bulbs multiplied.
Probably the best known oriental lilies are 'Stargazer' and 'Casablanca', but two more glorious lilies are out there. Lilium auratum is from Japan. It MUST be acidified. But I have found that it returns well and multiples nicely. This is an oriental that is also a species lily.
If you want a very different experience, grow lilium auratum platyphyllum, the gold band lily. It is described as both division 7 lily and a species lily. It requires acidification, but the results are stellar.
Orienpets are the newest, hottest lilies. Orienpets are Oriental/Temple crosses. The description from the B&D Lily website says it all:
"These interspecific crosses between Oriental and Trumpet lilies have produced lily bulbs that easily weather late Midwestern frosts without bud kill, but have the sweet fragrance and shape of Oriental lilies. These improved hybrids have all been trialed under garden conditions, so now you can have solid yellow "Orientals" for late summer, with increased drought-resistance and reliability."
They can grow easily in zones 4 through 8, and can become quite tall. At first, they were very expensive, because a small and special group of hybridizers developed them. The most popular over the years has been 'Silk Road". I love putting them in shrubs or baptisia because the stem is thick.
My personal favorite orienpet is 'Anastasia' which is a gorgeous, refined and incredibly strong lily. It is downfacing, but in my new garden it also grows about six feet tall, so you can look up at its incredible beauty. Here it is with 'Crystal Blanca'. 'Crystal' is sold as an improved version of Casa Blanca with a stronger stem. The sales pitch is true. I inadvertently planted these two together, but it also shows the virtues of mixing lilies yourself. They bloom in late summer, and because orienpets have lots of buds, they bloom for weeks. They are also tough as nails.
For truly extended bloom look no further than lilium speciosum, which blooms into September in my zone. They are often planted in spring but bloom along with other lilies, just later in the season. A very special speciosum is 'Uchida' which was chose by the gentleman of that name. Truly exotic, is is in fact widely available. It has tons of secondary blooms, allowing it to bloom for many weeks, and, in my climate, into October.
And, just for fun, if you want lilies that bloom into October, you can easily grow them from seed. I found a seed on a web site called Lilium 'White Lancer'. It is a "formolongi" which is a longiflorum formosanum (tender lily) cross. If you sow the seed in January it blooms in fall. Here is a picture of lilium 'White Lancer' that I grew years ago. I would place it in a pot to grow, and take the pot indoors for winter, keeping it in the basement, giving it a bit of water from time to time, and each spring dug up more and more bulbs to add to my late season lilies. if you can grow annuals from seed indoors you can grow this beauty.
I hope that this article gives those of you who would like to extend your lily seasons the confidence to jump in and extend your season of color in your garden.