Bulbs and they are usually planted in fall, so if you want to plant them in spring you need to refrigerate them for about 2 months first. You can grow them from seed but you would not get flowers this year.

Alternatively, buy them live in pots in spring.

Also, look into the difference between types of lilies: daylilies are different from cala lilies are different from asiatics, orientals, easter (longiflorum), trumpets, and hybrids, not to mention species lilies.

No need to refrigerate or prechill lily bulbs purchased in spring before planting. They are either recent harvest and so have already gone through a sufficient chill period or they were dug in fall and kept in cold storage. Just dig a hole and plant - they are very easy to grow as long as you have well-drained soil and good sunlight.

FWIW, most lily bulbs are sold in spring for current season's planting and flowering. Lilies are very seldom grown by seed unless you are looking for very unusual species or you are a hybridizer. It takes a good number of years for seedgrown lilies to reach blooming maturity.

Daylilies and callas are not true lilies (not even bulbs) despite what appendages get attached to their common name:-) They are different types of plants and are treated differently. The FAQ for this forum has a good discussion regarding true lilies and other plants commonly called "lily".

"Alternatively, buy them live in pots in spring.

This would be my recommendation for someone just getting started with lilies. Here in the colder zones, lily bulbs available in stores in the spring are often leftovers from the last season. I don't do mail order, so I can't speak for what you might get in ordering any time of the year. Here, fresh lily bulbs will become available in the fall for fall planting and for bloom the next season.

If I were just getting started with lilies, I'd buy a potted, budded plant or two from any of the seasonal garden centers - even the big boxes - and dig a 6" hole where the soil drains well and carefully transplant it. No big investment and you get to watch how it blooms and behaves once blooming is over.

Although I have ideal lily conditions, I've had the best continuing success with the Asiatics. They're simple, good multipliers, come in a range of colors with and without spots - just not as elegant as the Orientals. For me and just my personal experience, the Orientals and fancier lilies have done well for a year or two, then produce fewer and fewer flowers, and finally disappear altogether.

I am very new to grow lilies .I have three Lilien Oriental x
Trumpet plants in a big pot .They have been doing very well
for one month they grew really big and healthy ,but when they started to produce a flower buds as they are new formed they
are getting yeallowish and then brown ,leaves are healthy
and stalks as well are strong so i do not understand the reason .I use to fertilize them with orchid type fertilizer
about once at week .I wonder is it possible that to be the
cause .I use the same fertilizer for my mini roses and
four leafed clovers and i have no problems with them .Please help .

I have to second the notion that Asiatic Lilies are a better buy for a lily newbie. They are not nearly as fussy and do indeed multiply over time instead of just slowly fading away like Orientals do.

If you would like to know particular lilies that do well, the North American Lily Society offers advice on that:

"Each year the North American Lily Society asks its members what their favorite lilies are. Of course, all of the lilies on the list are beautiful, but they are also lilies that perform well in the garden. The popularity poll is a great resource if you are looking for lilies to add to your collection, particularly if you are a new gardener."

Check the link for the results of their popularity poll for various years.

2008 Popularity Poll Winners
1. Conc D' Or
2. Anastasia
3. Iowa Rose
4. Oriana
5. Landini
6. Kentucky
7. Indian Summer
8. Robina
9. Embarrassment

10. Dot Com

(Of those I have added Landini and Dot Com recently, and they have both bloomed well and are increasing in numbers.)

Here is a link that might be useful: NALS Popularity Poll

Artemisia, Stop fertilizing your lilies. They do not need it. No plants require that much fertilizer.
Is your soil well drained?