I love crinums! Yes, fall is a great time to plant them.
You may or may not know that they hate being disturbed, and bloom best if left alone for years at a time. Expect your new one to wait two, maybe three years, before you see blooms. So, think carefully about where you want them (full sun, well prepared soil, and ample moisture is important). Mix a generous amount of Black Kow or other composted manure in the hole, and plan to top dress them with the same each fall and spring. I have read that slow release fertilizers can help the bulbs size up more quickly.

Most sources say to plant the bulbs deeply, 12-18 inches deep (from ground to base of plant), but I killed a small bulb by planting it that deeply once. So, I plant them with the neck at or slightly above ground level. They have contractile roots that will pull them in deeper if need be. In your zone, I would definitely recommend a heavy mulch in fall, maybe even a rock or paver over its roots for just a wee bit of extra warmth, especially the first year or two until it gets established.

According to Southern Living Garden Book, the following crinums are hardy in Maryland.
Moorei
Powellei
bulbispermum
And these hybrids:
Mrs. James Hendry
Bradley
Carnival
Hannibal's Dwarf

That's a pretty decent selection, and there may be more. All of these would be good, but I would like to give an extra toot of the horn to Mrs. Jame Hendry. First, it is not a gigantic plant, which is good. Many of my crinums have foliage that reaches 4 to even 6 FEET in diameter. They are space hogs. (I love them anyway). But, Mrs. James Hendry takes no more space than an amaryllis. And, its foliage is clean, neat, and doesn't develop rust in my experience. In addition to all that, it is nearly everblooming (assuming you get rain, which triggers blooms). It's well worth seeking out.

One other note. Since your bulb was in a combo pack, it's a good bet that it's Ellen Bosanquet. This is a great bulb that makes lots and lots of offsets. However, it is not rated hardy in your area. It also blooms but once a year. You could grow it in a pot and over winter inside, or put it in the ground with as much protection as you can give it and see what happens. If it dies, search out some of the above selections. I think everyone should grow crinums if they can. :)

I have c. Milk and Wine, and it has done well in my garden for years. as well as a big pink crinum that gets about 4'tall and the plant is huge with long strappy leaves. I garden in zone 6b so they should be hardy for you. I don't bother to cover them in winter but the bulbs are deep, about a foot down.

do you have a good source for crinum bulbs? I used Lushlife nursery before. Wonder if you have any other favorites? Thank you
c

There is an Ebay seller named bulbsnmore that I purchased many of my crinums from. He's in Florida and I was impressed with his service, his vast selection, and the quality of the bulbs I received. Plant Delight Nursery and Yucca Do also have a good number (and difficult to find) of crinums available. My first crinums were the old Milk and Wine lilies that I traded rooted rose cuttings for. Look around your area. They can be found in all kinds of places, especially, the so-called "poor" sections of town. (That's where the really good gardeners live.) Here, they are often planted all alone in a solitary clump in the yard by the street. I have been known to knock on the door of strangers and propose a trade. I have never been turned away without at least a new gardening friend. :)

THANK YOU DONNA
I have one milk and wine planted in a strange place between 2 driveways....yes, in a narrow strip. The old gardener who gave it to me told me it was an amaryllis! They look similar when you don't know better....and I didn't

What a treat. It has done well there only because it gets sun and the space was so darned dry that I leave a soaker hose with a drip on there.

I was given some others that are just getting settled in their new home but I want some for a gift. I'll check your recommendation here and see if I can get up the nerver to knock. Great suggestion! I know I wouldn't say no. I love to share plants.

c

I had no experience with Crinum, never saw them growing. When I saw some in Costco, sold by the package I decided to give them a try. The package contained about ten bulbs, some BIG and some small. I potted them all up in pots relative to the size bulb, some with three in a pot. The biggest bulbs grew like on steroids and bloomed the first year. The small bulbs lived but did not grow much. The second year the big plants had more than one flower stem, the smaller one grew well but did not bloom. I am beginning to get an idea of how big the bulb has to be to bloom. This winter I will put at least the largest ones in the ground. Al