How to Plant & Grow Swamp Lily (Crinum americanum)


Pond Informer is supported by it’s readers. We may earn commission at no extra cost to you if you buy through a link on this page. As an Amazon Associate we earn from qualifying purchases.

Help Spread Pond Keeping Knowledge!

Swamp Lily Growing, Benefits, Facts & Care (Crinum americanum)

bog lily growing in a fish pond
Photo by David J. Stang / CC BY-SA

Also known as bog lily, seven sisters, crinum lily, and Florida swamp lily, the swamp lily is not actually a true lily. Swamp lily belongs to the amaryllis family, Amaryllidaceae, and the subfamily Amaryllidoideae. For morphological reference, common daffodils also occur in this subfamily.

Native to the southeastern United States, swamp lily, like all of the other 180 species within the Crinum genus, are found seasonally in moist areas like bogs, fens, ephemeral pools, wet ditches or depressions, and along the banks of rivers, ponds, and lakes.

It should be noted that this plant was formerly contained in the Liliaceae family and Lilium genus, but modern phylogenetic research determined that it is not, in fact, a true lily and instead belongs in the amaryllis family. Some sources online have yet to be updated, so don’t be puzzled if you notice different classifications on different websites.

Facts, Benefits & Uses of Swamp Lily

Mexican violeteater hummingbird feeds on bog lily
Butterflies and hummingbirds, like this Mexican violet-eater, benefit from bog lily.

Swamp lilies grow in groups, classified technically as umbels, of most often seven stems and flowers, hence why it is also known as seven sisters. However, they can also grow in groups of as few as two or as many as twelve. Large flowers, each with 6 unusual-looking, long, highly dissected (separated) petals, begin blooming by early summer. These showy, sweetly scented flowers attract butterflies, bees, moths, birds (primarily hummingbirds), and just about anything else nearby looking for nectar and pollen.

Traditionally, Crinum species have been utilized (primarily in Africa) to treat a variety of ailments, from depression to Alzheimer’s. Specifically, the subfamily Amaryllidoideae has been found to contain over 500 alkaloids, including galanthamine, an alkaloid that is now known to inhibit acetylcholinesterase, thus potentially slowing the progression of Alzheimer’s. However, studies are still being conducted to determine the exact properties of these alkaloids, and which species contain adequate levels to be of certifiable medicinal use.

Check Pond Plant Prices

Swamp Lily Fact Sheet:
PLANT TYPE
Herbaceous Aquatic Perennial
HARDINESS ZONES
USDA 7 – 11
LIGHT REQUIREMENTS
Full sun, partial shade, full shade
BLOOM COLOR
White
BLOOM PERIOD
June – October (Summer to Fall)
MAXIMUM GROWTH
Height & spread both up to 60 cm (24 in)
PLANTING DEPTH
Just enough to cover the bulb
WATER QUALITY
pH 6.5 – 7.5

If grown from a bulb in the spring, bog lilies are generally able to flower a couple of months after planting. If planted as a seed, flowering can take anywhere from 3 to 8 years depending on conditions. Showy white flowers generally last from June through the beginning of October, if you live in USDA hardiness zone 7 or above, as this plant prefers temperate regions such as Florida, the Carolinas, and Louisiana.

Full sun or total shade both work well for this easy-going plant, the caveat being that constant moisture must be available in the soil if planted in full sun. Most often, a maximum height and spread of two feet can be expected, though some plants may only reach one foot while others could reach closer to three. Flowers are approximately four inches in diameter, with basal leaves a minimum of six inches in length.


Swamp lily bulbs should be planted in just enough damp soil to cover the bulb. Bulbs should not be planted in standing water. Aquatic soil, loam, peat, or any other rich, acidic, well-draining soil work well. Once established and sprouting stems, bog lilies can be placed in up to one to two inches of standing water along the shallow, marginal edge of your pond. The do have some rhizomes, but they’re not particularly aggressive and take some time to spread. Therefore, it’s not necessary to plant them in pots or baskets as their growth is not difficult to control.

Either full sun or partial shade work just fine for this plant. If not planted marginally in your pond, do keep soil consistently damp or growth may be stunted, or the plant could die altogether. Short durations of drought can be tolerated, so long as this doesn’t occur often. You can place mulch around the base of the plant to help hold in moisture, but turn over the mulch from time to time to discourage mold growth.


How to Care For Swamp Lily

Keep bog lilies well-watered if they’re not planted directly in your pond. A good rule of thumb is to keep the first inch of soil damp. Minimize the amount of times that this plant is transplanting, as swamp lilies are sensitive to transplanting and can become stressed. If you’ll need to bring them indoors for winter, consider keeping them planted in large pots outdoors during the spring and summer for easier transport.

The stems and roots can be trimmed as needed, and shouldn’t harm the plant overall. Be sure to clean up any clippings or dropped flowers from your pond to maintain healthy water quality. Try not to disturb the plant while blooming, however, else it may stress the plant and cause it to not bloom for a couple of years.


How to Winter Swamp Lily

Bog lilies do not tolerate winters well. You can either bring the entire plant indoors for the winter and care for it as a houseplant, or you can store the bulbs in peat in a cool, dark area such as a basement or garage. Bulbs left in the soil outside over the winter will likely not survive if temperatures fall below freezing.


Is Swamp Lily Toxic, Poisonous or Invasive?

Asian poison bulb, Crinum asiaticum, is invasive and toxic in the US and UK
Crinum asiaticum, the Asian poison bulb, is a bog lily lookalike that is both toxic and invasive in the US and UK.

There is little data regarding the invasiveness of this plant. Though it’s native to the south-eastern U.S., it can be obtained elsewhere around the world with relative ease. It’s not a prolific spreader, but nonetheless if you live outside of its native range, take precautions when planting to deter it from spreading into natural areas. This includes planting in pots and keeping it well within the bounds of your property rather than along property edges, and not planting along natural ponds, lakes, or streams where the native flora and fauna could be disrupted by its alien presence.

Better yet, if you live outside of the south-eastern U.S., search for a Crinum native to this area. For example, Crinum pedunculatum looks identical to C. americanum but is native to Australia. There are no known Crinum species native to the U.K., but it can be reasoned that Crinum americanum is suitable so long as the above precautions are taken.

Despite many Crinum species being used medicinally, swamp lily is listed as being marginally poisonous if ingested. This includes all plant parts, from the bulb to the flowers. Additionally, do not confuse swamp lily with the incredibly similar-looking Crinum asiaticum, or Asian poison bulb. As its name implies, the bulb and sap of C. asiaticum are very toxic and should not be planted anywhere children, dogs, fish, or anything else could get into them.


Is Swamp Lily Edible? Will Fish Eat it?

Swamp lily is not edible due to its slight toxicity. Luckily, most fish don’t seem to find this plant very interesting and should leave it alone. However, do have precautions in place, such as only planting on shallow shelves where your fish can’t swim and/or planting in pots so that your fish cannot access the roots or leaves. Clean any dropped or trimmed foliage from the pond immediately.


Where to Buy Swamp Lily & Seeds? (UK & US)

Bog lily can be found at plant nurseries and home improvement/gardening stores as well as via online retailers. A quick online search yielded about a dozen results throughout the U.S., and another search for retailers selling Crinum americanum in the U.K. produced similar results.

Check Pond Plant Prices

4 thoughts on “How to Plant & Grow Swamp Lily (Crinum americanum)”

  1. I live in North Florida and have one of these growing in my pond for a few years now. It is in a basket about 3inches down and does great. We had a few days of frost but no damage done to main plant. I have 3 Koi and 7 large goldfish that do not seem to bother this plant.
    Thanks for all your info

    Reply
  2. I have a friend that removed seeds from a plant in Florida about 20-25 years ago and brought them home to New Jersey. They planted them in a pot. They grew! They would put it outside during the summer months and bring it in when it started to get cold. Flowering for the first time this year!! It’s beautiful 🙂 I was going to share a photo, but it looks like I cannot do this here.

    Reply
    • Hi Susan,

      That’s exciting, though I wonder at the potential invasiveness of the species. It’s hard sometimes even for me to abide by this, but transporting plants to new places is a very bad idea as it helps invasive species spread and overtake natural areas even if you’re careful.

      Anyway, that’s exciting that after all of this time they’re flowering! We don’t allow images to be posted on the site for security reasons, but if you’d like to share any pictures with us/other readers, you can on postimage.org. After you upload the image(s), you’ll have to also leave a comment here with a link to the image you just uploaded so that we can find it. I know it might be a bit complicated – we’re looking into potential alternatives for image uploading in the future, but for now this is the safest option.

      Reply

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.