ʻIhiʻihi fronds; mature and developing. One of the best ways to keep ʻihiʻihi is in a large container like this one. It's easy to overlook ʻihiʻihi in the wild since it remains dormant beneath the soil during long dry periods, and even when the rains come to fill its temporary pools much of it can be hidden under the water's surface (Photograph courtesy of Vince Scheidt [snakeinmypocket] CC BY-NC 4.0).

Growth Requirements

General

    Perhaps, the easiest way to grow Marsilea villosa is in a container. Try keeping this unique little fern in a hanging basket, or, maybe, something larger like the wooden barrel pictured above. If you do opt to grow your ʻihiʻihi in a container, consider plugging up the drainage holes so you can occasionally flood the container when watering. ʻIhiʻihi can also be grown in a shallow pond or other water feature. We've found that in a pond or water feature, it's best to keep your ʻihiʻihi in its pot and place it so that the level of the media in the pot is about even with the water level. This may require you to prop up the pot with an attached inverted pot or a flat rock. If you have fish or other animals in your pond, watch to make certain they don't start eating your new addition.

    ʻIhiʻihi can be grown in the ground, but this normally requires more care and monitoring. Rather than just planting it directly in the ground, consider digging a shallow hole, lining the hole with a flexible pond-liner (or for smaller spaces, using something like a concrete mixing tub from your local hardware store), and then partially filling the hole with a media mix or soil. This homemade wetland will let you better control the media/soil moisture level surrounding your ʻihiʻihi without overwatering any surrounding non-wetland plants. It will also reduce the number of weeds sprouting up around the periphery of your ʻihiʻihi patch. 

    In the wild, Marsilea villosa grows in clay. However, it will also grow in lava/cinder and organic-dominant soils. And, since clays can be muddy and messy, using a standard non-clay peat moss and cinder (or perlite) media mix is our preferred choice for ʻIhiʻihi in containers. 

    Marsilea villosa naturally spreads by rhizomes (horizontal stems). Therefore, if you want to fill a large space, you can plant it out in small clumps about a foot apart and then simply wait for it to spread and grow together to form a dense interwoven mat.

    Too much shade reduces the overall vigor of ʻihiʻihi, while ʻihiʻihi grown in all-day full sun tends to produce smaller and redder leaves. Therefore, keeping you ʻihiʻihi in a site with partial sunlight is the best choice.

    While Marsilea villosa lives naturally in intermittent pools, it doesn't need to go through wet and dry seasonal cycles to be maintained in a landscape or container. Keep your ʻihiʻihi green and growing long-term by simply keeping the soil or media constantly moist to wet. Obviously, ʻihiʻihi is tolerant of waterlogged soil, but it can also tolerate drought (although its leaves may die, in which case new fronds will need to grow back after watering) and even a bit of salt spray.

    If your ʻihiʻihi begins to lose its color, try a small application of a balanced controlled-release fertilizer with minor elements or spray your fern with a water-soluble fertilizer diluted to ⅓ to ½ recommended strength — that is, unless your plant is growing in a pond or other water feature where the fertilizer will cause an unwanted algal bloom.

    ʻIhiʻihi requires very little pruning except to remove old dead fronds or to limit its spread into unwanted areas.

Pests and Diseases

    Marsilea villosa is occasionally attacked by snails and slugs, or sap-sucking insects such as aphids, mealybugs, thrips, and scale insects. Refer to the Pests & Diseases page for ways to combat these pests.

Special Features and Information

General

    Marsileaceae is a family of ferns with 50 to 80 species within three genera native to warm-temperate and tropical regions worldwide. Most of the species are in the genus Marsilea [WikipediA;Marsileaceae]. Many Marsilea species are unusual because they do not look like typical ferns but instead like clovers (Trifolium spp.) or Oxalis species (wood sorrels), both flowering plant genera and totally unrelated to ferns which have no flowers. 

Hawaiian Name

    Pukui & Elbert (1986) reference ‘ihi‘ihi as "An unknown plant formerly growing at ‘Ihi‘ihi-lau-ākea, the western side of Hanauma Bay, O‘ahu" and Ihi lāʻau as "Marsilea villosa. Lit. medicinal sorrel. Ni‘ihau."

Etymology

    The genus name, Marsilea, is in honor of Count Luigi Ferdinando Marsili or Marsigli (1656-1730), an Italian scholar and natural scientist of Bologna [Gledhill 2008; WikipediA;Luigi Ferdinando Marsili]. The species name, villosa, comes from the Latin word villosus, which means "hairy," in reference to the hairy rhizomes and sporocarps [Palmer 2003].