Irish moss is a term that applies to two different plants that have different colors and thrive in completely different environments. Terrestrial Irish moss prefers dry and even sandy soil, while seaweed Irish moss lives in water. Neither of these plants are even mosses, with the aquatic Irish moss being seaweed and the terrestrial Irish moss being a perennial evergreen.
Irish moss is mostly appropriately named, since it is often associated with the rolling hills of the Emerald Island in Ireland. However, Irish moss is not actually a moss and is instead a perennial plant. This Irish moss is popular because of the lush appearance and the softness that is felt underfoot. Irish moss is also the name of a type of red, white, brown or green seaweed which has flattened leaves. When this type of seaweed washes up on the shore, it turns white. The seaweed Irish moss has blades that are rubbery, flat and crimpled at the edges. This moss usually gathers together in clumps.
The seaweed Irish moss is found at inlets, tide pools and lower intertidal zones. This moss is found between the rockweed above kelp. The blades of the seaweed Irish moss extend broadly when they are in shallow water and are narrower in deep water. The terrestrial Irish moss is found on dry, open ground that is usually sandy or has gravel. Some moisture on the soil will not bother terrestrial Irish moss. This Irish moss is found mostly in the British Isles. The Irish moss prefers some sun and does not do well in full shade.
Seaweed Irish moss can be found all year round. It has the ability to survive extremely cold weather and can even survive being frozen. The terrestrial Irish moss blooms during the late spring and throughout the summer. This plant is an evergreen.
Attached to Irish moss seaweed are special roots called holdfasts, which serve as anchors for the Irish moss. While the seaweed Irish moss lacks flowers, the terrestrial Irish moss develops white flowers.
Seaweed Irish moss is used to thicken soap and dairy products. An extract called carrageenan is taken out of seaweed Irish moss and used in dairy products, cosmetics and baking. Seaweed Irish moss is also used in the making of beer, the tanning of leather and the packaging of seafood. Terrestrial Irish moss is usually used to fill in cracks in flagstone pavement.
Terrestrial Irish moss does not protect from weeds and weeds often spring up among the moss. Therefore, regular weeding must be done. This plant also does not like soggy soil and droughts.