Can Semi-Aquatic Plants Be Fully Submerged in an Aquarium?

Semi-aquatic plants, also known as marginal plants, are a unique group of plants that can survive both submerged underwater and emersed out of water. This amphibious nature makes them popular choices for paludariums and ripariums which contain both aquatic and terrestrial environments. But can semi-aquatic plants adapt to being fully submerged in an aquarium long-term? Or will they suffer without access to open air?

What are Semi-Aquatic Plants?

Semi-aquatic plants grow along the margins of bodies of water such as ponds, lakes, and streams. Their roots and lower stems are adapted to being underwater, while their leaves and flowers grow above the waterline. Many marginal plants also tolerate periodic flooding when water levels rise.

Examples of common semi-aquatic plants include:

• Cattails
• Pickerel weed
• Arrowheads
• Lizard’s tail
• Iris
• Taros
• Sweetflag
• Umbrella palm
• Parrot’s feather
• Water spinach
• Watercress

Being amphibious allows these plants to take advantage of their aquatic roots and emergent leaves. Their underwater roots access moisture and nutrients while their above-water foliage gets light and air. Semi-aquatic plants bridge the gap between land and water in wetland environments.

Challenges of Growing Semi-Aquatic Plants Submerged

While semi-aquatic plants are adapted to life at the water’s edge most are not truly aquatic. Over time keeping their entire plant structure underwater poses challenges including

• Lack of carbon dioxide (CO2) – Submerged leaves have limited access to atmospheric CO2 which is required for photosynthesis This can slow growth

• Lower light – Water filters out light. Less light reaching submerged leaves reduces photosynthetic activity and growth.

• Oxygen deficiencies – Submerged plants lack access to atmospheric oxygen. Some aquatic plants adapt via internal air spaces but semi-aquatic plants generally don’t have these adaptations.

• Buoyancy issues – The spongy stems and waxy leaf cuticles that allow emergent growth make some semi-aquatic plants buoyant. This makes keeping them anchored underwater difficult.

• Melting leaves – Emergent foliage often melts and rots when kept continuously submerged. New aquatic leaves may eventually form.

• Difficulty flowering – Few semi-aquatic plants flower underwater. Lack of atmospheric gases, humidity, light, and other factors limit blooms.

So while semi-aquatic plants can survive temporary submersion, over time they will struggle without access to air. Only a handful of species can truly thrive when permanently underwater.

Best Semi-Aquatic Plants for Full Submersion

While most marginal plants require emergent growth, a few exception species can adapt to life fully submerged in aquariums. Here are some of the best semi-aquatic plants to try fully submerging:

• Anubias – These tropical plants have thick waxy leaves that withstand submersion. Provide good light. Tie anubias to decor instead of planting in substrate.

• Cryptocorynes – Crypts grow slowly submerged but acclimate well. C. wendtii and C. undulata are good choices. Their brown leaves often melt but regrow bright green underwater.

• African water fern – A lovely open-leafed fern that attaches to decor. Keep in warm water with medium to high light.

• Java fern – Known for tolerating a wide range of water conditions when submerged. Use ties to attach to wood or rocks.

• Bucephalandra – Gorgeous flowers emerge above water but buces adapt well when kept submerged in high humidity.

• Crinum calamistratum – One of the few fully submergible Crinum lilies. It grows long strappy leaves underwater. Medium to high light.

• Acorus gramineus – An amphibious Iris species. Slender green leaves remain intact underwater. Tolerates a range of conditions.

• Spathiphyllum – One of the few peace lilies that adapts to full submersion. Provide high humidity and low to medium light.

This list shows that some of the most submersion-friendly semi-aquatic plants tend to be epiphytes that naturally grow attached to trees and rocks in humid tropical environments. Anubias, Java fern, and Bucephalandra species are prime examples. Their adaptability serves them well as aquarium plants.

Tips for Growing Semi-Aquatic Plants Submerged

If you want to try fully submerging marginal plants, here are some tips to help them adapt and thrive underwater:

• Select plants known for submersion tolerance like anubias and crypts. Avoid thinner-leaved floaters like parrot’s feather.

• Give plants time to acclimate. Many will melt at first but regrow aquatic leaves. Be patient!

• Increase water circulation around plants. Added flow delivers more CO2 and oxygen.

• Provide ample aquarium lighting. Plants need more light underwater to photosynthesize.

• Fertilize regularly with comprehensive liquid fertilizers. Submerged plants have higher nutritional needs.

• Use soil substrate capped with gravel. Soil provides nutrients missing underwater.

• Introduce CO2 if possible. Injecting or diffusing CO2 greatly benefits submerged growth.

• Maintain warm water temperature around 75-82°F. Heat speeds metabolism and growth.

With a few adjustments, many semi-aquatic plants can survive being permanently underwater. But growth is often slower compared to true aquatic plants. For the healthiest submerged specimens, give them the conditions they need to thrive!

Growing Semi-Aquatic Plants Emersed

Semi-aquatic plants really shine when allowed emergent foliage growth. This is how they naturally grow along pond banks and wetlands after all!

To grow marginal plants emersed in a paludarium or riparium:

• Select shallow water depth allowing leaves to reach the surface.

• Create sloped or tiered substrates with shallow sections.

• Provide very high humidity at plant leaves. Use glass tops to contain moisture.

• Ensure excellent drainage in emersed substrate areas. Avoid soggy soil.

• Give adequate lighting for both aquatic and emergent plant sections.

• Use a lower water current in aquatic areas where plants are submerged.

When allowed both immersed root growth and emergent leaf access to air, most semi-aquatic plants flourish. Creating a paludarium is an excellent way to grow marginal plants to their full potential.

Semi-Aquatic Plants Add Diversity

Semi-aquatic marginal plants give aquarists unique options beyond fully aquatic specimens. Their ability to survive both submerged and emersed makes them fun additions to mixed underwater-terrestrial displays. With care to meet their particular needs, many semi-aquatic plants can adapt to life fully submerged if desired. Or allow them to grow emersed for optimal health. Experiment with marginal plants to add new dimensions to your aquascape projects!