Question

Which of the following genera belong to marginal plants and suitable for planting in water gardens?
(A) Azolla caroliniana
(B) Acorus calamus
(C) Cyperus alternifolius
(D) Elodea canadensis
Choose the correct answer from the options given below:

• (A) and (C) only.
• (A) and (D) only.
• (B) and (C) only.
• (C) and (D) only.

Hint:

Water garden plant types:
Marginal: Roots in shallow water/wet soil, foliage above (e.g., Acorus, Cyperus at edges).
Floating: Float on surface (e.g., Azolla, water hyacinth).
Submerged: Grow mostly underwater (e.g., Elodea, hornwort). Acorus calamus and Cyperus alternifolius fit the marginal category.

Answer 1

The Correct Option is C

Marginal plants in a water garden are those that grow in shallow water or moist soil at the edges (margins) of ponds or water bodies. Their roots are typically in water or waterlogged soil, while most of their foliage is above water. Let's evaluate the given genera:
(A) Azolla caroliniana (Water Fern): This is a small, free-floating aquatic fern. It is not a marginal plant rooted at the edge; it floats on the water surface.
(B) Acorus calamus (Sweet Flag): This is a perennial plant with grass-like leaves that thrives in shallow water and muddy banks. It is a classic marginal plant.
(C) Cyperus alternifolius (Umbrella Palm/Sedge): This plant forms clumps of tall stems topped with umbrella-like bracts. It grows well in shallow water or very moist soil at the edges of ponds. It is a suitable marginal plant.
(D) Elodea canadensis (Canadian Waterweed): This is a submerged aquatic plant, meaning it grows entirely underwater, though its tips may reach the surface. It is not a marginal plant. Based on these characteristics, Acorus calamus (B) and Cyperus alternifolius (C) are marginal plants suitable for water gardens. Therefore, option (3) is the correct choice. (B) and (C) only.

Answer 2

Growth-habit sorting:
Water garden plants fall into distinct habit groups: free-floating, submerged, and marginal (rooted at the water's edge with foliage held above water). Sorting the four genera by habit quickly answers the question.

Azolla caroliniana floats freely on the surface with no rooting at the margin, so it is a floating plant, not marginal. Elodea canadensis grows fully submerged below the surface, so it is a submerged oxygenator, not marginal either.

Acorus calamus and Cyperus alternifolius both root in shallow water or wet mud at pond edges while holding their foliage upright above the surface - the defining trait of marginal plants. Hence only (B) Acorus calamus and (C) Cyperus alternifolius are marginal, giving option (3).