Ornamental Plants: Meaning, Types and Importance – Ornamentals (Senior 3 Agriculture) | Ganzaa

Ornamentals

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Senior 3 · Agriculture

Ornamentals

3 lessons

Lesson 1 of 3

Ornamental Plants: Meaning, Types and Importance

22 min

Let's begin

Walk along a main road in Kigali and count the plants that nobody eats: purple-flowered trees along the pavement, clipped hedges in front of offices, flower beds on the roundabouts, lawns outside hotels. Then think of the farms that grow flowers only to sell them: in the 2024–25 financial year Rwanda exported 748 tonnes of cut flowers, worth about US$4.6 million, mostly to the Netherlands and the United Kingdom (MINAGRI, Annual Report 2024–2025). Plants grown for beauty are a branch of agriculture, with their own crops, skills and markets. This lesson explains what they are, which ones are grown in Rwanda, and why they matter.

Definition

Ornamental plant: a plant grown mainly for its beauty, for its flowers, leaves, shape or scent, rather than for food or raw materials. Example: bougainvillea in a hedge.

Floriculture: the growing of flowers and ornamental plants, especially for sale; cut flowers are flowering stems cut and sold for vases and bouquets, such as roses.

Landscaping: planning and planting an outdoor area (trees, hedges, lawns and beds) so that it is attractive and useful.

Hedge: a line of shrubs planted close together and trimmed to form a living wall.

Annual: a plant that completes its life (seed to seed) in one growing season, e.g. marigold. Biennial: one that takes two seasons. Perennial: one that lives for more than two years, e.g. canna, roses, trees.

Types of ornamental plants

Ornamentals are usually grouped by their form and how they are used in a garden.

Group	Main use	Examples grown in Rwanda
Ornamental trees	shade, avenues, focal points	jacaranda (purple flowers), African tulip tree (Spathodea, orange-red flowers), cypress, palms, ficus
Shrubs and hedge plants	hedges, boundaries, screens	bougainvillea, hibiscus, duranta, acalypha, Kei apple (thorny), cypress
Climbers	covering walls, fences and arches	bougainvillea trained on a support, morning glory (Ipomoea), allamanda
Herbaceous flowers	flower beds, borders, cut flowers	annuals: marigold, zinnia, cosmos; perennials: canna, agapanthus, bird of paradise (Strelitzia); roses (woody shrubs) for cut flowers
Bulbs, corms and rhizomes	seasonal colour, cut flowers	gladiolus (corms), lilies (bulbs), canna (rhizomes)
Lawn grasses	lawns, sports fields, slope cover	Kikuyu grass, paspalum, Bermuda grass
Succulents	dry, sunny spots, rock gardens	aloe, agave, euphorbia
Indoor and pot plants	offices, homes, verandas	dracaena, snake plant (Sansevieria), ferns

In bougainvillea, the bright "petals" are not petals at all: they are bracts, papery coloured leaves that surround three small, pale, true flowers.

Why ornamental plants matter

Importance	How it works
Beauty and landscaping	Flowers, lawns and trees make homes, schools, roads, hotels and parks attractive, which also raises the value of a property and attracts tourists.
Shade and cooling	Trees shade paths and buildings; leaves give off water vapour, which cools the air around them.
Windbreaks and screens	Lines of trees and tall hedges slow the wind and give privacy.
Live fences and security	Thorny hedges such as Kei apple keep out animals and intruders and last longer than wooden fences.
Soil conservation	Grass and hedges on slopes and terrace edges hold soil against erosion (Unit 1).
Cleaner air	Leaves trap dust and absorb carbon dioxide; hedges reduce noise from roads.
Income and jobs	Nurseries, landscaping firms, florists and flower farms employ people; seedlings, cuttings and bouquets are sold.
Export earnings	Cut flowers bring foreign currency: 748 t worth US$4,603,575 in 2024–25, up from 413 t worth US$2,163,055 the year before (MINAGRI, 2025).
Food for pollinators	Flowers feed bees and other insects, which pollinate nearby crops (Unit 5).
Cultural and social use	Flowers are given at weddings, graduations and visits to the sick, and laid respectfully in remembrance.
Medicinal and other uses	Some ornamentals, such as aloe, are also used in traditional remedies and cosmetics.

Workers among rows of rose plants in a large plastic greenhouse in Kenya, in November 2017. Cut-flower farms like this grow roses under cover so that the stems stay clean and straight for export. Photo: Swamianandabhay, <a href="https://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA 4.0</a>, via Wikimedia Commons

Worked example 1: what is a kilogram of flowers worth?

Problem. In 2024–25 Rwanda exported 748 t of flowers worth US$4,603,575; in 2023–24, 413 t worth US$2,163,055 (MINAGRI, 2025). Find the value per kilogram in each year and say what changed.

Solution.

2024–25: $748\,\mathrm{t} = 748\,000\,\mathrm{kg}$ ; value per kg $= \frac{4\,603\,575}{748\,000} \approx 6.15$ US$.
2023–24: $\frac{2\,163\,055}{413\,000} \approx 5.24$ US$.

Answer: about US$6.15 per kg against US$5.24 per kg. Rwanda sold more flowers (81% more by mass) and earned more for each kilogram, so earnings more than doubled.

Worked example 2: planning a hedge

Problem. A school will plant a straight hedge of duranta along a 24 m boundary, one row, with plants 30 cm apart and one plant at each end. Rooted cuttings cost 150 Frw each (illustrative price). How many plants are needed, and what will they cost?

Solution.

Number of gaps $= \frac{24}{0.30} = 80$ .
Plants $= \text{gaps} + 1 = 81$ (a line with a plant at each end has one more plant than gaps).
Cost $= 81 \times 150 = 12\,150$ Frw.

Answer: 81 plants, costing 12,150 Frw.

Warning

Choose ornamentals with care

Invasive plants. Some ornamentals escape and become serious weeds. Lantana, once planted as a flowering hedge, now invades pastures and forest edges across East Africa. Water hyacinth, spread around the world as a pond plant, choked Lake Victoria after it arrived through the Kagera River.
Poisonous plants. Every part of oleander (Nerium oleander) is poisonous to people and livestock. Do not plant it where small children play or animals graze, and never burn its prunings, because the smoke is harmful too.

Tip

Memory hook for the uses of ornamentals: "SHADE PAYS": Shade, Hedges and security, Air cleaned, Decoration, Erosion control; Pollinators, Attracting tourists, Yielding income and jobs, Social and cultural use.

RwandaTV: "Bella Flowers: 85% of its production is exported to Europe". Listen for where the flowers are sold and how the farm plans to reach new markets.

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Practice

Define an ornamental plant and name two ornamentals grown in Rwanda.
Put each plant in its group (tree, hedge shrub, herbaceous flower or lawn grass): jacaranda, Kikuyu grass, duranta, marigold, cypress, canna.
Distinguish an annual from a perennial, giving one ornamental example of each.
State six ways in which ornamental plants are important.
Why is Kei apple a good choice for a boundary hedge round a farm?
A hedge 36 m long is planted in one row with plants 40 cm apart and a plant at each end. How many plants are needed?
Use the figures in Worked example 1 to find the percentage increase in Rwanda's flower export earnings from 2023–24 to 2024–25.
A primary school plans to plant oleander and lantana along the path to its nursery classes because "they flower all year". Evaluate the plan and suggest a better choice.

Show answersHide answers

A plant grown mainly for its beauty (flowers, leaves, shape or scent) rather than for food or raw materials. Examples: jacaranda, bougainvillea, roses, canna, Kikuyu grass (any two).
Trees: jacaranda, cypress (cypress is also used as a hedge). Hedge shrub: duranta. Herbaceous flowers: marigold, canna. Lawn grass: Kikuyu grass.
An annual completes its life in one season (marigold, zinnia, cosmos); a perennial lives for more than two years (canna, agapanthus, roses, trees).
Any six: beauty and landscaping; shade and cooling; windbreaks and screens; live fences and security; soil conservation; cleaner air and less noise; income and jobs; export earnings; food for pollinators; cultural and social use; medicinal use; higher property value.
It is thorny, so it keeps out animals and intruders; it is long-lived and dense, and it can be trimmed into a solid living fence.
Gaps $= \frac{36}{0.40} = 90$ ; plants $= 90 + 1 = 91$ .
Increase $= \frac{4\,603\,575 - 2\,163\,055}{2\,163\,055} \times 100 \approx 112.8\%$ : earnings more than doubled.
A poor plan: every part of oleander is poisonous to children, and lantana is an invasive weed that spreads into nearby land. A safe, non-invasive flowering hedge such as hibiscus or duranta trimmed low, or flower beds of marigold and canna, would be better.

Key points

Ornamentals are grown for beauty: trees, hedge shrubs, climbers, herbaceous flowers, bulbs and corms, lawn grasses, succulents and pot plants.
They give beauty, shade, shelter, security, soil cover, cleaner air, food for pollinators, jobs and export earnings (748 t of flowers worth US$4.6 million in 2024–25, MINAGRI).
Avoid invasive and poisonous ornamentals such as lantana, water hyacinth and oleander.

Sources and credits

Annual Report 2024–2025, Ministry of Agriculture and Animal Resources (MINAGRI): flower exports by mass and value, and their markets. Figures cited.
Photo Flowers sauvage des arbres, by IGANZE, via Wikimedia Commons, licensed under CC BY 4.0.
Photo Bougainvillea sp. hedge habit, Kula 200, Maui, by Forest and Kim Starr, via Wikimedia Commons, licensed under CC BY 3.0 US.
Photo Rose Greenhouse, by Swamianandabhay, via Wikimedia Commons, licensed under CC BY-SA 4.0.
Video: Bella Flowers: 85% of its production is exported to Europe, RwandaTV, embedded from YouTube.

Written by Ganzaa: the text, the tables and the worked examples. The price of cuttings in Worked example 2 is illustrative.

This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.

1Types of ornamental plants

2Why ornamental plants matter

Types of ornamental plants

Why ornamental plants matter