Types and features of flowers
Flower plants are grouped by how long they live.
- Annual: grows, flowers and dies in one season, such as marigold and zinnia.
- Biennial: flowers in the second year.
- Perennial: lives for many years and flowers again each year, such as chrysanthemum and rose.
- Bulb plant: stores food in a bulb or tuber under the soil, such as tulip and lily.
Flowers are also grouped by use: cut flowers, pot plants and bedding plants.
Flower growth and physiology
A flower plant grows in stages: seed → germination → seedling → leafy growth → bud (flower bud forming) → flower → seed. Growth first makes leaves and stems (the vegetative stage). Later the plant makes buds (the reproductive stage).
Two big signals start flowering. Photoperiod is the length of the day. Long-day plants bloom when days are long; short-day plants bloom when days are short. Temperature also matters: some plants, like tulips, need a cold period before they bloom.
Cultivation environment and growth regulation
Plants need the right light, temperature, water, air and soil. Every plant has a best temperature; far above or below it growth slows.
Growers regulate growth in a greenhouse: black cloth to shorten the day, lamps to lengthen it, heaters or fans for temperature, drip pipes for water. They also use pinching (cutting the tip to make the plant bushy) and growth regulators carefully, so flowers open on the date buyers want them.
Breeding and propagation
Propagation means making new plants.
- Seed: cheap, but plants may differ.
- Cutting: a piece of stem put in water or soil grows roots; the new plant is a copy of the parent.
- Division: a bulb or clump is split into pieces.
- Tissue culture: many tiny plants from a small piece in a lab.
Breeding makes new varieties. Pollen from one flower is placed on another, the seeds are grown, and the best plants (colour, size, long vase life, disease resistance) are kept. The result is a hybrid.
Try it
In the 3D, set the day length to 9 hours and then 15 hours and watch the middle plant. Then slide the temperature from 30 to 14 and watch the bulb plant. At home, put a cutting of money plant or basil in a glass of water and write the day roots appear.
Key formulas and definitions
- Growth stages: seed → seedling → leaves → bud → flower
- Long-day plant blooms when day length is more than its limit
- Short-day plant blooms when day length is less than its limit
- Key terms: annual, perennial, bulb, photoperiod, cutting, division, hybrid
Worked examples
1. A plant lives one season and then dies. What type is it?
An annual, for example marigold.
2. A grower wants chrysanthemums to bloom in autumn, when days are getting shorter. What can the grower do in a greenhouse?
Chrysanthemum is a short-day plant, so the grower covers it with black cloth to make the day shorter and trigger buds.
3. Which propagation method gives an exact copy of the parent plant?
A cutting (or division or tissue culture), because no seed mixing happens.
4. Why do tulip bulbs go in a cold store before planting?
Tulips need a cold period before they will bloom, so cold storage makes them ready.
5. A breeder wants roses with a long vase life. Describe the steps.
Move pollen between two roses, sow the seeds, grow the seedlings, test the vase life of each flower, keep the best plants and repeat.
Common mistakes
- Thinking all flowers need the same day length. Long-day and short-day plants are different.
- Saying a perennial is the same as a bulb. A bulb is a food store; a perennial is a plant that lives many years.
- Believing seeds always give an exact copy of the parent. Cuttings do.
- Forgetting that too much heat also slows growth. Every plant has a best temperature.