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Flowers in the summer heat

Published on December 9th 2021

by Unknown.

A close up of a flower
To stroll into a meadow and experience the joy of a thousand blooms is the height of spring delight. Then why do these blooms fade so quickly in a hot spell? Why do picked flowers wilt within a matter of hours? Why does a plant suffer in the car ride home?
We try to answer all your questions regarding the fragile relationship between delicate bloom and heat.
A vase of flowers on a plant
Heat reduces the lifespan of a flower.

Heat and flowers

The rekindled interest in cut flowers gardens has led many to experiment with a wide range of flowers. If you are one of these enthusiasts, you have most likely come across some pricey delicate varieties you want to include in the garden. What many soon learn is that there exists a delicate balance between heat/temperature and how long the blooms last.
The flower industry raked in 10.6 Billion pounds in 2015, which has put a large incentive on research regarding the best temperatures to transport flowers and potted plants.
Some interesting facts on temperature & flowers:
  • Cut flowers are kept at 1-8C for transportation.
  • Plants in soil are kept between 0-2C for transportation.
  • Anthurium, orchids and other tropicals incur damage below 10C but lose moisture rapidly above it.
  • Respiration increases with temperature and so does ageing.
  • High temperature affects petal colour and flower size.
  • A flower will age 45 times faster at 30C than at 2C.
  • Cut flowers require ‘breathing’ to ensure longevity.
  • The thinner the petals, the easier they lose moisture (on average).
A tree with a mountain in the background

South African climate

The South African climate suffers from heat waves and sudden cold spells. These events shorten the lifespan of a flower. We mentioned this in the Namaqualand flower series. The reason why the time to view is so specific is that the flowers are negatively affected by unseasonably warm days or sudden frosts.

Namaqualand - Introduction to the Flower Capital


This is also the reason why maintaining an English style cottage garden is so difficult as we just do not have the mild temperature and humidity required to maintain it. It does not mean you cannot create a small microclimate in the garden.
Things to do for delicate blooms:
  • Try to pinpoint a low lying area of the garden.
  • Increase shading as the heat of summer progress.
  • Increase watering with heat, but maintain good airflow.
  • Water features increase local humidity and can mitigate some effects.
  • Start seedlings inside to maximise the flowering season.
A close up of a flower
Some flowers are short-lived, but the plant will keep on producing flowers right through summer.

Flowers that love the heat

Some flowers need high temperatures to flourish, but these do not necessarily tolerate the frosts of winter. A good example is Garden Dahlias or Cattleya. Both have been in the industry for decades. Cattleya orchids tend to love the warmth year-round, while dahlias go dormant as the temperatures drop.
Another option is to try indigenous species that provide cut flowers of equal flair but are more robust. Some have equally delicate blooms but will produce several short bursts of blooms throughout the summer months.
Summer flowering plants:
For more options see the article below:
If you would like an even longer flowering time consider something like Selago villicaulis ‘Purple Turtle’. It flowers in both late winter and midsummer while providing a great source of nectar for bees and butterflies.
Hegde, S., Umekawa, Y., Watanabe, E., & Kasajima, I. (2020). High-temperature tolerance of flowers. In Plant Ecophysiology and Adaptation under Climate Change: Mechanisms and Perspectives I (pp. 343-371). Springer, Singapore.
Rudnicki, R. M., Nowak, J., & Goszczynska, D. M. (1991, March). Cold storage and transportation conditions for cut flowers cuttings and potted plants. In Hortifroid, V International Symposium on Postharvest Physiology of Ornamental Plants; Importance of Cold in Ornamental 298 (pp. 225-236).
Reid, M. (1999, November). Advances in shipping and handling of ornamentals. In VII International Symposium on Postharvest Physiology of Ornamental Plants 543 (pp. 277-284).
Eason, J. R., Clark, G. E., Mullan, A. C., & Morgan, E. R. (2002). Cyrtanthus: an evaluation of cut flower performance and of treatments to maximise vase life. New Zealand journal of crop and horticultural science, 30(4), 281-289.

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