7 top tips for hot summer days: How to help geraniums through intense heat

What used to be exceptional is increasingly becoming the norm:

Unbearably hot summer days on which the pavement seems to glow. Such periods now last for weeks. It’s not only people who suffer in the shimmering heat, nature is struggling with the extreme temperatures too. Geraniums are better equipped to withstand summer heatwaves than most other balcony flowers. The experts at Pelargonium for Europe explain why this is so and how you can make life easier for geraniums on balconies and terraces on hot days.

Geraniums love sun and heat. After all, these magnificent summer ambassadors originate from South Africa. Geraniums can withstand temporary drought without suffering permanent damage because their stems and fleshy leaves store water. Geraniums, which transform balconies and terraces into a low-maintenance sea of flowers from spring to autumn, still carry this South African heritage. At the same time they’ve been bred for high performance in terms of flowering.

And this high performance requires one thing above all:

Water. In the hottest months, they need more water than on normal summer days in order to develop the abundance of flowers that we expect from them.

Tip 1: Water in good time

Geraniums need water to bloom and grow. So it’s important to make sure the soil is moist enough. If the compost feels fresh and cool, there is no need to water. If it’s dry and warm, it’s worth reaching for the watering can. If the soil is already loosening from the rim of the pot, it’s high time to do it!

Tip 2: In the morning or evening

In the morning or evening, when the sun is low in the sky, less water evaporates when watering than during the midday hours. Geranium can use the moisture better.

Tip 3: Directly to the roots

It’s best to hold the watering can spout directly between the plants, very close to the soil, so the water reaches where it’s needed. It’s easier to plant in containers with a water reservoir. You fill the reservoir directly and the plants help themselves.


Tip: Stale water is better for the roots than cold water from the tap.


Tip 4: At least one large glass per plant

The aim of watering must be to soak the soil. This is achieved by adding about ten percent of the pot volume of water per watering. In concrete terms, this means that an 80cm long balcony box swallows about 2.5 litres. If you want to know exactly, you can find various volume calculators for different pot shapes on the internet to help you to determine the exact capacity. Otherwise, you can simply use a large glass of water per plant as a rule of thumb.

Important: Excess water must be able to drain off, but dry soil also needs time to swell. It does not absorb water well. That’s why we recommend watering in sips.

Tip 5: Good soil

The quality of the potting compost has a big influence on how much water is available to the geraniums. Good compost holds many times its own weight in water and still remains structurally stable due to a balanced ratio of coarse and fine pores. So a high-quality compost is good for the roots.

Tip 6: The trick to fertilising

Because of the high evaporation rate during hot spells, it’s better to fertilise twice a week with half the dosage of liquid fertiliser than once with the full amount. Never pour liquid fertiliser onto dried-out soil as this can lead to root damage.

Tip 7: Water less

You can reduce the amount of watering you have to do by giving your plants a sunshade or moving them to a shadier spot. Light-coloured planters heat up less than dark ones and glazed clay pots evaporate less moisture than unglazed ones. How clever!


What heat does to plants

On hot days and tropical nights, evaporation increases. The soil evaporates water, and so does the plant. If the soil is too dry, metabolism comes to a standstill. The plants flower and grow more weakly than they should. If it stays dry for too long, the plants fall back on stored water. They become flabby because the supply is used up and the internal cell pressure drops as a result. If this condition, called plasmolysis, lasts too long, it can no longer be reversed. The plant dies. This happens extremely rarely with geraniums, because they store plenty of water in their fleshy stems and leaves for a rainy day.