Various geraniums, planted in window boxes. A watering can stands on a table.

Watering geraniums: Everything you need to know

Geraniums are among the hardiest and most easy-care summer flowers of all. For them to bloom adundantly and grow vigorously, they need the right amount of water. We explain the best way to water geraniums for maximum blooms.

You can tell when many summer flowers are thirsty. They start to wilt and their leaves and shoots start to droop. Geraniums don’t do that. Due to their origin (in the South African veld), these popular flowers are adapted to dry periods and store moisture in their fleshy stems and leaves. They can survive periods of water shortage, even if the quantity of flowers suffers a little.

In this article, we explain how you can use simple tricks to keep your geraniums (botanically from the Pelargonium genus) supplied with water so they transform your balcony into a sea of flowers.

We explain how to recognise when your geraniums need water, the best time to water them and tips on efficient irrigation. And we take a look at how watering in combination with fertilising promotes the magnificent blooms.

Short and sweet: the basics of watering

  • When to water: In the morning or evening, but only when the soil has dried out.
  • How much water: About 0.5 litres per plant. It’s better to keep it drier than risk waterlogging.
  • How to water: Water directly onto the soil, not over the leaves and flowers.
  • What to water with: Preferably use warm rainwater and a watering can without a spray.

How much water geraniums need: the 10 per cent rule

Geraniums are hardy and won’t die immediately if they don’t have enough water. However, for them to bloom freely and grow vigorously, they need the right amount of moisture.

The general rule for watering potted and container plants is to use about 10 per cent of the volume of soil.

For an 80cm window box, this is about 2.5 litres of water, while a pot with a single geranium needs about half a litre.

You can judge the right amount of water by the way it moistens the soil, but doesn’t soak it. If you have to water several times a day using this rule of thumb, you can increase the amount of watering by using your instincts.

How often to water geraniums in summer

Geraniums need more water on days with very strong sunlight. You may have to water them daily, but be careful not to let them get waterlogged.

The bigger problem is not usually temporary dryness, but prolonged wetness. If your boxes and pots are always completely saturated after watering, try using less liquid.

How to know if your geraniums need water

The finger test: Insert your finger about 2-3cm into the compost. If it feels warm and dry, it’s the right time to water your geraniums. If the soil is still cool and moist, your plants don’t need any more moisture yet.
Alternative weight check: If the soil is full of roots and you can’t insert a finger, the weight will give you an indication of the amount of water required. You don’t need to water if the planter feels noticeably heavy when you lift it. If it seems light, your geraniums need water. You will develop a feeling for this over time.
Take a look: If the soil is coming away from the edge of the pot, you’ve already missed the best time to water. Geraniums are hardy and can even tolerate this extreme drought at times without dying immediately, but you should wet the compost as soon as possible.

Remember: Short-term drought is less harmful to geraniums than waterlogging!

Tip: On particularly hot summer days, check in the morning and evening to see if your geraniums need water again. Check the moisture level of the soil when it rains too. The leaves can grow so densely that sometimes only a little water from above reaches the roots in the container.

Watering geraniums correctly: How you do it makes all the difference

When it comes to watering geraniums, the how is almost as important as the when. Here are three essential tips:

Slowly and evenly: Go under the foliage between the plants with the watering can (don’t use the spray head) and let the water flow gently onto the soil. Room temperature water is best, which is why we recommend watering with a jug. If you water with a hose, be sure to place the jet under the foliage.
Avoid leaves and flowers: Don’t water from above or with a sprinkler. Firstly, the water droplets will age the flowers more quickly, especially on upright geraniums. If this happens, it can lead to the fungal disease grey mould. Secondly, geranium foliage usually grows so densely that the water cannot reach the roots.
No waterlogging: Make sure any excess water can run off easily to prevent root rot. Holes in the bottom of the containers ensure drainage. Empty the saucer within 15 minutes of watering. Of course, this doesn’t apply to balcony boxes, pots and hanging baskets with water reservoirs. These are designed to prevent waterlogging.

First aid: How to get dried-out soil moist again

A better way to moisten completely dry compost than using a watering can is to place the pot, window box or hanging basket in a tub filled with water for half an hour. This gives the soil enough time to swell and store water in the pores. After 30 minutes, remove the saturated pots from the tub and allow them to drain well.

Straight into the tub? Yes! If you were to water with a watering can, the liquid would simply run straight through the dried-out soil.

Why geraniums are ideal plants for beginners

Geraniums, also known as pelargoniums, are the easygoing stars among balcony plants. They’re not only colourful and versatile, but also surprisingly hardy. This means:

  • Tolerance of beginner’s mistakes: too much or too little water? No problem, geraniums will forgive you.
  • Easy to care for: These perennial balcony box favourites don’t need much attention; perfect for people who also have other hobbies.
  • Lots of blooms and a long flowering period: They reward you with lush blossoms from spring to autumn.

The secret to ideal watering times

The morning or evening is best for watering flowers. Outside the hottest midday hours, less water evaporates and the geraniums can utilise the moisture better. Leave the watering can alone in the late evening, so the plants will go into the night having dried out. With unfavourable conditions, fungal diseases can develop on damp leaves.

How to make watering your container garden even easier

Containers with water reservoirs make watering easier in two ways. Firstly, they store moisture and release it to the plants as needed. Secondly, you don’t have to worry about how to water. Simply pour fluid into the inlet at the edge of the box until the indicator shows ‘full’. Water storage containers are designed so any excess water drains away, making waterlogging impossible.

Tip: For plants in storage systems, keep watering from above until the roots have reached the reservoir.

DIY plastic bottle watering solution

Containers with water reservoirs aren’t cheap. If you’re on a budget, experiment with empty plastic bottles. For example, poke a few holes in the body of a bottle and bury it the right way up in your flowerpot when planting up. Leave the opening above the soil and top up the bottle with water through this.

Another option is to fill a bottle with water, screw the lid on, then perforate the lid and place the bottle upside down in the soil. Due to physical forces, the compost will suck the water out of the bottle when it becomes dry.

Special watering attachments for plastic bottles, which allow you to set the desired drip rate, work on a similar principle.

Beware of waterlogging! How to avoid the beginner's mistake

Waterlogging is one of the main enemies of healthy geraniums. It occurs when the soil in a planter remains too moist for long periods. The excess moisture saturates the soil, displaces oxygen and suffocates the roots of the plants. This can cause them to rot, which impairs nutrient uptake and ultimately leads to the death of the plant.

How to protect your plants:

Good drainage: Make sure your pots or balcony boxes have enough drainage holes. A layer of gravel or expanded clay at the bottom allows excess water to run off. Adding drainage afterwards will not work, so do this when planting. Read our detailed guide to planting geraniums here.
Water carefully: Always wait until the top 2-3cm of soil is dry before watering again. This is particularly important in cool weather.
Check the moisture regularly: Use the finger test to make sure you’re not watering too much.

For even more flowers: combine watering with fertilising

Geraniums are easy to care for. If you water them regularly and remember to fertilise them, these vigorous growers will thank you with boundless blooms. The classic method of liquid feed is to mix geranium fertiliser into the water once a week or every 14 days. Adjust the amount of fertiliser if you notice changes in your plants.

Extra: Watering geraniums in autumn and winter

When autumn arrives, it’s not just the weather that changes, but also your geraniums’ requirements. They need less water when the sun shines less. Here’s what to bear in mind:

Reduce the amount of watering: plants grow more slowly in reduced light and evaporation is lower in cooler conditions, so they need less water.
Check the soil moisture: Before watering, double check whether the soil is still moist. In the cooler months of the year, it can stay damp for much longer than in hot weather. The dew at night is like an additional little freshener.
Avoid waterlogging: Saturation is a particular problem in autumn as, in combination with cooler nights, it can lead to root rot more easily than in midsummer. Make sure any excess water can drain away easily.
• Move your geraniums to a sheltered spot when there is a lot of rain and the nights get colder. If it rains regularly, you may not need to water them at all.

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Watering during overwintering

Geraniums stop growing during the winter, which also means they need very little water when overwintering.

Keep the soil barely moist. If you still need to water from time to time, use just enough to prevent the soil drying out completely. Check first, then water!

A bright, cool room with temperatures between 5 and 10°C is ideal for overwintering.

FAQ Watering and flowering: how are they connected?

Geraniums are easy to care for and flower easily and profusely. If they do stop blooming, it could be due to watering in certain, very rare cases. Possible reasons could be:

Overwatering: too much water can damage the roots and cause the plant to stop putting energy into flower production.
Underwatering: Too little water can also be problematic. Geraniums need sufficient moisture to generate energy for a plant that deserves the nickname ‘sea of flowers’.
Incorrect watering: Too frequent or irregular watering can, in extreme cases, stress the plant to such an extent that blooming takes a break.

But geraniums aren’t normally sensitive to these things as long as they don’t get completely out of hand. More often, if your plants aren’t flowering profusely, it’s probably due to their location or nutrient supply.

Geraniums need plenty of light. At least six hours of direct sunlight per day is ideal. Full midday sun is welcome!

Imbalanced fertilisation can also have an impact. Too much nitrogen promotes leaf growth at the expense of flowers.

FAQ: Can you water geraniums too much?

The section ‘Watch out for waterlogging! How to avoid the beginner’s mistake‘ explains how to protect your geraniums from overwatering. Nevertheless, it can sometimes happen that your plants get too wet. But with the right steps, you can still save them.

Immediate measures for overwatered geraniums

Step 1: Dispose of water Start by removing excess liquid from the saucer or pot.
Step 2: Check the roots Carefully remove the plant from the pot and check its roots. Healthy roots are firm and white or light brown in colour. Black, mushy roots are a sign of rot.
Step 3: Remove rotten roots: Carefully cut off any decayed or damaged parts of the plant affected by rot. Use clean, sharp scissors or a knife.
Step 4: Allow to dry: Let the roots and soil air dry a little before repotting the plant in fresh compost.
Step 5: Repotting in new compost: Choose a high-quality potting compost that drains well. With peat-free compost, you’re also gardening in a climate-friendly way. Make sure your pot has enough drainage holes. Find out more about planting geraniums by clicking this link.
Step 6: Add drainage: By watering regularly as required and making sure your pots are well drained, you can prevent your plants getting too much water.

With the basics covered in this post, you’ll be well equipped to give your geraniums the best possible care. Don’t worry; it’s remarkable how resilient these plants are.

Just make a watering check part of your daily routine. Then you’ll do everything right and your balcony plants will return the favour with a sea of flowers.

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