We’ve got a few tricks to help you create the perfect conditions in your balcony box and lay the perfect foundations for a flower-filled summer.
On this page you will learn:
- What you need to plant geraniums in a balcony box
- How to plant a regular balcony box like a pro
- What to do with water storage boxes
- How to get hanging geraniums into the box without damaging them
- What to look out for when planting mixed summer flower arrangements
You will need:
- Vigorous geranium plants in 11 or 12 cm pots
2 to 3 plants for a 60 centimetre box, 4 to 5 plants for a 100 centimetre box
- One window box
Recommended height: 20 centimetres; recommended colour: light
- Geranium soil or good-quality flower soil
About three litres per 10 centimetres of box length
- Slow-release fertiliser for balcony and tub plants
(Not for soil pre-fertilised with slow-release fertiliser)
- Drainage material
Shards of clay, expanded clay or small stones (no marble chippings)
How to plant a regular balcony box like a pro
You can find more information about these steps further down the page. Click here to go directly there.
1. Are the water drainage holes open? If not, cut them open! Thoroughly brush out older flower boxes. .
2. Spread a drainage layer of broken clay, expanded clay or small stones two centimetres high on the bottom of the box.
3. Immerse the geraniums in the pot in a bucket of water until no more bubbles appear. Remove from the water. Allow to drain off.
4. Fill the balcony box three-quarters full with fresh potting soil.
5. If the soil has not been pre-fertilised, add slow-release fertiliser according to the dosage instructions. Mix in with your fingers or a fork.
6. Press the soil along the edges with the side of your hand. By compacting the soil, it will not sink later.
7. Smooth over the soil to even out the soil level.
8. Pot out the geraniums. Push the soil to the side with your hand or a planting trowel and plant the geraniums. The root balls should be flush with the top of the soil. Distance between the plants: 20 centimetres or more.
9. Press the plants lightly with the thumbs and index fingers of both hands.
10. Add more soil if necessary. Leave a watering margin of two centimetres in the box.
11. Water thoroughly.
12. Place the box in a warm and bright place.
13. Remove any leaves and shoots damaged during planting and transport.
Why is water drainage so important?
If there is no drainage, a day will come in the summer when the box will overflow – either because it rains a lot, or because you are too generous with your watering. The roots will be standing in water, and if this goes on for too long they will start to rot.
Why do you need to pre-water the geraniums in a bucket?
When pre-watering, the root ball soaks up water. This helps the plants until they have new roots. It’s only when they have new roots that they can they tap into the water supply in the potting soil.
Why not fill the box completely with soil?
Planting adds material, and the volume of the root ball has to go somewhere. If you fill the box to the brim, you will have to remove some soil afterwards.
Why should I buy slow-release fertiliser for my geraniums?
Geraniums are vigorous growers and need a lot of nutrients. Slow-release fertiliser has the advantage that it feeds your geraniums for months and you don’t have to think about fertilising. We highly recommend using it.
However, there is one exception: some potting soils already contain slow-release fertiliser. If you were to add fertiliser to these products when planting, it would be too much for the geraniums.
Instead, you can help them out with liquid fertiliser when the time comes. You will know that it is time to fertilise when your geraniums no longer bloom so beautifully, even though all the other conditions are correct.
We explain how to use liquid fertiliser here.
Why does it matter how deep the root ball sits in the soil?
Geraniums grow best when the root ball is flush with the soil surface. If the root ball is too high, evaporation will occur and you will have to water more than necessary. If you bury the root ball too deep, the geraniums will not grow well.
Why should I plant geraniums so far apart?
Geraniums grow quickly and vigorously. If they are closer together than 20 centimetres (two hand widths), they will not develop optimally. Don’t worry: the gaps will close up in no time.
Top tip: For even spacing for an odd number of plants, start planting in the middle of the row. For an even number, plant the geraniums near the edges first.
What effect does pressing the soil have?
Pressing the root balls down ensures that the soil is sealed. This is important so that no cavities remain and the new roots immediately absorb water and nutrients through direct contact with the soil.
What is the purpose of the watering margin?
The watering margin will help you keep your geraniums hydrated all summer long. The margin allows more water to be in the box than is immediately absorbed by the soil. This extra water will not run away through the edges of the box.
What does water thoroughly mean?
Watering thoroughly means that the water not only moistens the surface of the soil, but reaches all the way down. The roots are at the bottom – and they need the water. If you only wet the top layer of soil, the moisture evaporates without the plants benefititng.
Watering thoroughly does not saturate the root balls of freshly planted geraniums with moisture. This is why you should still soak the geraniums in water before planting them, until no more bubbles rise.
What happens to the geraniums after planting?
After planting, place the box in a bright, warm place. Do not water during the first few days.
Important note: You must immediately protect your geraniums from frost, otherwise they will die. Even temperatures below five degrees Celsius are not ideal. This article explains how to protect geraniums from the cold.
What about water storage boxes?
Water storage boxes work with a double base. The water reservoir is at the bottom and the geraniums are planted on the top.
With some models, you pour a special granulate layer onto the tray and only then do you put the soil on top. Otherwise, planting is the same as with a normal flower box.
In the first few weeks, you must water plants in a water storage box from above. They can only water themselves from below when the the roots reach the reservoir.
hen top up with water through the water reservoir. Liquid fertiliser can also be applied this way.
Planting hanging geraniums
You can often buy hanging geraniums with a basket over the shoots. The basket protects the shoots from breaking off in the shop and during transport.
The easiest way to get the basket off after planting is to cut the mesh with scissors. You can then remove it without damaging the shoots and leaves of the geranium.
Tips for planting mixed summer flower arrangements
- Group plants which have the same location requirements together! You can find a list of suitable partners for geraniums in our FAQ.
- Large, upright plants draw the most attention in a balcony box. Plant them at the back edge of the box and in the middle. Accompanying flowers of medium height mask the differences in size. Shorter plants look best around the edges, or overhanging the box. Standing geraniums can be the main attraction or companion flowers, while hanging geraniums will grow over the edges of the box.
- Don’t make it too colourful! A colour trio is enough. White and green go with everything.
- Tonal arrangements look particularly harmonious. How about a balcony in shades from dark pink to light pink?
- Mixed summer flower arrangements have lots of appeal for bees. Combine geraniums with ornamental sage and scented stonecrop, for example, and enjoy the colourful hustle and bustle.