May is the month when pelargoniums begin to gather pace.
The light is stronger, days are longer, and plants start to respond quickly to the warmth. After the slower rhythm of early spring, this is when you begin to see real movement, fresh growth, stronger stems, and the first proper signs of the season ahead.
It is also a month that asks for a little judgement. The weather can feel generous one day and cold the next, so the aim in May is to encourage growth without rushing the plants too quickly.
Bringing pelargoniums outside
By May, many pelargoniums can begin moving outside during the day, especially in milder parts of the UK. The important thing is to watch the nights.
Pelargoniums dislike cold, wet conditions, and a sudden drop in temperature can set them back. If nights are still cold where you are, keep plants in a greenhouse, porch, conservatory, or bright sheltered position until things settle.
If moving plants outside, do it gradually. Start with a sheltered spot for a few hours in the day, then build up from there. Avoid placing them straight into exposed wind, heavy rain, or full midday sun if they have been under glass.
A gentle transition helps them toughen up without stress.
Watering in May
As growth increases, pelargoniums will begin to need more water than they did earlier in spring.
The key is not to water by habit, but by feel.
Let the compost dry slightly between watering. Pelargoniums prefer a proper drink followed by time to breathe, rather than constant small amounts of water. If the compost is still cool or damp beneath the surface, leave it a little longer.
When you do water, water thoroughly and allow excess water to drain away. Avoid leaving pots standing in water, especially overnight.
Water at the base of the plant where possible. Pelargoniums do not particularly enjoy being watered over the foliage, and keeping leaves too wet can encourage problems, especially in cooler or still conditions.
Feeding little and often
By May, plants in active growth will benefit from regular feeding.
Rather than feeding heavily, think little and often. A balanced liquid feed, used regularly through the growing season, supports steady growth and flowering without pushing the plant too hard.
If a plant has only recently been potted on, or is still settling, give it a little time before feeding strongly. Once you see clear new growth, it is ready for more consistent support.
Shaping and pinching out
May is a good time to shape your pelargoniums.
If a plant is becoming leggy or uneven, do not be afraid to trim it back lightly. Cutting just above a leaf joint encourages new shoots to break lower down, helping the plant become fuller and more balanced.
For younger plants, pinching out the growing tips can encourage a bushier shape. It may feel counterintuitive, especially when the plant is growing well, but a little shaping now often leads to a stronger plant later in the season.
If a plant has gone off to one side, you can reset it gently. Remove overly long side growth if needed, then stake the main stem back towards the centre. Once the new growth has firmed up and the plant is holding itself, the stake can be removed.
Early flowers and buds
It is always tempting to keep the first flowers.
If your plant is still small or establishing, removing early buds can help it put energy into roots and growth rather than flowering too soon. This is especially useful if you want a fuller, stronger plant for later in the season.
For established plants, you can begin to enjoy the flowers. Deadhead regularly by removing spent blooms and flower stems. This keeps the plant tidy and encourages more flowering over time.
Taking cuttings
May is an excellent time to take pelargonium cuttings.
Plants are actively growing, temperatures are warmer, and cuttings often root readily at this stage.
Choose a healthy, non-flowering shoot and make a clean cut just below a leaf joint, as this is where roots will form. Remove the lower leaves, then allow the cut end to dry for a few hours so it can callus over.
Place the cutting into seed compost or a very free-draining mix. Keep it lightly moist while roots establish, but never wet. Cuttings need moisture, warmth, light, and air, not heavy, cold compost.
Roots will usually begin to form within a few weeks, depending on the variety and conditions.
Repotting and pot size
If your pelargonium has filled its pot and is drying out very quickly, May is a good time to move it on.
Avoid over-potting. Pelargoniums often do better slightly snug than sitting in a large volume of cold, wet compost. Move up gradually, choosing a pot just a little larger than the current one.
Terracotta is a good choice for established plants, as it allows the compost to dry more naturally and gives the roots a steady environment. Plastic pots still have their place, especially for younger plants, but terracotta can be particularly helpful once plants are growing strongly.
Use a free-draining compost. A loam-based compost opened up with grit or perlite works well, giving both structure and air around the roots.
Light and position
Light makes all the difference.
Pelargoniums need bright conditions to grow well and flower properly. A sunny windowsill, greenhouse, conservatory, or sheltered outdoor position can all work, depending on the variety.
If plants are not flowering, light is often the first thing to consider. Too little light leads to soft, stretched growth and fewer flowers.
As the weather warms, increase ventilation in greenhouses and conservatories. Pelargoniums enjoy warmth, but stagnant heat without airflow can cause stress.
Watch for pests
As growth increases, keep an eye out for pests.
Check underneath leaves and around soft new growth. Aphids can appear quickly at this time of year, especially on fresh shoots and buds. Catching them early makes them much easier to deal with.
Good airflow, clean plants, and regular observation are often the best first defence.
A simple May checklist
In May, focus on:
- Moving plants outside gradually, once nights are mild
- Watering a little more, but only when the compost needs it
- Feeding little and often
- Shaping and pinching out where needed
- Taking cuttings while plants are actively growing
- Deadheading established plants
- Repotting only when necessary
- Giving plants as much light and airflow as possible
Final thought
May is not about forcing pelargoniums forward. It is about responding to the season.
A little more water, a little regular feeding, careful shaping, and the right amount of light will set plants up beautifully for the months ahead.
Small things, done at the right time, make all the difference.