Courgette plant care: tips on watering, fertilising & diseases

Regina
Regina
Regina
Regina

I studied horticultural sciences at university and in my free time you can find me in my own patch of land, growing anything with roots. I am particularly passionate about self-sufficiency and seasonal food.

Favourite fruit: quince, cornelian cherry and blueberries
Favourite vegetables: peas, tomatoes and garlic

After planting, courgettes need a little extra care and plenty of nutrients for a bountiful harvest. Here is our courgette plant care guide, with tips on watering and fertilising your courgette plants and dealing with some of the most common courgette diseases.

Green courgettes ready to harvest
Courgettes are heavy feeders so they need plenty of fertiliser [Photo: tchara/ Shutterstock.com]

Courgette (Cucurbita pepo subsp. pepo convar. giromontiina), like pumpkins (Cucurbita maxima, C. moschata and C. pepo) and cucumbers (Cucumis sativus), belong to the gourd family (Cucurbitaceae). The right care for your courgette plants will ensure an abundance of fruit until late in the season. But how often do you have to water courgettes? What is the right plant food for courgettes? When is the best time to fertilise? And do courgettes like nettle tea fertiliser? Below you will find our top tips and advice on courgette plant care.

Courgette plant care: watering courgettes

Courgettes need quite a lot of water to develop their juicy, crunchy fruits. In dry conditions, the plant suffers, soon wilts and produces significantly fewer flowers and fruit. Regular watering is therefore extremely important for courgettes. Depending on the weather, water once or twice a week; in midsummer you usually need to water more often. When watering, the water should never be cold, because the sensitive courgette plants do not tolerate temperatures below 10 °C well. It is also best to water in the morning before the afternoon heat, allowing the plant to absorb enough water to see it through the day. As a rule of thumb, always water directly onto the soil and not onto the plant, to help reduce the risk of fungal infections.

Courgette plant sprouting flowers
A good water supply stimulates the courgettes to develop more flowers [Photo: By Ana/ Shutterstock.com]

Tip: A mulch layer of plant material reduces loss of water through evaporation in summer and helps reduce the growth of weeds too. On top of this, it prevents the fruits from lying directly on the ground when ripe, meaning they are less prone to rotting. However, mulch binds nitrogen as it breaks down, so it is important to consider applying extra fertiliser to compensate for this.

Fertilising courgette plants

Courgettes and other cucurbits are very vigorous growers. They therefore require large amounts of nutrients for healthy growth. However, not all fertilisers are created equal when it comes to fertilising courgette plants.

Courgette seedlings in pots
In the first few weeks, seedlings do not need any additional fertiliser [Photo: Alina Demidenko/ Shutterstock.com]

The best fertilisers for courgettes

Mineral fertilisers are very soluble and can be absorbed easily by the plant. However, this quick but short-term nutrient boost is not enough to support your courgettes in the long run. Mineral fertilisers can also soon lead to over fertilisation of the soil and permanently damage the sensitive roots of the plant if used incorrectly. It is not uncommon for the nutrients to be washed out into deeper soil layers. There, they lead to increased nitrate levels in the groundwater.

Slow-release fertilisers with a high content of organic matter – like our Plantura Tomato Food – are the better choice from a scientific and sustainable point of view. They have many advantages when fertilising courgettes, such as promoting healthy and active soil life, as microorganisms feed on the organic matter. At the same time, the production of plant-based fertilisers saves resources and energy compared to the unsustainable extraction processes involved in making mineral fertilisers.

young courgette plant in soil
When planting, a plant-based slow-release fertiliser can be applied to give your courgettes a vital kickstart to their growing [Photo: By vaiv/ Shutterstock.com]

When and how often should you fertilise courgettes?

The nutrient supply should always be adapted to each stage of development of the courgette plant. In the period after planting, courgettes mainly need nitrogen to form leaves and grow rapidly in size. In the flowering and fruiting phase, the potassium supply is a bigger priority.

When should you fertilise courgettes?

  • After sowing, no fertilisation is necessary until planting.
  • Before planting, enrich your garden soil with compost and plant-based slow-release fertiliser.
  • Fertilise again after about two months during flowering and fruiting.

If you start your courgettes indoors, the seeds usually germinate very easily and quickly and will develop into strong seedlings. It is best to do this in a greenhouse or on a windowsill from mid-April onwards using low-nutrient compost. In the first few weeks, the seedlings will get enough nutrients from the supply stored in their seeds and the compost. Therefore, they do not need any additional fertiliser. Here you will find detailed instructions on how to grow and plant courgettes.

To give the courgette plants a good start, you can work some compost or fertiliser granules into the soil when planting. It is best to use a plant-based slow-release fertiliser with a high potassium content, such as our Plantura Tomato Food. The fertiliser granules break down slowly over a period of weeks, releasing their nutrients gently to the plant and the environment. After about two months, apply a top up of fertiliser to provide your courgettes with all the essential nutrients to see them through the rest of the season.

Tomato Food, 1.5kg
Tomato Food, 1.5kg
  • Perfect for tomatoes, chillies, courgettes, cucumber & more
  • For healthy plants & an abundant tomato harvest
  • Long-lasting fertiliser that is free from animal products - child & pet friendly

Fertilising courgettes in pots

When growing courgettes in pots, it is difficult to work in granular fertilisers, as this can easily damage the roots. For courgettes in pots on a balcony or patio, we therefore recommend using a liquid fertiliser – for example our Plantura Liquid Tomato Food – which is simply applied when watering. This flushes the nutrients straight to the roots and can also quickly remedy acute deficiency symptoms, such as a yellowing of the lower leaves.

Courgette leaf showing yellow mosaic virus
Aphids are the main transmitters of courgette yellow mosaic virus [Photo: Paul Maguire/ Shutterstock.com]

Courgette diseases

Courgettes are generally not susceptible to diseases. However, in unfavourable growing conditions and especially in wet summers, diseases can occur.

Flower and fruit rot is a physiological disease caused by a calcium deficiency. This is when the young courgettes start to rot from the end. At first a sunken dark brown spot appears, which quickly spreads. With slightly acidic garden soils, calcium deficiency can often develop. If you have acidic soils, add some lime when planting to help prevent this. Calcium fertilisers can supply courgette plants with the nutrient in the short term, alleviating symptoms that have already occurred.

Aphids (Aphidoidea) can multiply rapidly in early summer and form large colonies on courgettes. Aphids can be controlled with sprays or beneficial insects.

The yellow mosaic virus can be transmitted by infected tools, but mainly by aphids. The leaves change colour to a mosaic-like yellow-green pattern and the plant shoots begin to display stunted growth. Remove any infected plants and dispose of them completely. The best strategy for preventing the viral disease is to control aphids.

White powdery mildew on courgette leaf
A powdery mildew occurs on courgettes in warm, humid weather [Photo: KanphotoSS/ Shutterstock.com]

Powdery mildew (Erysiphaceae) on courgettes causes a white coating first on the top of the leaves, which later spreads to the underside. Cut back the affected courgette leaves at the first signs. Avoid watering directly onto the plants, otherwise powdery mildew will spread further.

Grey mould (Botrytis cinerea) also usually occurs in very humid, warm weather and mainly affects the fruit. Avoid planting your courgettes too close together – this allows air flow between the plants to dry them out after rain. Proper watering (only directly on the ground) is also crucial here to prevent the spores of the fungus from spreading.

Tip: A home remedy for fertilising courgettes is liquid nettle fertiliser. As wells as promoting growth, nettle tea fertiliser also bolsters the courgettes’ resistance to disease. When sprayed undiluted, it repels aphids and other insects.

Given the right care and growing conditions, courgette plants will bear their first fruit from the end of June which can be harvested soon afterwards. Discover our tips on how to harvest and use courgettes.

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