Mulching & watering tomatoes: expert tips & instructions


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

When and how often should you water tomato plants? What are the benefits of mulching tomatoes? Find out all you need to know about mulching and watering these juicy fruits.

Ripe tomatoes growing on vines
Tomatoes are very popular in home gardens crop [Photo: Fotokostic/]

Summertime is tomato-time − you see your plants grow, blossom, and then bear the first little, green fruits. This is also the time to pay extra attention to how you water your tomato plants. Tomatoes need plenty of nutrients and water, which can sometimes be hard to satisfy. To help with watering and mulching, we have put together some useful tips to get those thirsty plants through the summer.

Watering tomato plants

Tomato plants need to be watered regularly and ideally in the morning. Watering tomatoes in the morning allows the plants to absorb as much water as possible before drying out in the heat of the day − this drying out also helps to prevent fungal diseases. In general, tomatoes prefer room temperature to lukewarm rainwater rather than cold tap water which can have too much lime.

During the hotter months, it may be necessary to water potted tomato plants several times a day, as the soil can dry out particularly quickly. In a greenhouse, the moisture in the soil is retained for much longer; here, watering can be done generously every two days. That said, it is very important never to over-water the plants. You should also avoid wetting the leaves when watering tomatoes. Just pour a generous amount directly around the base of the plant. Wet leaves − and moisture in general − allow the spread of many tomato diseases. Also, watering the plant from above (i.e. getting the leaves wet) makes it easier for pests that live in the soil to spread onto the plant.

Although many gardeners may find it hard to believe, watering tomatoes in this way really pays off. Here is a summary of our tips:

  • Water in the morning so that the plants dry out during the day.
  • Water regularly with room temperature rainwater.
  • Never overwater tomatoes, and only water around the base of the plant.
A young tomato plant being watered with watering can
Make sure to water the tomatoes only at the base of stem if possible [Photo: Ja Crispy/]

Tip: With the right watering methods, you can prevent a wide variety of tomato disorders. Read our article on tomato problems to find out more and learn how to prevent them.

Mulching tomatoes

Mulch refers to the material used to cover the surface of exposed soil.

There are two different kinds:

  • Artificial mulch materials such as plastic or gravel
  • Organic materials such as plant cuttings, compost or tree bark

The following information focuses on organic mulches, as they are sustainable and have particularly positive effects on the soil.

Why should you mulch tomatoes?

Mulches made from plant material such as straw and lawn clippings inhibit weed growth and help the soil to retain moisture. Organisms that live in the soil gradually break down the mulch, releasing nutrients into the soil for the tomatoes. Tomatoes with mulch grow better and are often healthier because the soil underneath is under less strain. Also, as mulch reduces evaporation, you do not need to water the tomatoes as often. Mulch actively improves the soil structure and protects it from compression and erosion by wind, rain and overwatering.

Laying straw mulch around tomato plant
Mulch not only helps your tomatoes grow better, but also actively improves the soil [Photo: Jurga Jot/]

When to mulch tomatoes

In principle, mulching is worthwhile throughout the season, but the first mulching for tomatoes is best done as early as March or April. As the soil is beginning to warm up, mulch helps the soil retain the warmth, and prepares it for the cold-sensitive roots of the tomatoes. Any springtime rain can also speed up the breakdown of mulch into organic matter and nutrients in the soil. Nutrients are then readily available for the tomato plants come May. After the tomatoes have been transplanted to their garden bed or pots, add a little more plant material to the mulch layer regularly so that the soil is always thinly covered.

How to mulch tomatoes

Depending on the mulch material, cover the soil with a layer two to five centimetres thick. The finer the material, the less thick the layer should be − mulch piled too thickly can rot and make the tomato plants diseased. Leave a little space around the base of the tomato stem. Compost that has not yet completely rotted can be spread around the plant. This can be worked into the soil, which not only improves the nutrient levels but also loosens the soil itself. In addition, some organic manure and bone meal can also be worked into the soil. Bear in mind, you should avoid using acidic bark mulch on tomatoes.

Nettles are also ideal for mulching. You can spread them as whole plants on the topsoil or chop them up so that they can be broken down quicker by soil organisms. As the nettles decompose, nitrogen is released to the tomato plant, helping it grow.

The mulch layer influences tomato growth in three ways. Firstly, less water evaporates, which keeps the soil evenly moist − stress caused by a lack of water leads to a smaller harvest. Secondly, mulch stores warmth during the day and releases it during the night. Lastly, mulch supports the nutrient supply, which, when combined with a natural long-term fertiliser, ensures an abundant harvest of tomatoes.

Tomato Food, 1.5kg
Tomato Food, 1.5kg
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  • 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 tomatoes during the growing season

A healthy balance of fertiliser is very important in tomato cultivation. Too little fertiliser, and the yield will suffer. Too much fertiliser, and the plants become more susceptible to disease and produce bland tasting tomatoes. For this reason, we recommend a slow-release fertiliser, such as our Plantura Tomato Food, that steadily releases a good balance of nutrients. If you are growing your tomatoes in pots, you can also apply a liquid fertiliser such as our Plantura Liquid Tomato Food every one to two weeks when watering. This is a preventive measure against nutrient deficiency symptoms, such as yellowing of the lower leaves due to nitrogen deficiency. In case there is already a deficiency, the liquid fertiliser is a quick remedy to nurse the tomato plant back to health.

Liquid Tomato Food, 800ml
Liquid Tomato Food, 800ml
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  • Perfect for tomatoes & other vegetables
  • Liquid fertiliser for healthy plant growth & an abundant harvest
  • Quick & easy application - child & pet friendly

If you want to learn more, read our article on how to fertilise tomatoes.