Mulching Tomatoes

Things are changing quickly in the gardening world, with many gardeners shunning labour-intensive methods such as double digging. Instead, the ‘no-dig’ approach is fast increasing in popularity, and with this, the use of mulch is becoming more popular in countries around the world.

But what exactly is mulch, and why should we be using it while growing our own tomatoes? How should it be applied and when is the best time to do it? Keep reading to find out how unlocking the world of mulch can work wonders for your homegrown tomato yield!

What is mulch?

The term mulch is used to describe a substance that is applied to the soil surface, normally to suppress weeds and boost water retention.  In addition, some mulches also improve the structure of the soil below and boost nutrient levels. Most mulches are made from organic matter, although inorganic substances like rubber are sometimes used.

Mulches have been popular in ornamental flower gardens for many years – we’ve all seen beautifully maintained floral borders with layers of bark chippings covering the soil. However, it is only in recent years that the advantages of this approach have become apparent in the vegetable garden. Mulching the vegetable plot brings a huge range of benefits, and one crop that thrives on this approach is the much-loved tomato plant.

What are the benefits of mulching tomatoes?

Mulching tomato plants helps to suppress weeds, improves water retention, and can boost levels of fertility in the soil. This leads to stronger, healthier plants that are more resilient and less prone to disease and pest damage. Mulching tomatoes also reduces the workload for the gardener – a definite win-win situation!

The aim of mulching is to create a breathable layer that moisture and air can move through, whilst preventing sunlight from reaching the soil surface. This not only stops weed seeds from germinating but also slows down water evaporation. When the ground is watered or rainfall occurs, the damp soil surface is better able to soak up all the extra moisture it needs.

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The reason why tomatoes in particular benefit from mulching is because they are very fussy about moisture levels, and mulch helps to create the perfect conditions for them to thrive. The soil below the mulch layer remains damp for longer after each watering, without becoming oversaturated and waterlogged. These constant moisture levels help to stimulate vigorous growth and also reduce the risk of diseases such as blossom end rot and split tomatoes.

When should tomatoes be mulched?

Timing is everything when it comes to mulch, particularly in areas with a shorter summer growing season such as the UK. The soil must be given time to warm up before mulch is applied, otherwise plant growth will be poor. Mulching too early can be more detrimental than not mulching at all, so be patient and wait until the chilly spring days are well behind you!

Tomatoes are a warm-season crop originating from tropical regions. Like all warm-season crops, it is not just the air temperatures that matter – how warm or cool the soil itself is has a huge effect on growth rates. Applying mulch to cold soil means the warming effect of sunlight is reduced and plant growth will be slow.

Tomatoes thrive in soil temperatures of 16 degrees Celsius (60 degrees Fahrenheit) and above – a regular food thermometer or purpose-made soil thermometer is a quick and easy way to check.  In the absence of a thermometer, avoid mulching until late spring or early summer, when tomato transplants are well established and have vigorous growth.

What is the best mulch for tomatoes?

The best mulch for tomatoes is one that retains moisture, suppresses weeds, and provides added nutrients to boost plant growth and crop yields. Well-rotted compost made from green waste and animal manure is a good option, provided it is free from weed seeds. Straw, shredded leaves, and dry grass clippings are all also ideal for mulching tomato plants.

  • Mulching tomatoes with compost

Compost is often overlooked as a form of mulch, but in fact, it is one of the best choices you could make. Nutrient-rich homemade compost will boost soil health and fertility and absorb water like a sponge, creating the ideal conditions for tomato plants to thrive. However, take care to regularly hoe any weed seedlings that do emerge.

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Commercially-produced compost can also be used to mulch tomato plants, but this can be expensive if you have a large area to mulch.

  • Mulching tomatoes with straw

Straw is a great mulch for tomatoes, as it creates a heat-retaining barrier that prevents moisture loss. Make sure to opt for seed-free wheat straw and never mulch with hay, as this can contain vast numbers of grass seeds.

  • Mulching tomatoes with shredded leaves

Shredded leaves make an excellent mulch for tomato plants, and it is well worth going to the effort of collecting fallen leaves in the autumn and leaving them to decompose ready for the following growing season. If a shredder is not available, running over them with a lawnmower is equally as effective.

  • Mulching tomatoes with grass clippings

Grass clippings are another readily available and free resource that can be used to mulch tomatoes. Leave fresh grass clippings to dry for a few days before applying them as a mulch, and make sure they are free of seeds that may germinate in your vegetable plot.

How to mulch tomatoes

Mulch should be applied to cover an area 12-18 inches from the base of the plant. If the plants are grown in rows, mulch along the entire length of the row. Clear a small zone around the stem of each tomato plant to allow air to circulate freely – this reduces the risk of stem rot and fungal diseases.

Should mulch be removed?

Organic mulches used on tomato plants do not have to be removed, as they will gradually decompose as the growing season progresses. If you are concerned that the mulch may harbour slugs and snails through the winter months, gently scrape it away from the soil surface and leave it in the compost bin to turn into fabulous homemade compost.

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