Tomatoes: Banana Skins and Wood Ash for an XXL Harvest

Tomatoes thrive on warmth, water and light – but without suitable feeding, the crop will remain disappointing. Rather than buying costly specialist fertiliser from the garden centre, two everyday household leftovers can turn a tomato plant that produces little beyond foliage into a remarkably productive plant within a few weeks. Timing, quantity and a few straightforward steps are what matter.

Why many tomato plants look lush but produce hardly any fruit

It is a familiar summer sight: a tomato plant reaches knee or chest height, with rich green, dense foliage, yet carries only a handful of small, firm fruits. The cause is usually not watering or position, but the balance of nutrients.

Tomatoes are heavy feeders. Compared with lettuce or herbs, they require considerably more nutrients, especially:

• Potassium – for plump, large and flavoursome fruit
• Magnesium – essential for metabolism and photosynthesis
• Nitrogen – promotes leafy growth, but must not dominate
• Phosphorus – supports roots and flower formation

Many general-purpose garden fertilisers contain plenty of nitrogen. This can make a plant produce masses of leaves and look impressive, while forming far fewer flowers. And without flowers, there will be no tomatoes.

A good tomato fertiliser does not create even more foliage; it directs the plant’s energy specifically towards flowers and fruit.

This is where natural nutrient sources come in: they act more gradually, provide a more balanced supply and can be matched to the plant’s stage of growth.

The secret booster: two free leftovers from the home and garden

Many gardeners throw them away or put them in the ash bin, yet banana skins and wood ash are extremely valuable. Used together, they provide tomatoes with precisely the minerals often lacking during the fruiting stage.

Banana skins: a potassium boost for sweet, juicy tomatoes

Banana skins are rich in potassium and also contain magnesium, phosphorus and a little calcium. They are therefore ideal once the first green tomatoes begin appearing on the plant.

Two simple approaches have proved effective in the garden:

• Burying them around the root area
  Chop the skins into small pieces and work them 5 to 8 centimetres deep into the soil around the root ball. They will break down quickly without smelling or attracting pests.
• Liquid feed made from banana skins
  Soak the chopped skins in a bucket of water for 24 to 72 hours, then strain the liquid and water the tomatoes with this “banana water”. Use very sparingly for container-grown plants to avoid odour and fruit flies.

Important: choose organic bananas where possible and do not overdo it. During the fruiting period, one to two skins per plant every two to three weeks will generally be enough.

Wood ash: a mineral boost against small fruit and blossom end rot

Anyone with a fireplace, stove or fire bowl has access to the second valuable resource: ash from untreated natural wood. It contains plenty of potassium, along with calcium and phosphorus – a combination that encourages plentiful, healthy fruit.

Wood ash can be particularly helpful with an issue feared by many tomato growers: blossom end rot. In this condition, the bottom of the fruit turns black and may partly rot away. Calcium deficiency and uneven watering are among the usual triggers. Ash supplies calcium in a readily available form.

Use it safely as follows:

• Only use ash from untreated, natural wood.
• Sieve the ash to remove nails, charcoal remains and larger pieces.
• Scatter around 20 to 30 grams per plant between mid-July and early August – roughly one level tablespoon.
• Apply ash to the soil only, never to leaves or stems.

Wood ash works like a targeted mineral boost – it will not turn an attractive but unproductive tomato plant into a record holder, but it can noticeably improve fruit quality.

A second, lighter application of ash around 14 days later is possible if the soil is dry. Rain quickly washes ash away and may raise the soil pH too much.

A sound foundation is essential for an XXL tomato harvest

As effective as banana skins and wood ash can be, their benefits will be limited without a solid foundation. Anyone serious about tomatoes should lay the groundwork at planting time.

Spring start: feed rather than simply plant

When planting young tomatoes, it is worth preparing a small “nutrient pocket”:

• Work mature compost or well-rotted farmyard manure into every planting hole.
• Optionally add a little horn shavings as a slow-release nitrogen source.
• Plant the root ball deeply enough for the lower section of the stem to be covered with soil, as this is where additional roots will form.

This allows the plant to largely provide for itself during its first few weeks. From June onwards, it needs regular additional feeding.

The right summer routine

From early summer, a two-stage approach is worthwhile:

• At the beginning of the season (June): apply a mild organic fertiliser, such as diluted nettle feed, every 14 days. This supplies nitrogen for growth.
• Once fruit formation begins: shift the focus to potassium-rich additions – banana skins, comfrey feed or specialist organic tomato fertilisers.

At the same time, consistent watering remains vital. The soil should neither dry out nor remain permanently waterlogged. A mulch of grass clippings or chopped straw helps retain moisture and nutrients.

Common mistakes that can still limit the crop despite natural fertilisers

Anyone using kitchen and garden waste as fertiliser for the first time can easily fall into traps, but a few basic rules will prevent them.

• Too much of a good thing: Generous amounts of ash can make the soil strongly alkaline. Tomatoes prefer slightly acidic to neutral soil, not an “ash desert”.
• Skins left too large or too close to the surface: Whole banana skins placed on top of the soil attract slugs and flies, and decompose too slowly.
• Poor timing: Heavy nitrogen applications late in summer encourage foliage alone, just when the plant should be directing its energy into fruit.
• Neglecting side-shoot removal: Too many side shoots drain the plant’s energy. Combined with heavy feeding, this creates an overloaded bush with little fruit.

How long does it take to go from foliage monster to an XXL harvest?

If, in high summer, tomato plants appear healthy but carry very little fruit, the banana skin and wood ash combination can be used to correct course. Depending on the variety, weather and starting condition, results may become apparent after two to four weeks: the plant produces more flowers, while existing fruit develops more smoothly and with better flavour.

Patience is still essential. Vegetables do not respond like chemically boosted sprinters fed from a fertiliser shelf. Natural nutrients work more slowly but more sustainably, while also improving soil structure.

Extra tips for anyone who wants to take it a step further

Those looking to make yields even more reliable can sensibly expand this natural feeding system. Marine lime, rock dust or a small amount of algae lime broaden the mineral profile and bind excess acids in the soil. Tomatoes can also benefit from companion planting with basil, French marigolds or pot marigolds: these companion plants help keep pests in check and loosen the soil.

It is also worth considering other heavy feeders. Peppers, chillies and aubergines respond just as well to banana skins and moderately applied ash. Once you start, you may think twice before putting kitchen scraps and stove ash in the bin – and the vegetable garden will show its appreciation.