Fruit Trees & Soft Fruit

Feeding fruit

Fruit has a different nutritional shape from the rest of the garden. A plant asked to carry a crop to ripeness needs potassium above all — it drives sugar transport into the fruit, and it is the single nutrient most closely tied to size, flavour and keeping quality. Nitrogen matters, but in moderation: too much and you get a vigorous tree covered in leaf that flowers poorly and produces soft fruit that will not store. The rhythm most fruit follows is nitrogen early for growth, potassium through the season for the crop, and very little of either after midsummer so the wood ripens before winter.

Potassium, the fruit nutrient

Sulphate of Potash is the traditional fruit feed and still the most direct: chloride-free potassium, applied in late winter or early spring around the drip line. Chloride matters here — muriate of potash is cheaper and fruit does not thank you for it. Polyhalite, mined in North Yorkshire, supplies potassium alongside calcium, magnesium and sulphur from a single mineral, which suits an established tree that wants a broad feed rather than one nutrient. Liquid Fertiliser 3-2-6 is the high-potash liquid for pots, grow bags and anything that needs feeding through the watering can.

Magnesium, the deficiency you will actually see

Magnesium shortage is common in fruit and easy to recognise: yellowing between the veins of the older leaves, working inwards from the margins, often on apples and gooseberries, and worst on light soils and in wet seasons that leach it away. Heavy potassium feeding without magnesium to balance it makes it more likely, which is the trap in feeding fruit hard. Kieserite is magnesium sulphate, soluble and quick to act.

Blueberries and the acid-lovers

Blueberries, cranberries and lingonberries want a soil pH of roughly 4.5 to 5.5, which is well below what most British gardens offer. Feeding them without addressing pH is wasted effort — at neutral pH they cannot take up iron, and the plant goes yellow while sitting in perfectly adequate nutrition. Sulphur Soil Acidifier lowers pH, slowly, as soil bacteria oxidise the sulphur; it needs warm soil and several months, so autumn application for the following season is the sensible approach. In containers, ericaceous compost does the job more reliably than trying to acidify. The rest of the acid-loving range is in hydrangea and ericaceous feed.

Soft fruit and the strawberry bed

Strawberry Fertiliser is the high-potash slow-release blend for the strawberry bed and for runners going into new ground. Fruit & Vegetable Fertiliser 4-5-6 is the general feed for cane fruit, currants and gooseberries. Alfalfa Meal Pellets supply gentle, slow nitrogen in spring where a bush or tree needs growth rather than crop.

Planting a new tree or bush

Rock Phosphate mixed through the backfill puts slow-release phosphorus and calcium where new roots will find it, from a mined mineral that stays available for several seasons. Mycorrhizal Fungi Powder is applied to the roots at planting. We will be straight about the evidence here: independent testing has repeatedly found commercial mycorrhizal products that contain far less viable inoculum than the label claims, and the benefit in an already biologically active garden soil is uncertain. It is most defensible on disturbed, new-build or long-cultivated ground where native populations are depleted.

The straight potassium sources are compared in Potash & Potassium Fertilisers.

Common questions

When should I feed fruit trees?

Late winter to early spring, before bud break, is the main application. A second potassium feed in late spring suits heavy croppers. Stop feeding by midsummer so growth hardens before autumn.

Can I feed a tree in grass?

Yes, but clear a circle of turf around the base first, or the grass takes most of it. Apply out to the drip line rather than against the trunk — the feeding roots are at the canopy edge, not the stem.

My apples have sunken brown spots in the flesh. Is that a feeding problem?

Bitter pit is associated with calcium not reaching the fruit, which is usually a water and vigour problem rather than a shortage of calcium in the soil. Consistent watering, avoiding heavy nitrogen and not over-thinning all help. Cal-Mag addresses the soil side; it will not fix erratic watering.

What about the vegetable plot?

See vegetables and allotment, and tomatoes and edibles for the greenhouse crops.