Fertilising guide

How to fertilise All Blue Potato (Solanum tuberosum 'All Blue')— schedule & NPK

Also called All Blue potato, blue potato, purple-blue potato.

More about all blue potato

About All Blue Potato

Solanum tuberosum 'All Blue' · also called All Blue potato, blue potato · edible

'All Blue' is a maincrop heirloom potato with deep blue-purple skin and dense violet flesh that holds its colour when cooked, thanks to high anthocyanin content. It is grown for boiling, roasting and vivid mash. Plant seed tubers in spring, hill the stems, and harvest tubers once the foliage yellows and dies back.

Growth habit: Herbaceous, bushy annual with sprawling green haulm; tubers form on underground stolons and must be kept covered (hilled) to prevent greening.

What fertiliser all blue potato actually wants — and why

All Blue Potato stores its crop underground, so the rule is the reverse of leafy plants — go easy on nitrogen, which sends energy into tops at the expense of roots.

For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for all blue potato: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.

How often to feed all blue potato, and which months

Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For all blue potato:

Moderate-to-heavy feeder. Incorporate a balanced fertiliser (e.g. 5-10-10) at planting, then side-dress with potassium-rich feed at hilling. Avoid excess nitrogen, which drives foliage at the expense of tubers. In practice: prepare the bed with well-rotted compost (not fresh manure), then little or no extra feeding through the season (spring through early autumn); a light potassium feed mid-growth at most.

The dormant-season rule matters more than the exact interval: skip feeding entirely when all blue potato is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.

What strength to mix for all blue potato

Less is more for all blue potato. If you feed at all, keep it light and low-nitrogen — the soil preparation does the work, and over-feeding actively spoils the crop.

Feeding always goes onto already-damp soil, never dry roots — water all blue potato first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the all blue potato watering schedule.

Signs you are over-feeding all blue potato

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for all blue potato:

Large lush leafy tops and small, forked or hairy roots.
Split or cracked roots from a nitrogen-and-water surge.
All foliage and no usable crop at harvest.

Signs you are under-feeding all blue potato

Genuinely uncommon in reasonable soil — these are not hungry plants.
Pale, weak tops and small roots only in very poor, exhausted ground.
Slow growth across the whole bed in long-uncultivated soil.

If the symptoms point at watering, light or roots rather than nutrition, the full all blue potato care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

Flushing is not the issue for all blue potato — the equivalent care is avoiding fresh manure and high-N feeds entirely, and rotating beds so the soil is not over-rich from a previous hungry crop.

Organic vs synthetic feeds for all blue potato

Organic options

Well-rotted compost worked in the season before, or for a previous crop, is ideal — never fresh manure. UK: garden compost, low-N blends; US: Espoma Garden-tone sparingly or finished compost. Lean and well-worked beats rich.

Synthetic / liquid feeds

If anything, a low-nitrogen, potassium-leaning feed only — UK: a high-potash feed mid-season at most, never a general high-N; US: a 5-10-10 sparingly. Most root crops crop best with no synthetic feed at all.

Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.

Fertilising all blue potato — frequently asked questions

What fertiliser does all blue potato need?

Low-nitrogen, with modest phosphorus and potassium for root development — ideally compost-improved soil rather than a high-N feed. Excess nitrogen forks the roots and grows lush tops instead of a crop. All Blue Potato stores its crop underground, so the rule is the reverse of leafy plants — go easy on nitrogen, which sends energy into tops at the expense of roots.

How often should I feed all blue potato?

Moderate-to-heavy feeder. Incorporate a balanced fertiliser (e.g. 5-10-10) at planting, then side-dress with potassium-rich feed at hilling. Avoid excess nitrogen, which drives foliage at the expense of tubers. Moderate-to-heavy feeder. Incorporate a balanced fertiliser (e.g. 5-10-10) at planting, then side-dress with potassium-rich feed at hilling. Avoid excess nitrogen, which drives foliage at the expense of tubers. In practice: prepare the bed with well-rotted compost (not fresh manure), then little or no extra feeding through the season (spring through early autumn); a light potassium feed mid-growth at most.

What strength of feed for all blue potato?