Fertilising guide
How to fertilise Issai Kiwi (Actinidia arguta 'Issai')— schedule & NPK
Also called Issai kiwi, self-fertile hardy kiwi.
More about issai kiwi
About Issai Kiwi
Actinidia arguta 'Issai' · also called Issai kiwi, self-fertile hardy kiwi · edible
'Issai' is a self-fertile hardy kiwi that fruits without a separate male pollinator, making it ideal for small gardens. It bears smooth-skinned, grape-sized kiwi berries on a vigorous deciduous vine and can crop young. Less rampant than the species, it still needs sturdy support, full sun, and free-draining soil to ripen well.
Growth habit: Self-fertile, twining deciduous vine; more compact and less vigorous than wild A. arguta but still needs permanent support. Fruits on current-season shoots from one-year-old wood; suits training on wires or a trellis.
Watch for — Light or late first crops: Although self-fertile, 'Issai' often yields modestly and can take a few years to fruit well; a nearby male A. arguta can boost both yield and berry size.
What fertiliser issai kiwi actually wants — and why
Issai Kiwi feeds in two distinct phases — balanced to build the plant, then high-potassium the moment flowering starts to set and fill a heavy crop.
Balanced (even N-P-K) at planting for roots and frame, then switch to a high-potassium ("high-potash") tomato-style feed once the first flowers open — potassium is what sizes and ripens fruit, not nitrogen.
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 issai kiwi: 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 issai kiwi, 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 issai kiwi:
Feed in spring with a balanced fertiliser and mulch with compost or well-rotted manure; container plants benefit from a controlled-release feed. A light summer feed supports cropping. Avoid heavy nitrogen, which favours leaf over fruit. So: a balanced feed or compost at planting, then a high-potash liquid every 1-2 weeks from first flower through harvest across the main season (spring through early autumn).
The dormant-season rule matters more than the exact interval: skip feeding entirely when issai kiwi 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 issai kiwi
Follow the crop-feed label rate for issai kiwi — these are calibrated for hungry vegetables. Consistency through fruiting matters more than strength; erratic feeding causes problems like blossom-end rot.
Feeding always goes onto already-damp soil, never dry roots — water issai kiwi first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the issai kiwi watering schedule.
Signs you are over-feeding issai kiwi
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for issai kiwi:
- Vigorous dark-green leafy growth but few flowers or fruit (excess nitrogen).
- Lush foliage hiding the crop; soft growth prone to pests and disease.
- Salt crust on the soil and scorched leaf edges in containers.
Signs you are under-feeding issai kiwi
- Pale, yellowing lower leaves and stunted growth.
- Small fruit, poor set, and a quickly exhausted plant.
- Blossom-end rot and weak cropping from erratic or insufficient feeding.
If the symptoms point at watering, light or roots rather than nutrition, the full issai kiwi care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
In containers, fertiliser salts build up fast — water issai kiwi thoroughly so excess drains from the base each time, and flush pots with plain water every few weeks to prevent a damaging salt build-up.
Organic vs synthetic feeds for issai kiwi
Organic options
Garden compost or well-rotted manure dug in before planting, plus a liquid comfrey or seaweed feed once fruiting starts. UK: comfrey feed or organic Tomorite; US: Espoma Tomato-tone or Neptune's Harvest. Builds soil and feeds in one.
Synthetic / liquid feeds
A balanced feed at planting then a high-potash tomato feed in fruiting — UK: Growmore at planting then Tomorite (Levington) or Phostrogen; US: a balanced 10-10-10 then Miracle-Gro Tomato or a bloom booster.
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 issai kiwi — frequently asked questions
What fertiliser does issai kiwi need?
Balanced (even N-P-K) at planting for roots and frame, then switch to a high-potassium ("high-potash") tomato-style feed once the first flowers open — potassium is what sizes and ripens fruit, not nitrogen. Issai Kiwi feeds in two distinct phases — balanced to build the plant, then high-potassium the moment flowering starts to set and fill a heavy crop.
How often should I feed issai kiwi?
Feed in spring with a balanced fertiliser and mulch with compost or well-rotted manure; container plants benefit from a controlled-release feed. A light summer feed supports cropping. Avoid heavy nitrogen, which favours leaf over fruit. Feed in spring with a balanced fertiliser and mulch with compost or well-rotted manure; container plants benefit from a controlled-release feed. A light summer feed supports cropping. Avoid heavy nitrogen, which favours leaf over fruit. So: a balanced feed or compost at planting, then a high-potash liquid every 1-2 weeks from first flower through harvest across the main season (spring through early autumn).
What strength of feed for issai kiwi?
Follow the crop-feed label rate for issai kiwi — these are calibrated for hungry vegetables. Consistency through fruiting matters more than strength; erratic feeding causes problems like blossom-end rot.
What does over-feeding issai kiwi look like?
Vigorous dark-green leafy growth but few flowers or fruit (excess nitrogen). Lush foliage hiding the crop; soft growth prone to pests and disease. Salt crust on the soil and scorched leaf edges in containers. Staying on a high-nitrogen feed once issai kiwi starts flowering is the classic error — you get a huge leafy plant and a disappointing crop. Switch to high-potash the moment flowers appear.
Should I flush the soil of issai kiwi?
In containers, fertiliser salts build up fast — water issai kiwi thoroughly so excess drains from the base each time, and flush pots with plain water every few weeks to prevent a damaging salt build-up.
Keep reading
- Issai Kiwi care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water issai kiwi — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise tomato
- How to fertilise pepper
- How to fertilise cucumber
- All 3899 fertilising guides in the Growli library