Fertilising guide
How to fertilise Glaskins Perpetual Rhubarb (Rheum × hybridum 'Glaskin's Perpetual')— schedule & NPK
Also called Glaskin's Perpetual rhubarb, seed-grown rhubarb.
More about glaskins perpetual rhubarb
About Glaskins Perpetual Rhubarb
Rheum × hybridum 'Glaskin's Perpetual' · also called Glaskin's Perpetual rhubarb, seed-grown rhubarb · edible
Glaskin's Perpetual is the rhubarb most reliably raised from seed, with a long picking season and low oxalic acid that lets you harvest into late summer. Its green-to-red stalks are pleasantly tart. Grow in full sun and rich, moist soil; a vigorous, fully hardy perennial ideal for impatient gardeners who want a crop fast.
Growth habit: Clump-forming herbaceous perennial; raised from seed it forms a crown in its first year and can be picked from the second. Dies back over winter and regrows each spring, cropping longer than most cultivars.
What fertiliser glaskins perpetual rhubarb actually wants — and why
Glaskins Perpetual Rhubarb 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 glaskins perpetual rhubarb: 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 glaskins perpetual rhubarb, 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 glaskins perpetual rhubarb:
Feed generously to fuel its extended season. Mulch with well-rotted manure in late winter, apply a balanced fertiliser in spring, and side-dress with compost mid-season. Reduce feeding by late summer so the crown can harden off before dormancy. 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 glaskins perpetual rhubarb 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 glaskins perpetual rhubarb
Follow the crop-feed label rate for glaskins perpetual rhubarb — 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 glaskins perpetual rhubarb first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the glaskins perpetual rhubarb watering schedule.
Signs you are over-feeding glaskins perpetual rhubarb
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for glaskins perpetual rhubarb:
- 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 glaskins perpetual rhubarb
- 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 glaskins perpetual rhubarb 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 glaskins perpetual rhubarb 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 glaskins perpetual rhubarb
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 glaskins perpetual rhubarb — frequently asked questions
What fertiliser does glaskins perpetual rhubarb 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. Glaskins Perpetual Rhubarb 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 glaskins perpetual rhubarb?
Feed generously to fuel its extended season. Mulch with well-rotted manure in late winter, apply a balanced fertiliser in spring, and side-dress with compost mid-season. Reduce feeding by late summer so the crown can harden off before dormancy. Feed generously to fuel its extended season. Mulch with well-rotted manure in late winter, apply a balanced fertiliser in spring, and side-dress with compost mid-season. Reduce feeding by late summer so the crown can harden off before dormancy. 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 glaskins perpetual rhubarb?
Follow the crop-feed label rate for glaskins perpetual rhubarb — 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 glaskins perpetual rhubarb 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 glaskins perpetual rhubarb 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 glaskins perpetual rhubarb?
In containers, fertiliser salts build up fast — water glaskins perpetual rhubarb 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
- Glaskins Perpetual Rhubarb care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water glaskins perpetual rhubarb — 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 5561 fertilising guides in the Growli library