Mature size & growth rate

How big does Prince's feather (Amaranthus hypochondriacus) get?

Also called Prince's feather, grain amaranth, purple amaranth, prince-of-wales feather.

More about prince's feather

About Prince's feather

Amaranthus hypochondriacus · also called Prince's feather, grain amaranth · flowering

Prince's feather is a tall, imposing warm-season annual bearing erect, bristling plumes of deep maroon-red to purple flowers on strong stems above large burgundy-flushed leaves. Also grown as a grain crop, its seeds are a nutritious pseudo-grain rich in protein. It thrives in full sun, heat and well-drained soil. Apply genus-level caution for pets, as Amaranthus retroflexus is ASPCA-listed as toxic.

Mature size: 120-180 cm tall, 45-60 cm spread

Watch for — Stem lodging in wind: Very tall plants can topple in exposed, windy gardens — stake with sturdy canes from mid-growth, or shelter plants from prevailing winds; avoid excess nitrogen which weakens stems.

Indoor size vs how big it gets in the wild

Prince's feather reaches its full size within one growing season — there is no "long-term" size, just how big it gets before you harvest or it dies back. Indoors and in a pot, expect 120-180 cm tall, 45-60 cm spread. A pot, your light levels and a little pruning are what set the final size in a home, far more than the plant's theoretical potential.

It sizes up fast and once, racing from seedling to full size in a single season; after cropping it is finished, so size is a within-season question.

Growth rate and years to mature

Prince's feather is a fast grower. Realistically, expect a single growing season — it reaches full size in one year, then is done. Its feeding profile backs this up: incorporate a balanced granular fertiliser at planting. for ornamental use, a monthly balanced liquid feed supports large plumes. for grain use, a lower-nitrogen feed is preferred to encourage seed production over leafy growth. overly rich soil produces excessive foliage and weakens stems.

Want this turned into the right next pot at the right moment? The pot size calculator and the prince's feather repotting guide cover when and how much to size up — pot size is one of the biggest levers on how fast prince's feather grows.

How to keep prince's feather smaller

You are not stuck with the maximum size. For prince's feather specifically, these are the levers, in order of impact:

Choose a compact or dwarf variety of prince's feather from the start — that is the most reliable size control for an annual.
Grow it in a smaller container to naturally limit how large it gets.
For some crops, pinching or pruning the growing tips keeps the plant shorter and bushier.
Sow a little later or space plants closer if you specifically want smaller individual plants.

How to grow prince's feather bigger or faster

If you want it to fill the space sooner, push the conditions rather than hoping — for prince's feather the accelerators are:

Full sun, warm soil and steady water are what drive a crop to full size fastest.
Sow at the right time for your zone so it gets the whole season to size up.
Feed appropriately for the crop and never let it check (stall) from drought or cold.

Light is almost always the ceiling. The prince's feather light requirements page covers exactly how bright a spot it needs to grow at its potential instead of stalling.

When prince's feather outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for prince's feather:

It sprawls beyond its bed or container before harvest — usually a spacing or support issue.
It flops or needs staking once it hits full height.
Once it has fruited or bolted, it is at its final size for good — the next plant is a new sowing.

If it is the pot rather than the room, it is a repotting job, not a goodbye — see the prince's feather repotting guide. If you want more of this plant instead of a bigger one, the prince's feather propagation guide turns prunings into new plants.

Prince's feather size — frequently asked questions

How big does prince's feather get?

Prince's feather reaches 120-180 cm tall, 45-60 cm spread when grown indoors. It sizes up fast and once, racing from seedling to full size in a single season; after cropping it is finished, so size is a within-season question.

Is prince's feather slow or fast growing?

Prince's feather is a fast grower. Expect a single growing season — it reaches full size in one year, then is done. Prince's feather reaches its full size within one growing season — there is no "long-term" size, just how big it gets before you harvest or it dies back.

How long does prince's feather take to reach full size?

Roughly a single growing season — it reaches full size in one year, then is done. Light, pot size and feeding move that timeline more than anything else.

How do I keep prince's feather smaller?

Choose a compact or dwarf variety of prince's feather from the start — that is the most reliable size control for an annual. Grow it in a smaller container to naturally limit how large it gets. For some crops, pinching or pruning the growing tips keeps the plant shorter and bushier. Sow a little later or space plants closer if you specifically want smaller individual plants.

How can I make prince's feather grow bigger or faster?

Full sun, warm soil and steady water are what drive a crop to full size fastest. Sow at the right time for your zone so it gets the whole season to size up. Feed appropriately for the crop and never let it check (stall) from drought or cold.