Mature size & growth rate

How big does Spencer Mixed sweet pea (Lathyrus odoratus 'Spencer Mixed') get?

Also called Spencer Mixed sweet pea, Sweet pea, Spenser sweet pea.

More about spencer mixed sweet pea

About Spencer Mixed sweet pea

Lathyrus odoratus 'Spencer Mixed' · also called Spencer Mixed sweet pea, Sweet pea · flowering

Spencer Mixed sweet pea is the classic large-flowered, intensely fragrant climbing annual, producing ruffled blooms in mixed shades of white, pink, lilac, mauve, and purple from early summer. It climbs to 1.8–2.5 m and needs cool roots, a support structure, and regular picking to keep flowering. Seeds and pods are toxic — do not eat.

Mature size: 180–250 cm tall (6–8 ft) with support, 30–45 cm spread (12–18 in)

Watch for — Powdery mildew: White powdery coating on leaves and stems, particularly in warm dry spells or crowded plantings. Improve air circulation, water at the base, and apply a potassium bicarbonate spray or sulphur-based fungicide at first signs. Remove badly affected growth.

Indoor size vs how big it gets in the wild

Spencer Mixed sweet pea 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 180–250 cm tall (6–8 ft) with support, 30–45 cm spread (12–18 in). 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

Spencer Mixed sweet pea 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: apply a balanced slow-release fertiliser or well-rotted compost before planting. feed every 2–3 weeks with a high-potassium liquid feed (e.g., tomato fertiliser) once flowering begins to prolong blooming. avoid high-nitrogen feeds, which produce lush stems and poor flowers.

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

How to keep spencer mixed sweet pea smaller

You are not stuck with the maximum size. For spencer mixed sweet pea specifically, these are the levers, in order of impact:

Choose a compact or dwarf variety of spencer mixed sweet pea 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 spencer mixed sweet pea bigger or faster

If you want it to fill the space sooner, push the conditions rather than hoping — for spencer mixed sweet pea 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 spencer mixed sweet pea light requirements page covers exactly how bright a spot it needs to grow at its potential instead of stalling.

When spencer mixed sweet pea outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for spencer mixed sweet pea:

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 spencer mixed sweet pea repotting guide. If you want more of this plant instead of a bigger one, the spencer mixed sweet pea propagation guide turns prunings into new plants.

Spencer Mixed sweet pea size — frequently asked questions

How big does spencer mixed sweet pea get?

Spencer Mixed sweet pea reaches 180–250 cm tall (6–8 ft) with support, 30–45 cm spread (12–18 in) 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 spencer mixed sweet pea slow or fast growing?

Spencer Mixed sweet pea is a fast grower. Expect a single growing season — it reaches full size in one year, then is done. Spencer Mixed sweet pea 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 spencer mixed sweet pea 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 spencer mixed sweet pea smaller?

Choose a compact or dwarf variety of spencer mixed sweet pea 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 spencer mixed sweet pea 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.