How to Grow Cosmos
'Lemonade' from Seed
Soft primrose-lemon cosmos that fade to cream, on compact, well-branched plants that rarely need staking. A cosmos for small gardens and pots.
'Lemonade' brings a colour that cosmos did not offer until recently: a clear, pale primrose yellow. As each flower ages it fades towards cream, so a single plant carries both shades at once and looks fresh all season.
It is also much shorter and bushier than the tall Sensation types, making a well-branched plant of around 75cm. That makes it far easier to fit into a smaller garden or a large pot, and it rarely needs a stake. Otherwise it grows like any cosmos, and it is one of the easiest flowers to raise from seed.
Quick Facts at a Glance
Plant Type
Half-hardy annual
Sowing Time
Mar to Jun, under cover
Flowering
July to October
Position
Full sun
Height
Around 75cm
Difficulty
1 out of 5, very easy
Understanding the Plant
'Lemonade' is a variety of Cosmos bipinnatus, the common cosmos. Most cosmos come in pinks, whites and crimsons, and pale yellow is a recent addition. The flowers are simple and open, which makes them easy for bees and hoverflies to feed from.
It is frost-tender, so it is raised under cover and planted out once the frosts are over. Its compact, branching habit comes from breeding, and it gives plenty of flowering stems without the height of older varieties.
A cosmos for containers
At around 75cm, 'Lemonade' suits a large patio pot. Use a container at least 30cm across with multipurpose compost, one or two plants per pot, and water regularly in summer. Pots dry out far faster than borders.
When & How to Sow
Cosmos seed is long and easy to handle, and it germinates quickly in warmth. Sow under cover between March and June, aiming for plants ready to go out at the end of May.
Don't rush to sow
An April sowing is usually ideal. Plants sown in February or early March outgrow their pots before it is safe to plant out and can end up leggy.
Sow in modules, 5mm deep. Sow one or two seeds per cell, cover lightly and keep at around 18 to 20°C. Seedlings appear in 7 to 14 days.
Pinch out the tip. At three or four pairs of leaves, nip out the growing tip for an even bushier plant.
Harden off and plant out after frost. Plant out from the end of May, 30 to 40cm apart, in full sun.
Growing On Tips
Full sun
Plant somewhere sunny in ordinary soil. Rich ground and feeding give leaf at the expense of flowers.
Cut and deadhead
The more you cut, the more it flowers. Remove faded flowers before they set seed.
Great in pots
Its compact size makes it one of the best cosmos for containers. Water pots regularly through summer.
Planting partners
Pale yellow and cream sit well with blues, purples, white and soft grasses.
In the vase
Cut when flowers are just opening. Stems are shorter than tall cosmos, so they suit small jugs and posies.
Pollinators
The open flowers are visited by bees and hoverflies right through to autumn.
Common Problems & How to Fix Them
| Problem | Likely Cause | What to Do |
|---|---|---|
| Lots of leaf, few flowers | Soil too rich or overfed | Stop feeding plants in the ground. In pots, use a low-nitrogen feed only once flowering has started. |
| Flowering slows | Seed heads left on the plant | Deadhead or cut regularly. Plants left to set seed quickly slow down. |
| Leggy seedlings | Sown too early or too little light | Sow in April and grow seedlings in bright light. Pinch out to keep them compact. |
| Pots wilting in summer | Compost drying out | Water daily in hot weather and use a large container. |
| Young plants eaten | Slugs and snails | Protect new plantings for the first few weeks until they are established. |
When to Expect Flowers
Plants sown in April and planted out at the end of May usually flower from July. With regular cutting, they carry on until the first frost.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 🌱 Sow under cover | ||||||||||||
| 🪴 Plant out | ||||||||||||
| 🌸 Flowering |
Plant Specifications
Pale lemon cosmos for pots and smaller gardens
Sow under cover in April, plant out at the end of May and keep cutting. You will have soft yellow and cream flowers from July until the frost.
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