Growing annual special climbers for joyful summer drama

Cobaea scandens

Annual climbers are the extroverts of the garden. Loud, fast, occasionally unruly, and utterly joyful. They take a bare fence or pergola and turn it into something theatrical within weeks. No long-term commitment, no digging out woody roots later, just one glorious season of excess.

For the horticulturally inclined, annual climbers are also deeply satisfying. They reward good technique, punish impatience, and clearly separate the calm, methodical grower from the optimistic soul who puts tender plants out in March and then blames the weather.

This is a proper grower’s guide to the best annual special climbers, graded by difficulty, with honest advice, a few cheats, and the golden rule repeated loudly for those at the back.

Get them germinated early, but do not put them outside until April.

The grading system (honest and unapologetic)

• Expert Percy Thrower level

  
  

  For growers who enjoy coaxing slow seedlings and accept losses as part of the process.

• Tricky but doable

  
  

  Needs care, warmth, and a gentle hand, but achievable without saint-like patience.

• Easy peasey

  
  

  Reliable, forgiving, and ideal if you want results without drama.

Cobaea scandens

(cup and saucer vine)

Grade: Expert Percy Thrower level

This is the grande dame of annual climbers. Fast growing, massive leaves, and extraordinary bell-shaped flowers that open pale green and mature to deep purple. It can reach several metres in a single season and will happily engulf a pergola if given half a chance.

Why serious gardeners love it

• Flowers are genuinely architectural

• Long season from midsummer to autumn

• Excellent tendril climber, very elegant once trained

Why it earns its Percy Thrower badge

• Seeds are slow and awkward to germinate

• Seedlings resent disturbance

• Very prone to damping off if overwatered or chilled

Expert tips

• Start seeds in February or early March with bottom heat

• Sow on edge to reduce rot

• Prick out only once roots are visible and handle by the leaves

• Pot on carefully and keep evenly moist, not wet

This plant rewards patience and good hygiene. Sloppy watering will end it.

Rhodochiton atrosanguineus

(purple bell vine)

Purple bell vine

Grade: Tricky but doable

This climber looks delicate but hides surprising vigour. Its dangling purple bells with papery calyces are unlike anything else grown as an annual climber in the UK.

Why it is special

• Unique flower form, subtle and dramatic at the same time

• Excellent for sheltered patios and doorways

• Softer, more romantic than many climbers

Where growers go wrong

• Starting it too late

• Letting seedlings dry out then overwatering

• Rough pricking out

Expert tips

• Germinate early indoors

• Keep seedlings warm and bright

• Avoid cold draughts

• Plant out only when nights are consistently mild

If you want the look without the seedling stress, plug plants are a perfectly respectable cheat.

Ipomoea lobata

(Spanish flag vine)

Grade: Easy peasey

This is colour and movement in plant form. Flower spikes emerge red and fade through orange, yellow, and cream. It looks like it is constantly changing its mind.

Why it is a favourite

• Very fast growing

• Reliable from seed

• Brilliant for fences and obelisks

Growing notes

• Start indoors in March

• Likes warmth and sun

• Train early before it tangles

This is the climber you recommend to friends who want drama with minimal fuss.

Ipomoea tricolour

(morning glory)

Grade: Easy peasey

Classic for a reason. Trumpet flowers glow in the morning light and close as the day warms, adding rhythm to the garden.

Key points

• Soak seeds overnight before sowing

• Needs sun

• Grows rapidly once temperatures rise

It is honest, reliable, and quietly spectacular.

Dolichos lablab

(hyacinth bean vine)

Grade: Tricky but doable

This climber is all about colour. Purple stems, lilac flowers, and glossy burgundy pods make it feel almost tropical.

Why experienced growers like it

• Decorative even after flowering

• Strong design impact

• Long season if kept warm

Watch out for

• Cold soil

• Early planting

• Exposed sites

Warmth is non-negotiable here.

Thunbergia alata

(black eyed Susan vine)

Grade: Easy peasey (and the ultimate cheat)

Cheerful, obliging, and endlessly floriferous. Orange, yellow, cream, and peach varieties all perform reliably.

Why it is beloved

• Flowers continuously

• Ideal for pots and hanging baskets

• Very forgiving

Professional shortcut

Buy a ready-grown plant from Squires. They do excellent stock, and you skip every seed tray stage entirely.

Timing matters more than talent

This is where most failures happen.

• Germinate early indoors from February to March

• Grow on steadily without forcing

• Do not plant outside until April, and later if nights are cold

• Harden off gradually

A healthy plant planted late will outperform a stressed plant planted early every single time.

Pricking out without tears (or losses)

Annual climbers are particularly sensitive at this stage.

• Handle seedlings by the leaves, never the stem

• Use free-draining compost

• Water from below where possible

• Avoid overcrowding

• Ensure airflow but no cold draughts

Damping off is almost always a cultural issue, not bad luck.

FAQs

• When should I start annual climber seeds in the UK?

From February to March indoors, depending on heat and light levels.

• Can I plant them out earlier if the weather looks mild?

No. One cold night can undo weeks of careful growing. April is your friend.

• Why do my seedlings collapse at soil level?

Damping off, usually caused by excess moisture, poor airflow, or cold compost.

• Are plug plants cheating?

Only if you think buying bread means you did not bake. Plug plants are sensible.

• Can I grow annual climbers in pots?

Yes, and many thrive in containers, especially Thunbergia and Ipomoea.

• Do annual climbers need feeding?

Yes. Regular liquid feeding keeps growth strong and flowering continuous.

• Will they self-seed?

Some may drop seed, but most are treated as annuals and replanted each year.

Final thoughts

Annual climbers bring energy, speed, and joy to a garden in a way few plants can. For the horticulturally curious, they are a seasonal challenge worth taking on. For everyone else, they are a reminder that sometimes a bit of colour, a bit of height, and a bit of cheek is exactly what a garden needs.

Start early, be gentle, wait until April, and do not be ashamed of a good garden centre shortcut.