When to plant Hollyhock in Subtropical Australia

Subtropical zone — applies to Brisbane, Gold Coast, Sunshine Coast, Coffs Harbour, Lismore and similar areas. Growing elsewhere? Temperate · Cool · Tropical · Arid.

Raise hollyhock seedlings from March to July, sowing about 8 mm deep into trays or pots and transplanting once they are sturdy. In the subtropics this autumn-to-winter start suits these tall biennials, letting them establish over the mild winter before sending up their towering flower spikes. Seed germinates quickly at 6–20 days, but the plant is a slow burner, taking 200–220 days to flower. Space plants 30–50 cm apart in rows 45–60 cm apart, in full sun with shelter from wind. Around Brisbane and the Sunshine Coast, give them room and airflow to keep disease at bay.

Sowing calendar — subtropical zone

Green months are your sowing window: March to July.

Growing notes

Hollyhocks make a dramatic vertical statement, but in warm, humid gardens their nemesis is rust. This orange-brown fungal disease pocks the leaves and, in the subtropical wet, can strip a plant of foliage from the base up. Managing it is the whole job:

• Space plants well, at 30–50 cm, so leaves dry quickly after rain.
• Water at the base early in the day and keep foliage dry.
• Remove and bin the lowest leaves and any rust-spotted foliage as it appears.
• Grow them in full sun with good airflow, never a still, shaded corner.

Because they flower so tall, up to two metres or more, plant them against a fence or with a stake, as subtropical storms will otherwise snap or flatten the spikes. They are hungry plants, so work compost into the bed before transplanting and feed as the spike develops.

Hollyhocks are biennials that self-seed freely. Rather than fighting to keep an ageing, rust-worn plant going, let a couple of spikes set seed and drop it, then thin the volunteers — a fresh young plant always resists rust better than a tired old one. Sowing in autumn as advised also means the main growth happens in the drier, cooler months, reducing rust pressure before flowering.

Hollyhock at a glance

Common questions

When should I plant hollyhocks in the subtropics?

Raise seedlings from March to July and transplant them out, so the biennials establish over the mild winter. They germinate fast, in 6–20 days, but take around 200–220 days to flower, generally blooming the following spring and summer.

Why do my hollyhock leaves have orange spots?

That is hollyhock rust, a fungal disease that thrives in subtropical humidity. Space plants well, water at the base in the morning, and remove affected lower leaves promptly. Full sun and airflow are your best defences against it.

How do I stop hollyhocks falling over in storms?

They grow very tall, so plant them against a fence or stake each spike. Subtropical downpours and wind easily flatten unsupported plants, so provide support early rather than after the spikes have shot up.

Do hollyhocks come back each year on the Sunshine Coast?

They are biennials, so an individual plant flowers then declines, but they self-seed freely. Let a few spikes drop seed and thin the seedlings; young volunteers resist rust far better than old plants and keep a patch going year after year.

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