Blue Flowers: How to Grow & Care Guide

By Mohammad Barzegar, Director, TQN Mowing · Reviewed by an experienced Sydney gardener · Updated October 2026 · 8 min read

The best blue flowers for Sydney gardens are hydrangeas, agapanthus, plumbago, lavender, salvia and native fan flowers, which give colour from spring to autumn. Blue is the hardest colour to get right, so the usual mistake is planting a shy species, such as Ceanothus, in humid, poorly drained soil.

This guide lists reliable blue flowers by situation, explains what blue purple flowers need, and shows how to plant and keep them flowering. For the wider picture, see our types of flower guide.

Blue flowers at a glance

True blue is rare in nature, and many plants sold as blue are really violet or lilac. Use the table to compare popular choices.

Plant	Type	Sun	Flowering (indicative)	Native?
Hydrangea (blue soil-reactive types)	Deciduous shrub	Part shade	Late spring to summer	No
Agapanthus	Clumping perennial	Sun to part shade	Summer	No
Plumbago	Evergreen shrub	Sun	Spring to autumn	No
Salvia (blue sages)	Perennial or shrub	Sun	Spring to autumn	No
Fan flower (Scaevola)	Groundcover	Sun	Spring to summer	Yes
Native bluebell (Wahlenbergia)	Small perennial	Sun	Spring to summer	Yes
Ceanothus ‘Pacific Blue’	Evergreen shrub	Sun	Spring	No

Best blue flowers for Sydney gardens by situation

Pick the plant to suit the spot, not the other way around. A blue-flowering shrub that loves cool, moist soil will sulk against a hot western wall.

• Choose hydrangeas for shaded, sheltered beds on the south side of the house, where morning sun and afternoon shade keep the leaves from scorching.
• Use agapanthus for tough, dry borders and driveway edges, but pick sterile or dwarf cultivars to avoid weedy seedlings escaping into bushland.
• Plant plumbago against warm fences in full sun, because it flowers heavily and copes with poor soil and coastal wind.
• Try blue salvias in sunny borders where you want a long season of colour and a plant that bees and butterflies visit.
• Use native fan flower and bluebell as groundcover in rockeries, where they handle heat and drainage better than most exotic plants.
• Grow lavender in raised beds or pots if your soil is clay, since lavender dislikes wet feet more than most other blue flowers.

Blue purple flowers and similar shades

Many nurseries sell blue purple flowers under blue labels, so photos matter. Look at the colour on the plant tag and in real light.

• Expect lavender, jacaranda and wisteria to read as purple-blue, especially at dusk when the colour shifts toward violet.
• Compare shades in the pot at the nursery rather than on screen, because camera settings often exaggerate blue.
• Pair blues with white, silver foliage or yellow centres so the cool colour stands out in strong Sydney sunlight.
• Choose from our purple flowers guide if you want richer, warmer tones in the same bed.
• Check that the plant tag lists the botanical name, because common names for blue flowers often cover several different species.
• Searches such as “blue fliwers” or “blie flowers” are simply typos for the same range of plants listed here.

Ceanothus Pacific Blue in Australia

Ceanothus is a Californian shrub with intense blue spring flowers, but it is a fussy plant in warm, humid climates.

• Plant Ceanothus ‘Pacific Blue’ in full sun with excellent drainage, because wet roots in summer humidity are the most common cause of sudden death.
• Expect better results in cooler, drier districts such as the Blue Mountains than on Sydney’s humid coast.
• Avoid heavy pruning into old wood, since Ceanothus often fails to reshoot from bare stems.
• Skip rich fertiliser, as most Ceanothus prefer lean soil and respond to feeding with leaf instead of flowers.
• Treat it as a short-lived shrub in Sydney, and plan a replacement within a few years.
• If you want a similar blue in a tougher plant, try plumbago or a blue salvia and see our hydrangea guide for shade.

How to plant blue flowers

1. Choose the right season: plant in early autumn or spring, when soil is warm and rain is likely, so roots establish before summer heat.
2. Test your drainage by filling a hole with water; if it hasn’t drained after a few hours, build a raised bed or mound.
3. Dig a hole twice as wide as the pot and as deep as the root ball, leaving the crown level with the soil.
4. Loosen tight roots with your fingers and set the plant straight, then backfill with the same soil mixed with compost.
5. Water slowly until the soil is soaked, following Sydney Water’s Water Wise Guidelines by watering before 10 am or after 4 pm.
6. Mulch with a few centimetres of organic mulch (indicative — check the product instructions), keeping it clear of stems to avoid rot.
7. Stake taller perennials such as delphiniums early, before wind and rain flatten the flower spikes.

Caring for blue flowers

Task	When	How
Watering	Spring to autumn	Water deeply once or twice a week in dry spells, using a hose with an instant on-off nozzle.
Feeding	Early spring	Use a slow-release fertiliser suited to flowering plants and follow the label rate exactly.
Deadheading	Through the flowering season	Snip spent blooms to encourage more flowers on salvias, plumbago and fan flowers.
Pruning	After flowering	Cut back by about a third (indicative — check the plant label) to keep a compact shape.
Hydrangea colour	Late winter	Blue flowers depend on acidic soil, so use a product made for hydrangeas and follow the label.
Pest watch	Spring and summer	Check for aphids and caterpillars; for infestations, book a licensed pest controller.

Common problems with blue flowers

Symptom	Likely cause	Fix
Hydrangeas flower pink instead of blue	Alkaline soil	Use an acidifying product made for hydrangeas, following the label, or switch to a pot with the right mix.
No flowers	Too much shade or too much nitrogen	Move the plant to more sun and avoid high-nitrogen lawn fertiliser nearby.
Yellow leaves	Poor drainage or overwatering	Improve drainage and let the soil dry between waterings.
Leaf scorch	Hot afternoon sun or wind	Add afternoon shade and mulch, or relocate hydrangeas.
Sudden wilting in summer	Root rot in wet clay	Lift the plant, check roots and replant on a mound.
Weedy spread	Self-seeding agapanthus	Cut seed heads before they open, or choose sterile varieties.

FAQ: blue flowers

What are the easiest blue flowers to grow in Sydney?

Plumbago, blue salvias, agapanthus and native fan flower are the easiest. They handle heat, humidity and average soil once established. Hydrangeas are reliable too, but need shade and regular water. Choose plants to suit your sun and drainage first, then pick the shade of blue you like.

Why are my blue flowers turning pink or purple?

Hydrangea colour depends on soil chemistry. Acidic soil gives blue flowers, while neutral to alkaline soil gives pink. Colour can also shift with age, light and temperature. Use products made for hydrangeas, follow the label, and expect mixed shades in a bed with variable soil.

Does Ceanothus Pacific Blue grow in Australia?

Yes, but it prefers cooler, drier districts and sharp drainage. In humid Sydney summers it can struggle and often lives a short time. If your garden is clay or very humid, choose plumbago or salvia for a similar blue with fewer problems.

Which blue flowers attract bees and birds?

Salvias, lavender and native fan flowers attract bees and butterflies, and plumbago feeds smaller insects. Plant them in sunny spots where pollinators can reach them. Avoid spraying while plants are in flower, and follow product labels if you must treat pests.

Getting blue flowers growing in Sydney

If you want a blue border without the digging, we can prepare beds, plant, mulch and keep everything tidy through the season. Book garden maintenance in Sydney, or compare other plants such as bottlebrush, grevilleas, cactus and desert rose for contrast.

Related guides

• Hydrangea care for Sydney gardens
• Cactus types, care and rare varieties
• Grevillea varieties for Sydney
• Purple flowers that thrive in Sydney
• Bottlebrush: types, size and care
• Desert rose care and climate guide