Blue chalksticks is one of the most useful groundcovers for hot, dry, low-water Australian gardens. The chalky blue-grey finger foliage spreads into a dense mat, it needs almost no water once established, and it holds its colour through the worst of summer when most groundcovers look tired. It has exactly one weakness, and it is worth knowing before you plant a bed of it.
Quick facts
| Detail | What to expect in Australia |
|---|---|
| Botanical name | Senecio mandraliscae, sometimes sold as Curio repens |
| Mature size | 300-400 mm tall, spreading 600 mm-1 m |
| Position | Full sun. Colour fades and stems stretch in shade |
| Soil | Sharply drained. Sand and gravel are ideal, heavy clay is not |
| Water | Very little once established. Overwatering is the main risk |
| Frost | Tolerates light frost. Damaged by hard frost |
| Best climates | Perth, Adelaide, Melbourne, Sydney, inland and coastal SA |
| Toxicity | Toxic if eaten. Keep away from grazing pets |
Its one weakness: wet feet
Blue chalksticks dies from too much water far more often than from too little. It stores moisture in its leaves and its roots rot quickly in soil that stays damp, which is why it performs brilliantly in Perth and Adelaide and struggles through a wet subtropical summer in Brisbane.
If your soil is heavy clay, plant on a raised bed or mound, or grow it in pots and troughs instead. If you are in a summer-rainfall region, choose the most exposed, fastest-draining position you have and resist the urge to irrigate. A plant that looks slightly hungry will outlive one that is kept comfortable.
Where it grows well in Australia
- Perth and Adelaide are close to perfect. Dry summers, mild winters and sandy soils are exactly what it wants.
- Melbourne and coastal Victoria grow it well in a raised sunny bed.
- Sydney and coastal New South Wales work with sharp drainage, though a wet summer can cause losses in flat beds.
- Inland and semi-arid districts suit it. It handles reflected heat and long dry spells without complaint.
- Brisbane and the subtropics are the difficult case. Humid summer rain leads to rot unless it is raised, gritty and in full sun. Many gardeners here have better results in pots.
- Tropical north Queensland is too wet. Choose a different groundcover.
Choosing between the chalk sticks
| Plant | Look | Best use |
|---|---|---|
| Blue chalk sticks (S. mandraliscae) | Thick blue-grey fingers, 300-400 mm | Mass groundcover, borders, rockeries, coastal banks |
| Narrow chalk sticks (S. talinoides) | Finer, more upright, softer blue | Contrast planting, containers, tighter spaces |
| String of pearls (S. rowleyanus) | Trailing beads | Hanging baskets and pot edges, indoors or sheltered |
| String of bananas (S. radicans) | Trailing, faster growing | Hanging baskets, quicker cover than pearls |
| Dolphin necklace | Curved dolphin-shaped leaves | Novelty container plant, bright indirect light |
For a garden bed, blue chalk sticks is the one to plant. Narrow chalk sticks is finer and more upright, useful where you want the same colour in a smaller or more contained form. The trailing types are container plants rather than groundcovers.
How to plant
- Plant in autumn or spring, avoiding the wettest part of summer in subtropical regions.
- Pick full sun. The blue is a protective waxy coating that develops properly only in strong light. In shade the plant greens up and stretches.
- Improve drainage before anything else. Add coarse sand or gravel to heavy soil, or build the bed up 150-200 mm.
- Space 400-500 mm apart for a solid mat within a season or two.
- Use a gravel or pebble mulch rather than bark. Organic mulch holds moisture against the stems and encourages rot.
- Water lightly for the first few weeks only, then leave it alone.
Ongoing care
Watering
Almost none once established. Through a Perth or Adelaide summer a deep soak every three or four weeks is plenty; through winter it usually needs nothing at all. In summer-rainfall areas the aim is to keep water off it rather than put water on it. Wrinkled, softening leaves mean it genuinely needs a drink - that is the only reliable signal.
Feeding
Barely necessary. A light application of a low-nitrogen or succulent fertiliser in early spring is enough. Rich feeding produces soft floppy growth that loses the tight blue form and is more prone to rot.
Pruning and renewal
Over a few years the centre of a clump can open up and go bare while the edges keep spreading. Cut the whole planting back by about half in early spring and it will reshoot densely. The trimmings root easily - push them straight into the soil where you want more cover, and they will strike without any special treatment.
Common problems and fixes
- Blackening, mushy stems at soil level is root or crown rot from too much water or poor drainage. Remove affected plants, improve the drainage and replant from healthy cuttings.
- Green rather than blue foliage means not enough sun. The waxy blue coating develops in strong light.
- Long stretched stems with gaps is also shade, or overfeeding. Cut back hard in spring and move it if the position is the cause.
- Bare centre with growth only at the edges is natural ageing. Cut the planting back by half to renew it.
- Mealybug in leaf joints occasionally appears in humid weather. Treat with horticultural oil.
Where to use it in the garden
Blue chalksticks earns its place in low-water and coastal gardens. The blue-grey reads as a cool contrast against terracotta, gravel, sandstone and rendered walls, and it sits naturally alongside agaves, aloes, westringia and olives in a Mediterranean or dry-garden planting. It is genuinely useful on hot dry banks and slopes where irrigation is difficult, and along driveway edges and paths where its low mounding habit stays tidy without trimming. It also takes coastal salt wind well, which makes it a solid choice for beachside gardens.
Frequently asked questions
Why is my blue chalksticks going soft and black at the base?
That is rot, caused by too much water or soil that does not drain. It is the most common way this plant dies in Australia, especially through a wet summer. Improve drainage, stop watering, and restart from healthy cuttings taken above the damage.
How often should I water blue chalksticks?
Far less than you think. Once established, a deep soak every three to four weeks through a hot dry summer is plenty, and often nothing at all in winter. Wrinkling leaves are the signal it needs water - anything else is usually too much.
Will it grow in Brisbane?
It can, but humid summer rain makes rot much more likely than in Perth or Adelaide. Plant it raised, in gritty free-draining soil, in the sunniest and most open position available. Many subtropical gardeners have better results growing it in pots where drainage is fully controlled.
Why has my plant turned green instead of blue?
Not enough sunlight. The chalky blue is a waxy coating the plant produces to protect itself from strong light, so in shade it fades to green and the stems stretch. Move it to full sun.
How do I propagate blue chalksticks?
Take a stem cutting, let the cut end dry for a day or two, then push it into the soil where you want it. It roots readily without hormone or special care, which makes filling a large bed inexpensive.
Is blue chalksticks safe around pets?
No. Senecio species are toxic if eaten and are best kept away from dogs that chew plants, and from grazing animals. In practice the foliage is not appealing to most pets, but it is worth knowing before planting a large area.
Ready to plant?
We grow blue and narrow chalk sticks along with the trailing senecio types for pots and baskets. Browse our succulents and cacti collection, or the groundcover range if you are covering a larger area.
Planting a low-water garden? See our guide to agave garden ideas for plants that pair with it, and drought tolerant plants for the wider palette.
