Cousin It is one of the best native groundcovers available to Australian gardeners. It is a prostrate form of the swamp she-oak, Casuarina glauca, and it forms a low mound of fine weeping foliage that softens retaining walls, spills over rocks and covers slopes where mowing is impossible. Once established it needs no pruning, no feeding and almost no water. It is also slower to establish than most people expect, which is where most disappointment comes from.
Quick facts
| Detail | What to expect in Australia |
|---|---|
| Botanical name | Casuarina glauca 'Cousin It' |
| Mature size | 100-300 mm tall, spreading 1.5-2 m |
| Position | Full sun to part shade |
| Soil | Tolerates almost anything - sand, clay, poor soil, periodic wet |
| Water | Regular in the first year, then very drought tolerant |
| Frost | Hardy. Handles frost across southern Australia |
| Salt | Excellent. One of the best coastal groundcovers |
| Growth rate | Slow for the first year, then steady |
| Native | Yes - an Australian native cultivar |
Why it suits Australian conditions so well
Cousin It comes from a native species that grows naturally in coastal and estuarine country along eastern Australia, which means it already tolerates the conditions that kill imported groundcovers: salt wind, poor sandy soil, extended dry spells and periodic waterlogging.
It grows well in every mainland capital. Brisbane and Sydney give the fastest growth, Melbourne and Adelaide suit it without difficulty, and it handles both Perth's sandy soils and frost in inland districts. Coastal gardens are where it genuinely outperforms alternatives - it takes salt-laden wind directly off the water, which very few soft-looking groundcovers manage.
Where to use it
- Spilling over retaining walls and raised beds, where the weeping foliage hangs down and softens hard edges. This is what it does better than anything else.
- Slopes and embankments that cannot be mown, where its root system helps hold the soil.
- Under established trees, where it copes with dry shade and root competition.
- Coastal gardens, including front-line positions with salt spray.
- Between pavers and along path edges, where it stays low without trimming.
- Native and low-water gardens, alongside lomandra, dianella, westringia and grevillea.
- Large pots and troughs, where it cascades over the rim.
It is not a lawn substitute. Cousin It will not take foot traffic, so keep it out of areas people walk across.
How to plant
- Plant in autumn or early spring so it establishes before summer heat.
- Choose full sun for the densest mound. It grows in part shade but stays more open.
- Space 1 to 1.5 metres apart for solid cover. Closer planting fills in faster but costs more; wider spacing takes two to three years to close up.
- Do not over-improve the soil. Like most natives it performs well in lean ground and dislikes rich beds.
- Avoid phosphorus. Casuarina, like many Australian natives, is sensitive to it. Use a native-specific fertiliser or none at all.
- Mulch lightly between plants to suppress weeds while they spread, keeping mulch off the crowns.
Ongoing care
Watering
The first year is the only year that really matters. Water deeply once or twice a week through the first spring and summer while the root system develops. After that, Cousin It is genuinely drought tolerant and needs water only in prolonged dry spells. Established plants in coastal gardens often need none at all.
Feeding
Almost never. If growth is very slow in poor soil, a light application of native-specific low-phosphorus fertiliser in spring is enough. Standard garden fertilisers are high in phosphorus and can damage it.
Pruning
None required, which is a large part of its appeal. If a plant becomes untidy or you want to encourage denser growth, trim lightly in early spring. Do not cut back hard into old bare wood, as it regenerates slowly from there. Removing the occasional upright shoot keeps the prostrate habit looking deliberate.
The one thing to expect: slow establishment
Cousin It spends its first year building roots rather than spreading, and new plantings can look sparse and unimpressive for months. Gardeners often assume something is wrong and either overwater or overfeed, both of which make things worse.
Give it consistent water through the first summer, keep weeds down between plants, and leave it alone. Growth accelerates noticeably in the second year and plants usually knit together by the third. If you want faster cover, plant closer rather than trying to push growth with fertiliser.
Common problems and fixes
- Browning or dieback in the centre is usually poor drainage or water sitting around the crown. Check that mulch is not banked against the plant.
- Very slow growth in year one is normal. Keep water up and be patient rather than fertilising.
- Yellowing after fertilising is likely phosphorus toxicity from a standard garden fertiliser. Flush the area with water and use native-specific feed in future.
- Sparse, open growth means too much shade. It needs sun to stay dense.
- Upright shoots spoiling the mound occasionally appear as the plant reverts towards its parent form. Cut them out at the base.
- Weeds through young plantings are the main early problem, since it takes time to close over. Mulch and hand weed until it knits.
Frequently asked questions
How far apart should I plant Cousin It?
One to 1.5 metres apart for solid cover. At that spacing plants typically knit together by the third year. Closer planting gives faster coverage if the budget allows, and wider spacing simply takes longer.
How fast does Cousin It grow?
Slowly at first. The first year goes into root development with little visible spread, after which growth picks up noticeably. Expect two to three years for a mass planting to close over completely.
Can you walk on Cousin It?
No. It is a groundcover rather than a lawn substitute and will not tolerate foot traffic. Use it beside paths and over walls rather than anywhere people cross.
Does Cousin It grow in shade?
It tolerates part shade, including dry shade under established trees, but grows more openly there. Full sun produces the dense mounded form most people are after.
Is Cousin It an Australian native?
Yes. It is a prostrate cultivar of Casuarina glauca, the swamp she-oak, which grows naturally along eastern Australia. That native origin is why it handles salt, drought, poor soil and periodic waterlogging so well.
Why does my Cousin It look brown in the middle?
Usually water sitting around the crown, from poor drainage or mulch banked against the plant. Pull mulch back from the centre and check that the site drains after rain. Occasionally it follows a hard prune into old wood, which it recovers from slowly.
Ready to plant?
We grow Cousin It in sizes suited to mass planting and to feature positions over walls and pots. Browse our groundcover collection, or the hardy plants for tough spots range if you are covering a difficult slope or coastal bank.
Building a native or low-water garden? See growing lomandra and the best plants for coastal gardeners, both of which pair naturally with Cousin It.
