How to Grow Herb Robert in Australia

Herb Robert (Geranium robertianum, cranesbill family, Geraniaceae) is a small annual or biennial grown for its lacy, red-tinged leaves and small pink flowers. It comes from Europe, Asia and North Africa, and it grows happily in the damp shade under shrubs where many herbs sulk. Where gardeners go wrong is in letting it seed: its fruits throw seed several metres, and Victoria rates it an environmental weed.

Three mistakes that matter

1. Letting plants drop their seed. Ripe fruits snap open and fling seed up to about 6 m, and seed in the soil can stay alive for five years or more. Cut flowering stems before the beaks brown, as Thinning and Containing explains.
2. Giving up on the seed too soon. The seed carries a hard coat and an inner dormancy, so seedlings often arrive in flushes over weeks or months rather than all at once. Keep the pot moist and read Germinating the seed before sowing again.
3. Planting it in hot, dry sun. Herb Robert is a woodland plant that wants moist, humus-rich soil and light shade. In a hot, dry bed it struggles, so give it the shaded spot Site, soil and setup describes.

When to plant

Sow in autumn, or in early spring in the cooler zones. Seed sown in autumn sits through the winter cold, which wears down its dormancy, and usually comes up from late winter into spring. Under cover, seed comes up at about 20°C, so a spring sowing in trays is the other reliable route. One sowing is usually enough, because a plant left to flower sows the next generation itself.

At the cold edge of a window, sow in spring rather than autumn. In a study in Poland, few autumn seedlings survived the winter, while spring seedlings did far better. At the hot edge, sow only into shade and keep the mix moist, because heat and dry soil stress this woodland plant.

Site, soil and setup

Left to itself, herb Robert grows about 30 cm tall and as wide, sometimes to 50 cm, with stems that stand up or sprawl.

Plant it where you can see and pull its seedlings, and well away from bushland, creek lines and the fence you share with a neighbour. Safety sets out where it stands on each state's weed lists.

Container growing

A pot is the neatest way to keep herb Robert in bounds, because stray seedlings on paving are quick to spot and pull. Use a pot at least 30 cm across that holds 10 to 15 L, with drainage holes, and fill it with potting mix. It is sold as the species, with no compact varieties to choose between. The pot does not stop the seed flying, so trim flowering stems as Thinning and Containing describes.

• Water: whenever the top of the mix feels dry, until water runs from the holes. Pots dry fast in summer, so move them into shade. See watering pots in summer.
• Feed: seaweed solution at half strength, 15 mL per 9 L, fortnightly for the first month after planting, then nothing more.
• Position: bright shade, or morning sun with afternoon shade.
• Handling mix: potting mix can carry Legionella bacteria, so dampen it first, wear gloves and a P2 mask, and wash your hands afterwards.

Germinating the seed

Herb Robert seed has two locks. The coat is hard and keeps water out when the seed is fresh. The embryo carries a physiological dormancy (an internal brake that has to wear off before it will grow). Most seed needs two months or more after ripening before it will germinate at all. Dry storage opens both locks over time, and a spell of winter cold eases what is left.

Seed that has spent a few months in dry storage, as packet seed usually has, is ready to go, so no kitchen treatment is needed. Expect a slow and uneven start rather than one tidy flush. Some seedlings can appear in about 2 weeks, and others follow for weeks or months. In one British study, seed sown in trays in the autumn after collection gave 57 to 70 per cent. Sow two seeds to every cell or pot and keep the strongest.

When nothing comes up

• Sown too deep: the seed is small, so cover it only lightly and sow again on the surface.
• Mix dried out: a dry spell stalls germination, so keep the mix evenly moist under a clear lid. Lift the lid off once the first seedlings appear.
• Seed too fresh: seed you collected yourself needs two months or more of dry storage before sowing.
• No cold spell: some seed waits for winter, so leave the pot outdoors in shade through the cold months.
• Given up too soon: keep the pot for a full year before you tip it out. In one trial of autumn sowings, most seedlings came up the following year, and a few kept appearing for five years.

For the principles behind these treatments, see soaking, scarification and cold stratification.

Sowing Seeds

Start herb Robert seed in cells or small pots, where every seedling is easy to watch, or scatter it where it is to grow.

Starting under cover

• Fill cells or small pots with fresh seed-raising mix and water it well.
• Sow two seeds to each cell and cover them lightly with mix.
• Keep the tray in bright shade, at the temperature When to plant gives, and the mix moist, never soggy.
• Once true leaves appear, snip out the weaker seedling in each cell at soil level.
• Plant out when roots fill the cell, 30 cm apart, into moist soil in shade.

Sowing direct

• In autumn, rake a shaded patch of damp soil to a fine surface.
• Scatter seed thinly, press it in and cover it with a light sprinkle of fine compost.
• Mark the spot and keep it moist, because seedlings may come up over several months.
• Thin seedlings in stages to 30 cm apart.

Harden off tray-raised seedlings (get them used to outdoor wind, light and dryness a little more each day) for about a week before planting out. See hardening off seedlings.

Care by growth stage

Steady moisture and shade decide this crop. Feeding matters far less: herb Robert grows wild in soils of moderate fertility, and rich feeding gives soft, sappy growth that flops.

If growth stalls in very poor sand, one light application of all-purpose controlled release granular (NPK around 14-5-10) at the label rate can help.

Thinning and Containing

A wild plant carries from about 10 to a few hundred fruits, each of up to five seeds. A garden plant can carry five to ten times as many, so one plant left alone can restock a bed.

• Thin self-sown seedlings to 30 cm apart while they are small; the roots are shallow and pull up easily.
• Grasp each plant firmly at the base when pulling, so the roots come out with it.
• Cut flowering stems as the flowers fade, before the beaks brown and split.
• Bag pulled plants that carry fruits for the general waste bin. Pulled plants can still ripen seed, and a home compost heap rarely kills it.
• Pull the whole plant as flowering ends, before the beaks brown, because it flowers once and then dies.
• Check paths, pots and nearby beds through the growing season, and for several years, for seedlings from seed already in the soil.

Companion planting

Herb Robert fills the shade under shrubs and trees, so it shares a bed best with plants that want the same cool, moist conditions.

Grows well with

• Chervil, another herb that grows best in part shade and moist soil.
• Forget-me-nots, which brighten damp, shady corners and, like herb Robert, self-sow.
• Aquilegia, a woodland flower for part shade and moist, free-draining soil.

Keep apart

• Thyme and other sun herbs, which want full sun and lean, dry soil, the opposite of its needs.
• Rows of small sown crops in the vegie patch, where self-sown herb Robert seedlings compete for space and water.

Harvesting Leaves

Pick once the rosette is full and leafy, in winter as well as spring and summer, because the rosettes stay green through the cold.

• Cut whole leafy stems with scissors rather than pulling, which can lift the shallow roots.
• Choose leaves free of aphids and spotting, and leave the rest of the plant growing.
• Take off any fruiting stems at the same time, before the beaks split.
• Wear gloves if you mind the smell: the sticky hairs leave it on your hands.

To dry the leaves, tie stems in small bunches and hang them in a shaded, dry place with good air movement. In good weather they usually dry in about 10 days, and they are ready when brittle. Store them in labelled, airtight glass jars in a dark cupboard as soon as they are dry; condensation inside the jar means they need longer. The strong smell of the fresh plant fades as it dries.

Traditional use and history

The name has been traced to several Roberts. A German name, Ruprechtskraut, points to St Rupert. Others link it to St Robert of Molesme, or to Robin Goodfellow, a hobgoblin of northern European folklore. A third view sees nothing more than the plant's reddish stems. British country names such as robin-in-the-hedge and robin's-flower nod to the robin, for its colour and its hedgerow home.

The smell gave it stinky Bob in English and Stinkender Storchschnabel, stinking stork's-bill, in German. Geranium comes from the Greek geranos, a crane, for the beak on the fruit. Linnaeus fixed the name Geranium robertianum in the eighteenth century, borrowing a name that the botanist Dodoens had listed two centuries earlier.

Maud Grieve left it out of her influential herbal altogether. White-flowered forms have been grown in gardens for centuries. In the wild it is not rare or threatened, and in parts of North America and Australia it is managed as a weed.

Safety

Herb Robert is sold as seed for growing, and nothing here is advice to eat or take any part of the plant. Anyone thinking of using a plant should first seek advice from a qualified health practitioner.

No state or territory declares herb Robert, and Western Australia lists it as a permitted organism. In New South Wales, council weed officers can still use the general biosecurity duty to require control of an undeclared weed. It is naturalised in Victoria, New South Wales and South Australia. Victoria's advisory list of environmental weeds rates it high risk, at an early stage of invasion. That list guides land managers and is not a legal declaration, but it is the reason to keep plants from seeding.

Common problems

Leaves turn red. Bright sun and the cooler end of the season redden the leaves and stems, which is normal. A plant red all over in summer usually wants more shade and water.

Plants wilt in summer. The roots are shallow and dry out quickly, so mulch with compost and water whenever the top few centimetres of soil feel dry.

Tall, floppy stems. Plants grow taller when they compete for space and light, so thin crowded seedlings as Thinning and Containing describes.

Plants die after flowering. This is the end of its life, not a disease (see Thinning and Containing). Sow fresh seed in autumn to replace it.

Pests and diseases

No Australian source records a pest specific to herb Robert, and established plants are seldom troubled, though three problems are worth watching.

Geranium aphid (Acyrthosiphon malvae). Small green, yellowish or pinkish aphids that live on cranesbills and pelargoniums, with colonies on the leaf stalks and undersides. Hose them off with a firm jet of water, or spray an insecticidal soap, following its label. Read more

Garden snail (Cornu aspersum) and grey field slug (Deroceras reticulatum). They chew young seedlings, most often on damp nights, though established plants are usually left alone. Hunt with a torch about two hours after dark, or set beer traps. Read more

Damping off (Pythium species and Rhizoctonia solani). Seedlings rot at soil level and topple, most often in wet, crowded trays. Use fresh mix, water less often and thin seedlings so air moves between them. Read more

Prevention first

• Sow into fresh seed-raising mix in clean cells or trays.
• Water trays from below or with a fine rose, and let the surface breathe between waterings.
• Check leaf undersides when you pick, and squash small aphid colonies before they spread.
• Clear damp daytime shelter such as spare pots and boards away from seedlings.

Tips

1. Learn the seedlings: lacy, three-lobed leaves on reddish stalks, with a strong smell when crushed, so you can pull strays long before they flower. A native cranesbill, Geranium solanderi, grows wild across much of southern and eastern Australia. It has a swollen, turnip-like taproot, so leave any plant with one.
2. Brush off boots, gloves and the dog after working near fruiting plants, because the seeds cling to passing animals by a sticky thread.
3. Label the pot with the sowing month, so you know how long seed has been waiting before you decide it has failed.