How to Grow Yellow Gentian in Australia

Yellow gentian (Gentiana lutea, family Gentianaceae) is a perennial grown for its tall stems of starry yellow flowers and its thick, bitter taproot. In cool Australian gardens it builds into a stately clump that can live for decades. First, though, its seed needs months of cold, the step most growers miss. The small blue gentians of rockeries are separate plants with different needs.

Three mistakes that matter

1. Sowing without a long cold spell. This is the commonest failure. Seed sown into warm mix, or chilled for only a few weeks, gives little or nothing. Give it about three months of moist cold near freezing first, as Germinating the seed describes.
2. Planting it somewhere hot and dry. Yellow gentian comes from cool, damp mountain pasture and will not tolerate drought or waterlogging. In a sun-baked, exposed bed it scorches and stalls, so give it deep, moist soil and shade from the hottest sun.
3. Moving it once the taproot is down. The root heads deep and resents disturbance, so an older plant dug up and shifted often sulks or dies. Choose its permanent spot early and plant it out young, with the root ball intact.

When to plant

Cold, not warmth, decides when to sow. The seed needs at least 60 and ideally 90 days of moist cold near freezing, at about 0 to 2°C. It then sprouts best with the mix between 10 and 20°C, and falls away at 25°C and above. Sow in autumn for a winter outdoors, or chill the seed in the fridge and sow in late winter.

Pots left outdoors need weeks of frosty nights, as in Canberra. In Hobart and other mild coastal gardens, where July nights average about 5°C, use the fridge. For a late-winter sowing, start chilling in May or June, about three months ahead.

Site, soil and setup

In the wild, yellow gentian grows in grassy alpine and subalpine pasture, usually on limy soils. Its main root can pass a metre in length. Copy that in the garden: an open, cool spot with deep, moist soil that neither bakes dry in summer nor lies wet in winter.

Germinating the seed

Yellow gentian seed is dormant when it falls. Its embryo is small and underdeveloped, and it grows only after a long, moist spell near freezing, like a winter under mountain snow. In one trial, fresh seed chilled for 90 days at about 1°C germinated at over 80 per cent in mild warmth (see When to plant). After 60 days of cold it gave about 40 to 65 per cent, and after 30 days, about a third at best.

The temperature of the cold matters as much as its length. In a second trial, seed held for three months at 5°C did not germinate at all. A Spanish trial chilling at 4°C also gave poor results. No source gives a home-garden rate. A packet holds eight seeds: sow them all, expect only a few seedlings, and keep the strongest.

Researchers also break the dormancy with gibberellic acid, a plant hormone, and high rates of it give weak, off-type seedlings. For how chilling works in general, see soaking, scarification and cold stratification.

When nothing comes up

• Too little cold. Under 60 days of chilling rarely works, and nor does a fridge at 4 to 5°C. Return the seed to near 0°C for another month or two.
• Too warm after chilling. A warm sill or a hot greenhouse stops germination (see When to plant), so move pots into cool shade.
• The bag dried out or went mouldy. Seed that dries during chilling stalls, and soggy sand grows mould. Keep the sand just damp and open the bag weekly.
• Buried or smothered. Seed buried deeper than a light dressing can stall, and moss stops germination in constantly wet pots, so scrape it off.
• Old or warm-stored seed. The seed loses viability quickly in storage, and older seed comes up slowly and unevenly. Sow soon after buying.
• Given up too soon. Keep an empty pot moist and outdoors through a second winter before tipping it out, because slow seed can still come up the following spring.

Sowing Seeds

Start yellow gentian in pots and plant it out young. Fridge-chilled seed goes straight into the pot. Pots sown in autumn for a winter outdoors stay put until seedlings appear. Germinating the seed covers both routes.

Sowing in pots

• Fill a clay pot with fresh seed raising mix; clay drains more freely than plastic and grows less moss.
• Press the seed onto the surface and cover it with only a very light dressing of fine mix or washed sand.
• Stand the pot somewhere cool and bright, out of afternoon sun, and keep the mix evenly moist.
• Expect seedlings over several weeks as the mix warms in spring; stragglers can take up to three months.
• Raise pots off the ground, where snails graze tiny seedlings overnight.

Sources disagree about light and depth. The store's listing says the seed germinates best in the dark under 2 to 3 cm of compost. One British plant database also says to keep pots dark, but to sow on the surface or under a very light dressing. Laboratory trials germinated the seed well on damp paper under a daily light cycle, so light does not stop it. A very light cover suits both views.

Pricking out and planting out

• Pot each seedling into its own deep pot once it is big enough to handle, lifting it with the whole root.
• Grow seedlings on in light shade through their first winter; a small rosette after a year is normal.
• Harden off before planting out (leave the pot outdoors a little longer each day for a week or two, so it adjusts).
• Plant out in autumn or early spring of the second year, before the root circles the pot, with the crown level with the soil.
• Water each plant in well; Site, soil and setup gives the spacing.

More on the move from pot to garden is in hardening off seedlings before planting out.

Care by growth stage

Steady moisture and a cool root run decide how well yellow gentian grows, far more than feeding. It comes from unimproved mountain pasture, so feed lightly and at half strength at most.

If growth stalls in poor soil, a light application of all-purpose controlled release granular (NPK around 14-5-10) scratched in each spring can help. Keep weeds and grass pulled from around young rosettes, which compete poorly.

Cutting Back

Yellow gentian dies back to the ground each autumn, so the only regular jobs are tidying spent stems and old leaves.

• Leave a flower stem standing if you want seed, and cut it once the seed pods turn brown in late summer.
• Otherwise cut spent flower stems at the base when flowering ends.
• Remove yellowed leaves in autumn once they collapse, without cutting into the crown.
• Mark the crown with a stake, because nothing shows above ground in winter.
• Leave green leaves alone through summer, because they feed the root.

Companion planting

Choose neighbours that share cool, moist soil but stay small or shallow-rooted, so the slow rosette is never shaded or crowded.

Grows well with

• Aquilegia, which likes the same cool, moist, part-shaded ground and flowers earlier in the year.
• Chives, a small clump whose shallow roots leave the deep root zone to the gentian.

Keep apart

• Mint and comfrey, whose spreading roots and big leaves crowd and shade a slow seedling.
• False hellebore (Veratrum species), a poisonous plant whose leaves look like young gentian; see Safety.

Harvesting Roots

Lift a root in autumn, once the leaves have yellowed and died back, and only from a plant about five years old or more. The root takes years to size up, so a younger plant gives little for the digging.

• Dig a trench on one side of the clump, a little way out from the crown.
• Loosen the soil with a garden fork and work down steadily, since the main root runs deep.
• Wash off the soil and slice thick roots lengthways so they dry evenly.
• Start drying the same day in a dry, airy, shaded place, because roots left damp ferment and discolour.
• Dry until the pieces snap cleanly rather than bend.

Slow drying darkens the root, while sliced pieces dried quickly stay paler. Store dry pieces in a sealed glass jar in a cool, dark cupboard, labelled with the botanical name and the day they were lifted. Read Safety before any other use of the root.

Traditional use and history

The plant's name goes back to Rome. Pliny the Elder wrote that Gentius, who ruled Illyria in the second century BC, found the plant. The genus Gentiana still carries his name. Pliny also recorded that it grew most plentifully in subalpine mountains, and that its root and juice were the parts used.

In England, the herbalist John Gerard grew plants sent to him from Burgundy in his London garden. Grieve's herbal later called it one of the most stately hardy perennials for a border.

Home-made gentian liqueur is still widely made in northern and central Italy and across the Alpine regions of France, Switzerland, Germany, Austria and Slovenia. Every bottle needs large roots from plants at least five years old, and wild stands recover extremely slowly. Collection from the wild is regulated under the European Union's Habitats Directive, and the plant is protected in several European countries.

Because the wild plant is protected, it is farmed for its root, mostly in Germany and France. In the Cantabrian mountains of north-west Spain, an orange-flowered form, var. aurantiaca, has been heavily dug. Researchers there are working out how to grow it from seed. Garden plants raised from seed take nothing from those wild populations.

Safety

Happy Valley Seeds sells yellow gentian as seed for growing. Nothing here is advice to eat or take any part of the plant. Anyone considering using a plant should first seek advice from a qualified health practitioner.

If someone collapses, stops breathing or has a seizure, call triple zero (000). For any suspected poisoning, call the Poisons Information Centre on 13 11 26 without waiting for symptoms.

Common problems

No seedlings. Usually too little cold or too much warmth after chilling; see Germinating the seed and its list, When nothing comes up.

A tiny rosette after a whole year. This is normal (see Pricking out and planting out). Keep it moist and weeded rather than feeding it harder.

No flowers after several years. Plants take about 2 to 7 years from seed to flower, and longer in dry or shallow soil. Deep, moist soil and good light in a cool district bring flowering on sooner.

Scorched, browning leaves in summer. Heat and dry soil stress this mountain plant. Mulch, water deeply and give it shade during the hottest part of the day.

A plant that dies after moving. The deep taproot resents disturbance; see Three mistakes that matter.

Pests and diseases

Few pests trouble an established clump; seedlings and wet roots carry most of the risk.

Common garden snail (Cornu aspersum) and grey field slug (Deroceras reticulatum). Both graze seedlings and young rosettes at night in damp weather. Hand-pick them after dark, including from under pot rims. Where that is not enough, scatter an iron-based snail bait thinly around the pots, as the label directs. Read more

Damping off (Pythium species and Rhizoctonia solani). Seedlings rot at soil level and collapse, most often in wet mix. Use fresh seed raising mix and clean pots. Read more

Root and crown rot (Pythium and Phytophthora species). In soil that stays wet, roots blacken, the crown softens and the plant wilts and collapses. Remove badly affected plants with the soil around their roots, clean the tools, and plant a healthy seedling only in raised, free-draining ground.

Prevention first

• Keep seed pots clear of rain and hose splash, which spread damping off.
• Scrub tools before reuse and store unused mix covered, off the ground.
• Avoid overwatering pots through cool, wet weather.
• Clear leaf litter, boards and loose pots from around seedlings, where snails shelter.

Tips

1. Sow a few seeds each year for the first two or three years. Plants flower at different ages, and a spread of ages gives flowers, seed and a root to lift in turn.
2. Keep a spare seedling or two in deep pots for another year, to replace any plant lost to rot or snails.
3. Plant it where the flower stems show from a distance: they stand above most perennials, and bees, flies and beetles visit the flowers.