False yellowhead

Family

Asteraceae

Habit

Shrub

Height

1.1 m

Spread

1 m

Growth

very fast

Lifespan

15 years

First yield

after 1 year

Hardiness

zone 8–10

Shade tolerance

full sun

Soil

Sand, Silt, Loam, Clay

Soil moisture

very dry – very moist

pH

6 – 8.5

Synonyms

Inula viscosa; Cupularia viscosa; Olivarda

Times apply to the northern hemisphere in a temperate climate and shift with altitude and cultivar.

Medicinal: False yellowhead is one of the most important folk medicines of the Mediterranean. The glandular leaves contain sesquiterpene lactones (inuloxins, tomentosin), flavonoids and essential oils with documented antibacterial, anti-inflammatory and wound-healing activity. Traditionally, crushed fresh leaves are laid directly on wounds, grazes and insect bites; an oil extract serves as a rub for muscle and joint pain, an infusion internally for stomach complaints. Recent work examines the compounds for antidiabetic and cytotoxic effects. Because of the sesquiterpene lactones, repeated skin contact can cause allergic contact dermatitis — patch-test a small area before any larger application.

Other uses: Its best-known practical use is indirect pest control in olive groves. The flower heads are attacked by the gall fly Myopites stylata, whose larvae are in turn parasitised by wasps such as Eupelmus urozonus and Eurytoma species — and those same wasps attack the olive fruit fly Bactrocera oleae in summer, by far the most important olive pest. A stand of Dittrichia along the edge or in strips between olive rows therefore keeps these parasitoids on site year-round instead of waiting for them to arrive each season. Then there is the flowering period: September to November, exactly when nothing else is in flower in the Mediterranean and beneficials and bees find nothing to eat. Studies in olive groves accordingly identify false yellowhead as one of the richest arthropod reservoirs in the system. Traditionally the sticky shoots were also hung indoors as flypaper — hence the Spanish name mosquera.

Full sun and heat, otherwise practically undemanding. It grows on sandy, stony, clayey, calcareous, saline and even contaminated soils at pH 6 to 8.5, and is extremely drought-tolerant once established. What it will not take: shade, waterlogging and hard frost — hardy to about -8 to -10 °C (USDA 8-10), so in Central Europe only in wine-growing areas and there with winter protection. Do not feed it; on rich soil it goes soft and flops. The main management point is containment: it self-seeds heavily and is allelopathic towards neighbours. Place it deliberately — as a strip along an olive grove, along an embankment, as terrace reinforcement — and cut off the seed heads wherever spread is unwanted. Cut back to the ground in late winter. Idea for the olive grove: one continuous Dittrichia strip per 5 to 10 olive rows, cut in sections in late winter so part of the stand always stays uncut and the parasitoids can overwinter.

Sowing is the easiest route, and seed is abundant: collect the feather-light achenes in late autumn and sow shallowly in autumn or early spring — a light germinator, press in but do not cover. Germination at 15 to 20 °C within two to three weeks, at a high rate. Direct sowing in situ works well because the taproot forms immediately and transplanting becomes difficult from the second year. Semi-ripe cuttings in late summer also root reliably. Using wild stands: cut a flowering shoot in autumn, dry it head-down over a paper bag, scatter the seed in spring. Cutting the subshrub back to the ground in late winter rejuvenates it and stops it going bare from below.

False yellowhead is among the most valuable beneficial-insect plants of the Mediterranean. Its flowering period from September to November fills the gap when no other forage is available in the south — honeybees, wild bees, hoverflies and butterflies use it intensively. At the same time it acts as a year-round reservoir for parasitoids and predators: gall flies, ichneumon and chalcid wasps, ladybirds, lacewings and assassin bugs overwinter in and around the stands. Through the galls of Myopites stylata it maintains parasitoids that attack the olive fruit fly in summer. The sticky glandular hairs passively trap small insects. Goldfinches and other finches eat the seed in winter.

A subshrub that grows exactly where nothing else will: raw soils, road embankments, rubble, saline and even heavy-metal contaminated ground. The deep taproot finds water when everything else has dried out, holds embankments together and makes it a standard species for restoring landfills and mine sites. Two traits make it interesting for permaculture in the south. First, the flowering period from September to November — the last major nectar and pollen source of the year, when bee colonies and beneficials would otherwise starve. Second, its role as a beneficial-insect reservoir in olive groves that keeps the olive fruit fly in check. The price: it self-seeds heavily, is allelopathic and can take over a fallow on its own — so use it deliberately in strips and margins, not in beds.

Throughout the Mediterranean from Portugal to the Levant, North Africa and Macaronesia; it has been spreading northwards and upslope for decades and counts as a climate-change winner. Introduced and locally invasive in Australia and parts of North America. In Central Europe so far only casual.

Pioneer of open, disturbed and dry ground: embankments, road and field margins, fallows, abandoned olive groves, stream gravel, landfills and mine sites. From sea level to about 1,000 m, on almost any soil — sandy, stony, clayey, calcareous, saline or heavy-metal contaminated.