Grindelia: Planting, Growing, and Care

Botany

Grindelias comprise a total of 73 species of perennial plants, annuals or undershrubs, native to North, Central and South America. They typically grow in hot and dry conditions, by roadsides, in rockeries, on dry slopes, wastelands… They are still little known in France and rarely cultivated in gardens, despite their fine ornamental qualities, with very bright flowering that integrates easily into naturalistic gardens, rockeries and dry gardens. They are generally hardy plants, capable of withstanding temperatures of around -15 to -20 °C in well-drained soil.

Grindelia belongs to the large Asteraceae family, which includes over 23,000 species, such as daisies and dandelions, but also many ornamental flowers cultivated in gardens: asters, marguerites, gazanias, sunflowers, rudbeckias, marigolds, calendulas… These plants are characterised in particular by their inflorescences in heads: what is commonly considered a single flower is in fact a multitude of tiny flowers grouped together on the same floral receptacle.

Grindelia inuloides: Botanical illustration

Grindelia was named in 1807 by Wildenow (director of the Berlin Botanical Garden) in honour of the Russian botanist and physician David Hieronymus Grindel. Grindelia is nicknamed Gumweed in English, which can be translated as “gum herb” or gum plant, alluding to the sticky resin that covers the flower buds.

Depending on the species, grindelias have a fairly variable habit, with erect or spreading stems, or even creeping (like Grindelia stricta var. platyphylla), but generally they are well branched and give the plant a very natural, lanky style. They can measure between 15 cm (for ground-covering species) and up to 1.50 m in height. Their stems are often well branched and sometimes take on a reddish hue.

Grindelias generally flower from July to October. The flower buds are covered with abundant sticky resin, making them shiny. They then open to reveal golden yellow heads, in the shape of daisies or dandelions, typical inflorescences of the Asteraceae family. What is taken for a flower is in fact an inflorescence in a head, made up of two types of tiny flowers, grouped together on the same receptacle: the ligulate flowers on the periphery, consisting of a long petal, and the tubular flowers in the centre, consisting of small petals fused into a tube.

The heads, 4 to 7 cm in diameter, are borne at the top of the flowering stems and are generally solitary, but can also be grouped in corymbs. They are surrounded by numerous imbricate bracts, long and thin, with a curved tip. Highly visible and rather decorative, they form a green, thorny swelling beneath the head, as if bristling with spikes.

Grindelias are melliferous plants, producing nectar appreciated by pollinating insects such as bees, butterflies and hoverflies. You can combine them with other melliferous plants in a naturalistic meadow (thistles, sunflowers, cornflowers, catmints, sages, vervains…), to create a garden that is favourable to biodiversity, allowing insects to feed and take refuge.

The leaves of Grindelia are long and thin, lanceolate, with finely dentate leaf margins. They measure 20 to 35 cm long and have a fairly ordinary wild plant style. They are arranged alternately on the stems (one leaf after another) and are evergreen. Like the flower buds, Grindelia leaves are dotted with glands that produce a sticky resin, earning the plant its nickname of gumweed. The stems that bear them sometimes take on a beautiful reddish hue, contrasting with the green foliage.

Grindelia fruits are oblong achenes topped with a pappus (a group of bristles allowing the seed to fly away, like a parachute), in the same way as dandelions. They are dispersed by the wind.

Grindelia robusta has medicinal properties, concentrated mainly in its resin. It has antispasmodic, anti-inflammatory and expectorant properties. It is beneficial for the respiratory system, and is said to be effective against coughs, bronchitis and asthma. The flowers are used, mainly in infusions. They can also be used in mother tinctures, capsules or homoeopathic granules.

These properties were already known to the Native Americans, who traditionally used the roots of Grindelia robusta to combat liver ailments, and the resin to treat ENT problems.

Grindelia flowers are characterised by: flower buds covered in resin (first photo), heads combining numerous small tubular and ligulate flowers (second photo), and long, thin, hook-shaped bracts (third photo). Here, the species Grindelia integrifolia (photo: Doug Murphy), Grindelia robusta and Grindelia camporum (photo: Joe Decruyenaere)

The main varieties of Grindelia

The Most Popular Varieties

Grindelia camporum

Native to California, Grindelia camporum produces bright yellow flowers from July to October, adorned with thorny bracts and borne atop ramified stems.

• Flowering time August to November
• Height at maturity 1,50 m

See the product sheet

Grindelia integrifolia

This grindelia also boasts stunning golden-yellow flower heads, with the particularity of thriving in moist soil, as it naturally grows along riverbanks, in salt marshes and wet prairies. It is ideal for coastal gardens.

• Flowering time August to November
• Height at maturity 1,50 m

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Planting

Where to plant?

Grindelias are plants that thrive in warmth: they prefer full sun, in rather dry, very well-drained soil, even sandy or stony. They grow in rather poor, low-fertility soils. These are ideal perennials for challenging soils, where other plants struggle to grow. Most grindelias dislike wet soils in winter, which could cause their roots to rot, with the exception of Grindelia integrifolia, which grows naturally along riverbanks, in damp meadows and marshes. Tolerant of salt and sea spray, it is perfect for coastal gardens.

Grindelias integrate easily into sunny rockeries and gravel gardens, alongside other sun-loving, dry-soil plants such as eryngiums, centranthus, sedums, lavenders, verbascums… They can also be used to cover a slope or incorporated into a sunny border or naturalistic garden.

When to plant?

Plant grindelia in spring, in April-May, or in autumn, around October. Plant during mild weather, avoiding frosty periods and extreme heat, which are less favourable for establishing young plants.

How to plant?

You can plant several together, but space them at least 50 cm apart.

1. Once you’ve chosen the location, dig a planting hole, two to three times the size of the root ball.
2. Feel free to mix coarse sand or gravel into the soil to improve drainage.
3. Remove the grindelia from its pot and place it in the centre of the planting hole, ensuring the collar sits just at soil level.
4. Backfill with soil around the plant and firm gently.
5. Water thoroughly.

Continue watering in the weeks after planting until they are well established and develop their root system.

Grindelia squarrosa

Maintenance

Once planted in the garden, grindelias require very little maintenance: they prefer rather dry and well-draining soil, and therefore generally won’t need watering, except during the first year after planting, and subsequently during prolonged drought. Direct the water at the base of the plant, avoiding wetting the foliage. With the exception of Grindelia integrifolia, other species are sensitive to winter moisture: you can protect them from rain by sheltering them with a transparent plastic or glass sheet.

We recommend pruning dry or damaged stems as you notice them, particularly at the end of winter. Similarly, don’t hesitate to regularly remove faded flowers, both for aesthetic reasons and to encourage the emergence of new blooms.

Grindelias are rarely affected by diseases and parasites.

If you’re growing Grindelia robusta for its medicinal properties, harvest the heads in summer, around July, at the beginning of flowering. They should be closed or just beginning to open. They then need to be dried before being used to make herbal tea.

Propagation

Grindelia is primarily propagated by sowing, but it is also possible to take semi-ripe cuttings in summer.

Sowing

Sow the seeds in late winter – early spring, under cover.

1. Prepare pots with a fine, well-draining substrate, such as a special seedling compost.
2. Lightly firm and level the surface.
3. Place the seeds on top.
4. Cover them with a thin layer of seedling compost.
5. Water gently with a fine spray.
6. Position the pots in a warm, bright spot, out of direct sunlight, ideally at a temperature between 16 and 20 °C.
7. Ensure the substrate remains slightly moist until germination.

Grindelia usually germinates within two to three weeks, though this may vary depending on temperature. Once the seedlings are large enough to handle, transplant them into individual pots.

Propagation by cuttings

You can take cuttings in summer, around August.

1. Select a healthy, semi-ripe stem, 10 to 15 cm long. Cut just below a node (the point where leaves attach to the stem), making a clean cut with a sharp, clean knife.
2. If it bears flowers or flower buds, remove them. Also strip the leaves from the lower half of the stem, leaving only a few at the top.
3. Prepare a pot with a fine, well-draining substrate, such as seedling compost.
4. Water thoroughly to moisten it.
5. Insert the stem into the substrate.
6. Firm gently around the base to ensure good contact and eliminate air pockets.
7. Place the pot in a bright, sheltered spot, out of direct sunlight.

Keep the substrate slightly moist until the cutting takes root. To improve success rates, we recommend taking several cuttings at once.

Association

Grindelia, particularly Grindelia camporum, will thrive in a sunny rock garden or scree garden. Pair it with other dry-soil plants, such as pinks, rose campion Lychnis coronaria, eryngos, and red valerian. The striking yellow flower spikes of Verbascum ‘Polarsommer’ will add rhythm and height to the planting, creating a contrast with the wild appearance of grindelia and rose campion. At the front of the border, place low-growing carpeting plants like Corsican spurge (Euphorbia myrsinites) and sedums. Also consider Mediterranean perennials such as lavender, thyme, rosemary, cotton lavender, rockroses, and sunroses. Bringing together water-wise and low-nutrient plants, this garden will require minimal maintenance!

For more ideas, check out our inspiration page “Dry Garden” as well as our advice sheet “10 Drought-Resistant Perennials for a No-Water Garden”

Scene featuring Verbascum ‘Polarsommer’, Eryngium oliverianum, Centranthus, Salvia ‘Caradonna’, Stipa tenuifolia (photo: Nathalie Pasquel – MAP – Landscape Designer Robert Myers), Grindelia camporum (photo Joe Decruyenaere), Centranthus ruber, Dianthus carthusianorum and Stipa tenuifolia

With its yellow flower heads and untidy habit, Grindelia fits perfectly into naturalistic gardens! Pair it with other plants featuring delicate, airy flowering, such as gaura, purpletop vervain, penstemons, asters, and coneflowers. Also consider ornamental grasses, such as fountain grasses and feather grasses, essential in this garden style for their light foliage and silky flower spikes. Finally, enjoy the exceptional graphic quality of wild teasel, Dipsacus fullonum.

Discover our inspiration page “Naturalistic Garden”

→ Explore more beautiful pairing ideas with Grindelia in our advice sheet!