Plant of the Month (November) : Big (Bracted) Gumplant

Big gumplant (Grindelia camporum)

What
an unusual year! Hot and dry – rains in
summer; it’s no wonder plants are blooming at unexpected times. Among the species that keep on flowering are
the fall-blooming sunflowers. For example, the Big gumplant (Grindelia camporum) in Mother Nature’s
Garden of Health has bloomed off and on from June to now.

Big
(Bracted) gumplant has many common names, among them California gum plant,
Giant gum plant, Field gumweed, Bracted gumweed, Grindelia, Hardy grindelia,
Rosin weed and Scaly grindelia. To add
to the confusion, the local variant (formerly known as var. bracteosa) is also known by several
previous scientific names: Grindelia robusta var. bracteosa and Grindelia
robusta var. robusta. At
any rate, we’ll leave it at ‘Big gumplant’, since that name describes it so well.

There is even debate about whether Grindelia
camporum deserves its
own taxon. Some advocate lumping it with several other California gumplants
into the broader Grindelia hirsutula
Hook. & Arn. The
Integrated
Taxonomic Information System (ITIS) lumps; the USDA Plants Database, Jepson Manual and
Calflora still accord it species status.
For this posting, we’ll side with the splitters. We’ve grown both Grindelia camporum and G.
hirsutula in the garden. And while
they have their similarities, the two (at least those available in the local
horticultural trade) look and behave somewhat differently in the garden.

Big gum plant is native to North, Central and
Southern California as well as Baja California, Mexico. In Southern California it grows along the
coast, in the Coastal and Transverse Ranges, and in the Peninsular Ranges of
California and Baja California. Locally,
it grows in the Santa Monica Mountains and once did in the seasonal wetlands
near Long Beach, the Dominguez Hills and the Palos Verdes Peninsula (including the
San Pedro/Los Angeles Harbor area).

Big gum plant grows most often in seasonally moist
areas: along roadsides, in arroyos and washes, along seasonal streams/wetlands and
other places that get a little extra winter water. It’s a member of several lower elevation
plant communities, including the chaparral
and coastal sage scrub, occurring at elevations from near sea level to about
4000 feet (1200 m.). The local soils are
primarily alluvial – either sandy or clay – and may be saline and alkaline
along the coast.

Big gumplant (Grindelia camporum): a robust

perennial/sub-shrub

Grindelia camporum is a drought-deciduous, herbaceous
perennial or part-woody sub-shrub. It quickly
grows to 2-4 feet (about 1 m.) tall and about as wide. It spreads via both
rhizomes and seed, and will fill in bare patches in the garden. It has stout, erect stems that become woody
at the base with age.

The
entire plant has a robust appearance; if you need a more delicate appearing
gumplant, try Grindelia hirsutula. Young stems are quite erect, but they tend to
lean as the season progresses. The stems
are thick – almost succulent – and are smooth and somewhat sticky with resinous
secretions.

Big gumplant (Grindelia camporum) - foliage

The
leaves are medium green, alternate and clasp the stem. They are thick, leathery and quite sticky.
Foliage and flowers all have a strong, distinctive, resin-like aroma. You’ll get to know this fragrance well as you
handle the plants. We like the scent,
but some probably don’t; smell the plant before purchasing it. The basal leaves are largest (to 6 or 7
inches), oblong and usually sharply toothed.
Leaves become smaller – and more elongated – further up the stem.

Big gumplant (Grindelia camporum): mature and

immature floral heads

Many
gardeners love Big gumplant because of the flowers. A member of the Sunflower family, Grindelia camporum produces flowers in
typical ‘sunflower heads’. The flower
heads are of medium size (one to 1 ½ inches across), with about 25 bright
yellow ray flowers (the ‘petals’) and numerous yellow disk flowers in the
center. The flowers are decorative as
only sunflowers can be.

Big gumplant (Grindelia camporum): white 'gum' covers

immature flowers

Several
floral characteristics differentiate the Grindelias from other sunflowers. First, they produce a gummy white substance
that likely protects immature flowers from disease/predation. You can see the
gum in the picture above; it disappears as the flowers mature. This
‘gum’ was reportedly chewed by children as a gum substitute in previous
eras. We’ve tried it and concluded it
was probably chewed for pleasure only by pretty desperate kids! It was
chewed as a medicinal gum (more on that below).

Big gumplant (Grindelia camporum): note distinctive phyllaries

The
second unusual feature of Gumplant flowers are the green bracts surrounding the
flower head – the phyllaries. These are particularly showy in the Gumplants,
and can sometimes be used to distinguish between gumplant species. The phyllaries
of Big gumplant are flattened at the base, but cylindrical and hooked at the
tip (see photo above). The phyllaries
bend out in this species, forming a distinctive ‘cup’ below the flower head.

Big gumplant (Grindelia camporum) spreads via rhizomes.

Here it's re-sprouting after pruning

Big gumplant begins blooming in late spring (May) and can continue
well into the fall (October or even November this year). In drier local gardens – and in the wild –
this species often loses its leaves and even dies back entirely in summer. If rains occur in summer or early fall, the
plants may green up and bloom again in fall.
That’s what they did in our garden this year.

The gumplants, like sunflowers in general, are insect
pollinated. They attract a wide range of
pollinating insects including native bees, European honeybees, pollinator flies/wasps
and butterflies. In general, gumplants
are good all-round insect plants; many gardeners use them for just that
reason. The seeds are small and
distributed by wind – if not eaten by hungry birds. The plants may move around the garden via new
seedlings planted by Mother Nature.

Metallic Green Been on Big gumplant (Grindelia camporum)

In our gardens, Big gumplant looks good for 4-5 years, then either
dies out or is ready to be replaced.
Fortunately, it is easy to propagate from seed. Collect fresh, dry seed in summer; plant in
recycled nursery containers in late fall, and you’ll have replacement plants by
next spring. Remember to just barely
cover the seeds with potting soil – they need light to germinate.

Seeds of Big gumplant (Grindelia camporum) can be collected

when dry.

You can also easily propagate from stem cuttings in summer. Just stick 12 inch, semi-woody cuttings into
one-gallon pots (we stick up to 6 per pot; insert about 6 inches deep). Keep
the soil moist, then wait for the cuttings to leaf out and produce roots. Not all will take, but at least several should
do well.

Grindelia camporum is a facultative wetland plant in
California; it usually grows at wetland margins or other seasonally moist areas. So, this plant needs good winter/spring rains
to establish and succeed. If Mother
Nature doesn’t provide, you’ll have to do the honors. Once established, Big gumplant plant is quite
drought tolerant. If you don’t mind the
summer die-back, water only occasionally (or not at all). You can
get by with watering it once or twice a month in very well-drained soils. In clays, summer water appears to decrease
the plant’s life-span.

Big
gumplant tolerates a wide range of soil textures. We’ve grown it at both extremes; the only
difference is the need to limit summer water in the clays. Plants even tolerate the salty, alkali soils
sometimes found right along the coast.
They like full sun and will become leggy otherwise.

And
they look better if cut back to about 12-15 inches when they go dormant. Some cut them back in summer (they do look a
little ratty); others wait to prune in fall.
Those in moister, colder climates (where gumplants are winter-dormant)
may want to cut back in early spring.
That’s really all the management these plants need.

Two native Longhorned Bees on Big gumplant

(Grindelia camporum)

Big
gumplant is routinely planted in habitat gardens in western Los Angeles County.
It provides nectar/pollen for insects and seeds for the birds. It looks great with other local water-wise
natives including the bunch grasses, sub-shrubs (particularly the native
Buckwheats and Salvias) and larger chaparral shrubs. Just remember, this is a large,
robust-appearing plant - place accordingly. The cheerful yellow flowers and fresh scent
make it a nice addition to many gardens. The flowers contrast beautifully with the
spring penstemons and fall asters. Some
gardeners even grow Big gumplant in their herb or medicinal garden.

Big gumplant (Grindelia camporum): 'El Rincon' garden,

South Coast Botanic Garden

The
Grindelias, and Grindelia camporum in
particular, have a long history of use as medicinal plants. In fact the genus name honors David
Hieronymous Grindel (1776-1836), a German pharmacologist, physician and
professor of botany at Riga, Estonia. Native Californians traditionally used Big
gumplant both externally (as a poultice or infusion) and internally (as an
infusion - or gum chewed as a remedy for sore throat).

A
poultice made from fresh flowers and/or foliage or an infusion of the dried plant
is applied to skin rashes, minor burns, eczema, dermatitis and other superficial
skin conditions. This external use – along with appropriate antibiotic creams
if needed – may provide relief by numbing the nerve ends. We’ll discuss how to
make and use poultices later this month.

Big
gumplant has also been used as an infusion (tea) and tincture to treat
conditions associated with excess respiratory mucous: bronchitis, coughs and
bronchial asthma. It was used as a
homeopathic medicine in the U.S. and Europe until the 1960’s, when the U.S. FDA
required such products be formally tested for safety and efficacy.

While
Grindelia tinctures can still be purchased on-line, the needed clinical trials
have yet to be conducted. Several
smaller studies suggest that this medicinal should be used with caution, and should
not be used at all by patients who are pregnant or breast-feeding, or have
kidney disease, hypertension or heart conditions. Those aged 55 and older need be particularly
careful, since kidney function decreases with age, and many of the
active chemicals are excreted in the urine.

Grindelia camporum produces a wide range of plant
chemicals including grindelane diterpenoids, balsamic resin, volatile oils, other
terpenoids, saponins and many others.
The exact modes of action for most of these chemicals are currently
unknown. However, Grindelia camporum extracts appear to slow heart rate, decrease
mucous production, and decrease inflammation both by blocking nerve endings and
possibly acting as an antibiotic.

Future
research may support a role for this plant (or specific chemicals) in the
treatment of asthma and other conditions.
But for now, if you choose to take this medicine internally, do so with proper
caution. Some combination of the chemicals is known to
interact with common medications for hypertension (high blood pressure), with
diuretics, and possibly with other medications. You should never use this medicine without
first consulting your doctor. To
read more about Big gumplant as a medicinal, see references 1-4, below. For more on making tinctures see: http://mother-natures-backyard.blogspot.com/2015/10/garden-of-health-making-tincture-for.html

In
addition to its medicinal properties, Grindelia
camporum produces other potentially useful chemicals. The resin (diterpene resin acids) produced by
the foliage glands has qualities similar to wood rosin, a product with many
manufacturing uses (adhesives, rubber, coatings, textile sizing, dyes and more).
The Grindelic resins are currently being
evaluated as cost-effective wood rosin substitutes. And if you are a natural dyer, the flowers
and foliage produce lovely, color-fast yellow and green dyes. For more on
natural dyes see: http://mother-natures-backyard.blogspot.com/2012/10/solar-dyeing-with-native-plant-trimmings.html

In
summary, Big gumplant is a robust perennial sunflower with excellent habitat
value. It is easy to grow, requiring
little care and not much water. The
flowers are lovely and attract a parade of interesting insects. The blooms are particularly
attractive when contrasted with the purple flowers of the Salvias. The plants have useful properties, including
use as medicinals and dye plants. We
hope you’ll consider Big gumplant when you need a local sub-shrub.