Thursday, September 17, 2009

Leadwort Has Everything Going For It

Ceratostigma plumbaginoides - Leadwort
Leadwort.  The name doesn't sound very interesting, but it is an impressive ground cover providing wonderful color from spring through fall.  Its botanical name is Ceratostigma plumbaginoides (pronounced "ser-ah-toh-STIG-muh plum-bah-gih-NOY-deez").  It is native to western China.  The genus name refers to the horn-shaped stigma of the flower.  The species name means "similar to plumbago."  The plumbago the botanists had in mind is Plumbago auriculata, a South Africa native plant with light blue flowers.  Well, by golly, if you compare the flowers of C. plumbaginoides and P. auriculata you'll see resemblances in color and shape.  And, wouldn't you know it, they share the same common name, Leadwort, so there are created opportunities for confusion.

The name, Leadwort, comes from the fact that its relative, P. auriculata, was thought to be useful for treating lead poisoning.  I'm not sure how that came to be, but I'm guessing that it had something to do with the "doctrine of signatures", an ancient medical philosophy which taught that plants resembling certain body parts or other things were relevant to treating their afflictions.  So, for example, Hepatica was used to treat liver ailments because the leaf resembles, at some point in its life cycle, a liver.  Well now, if one were looking at the flowers of P. auriculata, he would notice their light, grayish-blue color, and it might occur to him that the color is similar to oxidizing lead.  Therefore, it might be good for treating lead-poisoning.

But Ceratostigma has no known medical value.  It is simply a beautiful plant.  Blue flowers are borne atop low-growing, semi-evergreen plants.  With a touch of cold weather, the foliage turns to rich scarlet, burgundy or bronze, so there is ornamental interest spring to fall.  It is most effective as a ground cover, especially under small trees and in bulb beds.  Though it grows a little tall for a lawn substitute (about 8"), it will tolerate some foot traffic when established.

Ceratostigma thrives in full sun to partial shade in USDA climate zones 6 through 9 in well-drained soils with pH ranging from 6.1 to 7.8.  It's somewhat drought-tolerant when established.  In the hottest climates, afternoon shade is beneficial.

Prepare the planting bed by cultivating at least 6" deep, removing all traces of weeds. Compacted soil should be cultivated to 10" deep.  Add enough soil to raise the bed at least 4" above the surrounding ground level. This will help to promote good drainage. Composted manure may be incorporated into the soil.  Incorporate 10-10-10 fertilizer at a rate of no more 2 lbs. per 100 square feet into the top 4" to 6" of soil. Avoid synthetic fertilizers contacting any part of your plants.

Space the plants 12" to 15" apart. Dig planting holes into the cultivated soil a little less deep than the depth of the growing container. Place the plants into the holes and back-fill, watering as you go. Press soil around the root balls. Do not cover entirely the root balls with soil. The tops should be slightly exposed. Add a top-dressing of mulch around the plants, not on top of them, about 1" deep.

Because it likes well-drained soil, plant Ceratostigma with other plants having similar cultural requirements.  Fertilize sparingly and allow soil to dry between watering.  Over-watering is the most frequent cause of failure.  To encourage dense growth on new stems, mow Ceratostigma to about 4" high in late fall or early winter.  If you use it as a ground cover for a spring bulb bed, mowing will allow the bulbs to show to good advantage.  When the bulb foliage begins to yellow and die, the ground cover growth will help to hide it.

Ceratostigma has no serious pests or diseases.  What's more, deer don't like it.  As mentioned before, the greatest cause of failure is over-watering.

Should you include Ceratostigma in your garden?  Read these reviews by people who grow it, then decide:

"Even though this reportedly is hardy only to Zone 6, if planted in a protected area (moist, well-drained, too) this is certainly hardy in our zone 5A/4B climate. Last winter was particularly rough in terms of zero-minus and no snow cover; lots of gardeners (me too) lost lots of perennials - but this one pulled through with flying colors! is so prolific as a ground cover! And the colors in late summer through fall are spectacular! The bright blue flowers against the burnt-red foliage is hard to beat!" - Karen, IL

"It is spreading which I don't like. I don't think I like groundcovers anyway."  Ginny, CA

"The only reason this isn't THE most popular groundcover is because it's herbaceous (dies back to the ground each winter.)  Other than that, it's got everything going for it - nice, lush foliage in the spring, turns a wonderful red color in the fall, and has electric blue flowers from mid-summer on." - Terry, TN

"I disagree with that lady from California.  I have a HUGE rectangular garden, with a round center that has creeping red sedum surrounding a bird bath.  In the two squares on either side of the circle are my plumbagoes.  The garden is bricked in, so they can't spread anywhere but in the garden.  Maybe she should try that?  I have them as a main focal point, and are in the biggest area of the garden.  Next to the fence are purple turtleheads? and yellow daylillies alternately, along with hostas that surround my patio.  I'll have to take a picture to show you, but yes!  The plumbagoes are the main attraction.  The bumbles (big black bees) and hummingbirds just love them!" - Ann, IL

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