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a mad scientist, searching out plants that most people have

never seen before & figuring out how to make them perform.- The Boston Globe

…Louis Raymond ensures that trees can grow in Brooklyn…

or just about any other place where concrete consumes

the dirt and skyscrapers shield the sunshine.- USA Today

 
 

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Myrtle's easy when the conditions are right.

 
 
 
 

NEW Plants to Try!

Louis tries to capture the exact words to describe the fleeting but deep pleasures to be found in these Summer-into-Autumn incredibles.

 
 
 
 

New Gardening to Do!

Allergic to bees? You can still have an exciting garden, full of flowers and color and wildlife.

 
 
 
 

Plant Profiles

Dwarf Broom

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The new stems and leaves of Genista lydia are fresh green.  As myriad chrome-yellow flowers open, the shrub becomes, briefly, the brightest plant in the entire garden.

 

It's a densely-twiggy tuffet, hugging the ground and cascading—just a bit—when the ground falls away.

 

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The flowers are typical of the pea family, with the high erect collar—the wing—above an inverted cape-like petal known as the keel. 

 

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But where are the, uh, "parts," the stamens and pistil?  From the flower's perspective, they're the whole point of any bloom, the means to pollination and seed production.  And yet, they're hidden.

 

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An insect that alights on the keel to nose around, literally, may well get quite a surprise.  See "Quirks or special cases" below.

 

 

Here's how to grow this tough and effective groundcover:


Latin name

Genista lydia

Common name

Dwarf broom

Family

Fabaceae, the Pea family. 

What kind of plant is it?

Prostrate shrub.

Hardiness

Zones 4 - 10.

Habit

Dense and twiggy growth arches up only modestly before arching right back down again, to form a slowly-spreading flat hummock. 

Rate of growth

Medium. 

Size in ten years

A clump four feet across and a foot tall.

Texture

Twiggy, but not chaotically.

Grown for

its stems: Green, bearing small leaves that are only secondary to the plant's capacity for photosynthesis. 

 

its flowers: Chrome-yellow, as ia typical for the genus, and with the distinctive pea-family form: a pair of upper petals, the wings, are held erect over a projecting petal that's shaped like a capsized rowboat, which, conveniently, is called the keel. 

 

its habit: so densely branching and twiggy that it creates an effective groundcover.  So ground-hugging that older shrubs seem to flow over and around rocks.  If the shrub encounters a sharp drop in grade, it will cascade for a foot or so.  

 

its all-around toughness and flexibility.  Genista lydia is highly drought-tolerant, and thrives in sandy poor soil.  The leaves are retained longer in moister circumstances, but the shrub is just as happy to shed them if drought arrives.  It has a wide range of hardiness, from climates with the arctic Winters of Zone 4 to the intense and enduring heat of low-humidity climates of Zone 10, such as Mexico and flatter islands in the Caribbean, where "Winter" usually means temperatures that are merely warm instead of scorching.  Some Genista species are well adapted to another stress of hot and dry climates: brush fires.  Not only do they resprout from their roots, the fire helps germination of their seeds while it also, conveniently, burns away any shade-providing competition.  I would be surprised if G. lydia wasn't one of these "pyro-phyllic" brooms. 

Flowering season

Spring; my shrub is in flower as I write.

Color combinations

The Spring flowers are a brilliant yellow whose disruptive intensity rivals that of forsythia.  The blooms are effective for only a couple of weeks, but in Spring there are plenty of other brash flower colors in play, so be careful.  Horticultural hell—for only two weeks, but that's hell enough for me—would be Genista blooming near red or pink azaleas.   

 

Consider siting Genista amid plantings that affirm yellow instead of ignoring it.  Other yellows that are paler ensure that Genista is the star-of-the-week.  Blue and indigo—especially if the flowers that feature it also have a dash of yellow in them—would be dramatic but not cacophonous, as would burgundy.  Orange neighbors would need even more yellow to partner successfully.  I'm hard-pressed to see how red or pink could coordinate, no matter how much yellow such pink or red flowers might also incorporate.  Better, perhaps, is to provide neighbors who are not in flower at all when Genista is, and so would bring only green to the party.

 

The real challenge with Genista is that the hot-and-dry habitat where it succeeds best often features lots of exposed stone, sand, and soil—whose usual shades of tan, gray, brown, and cinnamon don't have a thing to say to forsythia-yellow.  Not a thing.  Further, I'm hard-pressed to think of any stone that might be used in residential hardscape that is a natural partner to forsythia-yellow.           

Partner plants


Genista lydia is such a sun-lover that it should be paired with horticulture that doesn't cast it into shade.  If possible, plant anything taller than it to its North or East.  But the shrub's growth is so thick, and its habit so spreading, that anything shorter could be swamped.  

 

Plants that are upright but not spreading work best.  Given the dry conditions and sharp drainage Genista enjoys, partners had best be xeric as well.  Vertical forms of whatever cacti are hardy where you garden, say, or forms of yucca that develop trunks, or ocotillo, Fouquieria splendens, whose narrow and upright cane-like stems cast little shade at all.  Ocotillo will never be hardy for me in Rhode Island, although I couldn't rule out growing it in a container, to sit out Winter in the greenhouse.  For permanent outdoor companionship, I have a couple of the dry-country species of Mahonia on my wish-list—M. nevinii and M. repens—to plant near my Genista.  Their holly-like foliage would be a great contrast, and if I'm lucky, the last of their early-Spring flowers—also yellow—might just catch the first of the mid-Spring flowers of Genista

Where to use it in your garden

If you have areas with desperately dry and loose soil that's near rocks, or hardscape that gets hot as an oven in blazing full sun, Genista will be your salvation.  If those rocks or hardscape means that you can plant Genista at the top, so much the better: It will cascade slowly down the slope, flowing farther and farther if it can root as it goes.  

 

My garden's flat terrain, heavy soil, and high water table would probably kill any Genista in weeks.  Instead, I grow G. lydia in a hypertufa trough set up on blocks, so it's safe from the occasional day-long surface-floods after heavy rains.  Safer still, the trough is full of cactus-friendly medium: A third sand, a third perlite, and a third soil.  The Genista feels right at home.

 

The green stems remain so in the Winter, so Genista is a welcome sight year-round.   

Culture

Full sun and good drainage.  Genista isn't picky about soil provided the drainage is excellent.  There's no need to enrich soil on any broom's behalf; the advantage of the quick drainage provided by lean soils far outweighs their lack of organic matter and the easy nutrition it provides. 

My Genista lydia is thriving in one of my "dry" troughs, filled with soil that's a majority sand and vermiculite. 

 

In poor soils with great drainage, all brooms grow more slowly and more densely.  This is always an asset in a family of shrubs that, in easier circumstances, are all too prone to quick growth that the shrub's roots can't anchor well, and the shrub's structural branches can't support, either.  No garden needs another broom that's leaning and splayed open.  Dwarf broom's natural habit of tight and low-to-the-ground growth precludes either splaying or flopping, so the plant's preference for lean soils makes it a handy choice for habitat that is naturally dry, well-drained, and nutrient-poor.  You can save your compost for plants that need it.

How to handle it:  The Basics

Plant in Spring, and water once or twice to help establish.  Then let the plant bask in the sun on its own.  Established plants need no supplemental water, let alone fertilizer.  In my experience, little routine care is needed thereafter.

How to handle it: Another option—or two?

If you ever need to prune to control size, do so right after flowering, to give new growth time to harden before Winter—which also gives it enough time to initiate the buds for next Spring's flowers. 

Quirks or special cases


Stop-action photography please!  The flower of some Genista species ambushes insects that alight on its keel.  The style (the tiny stem-like structure that has at its tip the stigma, the structure that receives pollen) suddenly rips up through the seam of the keel and (presumably) gives the insect a whack on its abdomen.  Lots of pollen is whooshed into the air in all the excitement, and the insect becomes well-dusted.  Is G. lydia one of these frisky broom species?

 

Although container-grown brooms tolerate being planted into the garden, they normally refuse to survive transplanting.  You don't move a broom; you rip it out and plant another one in the other location.     

Downsides

Several species of broom in the Genista, Cytisus, Ulex, and Sparteum genera are notorious invasives in the dry habitat and climates in which they succeed best, such as the west coast of North America as well as, potentially, in areas of poor and sandy soil almost anywhere.  They are usually not invasive in eastern North America because the climate is wetter and the soil is usually so moisture-retentive that other plants compete successfully.  Check with the USDA's Cooperative Extension Service to see if any species of broom are not advised for your location.

Variants

There are several score of species of Genista, and as long as they are not planted in habitat where they can become invasive, they are worth exploring.  High heat and humidity combine with often heavy soil to make the southeast United States inhospitable, but farther north, and almost anywhere in the drier West, responsibly-planted Genista species and cultivars could grace almost any garden. 

 

Alas, few besides Genista lydia seem to be available in North America.  I was unsuccessful in my attempt to grow the queen of them, G. aetnensis, in a container.  Mt. Aetna broom is the only true tree in the genus, with sparse pendulous green branches that, as usual for Genista, are only briefly in leaf.  In the Summer, they cascade with fragrant yellow flowers.  G. aetnensis is hardy only to Zone 7 B—but with global warming underway, I should try to establish it directly in my garden in a few years.

 

Genista tinctoria is the same scale as G. lydia, but with branches that are almost vertical instead of prostrate.  It's also very hardy, Zone 4 - 7, and enjoys the same sandy and sharp-draining soil.  G. pilosa has similar habit and scale to that of G. lydia; it and some other dwarf forms are available at rock-garden specialists.    

Availability

On-line.

Propagation

By seed and by cuttings.  The shrub should layer well, but because brooms are loathe to be transplanted, you'd probably have little luck cutting the daughter from the mother and moving her to a new location.

Native habitat

Genista lydia is native to the Balkans and western Asia.

 
 
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