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FrontRangeLiving.com -> Garden -> Patio Garden
 THE PATIO GARDEN
By Niki Hayden
By early summer, patio pots yawn with wide mouths,
bored and ready to be filled. It’s time to turn that small strip of patio
into a real garden. No actual plot, of course, but pots redeem the smallest
space and transform even a city plaza into an extravagant display.
The end of May signals the planting of pots in full swing among Colorado
gardeners. It’s true for the Denver Botanic Gardens, too, which features
hundreds of pots--terra-cotta, glazed pottery, fiberglass and cement. On a
blistery May afternoon, the pots in progress are a glazed cobalt blue for the
South African garden. Just one day after a snowstorm, horticultural
director Rob Proctor and horticulturist Lauren Springer, who’s helping to
design the garden, somberly survey a bedraggled collection. Some have weathered
the snow expertly; others have given up.
 "We don’t usually plant a garden like this," Lauren says,
glancing over the hundreds of specimens set out in an array. "But we didn’t
know what the suppliers were sending us." They’re working quickly,
deciding against tall displays but placing prickly or sculptural plants against
those with ferny, billowing foliage.
The South African plants have arrived from a garden center in California. But
all, Lauren says, have their roots firmly in South Africa. Several are familiar,
such as the annual geraniums and daisies. The Agapanthus, or lily of the Nile, is
a favorite in southern California gardens, although rarely seen among annuals in
Colorado gardens.
Most are strangers to us: bold, waxy succulents, striking spiky marvels,
blue-leaved succulents round and bulging like sausage casings, sage-colored
leaves as thin and silky as a horse’s ear. These are the architectural plants
that will hold their own in a pot—or set the drama for a grouping.
Pelargonium geraniums, one of our most popular summer annuals, originate from
South Africa. But in these pots their foliage is lime green or striated with
reddish hues. And the familiar Gazania daisy is looking decidedly at home in
Colorado. "The American West has a lot of daisies," Lauren says,
"and South Africa does, too." But the bold succulents, looking
straight out of Jurassic Park are more reminiscent of the Arizona desert.
"People really relate to the cobalt blue pots," Lauren says,
"And I love the red, orange and bright yellow colors that mix so well with
them. I love vivid colors. I’m not really a pastel person."
 I’m the pastel person," Rob says. He’s quickly
arranging groupings: a spiky, big leaved plant alongside a draping mat of yellow
daisies. "Foliage is most important," he says, but unlike last year,
he doesn’t want all the drooping foliage to obscure the pot. These blue pots,
the color and shine of lapis lazuli, must carry the day. "There won’t
be a lot going on in one pot," he says, "but all the pots will work
together."
CHOOSE PLANTS WITH SIMILAR REQUIREMENTS
How you design a pot depends on a personal preference: select groupings of
look-alike plants massed in one color or boldly contrasting. Play
textures against each other: a spiky plant next to a draping vine, which is
flowing alongside a mass of tiny flowers. None dominates, but together all
create a pleasing dissonance.
Only one rule prevails: the plants must share equal needs. So planting a
clay-loving water plant next to a sand-loving succulent won’t work. Soil, sun
and watering needs come first; creativity will follow.
All of the South African plants originate from a similar locale—the Western
side of the Cape. It’s dry and Mediterranean on that side, so they share a
slight drought tolerance. Most importantly, they prefer a "lean" soil
with some nitrogen, but little phosphorus.
That raises a red flag. Horticulturist Margaret Foderaro points out that slow
release fertilizer has been added to the potting soil. Potting halts. There’s
too much phosphorus in a 14-14-14 balanced fertilizer called Osmocote that she
generally adds to their potting soil. All of the potting soil must be removed.
Instead, she’ll bring in last year’s potting soil--well used and depleted in
fertilizer.
 But that’s not commonly done
and not recommended for
most potted plants. The best potting soil allows for excellent drainage, and a
soil texture that will allow roots to grow quickly. Fertilizer must be added by
the gardener.
Margaret recommends adding a slow release fertilizer mixed into the potting
soil in the spring. In July, she begins to add a water-soluble fertilizer to
help boost flowering into the fall.
SCRUTINIZE GROWING CONDITIONS
 To begin with your patio, look carefully at the conditions. Is it shady or
sunny? That’s the first determinate of the plants you can grow. If you’re
planting under a pergola, choose shade-loving plants. If the patio bakes in the
sun, choose sun-loving plants that also are drought tolerant. Colorado pots in a sunny location dry out quickly.
Drainage is essential. Always check to see that
there are holes in the bottom of a pot. If not, you must either drill
holes, insert a liner with holes that is placed on a bed of pebbles to absorb excess
water or use the pots strictly for water plants.
"Water deeply and thoroughly," Margaret cautions. She’ll have 100
pots to attend to in the South African garden. Some pots, like the oil jars, are
giants. Others, containing tiny cacti and succulents, are diminutive. Each is
treated the same when it comes to watering. "You have to stick you finger
down into the soil and feel for wetness," she says. And the big pots
require considerable care because the majority of soil two-thirds of the way to
the bottom may be waterlogged.
Potting soil that is reused, as in the case with Margaret’s pots, will hold
more water, so these pots may not require quite as much water as new soil.
"As the summer goes on and roots get bigger, the plants may need more water," Margaret says. When roots swell as they
grow there's less soil to hold the water. And although a simple
terracotta pot will dry out faster than plastic or glazed pottery, the method
for identifying dryness in the pot is the same—the traditional finger method.
 Tiny exotic succulents arrived with gravel mulch spread on top. Margaret
doesn’t usually apply a top dressing to most pots. The plants are too
packed together for a mulch to be of any value. The exception is with
succulents. In the chance of a summer rain deluge, the gravel will protect the
crowns from rot, Rob suggests. Margaret says she also adds gravel mulch to her
potted succulents at home. It’s an aesthetic touch, too.
WINTERING THE POTS
 The blue glazed pots have weathered through the winter. That’s not ideal,
but the DBG owns hundreds of pots. There’s not enough space to store all of
them. It helps to raise them, Margaret says, either by inserting the decorative
little "feet" that are made to sit under the pot, or placing them on
pebbles. Remove all soil. If the pot has no drainage holes, turn it upside down
so water doesn’t freeze and thaw inside the pot. For best results, winter your
pots in a garage or shed.
A VOCABULARY OF POTTING SOIL INGREDIENTS
Potting soils usually contain elements for drainage, such as perlite,
elements that hold water, such as Canadian sphagnum peat moss, and elements for
good root development, such as compost. You can design your own potting soil,
and should, if you plan to grow exotics.
In the small planting beds for the South African Garden, tests indicated the
soil was too alkaline. And there was too much compost and phosphorus. Most
Colorado plants relish such a mixture. But the South African plants do not.
Sulfur
was added for acidity. Coarse sand diluted the phosphorus. Since most of us buy
plants that prefer a neutral soil with a balanced fertilizer, the needs will
differ. But that generalization doesn't work if you want to grow succulents,
cacti or water plants. If you want to dabble in plants from another part of the
world, or plants that come from extreme climates like the desert, it pays to do
some research. For ordinary flowering annuals, it's an easier task.
 Here’s a
vocabulary list of what you can work with, followed by some simple potting
recipes.
For drainage: Perlite comes from a volcanic glass that has been high fired.
It’s extremely lightweight and provides no nutrients. What it does provide is
drainage, which is essential to preventing a plant’s roots from sitting in water.
Vermiculite is similar, but unlike perlite it absorbs water and will
eventually break down in the soil. It’s better for water loving plants.
Pumice is crushed from volcanic rock. Like vermiculite, it will absorb water.
Sometimes gardeners will add two together: perlite for the drainage, pumice for
drainage but also some water retention. Use only very coarse sand for succulents
and cacti. Fine sand, when wet, forms a sort of cement.
For root development: Canadian sphagnum peat moss (not Colorado peat) will
retain water, although if it is allowed to dry out you’ll find it difficult to
saturate. By itself, it’s not helpful. But when mixed with perlite and
topsoil, peat moss will retain water without compacting the roots of the plant.
Topsoil is the wild card for pots since it varies widely. Topsoil by itself
is too dense for potting but provides micronutrients essential to good
growth. In the garden, Nature mixes topsoil with rocks and gravel to provide
drainage. In your pots, you must amend the soil so that it will hold the
roots securely without compacting them. Experiment with a variety of potting
soils or topsoils until you find the brand that you like best.
 Here’s a basic recipe to begin with:
2 parts perlite
3 parts Canadian peat moss
2 parts topsoil
14-14-14- Osmocote slow release fertilizer according to the directions
For succulents, consider a different recipe:
2 parts pumice
2 parts potting soil
1 part coarse silica sand
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