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Types of Aquatic Plantings
I've tried just about all available aquatic plants in the
larger pool but have settled on what I call "floaters".
Aquatic plants grow faster than anything else, and most types
will soon choke your pool. Water lilies, which bloom in my
garden from spring to winter, and a few other aquatics with
floating leaves, seem the easiest types to control. Even the
deceptively delicate water irises spread so quickly that after
a year they occupied almost half my pool, though some kinds
are slower spreaders. Aquatics with floating leaves, water
lilies included, also need yearly attention. Repotting is
a major project with the hardy lilies. In artificial pools,
grow aquatic plants in submerged containers so they can be
lifted out and maintained. However, heaving a plastic pot
filled with soggy soil is tricky-and messy, too.
If you follow a few simple rules, it's fall-down easy. The
rules may seem odd because all sorts of garden wisdom gets
turned upside down when you're gardening in water. For instance,
forget fast-draining soil mixes. Pot things up in the heaviest
clay soil you can find.
The Four Rules of Water Gardening
Pond gardening is easy but there are four very rules to remember.
They are: Ponds need aquatic plants, fish, and water snails
for ecological balance; Grow aquatic plants in their own pots,
in ordinary garden soil; Keep 75 percent of the water surface
covered with vegetation; and You should never need to change
the water.
Planting a Water Garden
Where to find plants. Once you have the pond, shop for plants.
Many nurseries carry them only in the summer, but many mail-order
sources are also available. Suppliers' catalogs have information
about installing a garden, pond-making supplies, snails, and
plants. However, if you know someone with a water garden,
you can probably get all of your plants free. They multiply
quickly, and every spring, gardeners compost many divisions.
Containers. Most aquatics grow best when planted in wide,
shallow containers that you submerge in the pond. I use old
plastic nursery cans and cheap plastic washtubs. Water lilies'
containers must be about 18 inches wide and 10 inches deep.
Plants with shorter stems and smaller root systems can grow
in smaller containers. Unlike aboveground containers, these
pots don't need drainage holes. If the pots have any, cover
them with two layers of newspaper so soil doesn't leak out.
(Newspaper takes years to decompose under water; even pulp
pots last a long time, like the timbers of a sunken ship.)
Soil. Forget what you've learned about potting soils. Avoid
regular potting mixes and soil amendments. They contain elements
that will rot, pollute, or float. Aquatics grow best in containers
filled with ordinary garden soil. The heavy clay garden soil
that you regularly curse over is fine for aquatic plants.
Dig some up, and break up clods to use it as aquatic potting
soil.
Some people cover the soil with sand or pebbles to keep it
from muddying the water and to prevent fish like koi from
digging up the plants. I don't. After planting, I simply soak
the soil in the container and then set the container in the
pool. It's heavy enough not to float, and the water clears
in about a day.
Fertilizer. At planting time, add a little aquatic-plant
fertilizer, especially for lilies. Cover the fertilizer with
soil, or it will escape and feed the pond's algae. I use tablets
made for aquatic plants, and place them next to the roots.
Stocking the Water Garden
Fish control algae and mosquito larvae. Ordinary goldfish
control both, though tiny, guppylike mosquito fish eliminate
mosquitoes completely. (Mosquito-control agencies often give
these fish away.) My first goldfish came from an elementary-school
carnival where my kids won them by tossing little white balls
into cups filled with the hapless fish. Pet stores sell them,
often as "feeder fish" for snakes and other reptiles
(imagine your fishes' delight when they find themselves in
a water garden instead!). If you like aquatic plants, don't
keep koi in the same pond. They'll eat everything (though
lilies usually survive).
Pest Note: If your neighborhood includes raccoons, they're
likely to climb into the pond, dig things up, and try to eat
the goldfish. In this case, the less attractive mosquito fish
are better bets than goldfish. To keep raccoons out, you must
install a single-wire electric fence, which greatly detracts
from the pond's beauty. However, not much else deters them.
Aquatic Snails. Water snails don't eat living plants, just
decaying vegetation and algae. Many garden rules are reversed
when you start water gardening: You don't want good drainage;
instead, you use crummy soil, and you actually encourage snails.
Types of Aquatic Plantings
I've tried just about all available aquatic plants in the
larger pool but have settled on what I call "floaters".
Aquatic plants grow faster than anything else, and most types
will soon choke your pool. Water lilies, which bloom in my
garden from spring to winter, and a few other aquatics with
floating leaves, seem the easiest types to control. Even the
deceptively delicate water irises spread so quickly that after
a year they occupied almost half my pool, though some kinds
are slower spreaders. Aquatics with floating leaves, water
lilies included, also need yearly attention. Repotting is
a major project with the hardy lilies. In artificial pools,
grow aquatic plants in submerged containers so they can be
lifted out and maintained. However, heaving a plastic pot
filled with soggy soil is tricky-and messy, too.
Keep about 75 percent of the water's surface covered with
vegetation in the summer to inhibit algae growth. Algae are
a natural part of pond life, and some forms always coat the
pond lining. Some shade minimizes algae. They cover my pool's
sides, but the water stays clear. Annually, after I repot
the aquatic plants, the pool briefly turns green as the algae
eat stirred-up nutrients. That's why you must never change
the water. If you do, the pond must achieve its natural bal
all over again.
Some Favorite Aquatic Plants
In my garden, water lilies (Nymphaea) start blooming when
the weather warms and last long into the fall. Their starlike
flowers are bright and magical as they float serenely on the
water's surface. I grow tropical and hardy water lilies.
Tropical Water Lilies
Most flowers are lavender, purple, or fluorescent pink. Some
bloom at night. Most tropical lilies spread widely. Small
ones are available; my favorite is 'Edward D. Uber', with
purple flowers. In my garden, this variety stays in the pool
all year. I repot them only every few years because they don't
spread like the hardy lilies, though they bloom just as profusely.
Where winters are cold, treat tropicals as annuals.
Hardy Water Lilies
These plants are hardy from USDA Hardiness Zones 3 to 11,
but whether you must move them indoors depends on the pond
or container they're planted in and the extremes of cold in
your area. In very cold-winter regions, you must take in hardy
lilies growing in small tubs; store them in a garage or basement.
In milder cold regions, a de-icer that you float in the water
and plug into an electric outlet will keep the water from
freezing. You must take in lilies grown in containers in small
inground water gardens also. Cover them with wet newspaper
to keep them moist while dormant.
These lilies survive in natural outdoor ponds if the crowns
and rhizomes are not in frozen earth under the ice in winter.
The flowers, stems, and leaves die back, but the rhizomes
remain alive. Find out the extreme maximum ice depth in your
area. If your pond is deeper than that, your plants are probably
safe. If you're not sure, take them in.
These lilies come in wonderful shades of pink, white, red,
and yellow. During a season, the tuber will creep from one
side of the pot to the other and, if the pot is too small,
grow right over the edge. To contain them, repot when the
weather warms in spring.
Hardy water lilies must be repotted every spring in a process
that's similar to potting them up initially. With a serrated
knife, saw off several inches of the growing end (the end
with the leaves). Also, trim back roots so you end up with
a block of root-filled soil about 8 inches square. The old
soil will have turned jet black. It stains everything, so
quickly wash spills off paving and other surfaces.
In a container wide enough to allow room for the roots to
spread, plug any drainage holes with two layers of newspaper.
Then plant the chunk of roots and leaves in ordinary garden
soil at one edge of the container so that it can grow across
the container. All water lilies need fertilizer at planting
time and later in the season. Little tablets specifically
for aquatic plants are the easiest to work with if you follow
label directions.
After water lilies, my favorite additions to the water garden
are (in order of preference):
Yellow snowflake (Nymphoides cristatum). Flowers on this aquatic
plant are frilled like a snowflake. Its leaves are like a
lily's but extensively marbled with green and burgundy. It's
considered hardy from zones 6 to 10. In cold-winter areas,
protect it as you would tropicals.
Water poppy (Hydrocleys nymphoides). This aquatic also has
floating leaves, and it's adorned with clear yellow poppy
flowers. North of zone 8, it's grown as an annual. Though
quite hardy in my garden, it nearly disappears during the
winter, like most aquatics.
Water hawthorn, also called Cape pondweed (Aponogeton distachyus).
In my zone 10 climate, this aquatic takes the water poppy's
place in winter. Its floating leaves are long and narrow.
The white vanilla-scented flowers are floating racemes (flower
spikes) that bloom in winter. The whole plant vanishes below
water in summer and reappears in autumn. In cold climates,
this plant blooms only in summer.
Parrot's feather (Myriophyllum aquatica). This reasonably
well-behaved aquatic has feathery green foliage that floats
on the surface between the lilies in my pond. The "feathers"
stand about 6 inches above the water and add vertical form
to the pond. If I let them, they would take over, so I hack
away at them through the season.
Floating Plants. All of the above aquatic plants grow with
roots submerged and tops floating on the water, but some aquatics
actually float, roots and all, like little boats. You could
call these "nautical" plants. The lavender-blue-flowered
water hyacinth (Eichornia crassipes) is the best known but
is far too weedy in my zone, quickly forming an armada. I
like the gray-green leaves of water lettuce (Pistia stratiodes),
another boatlike floater, and the tiny fronds of Azolla filiculoides,
a fern that happens to float.
Submerged Plants. A few plants, called oxygenators, grow
completely submerged. Supposedly they add oxygen to the water
for the fish but actually they absorb extra nutrients that
might increase algae levels. I grow only the fluffy fanwort
(Cabomba caroliniana), and must remove lots of it every few
weeks because it grows very fast.
Bog Denizens. Bog plants grow with their roots just under
the water's surface. I've planted water irises, azure pickerel
weed (Pontederia cordata), and the tall and stately red-stemmed
thalia (Thalia dealbata). I have even added cannas, which
do better in the pond than they do in my garden. All have
quickly overgrown, so now I stick to the well-behaved water
lilies and their friends.
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