Oxygenators: Pond Plant Group
Oxygenators-
Other Names ( Submerged Aquatics, 'Water Weeds' )
Roots in moist soil but not permanently submerged in water, leaves and flowers
clearly above the surface.
Extremely
important for keeping the water clear and for providing both food and spawning
area for fish. The underwater leaves absorb both minerals and carbon dioxide
which helps to starve the algae. Oxygen production is of much less importance,
despite the common name. Nearly always sold in bunches- a group of cuttings
held together at the base by a lead strip. Don't just drop in water. In May
or June plant several bunches into heavy soil in a shallow basket- cover
the top with gravel and place the basket at the bottom of the pond. You will
need about 1 bunch per 3 sq. ft. Some are temperamental- plant a mixture.
Callitriche-
Water Starwort
Some species produce a star-shaped leafy rosete on the surface- hense the
common name. An example is
Callitriche
verna
which is suitablefor shallow ponds- the greenleaves die back in winter. The
best one is C. autumnalis with masses of pale cress-like foliage which is
evergreen- the leaves antirely submerged and remain active in winter. A good
choice, especially of Goldfish are present, but it can be temperamental.
Take cuttings in spring and summer.
Ceratophyllum-
Hornwort
Ceratophyllum
demersum
is at or near the top of every experts recommendation list. It will grow
in sun or shade and is easily kept under control as it does not root. Planting
could not be simpler- just drop the weighted cuttings into the water. The
branched stems bear crowded whorls of dark green bristly foliage, giving
a bottle-brushed effect. In late autumn the stems sink to the bottom and
the plant overwinters as dormant buds- these produce new stems in spring.
Take cuttings or divide clumps in summer.
Chara-
Stonewort
A native plant with bristly stems and bristly leaves which may find its way
into your pond whether you like it or not. A useful feature is that it helps
to remove lime from the water- the stems become encrusted with a chalky deposit.
There are several species, including the slender
Chara
aspera
which is almost white and the grey-colored
C.
vulgaris.
The problem with Chara is that it can spread very rapidly, and is generally
no recommended, which is why it is almost impossible to find in a
supplier.
Eleocharis-
Hairgrass
Eleocharis
acicularis
is something of a novelty- it is purchased in the form of small clumps and
after planting it covers the basket or soil at the bottom of the pond with
dense tufts of grass-like leaves. The mat is generally only a few inches
high and so an underwater lawn is produced. Propagation is easy- all you
have to do is break away clumps and plant in spring or summer, but it is
generally recommended for large aquaria rather then outdoor
ponds.
Elodea-
Canadian Pondweed
Everybody agrees that
Elodea
canadensis
is one of the most efficient of all oxygenating plants but can be very invasive
and get out of control. There is disagreement, however, on whether you should
ever plant it. The best advice seems to be to avoid Elodaea if your pond
is large, but to try it if other Oxygenators fail to thrive in a small pond.
Lance-shaped dark green leaves are borne on long stems. Take cuttings in
spring or summer.
Fontinalis-
Willow Moss
Fontinalis
antipyretica
is the popular one- a native plant which bears dark green oval leaves on
narrow stems. It has a number of virtues- it is evergreen, slow-growing,
thrives in sun or shade and bears all sorts of aquatic widelife on its leaves
and stems. unlike many aquatics, it prefers moving to still water. It is
an effective Oxygenator and excellent for spawing fish- the smaller species
F.
gracilis
is a rarity. Propagate by dividing the mossy clumps in spring and
summer.
Hottonia-
Water Viloet
Hottonia palistris
is
one of the few flowering Oxygenators. The bright green foliage below the
surface is finely divided into feathery leaves, and in early summer the
flower-stalks appear. The branching stems grow about 9 in. above the water
level and bear whorls of pale lavender flowers. In autumn the foliage dies
down and the plant overwinters as dormant buds. It is not an easy plant to
establish- it needs still and soft water.
H.
inflata
is a white-flowering species. Take cuttings in summer.
Lagarosiphon-
Goldfish Weed
 Largarosiphon
major
is the correct name for the plant often sold as
Elodea
crispa.
The long stems bear tightly-packed whorls of curled leaves and it is widely
sold for aquaria. It is a good Oxygenator which is easy to establish outdoors,
but it can be invasive and get out of control. Some experts recommend
Lagarosiphon, provided that the pond is small enough for the plants to be
reached for thinning and removal, but others advise against it under all
circumstances. Lagarosiphon tends to deteriorate with age. Replace with cuttings
every few years.
Myriophyllum-
Water Milfoil
The Water Milfoils have long trailing stems which are clothed with very fine
feathery folaige. A recommended Oxygenator as it is effective and suitable
for a small pond. The leaves are greenish or brownish, depending on the species,
and some produce flowers which are borne above the surface.
Myriophyllum
spicatum
produces red-petalled flowers about 1 in. above the water level. Another
popular species is
M.
verticillatum.
Take cuttings in spring and summer. Remember that some species are not hardy,
so check before buying.
Potamogeton-
Pondweed
Potamogeton
crispus
(Curled Pondweed) is a large-leaved Oxygenator which is quite restrained
and does not become an invasive weed. The long wiry stems bear strap-like
reddish leaves which are wavy-edged and look rather like seaweed. In poor
light the foliage remains green rather than turning red or bronze. Small
pinky-white flowers appear just above the water in early summer. It is happier
in moving water than a still pond.
P.
densus
is
an unusual and hard to find species. Take cuttings in spring and
summer.
Ranunculus-
Water Buttercup
Ranunculus aquatilis
has
two types of foliage. Below the water the green leaves are finely cut into
hair-like segments- on the surface float the Cover-like leaves. In early
summer branched stems carrying white Buttercup appear- these flowers are
held about 1 in. above the surface. After flowering the plant dies back.
A good choice for ponds of all sizes as it does not get out of hand and flowering
Oxygenators are uncommon. Take cuttings in spring and
summer.
Tillaea-
Swamp Stonecrop
Tillaea
recurva
(Crassula
helmsii)
is an Australian aquatic which has been grown in Britain for over 60 years,
but the experts still can't make up their minds. Some say it is far too vigorous
for a garden pond- others claim it to be "One of the finest Oxygenators
available". The stems and fleshy leaves form a dense evergreen mass which
is easily propagated from cuttings in spring or summer. The plan appears
to be; use it in a new pond but remove the plant when more desirable types
take over.
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