A Forest Bowl for Bog Plants
I should've gotten pictures of this when it had purple blossoms on the top, as this late-autumn portrait already shows die-back & decay, but what the heck, it looks interesting enough even at the start of winter.
The purpose of an aquatic forest bowl is to create, in a relatively small gardening area, a visual "surprise," a self-contained environment within an environment, such as can give the impression of gardens larger than they really are. We've other small "contained environments within environments" such as the rainbarrel corner, the birdbath shade garden, & A Tiny Rockery shoehorned between a staircase & the fireplace chimney.
An aquatic forest bowl is a nice way to have running water in the garden without going the more elaborate route of a pool, especially since prefab pools are ugly as all get out no matter how desparately their owners try to disguise them, whereas a perfectly constructed pond with rocks & concrete would be too much of an undertaking for my limited skills. A bog bowl has the benefit of being movable, removable, or changeable if I get tired of it sitting there. Indeed, since this photo was taken, the forest bowl was taken apart, moved elsewhere & half buried, with a spill-bowl above it to create a waterfall. I can always move it again, too, should mood provoke me to do so.
In summer I have to refill the bowl every couple days because of evaporation, but the rest of the year it evaporates slowly enough that rain refills it, & upkeep is minimal. At least one goldfish or a half-dozen tuffy-minows are a nice addition, as they gobble down any mosquito larvae & their poops automatically fertilize the plants.
When this pic was taken, tbe bowl sat between a sump pump & a basement window near the Black Swan Beech. The sump pump was an eyesore before we had stuff planted all around it, but now its lid is as attractive as any picnic table, or in our case a garden work-table.
In this first set-up for the forest bowl it had a very big "strawberry planter" sitting in the middle of it, with a fountain-pump forcing water up through the middle, cycling water back downward through soil, then gravel, & the roots of an assortment of bog plants. The water spilled out of the lower side-pockets of the planter, providing a gentle running water sound. Cycling the water through such a strawberry urn or planted spill-bucket functions in much the same way as an undergravel filtration system in an indoor acquarium. Healthful bacteria break down impurities in the water as it passes through the gravel & humous. Goldfish urine & poops & rotting vegetation are thus broken down into a good fertilizer for the swamp-plants in the strawberry urn, & the water around the base is invariably crystal clear.
The strawberry planter had several swamp plants growing on all sides in the pockets that poked out from the main pot. Variegated dwarf flag (Acorus gramimeus "Variegata") forms hardy clumps of striped grass. Native Pickerel Rush (Pontederia cordata) has purple blooms in summer. Chameleon Houttuynia (Houttuynia cordata "Chameleon") has multi-colored leaves; it grows equally well on land or in shallow water & spreads by thick underground runners, & easily becomes invasive & troublesome if not barriered or potted. So too Golden Creeping Jenny (Lysimachia nummularia "Area") can be invasive in a garden but when confined to a pot within a forest bowl is perfectly restrained & in spring & summer spills down the side of the pot into the water.
Floating on the surface was Water Velvet (Salvinia rotundifolia ) which has chained pairs of furry leaves less than an inch oval, & feathery water-cleaning roots. To be specific it has no real roots but has an additional submerged leaf the fur of which serves a purpose similar to roots. The fur on the two floating leaves function differently in holding air & keeping the surface of the floating portion dry. Though it doesn't look like a fern, that's what it is. It is sometimes called Water Fern, Butterfly Fern, Eared Watermoss, Floating Moss, Water Spangle, & other popular names. A variety called Salvinia molesta has gotten loose from the aquarium trade & is becoming an invasive weed in warm areas of the United States. In really cold places S. rotundifolia will die in winter & not return, but in our temperate area it returns if its pool has even moderate protection from long freeze. Despite that goldfish love to eat it, fusg seem to prefer that which has finished reproducing & is softening up to die. In summer the young tough mini-pads will quickly cover the whole surface of the water if the waterfall didn't push it aside a bit, & if I didn't skim handfuls to toss around in the garden as mulch.
A Japanese iris beside the bowl is barely visible in the picture, its tips in the lower lefthand corner. This became very large in the following spring. Behind the bowl, where the ground is sometimes a little dry, there is a groundcover called Creeping Raspberry (Rubus calycinoides). This year when I decided to move the forest bowl to make room for an outdoor table & chairs, we added a blue potato vine in the back corner, for which Granny Artemis built a beautiful high trellis. So this area around the Black Swan has been in considerable flux, & the present page is more or less a record of what was there before 2002.
The main bog plant was the one growing out of the top of the strawberry urn, the Pickerel Rush which has lavender-blue flower spikes in summer & autumn, & arrowhead leaves of considerable interest all by themselves. It dies back in winter & returns good as new the next spring. It is one of the drawbacks of a bog bowl that few suitable plants are evergreen, except for flag or reedgrass.