Water plants are divided into three groups. First, there are those that live entirely under the water and are known as oxygenating. These, as the name implies, give off oxygen which is beneficial to animal life in the water. This process is counteracted by the carbon dioxide given off by the animals and absorbed by the plants. It is obvious, therefore, that the ratio between the plants and animals in the pond must be balanced.
The next group is the floating aquatics in which the whole plant floats, and the last section is the aquatics that grow with their roots under water and throw foliage and flowers well above the surface.
Plants Under the Water
Of oxygenating plants, the most important are the Canadian water weed, water milfoil, and water crowfoot.
Elodea canadensis (Canadian Water Weed) is the most popular submerged plant, growing very rapidly. It will be necessary to reduce it periodically, by pulling out handfuls.
Myriophyllum spicatum (Water milfoil)
This is another excellent submerged plant, which makes very good spawning ground for fish. It has dainty feathery foliage.
Ranunculus aquatilis (Water Crowfoot) is very attractive with floating leaves and miniature white flowers in addition to its submerged foliage. It therefore serves a double use, as it not only acts as an oxygenator but is ornamental, too. It also has the advantage of growing successfully in either swift-running water or a still pool.
Floating aquatics are less popular for the outdoor water garden than they are for indoor aquariums. Duckweed is perhaps the most well known and yet unfortunately proves a nuisance, as it increases so rapidly. It has one advantage, however, in that nearly all hardy fish are very partial to it as a green food. If it becomes a nuisance it can easily be skimmed from the surface.
Frog-bit is a native floating aquatic with a profusion of small dark, green leaves and small white flowers.
Plants for the edge of the water are very numerous and our selections must be confined to the most popular. Some require about 9 in. of water, while others only need to have their roots just covered. The following list will give a representative collection.
Acorus calamus (Sweet flag)
This is a strong-growing grass with sword-shaped leaves similar to the iris. The variegated form in which the green foliage is striped with cream and rose is perhaps even more attractive. This plant requires only a few inches of water.
Aponogeton distaehyon (Water hawthorn)
This is a very great favourite, as it is easily grown and bears sweetly scented flowers which are in bloom for a long season, often as late as October. The leaves and flowers are both floating, and suitable for any pool.
Butomus umbellatus (Flowering rush)
This is a handsome reed that bears attractive umbels of pink flowers during summer. It stands out of the water to a height of about 3 ft. and requires to be planted in water 2 or 3 in. deep.
Caitha palustris. (Marsh marigold)
This is the wild marsh marigold or kingcup which many will have seen growing wild. It flowers early in the year and bears a mass of golden yellow blossoms, which give a continuous show for three or four weeks. The leaves, too, are quite attractive and, as it is an exceptionally easy plant to cultivate, it should find a home in every pool. There is a double-flowered form if this is preferred.
- Iris pseudacorus. This is the wild yellow water iris which only requires shallow water and will grow on the banks of a stream.
- Menyanthes trifoliata (Marsh Buckbean). This is an attractive little water plant with a profusion of white flowers which, when in bud, are bright rose colour. The trifoliate leaves are also quite attractive. This is another plant for shallow water.
- Mhnulus luteus (Water Musk). An attractive dwarf spreading plant for marshy ground that bears numerous rich yellow flowers throughout the summer.
- Sagittaria japonica (Arrowhead). A handsome plant with a profusion of snow-white flowers on slender stems.
- Scirpus zebrinus (Zebra Rush). This rush has curious green and white bands up its stems; hence the name. It will grow 4 to 5 ft. high.
- Typha latifolia (Great Reed Mace). This giant reed often erroneously called bull rush, needs no description.
As with water lilies these plants all need plenty of sun and air, and a growing medium of rich loam. It is important to watch the plants, for if they tend to become overcrowded they must be reduced in quantity.
No reference has yet been made to the bog garden. It is usuaf, particularly in the informal water garden, to construct the waterway so that the water can lap over the sides here and there into bays ol good rich soil. In these, numerous plants will flourish which otherwise, if completely submerged in water, would rot away. Primulas are perhaps, one of the most important plant families suitable for bog and marshy conditions, and with these alone it is possible to get a variety of colours and flowers at most seasons of the year.
In bog gardens it is important to plant in drifts or colonies, for single plants do not give a good effect, unless it be such large specimens as gunnera. Drifts of plants alone, however, do not comprise the ideal bog garden, for a background of trees or shrubs is necessary to enhance the colorful planting and, of course, these give shelter from winds. Shrubs such as bamboos willows and dogwood are particularly suitable. Of the many bog plants the following are a few of the best.
Astilbes. These should be planted in groups, close to the water, so that their graceful feathery plumes may be reflected. They are at their best in July and August. Some of the best varieties are amethyst (purplish-rose), diamant (pure white), King Albert (pure white), and gunther (brilliant pink).
Cimicifuga racemosa
The tall branching spikes of white flowers in August and September grow to a height of 5 ft.
Hemerocallis (Day Lily)
These bloom from June to September. The foliage is long and narrow, and the flowers vary, being yellow, orange, red or apricot. They require plenty of moisture and good vegetable soil. Good varieties are George Yeld (orange, with inner petals orange scarlet), and Kwanso plena (reddish bronze).
Iris icaempferi (Clematis-flowered Japanese Iris)
The flowers are often 8 or 9 in. across and they come in June and July. Their color ranges through all shades of blue, crimson, red, white and purple. They require plenty of water in the growing season.
Lythrum salicaria
These have carmine blooms and grow from 3 to 4 ft. high. The spikes contrast well with dark foliage.
Primulas
All the members of this family require a sweet, moist and well-drained soil, with leaf-mould and peat. Some varieties well worth growing are : primula Beesiana, rosy-purple, 2 ft.; P. Bulleyana, which pass through shades of apricot, orange, and scarlet, 2 to 2 ½ ft. May and June, 1 ft.; P. siklcirrzensis, yellow, 14 to 2 ft.
Ferns by the Waterside
There are a few species of ferns particularly suitable for waterside cultivation, the most important being the royal and lady ferns. Adiantum pedatum (hardy maidenhair) has graceful feathery fronds and grows to a height of 14 to 2 ft.
Athyrium fdix-foemina (lady fern) is a very easily cultivated fern that looks very attractive in crevices of stonework. It has graceful and delicate green fronds and grows 3 to 4 ft. in height. Osmunda regalis (the royal fern) reaches a height of 5 ft. and sometimes even 8 ft. The fronds are of a delicate green shade which become bronze in the autumn.
Funkia fortunei looks attractive in clumps beside the water, with its heart-shaped leaves, veined, green, glaucous blue, or yellowy green. The purple flowers are borne on spikes 2 ft. high. Gunnera manicata (Chilean rhubarb) has huge leaves shaped rather like an umbrella.
These die as soon as a sharp frost comes, after which they should be cut off and placed over the crown to protect it. When they rot they make an excellent mulch. Rodgersias have very handsome foliage and grow best in partial shade.
