524 



THE DICTIONARY OF GARDENING, 



SUBMERGED, SUBMERSED. Growing under 

 water. 



SUB-FETIOIiAR. Beneath the petiole. 



SUBSOIL. The layer of soil existing at such a 

 depth below the surface that it is not reached in the 

 usual operations of gardening and agriculture, i.e., from 

 about 1ft. below the surface downwards. In some 

 localities, the Subsoil is of almost the same composition 

 as the soil ; but there is usually a considerable difference 

 between them. Nor is it difficult to understand why this 

 should be the case, in so far, at least, as regards the 

 proportion of organic matter, and of the soluble foods 

 of plants, in each; for plants draw a large share of 

 their nourishment from the surface soil, and thus im- 

 poverish it of the substances used by them. On the 

 other hand, such plants as die and decay on any piece 

 of ground increase the proportion of organic matter in 

 the surface soil, but add little, if any, to the Subsoil. 

 The physical texture of the surface soil is also rendered 

 more open by the numerous roots that traverse it ; and 

 this greater looseness is much increased by the operations 

 of cultivation. The freer access of air and rain thus 

 afforded permits a more rapid decomposition of the soil. 

 The looser texture also permits rain-water to trickle 

 down till it reaches the Subsoil, carrying with it soluble 

 compounds out of the surface soil. If the Subsoil is clay, 

 it retains what is carried down in this way, whether 

 such additions are useful as food for plants, or poisonous 

 to them. Hence, the Subsoil may become rich, so as to 

 yield excellent crops when exposed to air and light ; 

 or it may be almost barren until the poisonous sub- 

 stances in it (e.g., Oxides of Iron) have been changed, 

 by the action of natural agents, such as air and rain, 

 or by the operations of agriculture, into harmless com- 

 pounds. 



The nature of the Subsoil exercises a very important 

 influence on the fertility of the surface soil. If it is 

 open and sandy, it allows the rain-water to drain away 

 rapidly; hence, there is no reserve, in times of drought, 

 to supply the place of that evaporated from the surface 

 of the soil, and from the plants thereon, which suffer in 

 their growth, or perish for lack of water. If, on the 

 other hand, the Subsoil is clay impervious to water, the 

 rain is caught, and collects in hollows, where it stag- 

 nates, with the usual ill -consequences of the surface soil 

 becoming saturated and cold, and being rendered sour 

 by the formation in it of organic acids, from the action 

 of the water on decaying plant-remains. Clay Subsoils 

 must, therefore, be broken up by the Subsoil plough, 

 or by the spade and fork; but they should be well 

 drained about one or two years before they are broken 

 up, as wet clay coheres very quickly if merely cut 

 through. Excellent results often follow the bringing of 

 the Subsoil to the surface, by means of Subsoil ploughs 

 or spades; and it is evident, from what is said above, 

 that it must be an advantage to bring within reach of 

 the roots of plant's new soil, richly supplied with sub- 

 stances required by them, and that have been used up, 

 to some extent, in the surface soil. Moreover, the new 

 soil, when exposed to the atmosphere and frost, breaks 

 up, and affords new food supplies, in addition to those 

 washed into it by rain from the higher layers. 



Where the Subsoil contains poisonous substances, it 

 should not be disturbed, unless it is possible to let the 

 ground lie fallow for a year or more. In this time, the 

 danger will probably be removed by the action of the 

 atmosphere upon the hurtful substances. To ascertain 

 whether the Subsoil is hurtful, the following method has 

 been employed : A flower-pot is filled with the Subsoil 

 to be tried, and another is filled with ordinary soil, for 

 comparison of results. Seed of the same kind is sown 

 in both, and, if the Subsoil gives a good crop, this shows 

 it to be safe, and worth bringing to the surface ; but, 



Subsoil continued, 



if the crop is sickly and weak in the Subsoil, while 

 good in the other pot, the Subsoil is evidently un- 

 wholesome in its natural state, though it may be 

 rendered fertile by exposure, for a time, on the surface. 



SUB-SPECIES. A rank higher than that of Variety, 

 but lower than that of Species. 



SUB-TROPICAL GARDEN. A term applied to 

 a portion of a flower garden or pleasure-ground devoted, 

 during summer, to stately-habited foliage plants, which 

 are arranged with a view to represent tropical vegetation. 

 Many of the plants used are natives of tropical countries, 

 and are, consequently, only available for placing outside 

 during the hottest part of the year ; but there are others 

 of stately aspect which are quite hardy, and are invaluable 

 for associating with them. Tropical plants of slow growth, 

 which have to be kept under glass all the winter, re- 

 quire a great deal more space than can generally be 

 afforded them; and as they are also very expensive sub- 

 jects to procure in the first place, comparatively few 

 gardeners have any at their command. One of the most 

 important provisions for sub-tropical plants is shelter ; 

 their leaves in most instances are soon torn, and the 

 plants disfigured, if exposed to rough winds. Shade and 

 moisture are also necessary for many Tree and other 

 Ferns and Cycads. There are numerous subtropical 

 plants which may readily bo raised from seed each spring, 

 as they are quick-growing, and form quite large specimens 

 before autumn, when planted out about the middle of 

 June, in rich soil. Of these Albizzia lophantha, Castor- 

 oil plants (Ricinus) in variety, Niootianas, Solanums, 

 Wigandias, and varieties of Zea are specially valuable. 

 Cannas, too, may readily be raised from seeds in spring; 

 but the plants are nearly hardy, and may afterwards be 

 increased by division of the rootstock in spring. Of 

 tropical plants the most serviceable are : amongst Palms 

 Chamcerops humilis, Livistona australis, L. chinensis, 

 Phoenix dactylifera, Ptychosperma Cunninghamiana (often 

 known in gardens as Seaforthia elegans), Tr achy carpus 

 excelsus and T. Fortunei. Musas M. Ensete and M. 

 superba. Tree Ferns Alsophila australis and A. excelsa, 

 Cyathea dealbata, Dicksonia antarctica. Cycas circinalis 

 and G. revoluta may be plunged in sheltered positions 

 along with the plants above-mentioned. Amongst other 

 subjects also available are Arundinarias, Bambusas, Cen- 

 taureas, Cordylines, Erythrinas, Fatsias, three or four 

 species of Ficus, Funkias, the New Zealand Flax (Phor- 

 mium tenax), Pampas Grass, &c. Other remarks on this 

 subject will be found under Garden, and the descriptions 

 and culture of plants referred to are given under their 

 respective headings. 



SUBULARIA (from subula, an awl ; alluding to the 

 form of the leaves). Awlwort. OBD. Cruciferce. A mono- 

 typic genus. The species, S. aquatica, is an annual, 

 aquatic herb, indigenous in Europe (Britain), Siberia 

 and North America. It has no value as a garden subject. 



SUBULATE, SUBULIFORM. Awl-shaped. 



SUCCISA. Included under Cephalaria and Scabiosa. 



SUCCISE. Abruptly cut or broken off at the lower 

 end. 



SUCCORY. Another name for Chicory (which see). 



SUCCOVIA (named after Professor Geo. Suckow 

 1751-1813, a botanist of Heidelberg). ORD. Cruciferce. 

 A monotypic genus. The species, S. balearica, an annual, 

 with yellow flowers and pinnatisect leaves, native of the 

 Canary Islands and the Mediterranean region, is pro- 

 bably not now in cultivation. 



SUCCUBOUS. When, in leaves crowded on a stem, 

 the base of each leaf covers the apex of the next below. 



SUCCULENT. Very cellular and juicy. 



