Mock oranges have been grown and loved in European gardens since the Middle Ages, and it is probable that they were among the first of the old favorites to be brought to this country. In addition to very pleasing wild species, the list of kinds available today includes many lovely selections from hybrids, particularly those originated by the famous French horticulturist, Lemoine, at Nancy.
Linnaeus gave them the name Philadelphus in 1754 for reasons that seem somewhat obscure, although it is often considered commemorative of the early Egyptian ruler Ptolemy Philadelphus. Unfortunately, a similarity in names has caused much confusion between mock oranges and lilacs. Both have opposite simple leaves but the two genera are not related and have only the most general characteristics in common.
The confusion has been lessened in recent years, however, by using the name Syringa only as the scientific name for lilacs and not applying it to Philadelphus, the mock-oranges. While there are small grounds for confusing mock-oranges with lilacs in garden plantings, they do have many traits in common with the deutzias. Philadelphus shoots have soft white pith and the buds are almost always hidden underneath the leaf-stalks while Deutzia branchlets have hollow pith and buds that are clearly evident in the axils of the leaves.
As garden subjects, mock-oranges are cherished for their masses of white flowers and, in many kinds, for their delightful fragrance. This is somewhat like that of orange blossoms but has an additional spicy quality which is most pleasing. The best forms of Sweet Mock-orange, Philadelphus coronarius, the species so long grown in Europe and also most popular in this country, have flowers of unusual fragrance. This species is a native of southern Europe and Asia Minor but over the centuries it has spread from gardens and become naturalized in many countries.
Despite its southern homeland, this species is very hardy and survives extreme temperatures without injury. Its fragrance and hardiness have been valuable assets to horticulturists developing new varieties but it is doubtful if either quality has been surpassed. The named selections (or clones) among the hybrid groups offer a very useful range in habit of growth as well as larger flowers of better form. Individual plants remain in bloom about 10 days but together the various species and varieties give a season of three or four weeks during late spring and early summer. Scattered bloom is sometimes produced later in the season.
Once their flowers have finished, mockoranges add little to the garden picture except a cheerful mass of green. Their fountain-like growth is usually so dense that it makes an effective barrier even in winter, although not such a complete screen as during the growing season. As in the case of the other shrubs lacking attractive fruits or some quality which gives them distinction later in the season, they rarely merit extensive use in feature positions in gardens, but there are many places where they can be used to advantage.
As a background for flower borders, mock-oranges furnish a mass of bloom which blends well with virtually any grouping of herbaceous perennials, particularly iris and peonies. These can be grouped to form a separate picture or even to make a separate garden. In season this section would be the focal point of the garden and after the bloom has passed the distinction would pass on to other pictures – annuals, shrubs with brilliant fruits or masses of late bloom.
Mock-oranges possess one great advantage lacked by forsythias, lilacs and other subjects with brightly colored flowers, and this is that their white blooms go well with practically all colors. These shrubs are also inexpensive. Plants are raised easily and quickly by either hardwood or softwood cuttings. In fact, this is the best method of keeping named hybrid clones true to name.
Cultural Requirements
The cultural requirements of Sweet Mock-oranges and practically all this group are far from exacting. They grow vigorously and rapidly in a wide range of soils and give the best performance in those not too sandy nor dry. Even though most are naturally woodland shrubs, as garden subjects they do best in the open with plenty of sunlight and no competition from tree roots. Even so, young mock-oranges set out with small trees thrive and hold their own many years even after the trees have over topped them.
Spring is usually the most convenient season for planting Philadelphus but autumn is equally good. Actually, if cut back somewhat and given proper treatment, specimens can be planted at any time. They are heavy feeders, and hearty growth can be encouraged easily by a generous addition of complete fertilizer, preferably in late winter or early spring. In moderately fertile soils, however, fertilizing is not necessary and not desirable ordinarily, has it tends to encourage too much growth.
Except for a dwarf form (pumilus) which rarely flowers and has little to commend it, Philadelphus coronarius and its double forms make sturdy shrubs with dense arching branches 6 to 10 feet high. Occasionally old specimens kept to a few stems become tree like.
Many directions for pruning have been set forth in detail but the essential point is that whenever extensive pruning is done it should be performed immediately after the shrubs have flowered. Uneven and irregular branches can be removed at any time but the provident gardener cuts them in the pearly-bud stage and presents them to friends or rivals from whom he hopes to obtain cuttings or layers of new varieties. Systematically removing all growth older than two years and encouraging new shoots from the base insures specimens of modest size and finer bloom since the flower clusters are produced only from short lateral growths along the shoots of the previous growing season.
When mock-oranges become overgrown make a clean sweep as soon as blooming is finished. Saw off all branches four or five inches above the ground. New shoots soon push up from the stubs and make strong growth before the end of the season. Some of these usually bloom well the following spring and by the next year the plants will be completely rehabilitated. Insects and plant diseases cause mock-oranges so little trouble that they are rarely a consideration.
