The cultivation of perennial plants varies slightly according to the tjpo of root – that is bulb, tuber or fibrous root.
All the so-called herbaceous perennials, however, have this in common, that the T require a resting period during which the tops of the plants die down to the ground level. This resting period may be either Bummer or winter, according to the type of plant. For instance, the spring-flowering bulbs die down about Juno, rest until early autumn, and then again begin to make fresh growth.
The ordinary herbaceous perennials of the Michaelmas Daisy type rest during the winter and send up fresh annual stems in the early spring.
Spring-flowering bulbs. The soil preparation for the cultivation of bulbs can be very similar to the soil preparation for annuals. They like good drainage and therefore deep digging of the soil, some lime, and a sufficiency of plant food – but not a superabundance.
Bulbs are storehouses of food and have already taken from the soil and air all the nourishment which they need to produce one seasons flowers. After the flowers have faded, the bulb (or a new bulb in its place) will again be making good its store of plant food ready for another seasons flower, and if the soil is very poor it will be unable to do this properly, and the bulbs will deteriorate.
In a garden where fresh bulbs are pur-chased each season this is immaterial, and no trouble need be taken to manure the soil. Elsewhere it is generally best to manure ground used for spring bulbs annually, cither in spring or autumn, as desired, using either a little very old decayed manure, or bonemeal.
This will keep the ground in good con-dition for the bulbs and also for annuals grown during the summer months.
Bulb planting. Drainage, to avoid any water collecting round the bulb, is all important. That is why the amateur is usually advised to put a little sand under the base of each bulb at planting time.
The simplest way to plant – where large quantities of bulbs are used for bedding – is to scatter sand over the surface of the bed after it is dug, to lay the bulbs out in the position where they are to grow, and then to make the holes with a trowol. A little of the sand will trickle into each hole, and the bulb will rest on this. There is no need to cover each bulb individually, as raking the surface of the bed afterwards will be sufficient.
If carpet plants are used, they must be put in at the same time as the bulbs.
Bulbs do not need staking. If they are set at the right depth below the surface of the soil they will be quite firm, oven in high winds. They can be grouped according to individual taste. Formal plantings are best in very formal gardens, but in other gardens, drifts of bulbs are often more effective.
Naturalizing bulbs. Under trees or in grass, bulbs can be grown year after year without disturbance, and for this purpose cheap, mixed collections of bulbs for naturalizing can be bought. To make them look more natural, the best way is to drop them in handf uls on the surface of the ground, and to plant them where they happen to fall. In turf, individual bulbs can be planted with a trowel or with a special bulb planter. If large quantities are to be planted, pieces of turf can be lifted, the undersoil forked, and the bulbs pressed into this. The turf should then be replaced and rolled.
It should be remembered that when bulbs are grown in turf the grass cannot be mown during the early part of the summer, as unless the bulbs are allowed to die down naturally, without having their leaves cut, they will not flower another season.
Summer-flowering bulbs. In general, the cultivation of the summer-flowering bulbs is similar to the cultivation of the spring-flowering bulb3, the only difference being that the season for resting h the winter. Some of the bulbs we use for summer-flowering are not hardy enough to remain outdoors all winter in this country. Gladioli are well-known examples of this type of plant. The gladiolus root is botanically a corm, not a true bulb, but foi horticultural purposes it may be regarded as in the same clase as the bulbs.
When these half-hardy bulbs are lifted in late autumn, they are generally best stored in dr sand in a cool but frost-proof shed. This prevents them from being damaged by frost, or started into growth. By moist heat, and it also prevents the bulbs from shrivelling.
Tuberous-rooted perennials. The herbaceous border is one of the finest features of any garden, but it is also one of the most difficult to keep always attractive.
The aim of every amateur gardener should be to have a border moderately full of colour and foliage for at least nine months of the year, and to have a few plants in flower or attractive looking even in midwinter.
The majority of the fibrous-rooted perennial plants rest during the winter months, and the time to make or remake the mixed border is in consequence at the end of the summer, or in early Bpring. Most plants do not like to be disturbed more often than is necessary to keep them from becoming overcrowded, but as a rough rule it may be taken that herbaceous perennials should be lifted and divided once in three years. Certain rank-growing perennials such as Michaelmas Daisies are best lifted annually, while others are best left undisturbed for six or eight years.
The longer the plant is to remain undisturbed, the more important it then becomes to prepare the soil for it. Herbaceous borders should be very deeply dug and plenty of rotted manure should be put into the bottom spit of soil. A good dressing of lime over the surface should also be given before a now border is planted.
Grouping the plants in the border is one of the most important points. It is not sufficient to arrango the plants in a regular slope from back to front. A few of the taller plants should be brought to the front of the border in order to break the monotony, particularly if the border is of a straight-edged type.
Colour is also important, and so is the form of each plant. Heleniums and hollyhocks for instance, though green and bushy at first, tend to become leggy at the base towards the end of the season. Some plants with bushy foliage should always be grown in front of them to hide the bare stems.
Foliage is another point to consider, and some of the finest effects in a mixed border can be obtained by contrasting dark and light green, bronze and silver foliage. White flowers and patches of ornamental gras6 are also of great use in the mixed border, where colours might be inclined to clash.