Three ornamental species of asparagus are of interest to the greenhouse owner: Asparagus plumosus, with fine feathery foliage: Asparagus asparagoides, the Smilax, with long green shoots; and Asparagus sprengeri, with needle-like, drooping foliage of considerable decorative value. All are splendid foliage plants for the conservatory or greenhouse, and they are easy to grow.
New plants can be readily raised from seed sown in the spring, summer or autumn in a propagating frame. A light compost is needed and a minimum temperature of 18°C. (65°F.).
The young seedlings which result are potted singly into 3-in. pots as soon as they are large enough to handle and are later moved on to 5- or 6-in. pots. The John Innes No. 1 Potting Compost is suitable for both stages.
Asparagus sprengeri is especially well suited for growing in hanging baskets suspended from the roof of the greenhouse but can also be well displayed as a pot-grown specimen. A. plumosus and A. asparagoides are plants for growing in pots or the greenhouse border. They should be trained to wires which will lead the growths up to the rafters.
Mature plants may be divided by pulling the growths apart in spring and potting each piece separately in a 5-in. pot using John Innes No. 1 Potting Compost.
Frequent spraying with water is necessary in summer and a minimum temperature of 10°C. (50°F.) should be maintained. Potting and planting should be carried out in March.
The colourfulof the Indian azaleas (forced plants of Azalea indica which is more correctly named Rhododendron simsii) can be seen in most florists’ shops in the winter and early spring, and if one has a cool greenhouse, and the plants are given a little attention, they can be kept for many years.
After flowering is over the remains of the withered flowers should be removed and the plants repotted, using larger pots if the plants are in 3, 4 or 5-in. pots, or the same size if in 6- or 7-in. pots. (In this case, some of the old compost should be scraped away.) Rhododendrons and azaleas (the latter are a branch of the large genus Rhododendron) will not tolerate lime or chalk in their compost and so a special potting mixture must be used. This can be made by mixing 2 parts of moist peat with 1 part coarse sand. The oldcrocks must be removed from the base of the plants and fresh compost worked in around the roots, firming it well with the fingers.
The peaty compost in which the plants are grown must never be allowed to dry out for if this happens it is extremely difficult to get it properly moist again. New growth soon begins after flowering and it is best to keep the plants in a warm part of the greenhouse; sprays of water over the plants will help to encourage good growth. If the tap water is hard, it is wise to use rain water for these plants.
From June to September the plants will benefit from being plunged outside in their pots. It is best to choose a position in partial shade as they do not like strong sunshine.
As the potting compost contains little plant food it is necessary to feed the plants regularly so that they make good growth and flower well. Numerous liquid or soluble fertilisers are obtainable from garden shops. One can use a dry feed of 2 teaspoonfuls of dried blood to 1 of sulphate of potash for each plant. This can be given once every 14 days in spring and summer.
As the nights become colder in September the plants should be returned to a cool greenhouse. Although high temperatures are not needed, sufficient heat should be turned on to keep the air fairly dry, otherwise the blooms will be spoiled by dampness.
When azaleas are plunged in the garden, pay particular attention to watering as the roots do not have access to the
The Indian azaleas which are imported to Britain from Continental sources to be forced for Christmas sale, are usually grafted plants. Grafting is a highly skilled job but new plants can be raised from cuttings. It takes longer to produce a sizeable plant by this method but it is a simpler procedure than grafting. Young shoots that have begun to harden at their base are selected and inserted in small pots of moist peat and sand. The pots should be stood in a warm, moist propagating frame until the cuttings have rooted, when they should be potted individually using the special azalea compost.
Plants which are taken into the home when in flower are best returned to the greenhouse immediately after flowering has finished as the dry atmosphere causes the leaves to scorch if they are kept there for any length of time.