When we first arrived in Knysna, I purged the property of all exotics with the exception of a few azaleas and one large magnolia. I was influenced by my conscience – how could I possibly rid my garden of two of the most ancient flowering plant families on this planet?
The Magnolia family is thought by many botanists to be the most primitive of the flowering plant families. It is also considered a very ancient group, with fossil records of many now extinct species dating to the Cretaceous Period, about 60 million years ago!
Rhododendrons (Azaleas fall under this family) belong to the family Ericaceae. They have also been around for a very long time – at least 50 million years.
Every spring I look forward to their beautiful fragrant blooms. This year the azalea buds are fat and promising, and the bushes are looking lush and healthy after the welcoming winter rains that we have had over the last two months. The Magnolia came into flower in the middle of July with a promise of masses of purple blooms, but alas the Mousebirds discovered this abundant food source and within two days the tree was stripped of all its buds!
Azaleas do well in Knysna, many of these beautiful shrubs adorn gardens in the older suburbs of our town. They seem to flourish on cool southern slopes facing the lagoon; in Old Belvidere they thrive under the dappled shade of trees, putting on an amazing show in spring.
Azaleas should be planted in the spring, preferably in cool, lightly shaded sites. Full sun can burn the leaves while heavy shade can deprive them of necessary oxygen, resulting in poor blooming and weaker growth. Azaleas have shallow roots and require a well-drained, acidic soil. In poorly drained areas, azaleas should be placed in raised beds. It helps to mulch these shrubs with pine straw or composted pine barks and replenish annually. Organic matter added to the soil and an adequate layering of mulch will generally provide azaleas with sufficient nutrients; therefore, frequent fertilizing is often not required. However, if there are low amounts of nitrogen in the soil, applying fertilizer may be necessary in order to prevent a nutrient deficiency. Symptoms of deficiency in azaleas include stunted growth, smaller greenish-yellow leaves, or early leaf drop. Fertilizing of these shrubs should take place in late spring to early autumn.
Fungus and Insect Problems
Older plants may develop a lichen-like fungal growth on the older stems and branches. This is normally due to the plant getting too much moisture in summer combined with poor air circulation. This condition is more likely to be associated with summer rainfall regions. This fungus can be controlled by spraying with Copper Oxychloride (widely used in the agriculture) at the rate of one tablespoon per 5l of water once every two months during the growing season.
Insects and diseases seldom bother healthy, vigorous plants. However, rhododendrons growing in heavy clay often fall victim to Phytophthora, a deadly soil-borne fungus that causes dieback.
Pruning rhododendrons is simple? pinch young plants to make them bushy; prune older, leggy plants to restore shape by cutting back to a side branch, leaf whorl, or cluster of latent buds. Do any extensive pruning in late winter or early spring
Most magnolias grow best in moist, well-drained, slightly acid soils but neutral to slightly alkaline soils are also suitable for growth. Magnolias are adaptable to clay, loam or sand soils, but most grow poorly in wet or poorly drained soils. Well-established plants can be moderately drought tolerant.
Tree leaf veins turn yellow if the soil lacks a sufficient amount of iron, so feed trees with a fertilizer rich in sulphur and iron. Plant trees at the end of summer.
Prune immature, slow-growing trees to direct their shape – cut back deciduous magnolias after flowering in late spring to early summer and evergreens just before they bloom. Cut slants on upward-growing branches. Pruned deciduous trees develop calluses slowly, so trim deadwood and new growth by removing twigs and limbs at the base of the tree. Prune mature trees only slightly, if branches become too heavy to sustain their weight. Large cuts on aging magnolia trees will not heal quickly, if at all, and may invite disease.
Fungus and Insect Problems
Magnolias need moist, well-draining soil because over-watering causes root rot and under-watering leads to premature leaf drop. Magnolia scale is one of the most common insect problem. Treat infected plants as soon as infestation is first noticed.
Despite all the goggas that may cause problems, these plants are so worthwhile growing!