Lagerstroemia shrubs receive enough water from the rains, and need to be watered mainly with low volumes of water at room temperature during periods of drought, frequent in the hottest periods of the year. Shrubs that grow in the wild have a very marked tolerance to drought, which will still limit the quality of flowering; on the contrary, the plants that are grown in pots are much less resistant to extreme conditions, therefore they need continuous watering in the hottest months of the year. In any case, the shrub strongly fears water stagnation, so it is important that the cultivation soil is well drained and that, in the case of cultivation in pots, no water is left inside the saucer.
Care to be provided
To stimulate and optimize flowering, with the production of a high number of lilac-colored flowers, the Lagerstroemia shrub requires many hours of exposure to sunlight, even if areas in dim light are tolerated. It requires calcareous or clay soils, well draining. Pruning interventions are recommended, to be carried out always in late winter or early spring (therefore never during flowering, which takes place towards the end of April), to favor the development of new branches more resistant than the previous ones; for this purpose all the parts damaged by the winter cold must be removed, and the longer branches must be shortened, even if in good health, to give shape to the shrub. The scars caused by pruning must be treated with a cicatrizant to prevent attack by fungi.
When and how much to fertilize
The plants present in the wild, being very resistant, should not be fertilized if they are in adequately fertile soil. Instead, the newly planted shrubs need to be fertilized about every 4 months, for the first few years, with small doses of mature ternary manure, containing nitrogen, phosphorus and potassium in similar percentages, with slow release; the planting must take place between March and May. In the case of a cultivated shrub, it must be fertilized even in adulthood at least once a year, always using a mature bovine or equine manure fertilizer; however, to stimulate flowering, it is advisable to give a granular fertilizer for flowering plants, rich in nitrogen. Also this fertilizer must be a slow release, in order to guarantee the right amount of substances during the whole flowering period.
Lagerstroemia: Diseases and parasites
It may happen that the lagestroemia is attacked by oidium, a disease caused by fungi that place their mycelium and their spores on the most active (therefore growing) vegetative organs of the plant, forming a white film that hinders photosynthesis and therefore brings a necrosis; in the most serious cases it can even cause the death of the plant. The products used against oidium (also defined as white mal) are mainly based on sulfur, which hinders the cellular membranes of fungi. It is recommended to carry out a preventive treatment against oidium already in winter, using sulfur-based solutions to be sprinkled very carefully on the most sensitive areas of the plant. Lagersemia may sometimes be attacked by aphids; these tiny insects can be either removed by manual methods or by using specific products.