A light pink specimen of Lagerstroemia indica in a south-facing border in my family's previous garden in Zone 6a suburban Michigan. At the time this picture was taken this plant had been growing in the garden for about three years. I originally brought it home from northern Florida, where I had bought it for $2.99 at a Walmart.
Origin: Despite its Latin name, Lagerstroemia indica is native primarily to East Asia, with a natural range including parts of China, Korea, and Japan.USDA Hardiness Zone: According to most sources, Lagerstroemia indica is hardy to Zone 7b but in my own experience the plant is hardy at least to Zone 6a. However, in much of Zone 7 and in Zone 6 or any colder area, crape myrtles will be grown almost exclusively as die-back shrubs that resprout every year from the base, whereas in warmer areas they develop substantial trunks and can grow into sizable trees. Hardiness in also dependent on summer climate, since the new wood of this shrub needs heat to ripen well. Thus the more summer heat the plant receives the more cold it can generally withstand during the colder months. This past summer the Lowe's near my parents' house in Michigan was also selling crape myrtles of a low-growing variety with deep pink flowers which were tagged as being hardy to Zone 5. I am not sure to what extent that is true but they were on sale and seeing as a regular variety bought in Florida has done fine for us in Michigan for over five years now I decided to give them a try. I guess we will see next summer if they really survived the winter any better than normal varieties.
A close-up of the flowers of the crape myrtle in my family's garden
Size: There is tremendous variation in crape myrtle size depending on the variety and the manner in which the plant is being grown. As a die-back shrub in cooler areas, Lagerstroemia indica will hardly exceed 6' (ca. 1.8m) but grown in warmer areas some varieties can reach heights of 25' (ca. 7.6m) and widths of 20' (ca. 6m).
Crape myrtle flowers in my parents' garden just beginning to open
Flowering Time: Flowering time for crape myrtles depends a lot on the local climate. In vey warm areas the plants will begin flowering in early summer and continue flowering for a good month or more, in cooler areas they will begin flowering later. Grown as a die-back shrub resprouting from the root each spring, my specimen in southeastern Michigan usually begins blooming between mid-August and the beginning of September, depending on how hot the summer has been up to that point, and continues flowering until late September or early October.
Light Requirements: Lagerstroemia indica needs full sun - generally the more sun and heat the plant receives, the sooner it will flower and the hardier it becomes.
Large specimens of Lagerstroemia indica in the park at the Florentinerberg in Baden-Baden, Germany (Zone 8a)
Soil Requirements: Crape myrtles appear to do just fine in a wide variety of normal garden soils ranging from sandy loam to clay, though in my experience they benefit a good deal from decent drainage, annual top dressings of compost and a good layer of leaf mulch.
Siting in the Garden: In areas that are warm enough - roughly Zone 7b and warmer - Lagerstroemia indica can be planted anywhere where it receives plenty of sun and its potentially sizable growth can be accomodated. Where winters are colder or summers are not very hot, care should be taken to plant this species in a very warm and sheltered spot, ideally in a border at the foot of a heat-retaining south-facing wall.
Crape myrtles grown as standards in the park between the Sultan Ahmet or Blue Mosque and the Hagia Sophia, Istanbul, Turkey (Zone 8b-9a)
Care: Ideally, crape myrtles should be planted in spring so they have plenty of time to get established before the winter but in warmer areas this is not essential. Even my first crape myrtle in Michigan was planted in August since I had brought it back from a summer trip to the South and it ended up making it through the winter more or less ok, though it failed to flower the following summer. At the time of planting, plenty of compost and bone or blood meal should be incorporated into the soil to give the plant a good start, and afterwards the area around the plant should receive a good layer of leaf mulch or wood chips to preserve moisture and to prevent extreme fluctuations in soil temperature. In warm areas, not much care is required during the growing season in first or subsequent year, apart from moderate irrigation during times of drought. However, in colder regions plants will have to resprout from the base and reach flowering size within a single season beginning their second summer in the garden and for this reason they benefit greatly from a biweekly feeding with liquid fertilizer to speed growth along. One should stop fertilizing once flowers begin to appear in late summer so the wood can ripen properly for the winter. In late fall, plants grown in Zone 7 or colder should be given a heavy leaf mulch for winter protection. I like for the mulch to stand at least 1' (ca. 30cm) - the higher the better. For this one can simply pile up the leaves over the plant or one can build a simple wire cage around the plant to keep the leaves together. The mulch can be left on the plants until mid-spring, when it should be removed very carefully so as not to damage any new sprouts that might already be emerging. They will be extremely pale due to the lack of light but will quickly begin to turn green or reddish-green once exposed to the sun. However, if the plant has not yet begun to resprout when the mulch is removed that is not necessary a reason for worry since Lagerstroemia indica can be extremely slow to leaf out in the spring. Give the plant at least a month before giving up on it or discarding it because might very well come back! In warm regions where the plant requires no special winter protection and grows into a large shrub or tree the main care to be undertaken in late winter is pruning, which is not necessary for the health of the plant can be carried out to keep it to a specific size or give it a desired shape. Since Lagerstroemia indica flowers on this year's wood, it can take a strong pruning and still flower well as long as thhe pruning is carried out in the dormant period. In much of southern Europe, crape myrtles are commonly pruned like osiers (Salix viminalis), whose flexible twigs are used for basket weaving: grown as a standard, the branches are cut back hard every winter to only a few inches/cm above the top of the main trunk, encouraging the plant to produce a head full of strong young shoots every year. The main pest problem that appears to affect Lagerstroemia indica consists of mildew and other fungal infections, though I have never had any problem with this in Michigan, and it does not appear to be too much of an issue in most warmer regions either. In general, good ventilation and plenty of sun appear to be the most important strategies in keeping such afflictions at bay. The one pest problem I have encountered in Michigan are Japanese beetles (Popillia japonica), which are very fond of the buds and flowers of this plant. In a domestic garden setting, I have found it the best strategy of defense to go around the garden collecting and destroying the beetles once or twice a day from the day when they first begin to appear. This might seem tedious but they are actually quite easy to collect off the plants since they are suprisingly slow, especially early in the day when it is still relatively cool. Besides, manual collection means that no other plants or beneficial organisms are harmed in the process. In the long run, the numbers of beetles will diminish drastically.
An old specimen of Lagerstroemia indica in the gardens of the Dolmabahçe Palace in Istanbul, Turkey (Zone 8b-9a)
Propagation: Crape myrtles can be propagated from seeds as well as from softwood cuttings taken in summer or hardwood cuttings taken in late fall. For softwood cuttings a rooting hormone might be used. By and large, however, relatively few home gardeners propagate Lagerstroemia indica themselves since it can be easily and relatively cheaply bought in most places.
A deep pink crape myrtle in the Katz'sche Garten in Gernsbach, Germany (Zone 8a)
Use in the Garden: Lagerstroemia indica is a beautiful, eye-catching flowering shrub or tree that will bring stunning late summer color to a sunny shrub border. Where the climate is warm enough, it can look wonderful as a large solitary shrub or tree surrounded by lawn or groundcovers, which highlights not only the plant's brightly colored flowers but also the pretty bark of its trunk and branches. In areas where the plant dies back to the ground in winter, it is best integrated into a sunny perennial border or a planting of relatively small shrubs not likely to overtake it while it is rebounding in spring and early summer.http://davesgarden.com/guides/pf/go/1/