Crape Myrtles Cultivation and More Information:
Popular in hot summer climates they thrive in the most torrid environments- in fact they require a certain amount of hours above 85ºF to cease growing and commence flowering. Luckily our climate there is adequate heat for many cultivars to thrive and bloom. The amount of heat that each cultivar requires is distinct. And those that we have chosen will bloom annually with correct siting and cultural care in an average warm summer. This means you can get a tree to flush into bloom in July and remain blooming for at least 2 months. Nearly all cultivars will re-bloom once the main flowering has commenced. Few trees can match that. Crape myrtles adore full all day sun and will not deal with shade in any capacity. Full all day sun in a hot position and consistent summer water ensures excellent performance.
Water correctly- its easy
We cherish Crape Myrtles for their ability to bloom for the last half of summer. Few trees bloom then and the vivid colors are both spectacular and long lasting. When a cultivar has received adequate heat it will stop growing and commence blooming. This can happen very quickly- often after a heatwave in combination with regular irrigation flowers and growth will happen in just a week or less. Crape myrtles are drought adapted but this will be at the expense of growth and bloom. The best way to determine if they are adequately hydrated is that the leaves will be glossy, shiny, and lustrous and growth will be robust. The most CRITICAL time to water Crape Myrtles is just as they are leafing out and for a month after that. These are summer rainfall trees and they do best when consistent spring moisture is followed by water into summer. Often, if you water during dry springs and early summer trees will happily commencing blooming and continue for the duration of summer. Drought stressed trees will NOT BLOOM WELL or not bloom until September. If a crape myrtle has become drought stressed its leaves will first lose their glossy luster and appear matte long before wilting. At this point the tree will stall in its annual growth and will probably not bloom. If you have had problems with your crape myrtle not blooming well try watering it consistently from the emergence of leaves well into summer. A thick layer of mulch will help as well evening out soil moisture and maintaining consistent growth. To re-hydrate a drought stressed tree simply put the end of the hose near the base of the trunk and turn the water on very lightly and soak for 3-4 hours. To be efficient create a basin around the base of the tree and fill it repeatedly. This will direct water directly down to the roots. Done in the heat of summer this can wake the tree in just a week or two. And flowers will often appear. Consistency above all else makes them happy. Put them on a regular- deep but infrequent watering regime and you will be amazed at the results.
Companions for Crape Myrtles
Crape myrtles are summer rainfall trees that means they appreciate regular irrigation during summer. This makes them ideal trees for the back of a border or for gardening beneath. Remember that Crape myrtles don’t leaf out until the middle of May in most years. This makes them great for underplanting such shade loving perennials as Hellebores and Fuchsias. Just as these plants require protection from hot sun the leaves on Lagerstroemia arrive for a cooling shade layer. All Crape myrtles require as much sun as possible. They are completely intolerant of shade in our climate- so at least 6 hours of sun per day is ideal. They also appreciate and tolerate very hot conditions, combined with regular irrigation this can also cause them to bloom earlier and longer. They can tolerate they heat of south facing walls as well as asphalt and concrete. Its best to not plant them against east or west facing aspects as lack of sir circulation and a half day of shade can produce mildew on susceptible cultivars. On a west or eastern aspect locate at least 10′ away from wall with hot sun and good air circulation. Crape myrtles are excellently sized trees for small gardens. They range from true dwarves (just 4′ tall ) to 25′ + shade trees with all sizes represented between. They are a similar size and dimension to many cultivars of Japanese maple and they make great companions with identical cultural requirements. Other companions are Hibiscus syriacus Rose of Sharon which blooms at the same time as well as many late perennials. Asters make a very flowerery show at the base of crape myrtle cultivars well into autumn.s
There really is no completely incorrect way to prune crape myrtles. They bloom on wood from the current season so errant clipping will not eliminate flowers. For tired and neglected trees you may prune back the strongest leaders by 1′-3′ but no more. Pruning stimulates these trees to grow vigorously and bloom. Avoid stumping them back to big trunks. This harmful method of pruning is called “Crape Murder. Unfortunately, It results in mis-shapen scarred trunks and rank weak growth which is unable to hold the huge heavy flower trusses. They droop and can snap and makes rare summer rain destructive. It also destroys the natural grace and character of each cultivar. On average little pruning is necessary aside from training or shaping the tree in the habit it will naturally attain. Pruning of crape myrtles is best done in early spring before plants have broken dormancy. It is common to remove the lower limbs of all Crape myrtles. This attains two things. It reveals the beautiful sinuous, colorful trunks as well as improving air circulation which they all very much appreciate. Poorly ventilated crowded trees especially in too much shade can result in the disease powdery mildew. The cultivars that we grow are all naturally resistant to this disease but correct cultural conditions reduce this risk. Crape myrtles are heat loving trees and often they are one of the last trees to leaf out in spring. They require at least three days above 70ºF to wake and show bud break. This can be as early as April or as late as early May. Once warm weather arrives in earnest they will grow steadily. No tree looks more dormant than a Crape Myrtle- heat will arrive and so will leaves- be patient.
Bark and cold hardiness- the correlation
Exfoliating showy bark is one of their most admirable traits. Each individual cultivar has its own distinct coloration. Crape Myrtle (fauriei) hybrids inherit that species amazing red/ orange/ muscular showy exfoliating bark- hence the amazing display of ‘Natchez’, ‘Osage’, ‘Pecos’. A feature as striking as flowers or fall color. Lagerstroemia on average begin losing their bark at three or so years after planting. Some cultivars earlier (‘Yuma’, ‘Hopi’, ‘Pecos’) when younger and straight L. indica varieties exhibit this trait a little later. Once a Crape Myrtle begins to exfoliate its bark (this happens in early summer) the tree has essentially achieved its full hardiness to cold which is 0ºF or quite a bit lower in established trees. The exposed new bark remains showy through the following spring. It should be noted that the species L. fauriei which was crossed with L. indica- the common species also have imparted resistance to disease. New L. indica selection on the market have also been selected for resistance. None of the varieties we grow susceptible to this disease and all have proven to be cold hardy in the worst winters.
They like it hot
Crape myrtles require as high amount of heating calories during the summer not just for flowers and robust growth but to ensure that they are cold hardy for the following winter. Cool, shady, or cold gardens will not achieve this and even hardy trees can suffer cold damage at relatively mild temperatures. This is common in cooler rural areas where summer time lows rarely stay above 60ºF. In these locations careful attention must be paid to siting. Near a hot, south facing wall, or the reflective heat of asphalt paving. Anywhere you would be distinctly uncomfortable yourself on a hot day. They make excellent urban heat island occupants- absorbing the heat that is discharged at night from brick, glass, and concrete. This is a trait we should use to our advantage.
As street trees:
Crape myrtles as street trees: There has been great interest in the larger cultivars as street trees and in fact they have become popular in Portland and are being planted more and more. The largest varieties makes fantastic street trees and even the mid-sized cultivars (10-20′) eventually develop even greater stature than such commonly planted trees as Flowering Plums (Purple leaved plums) and that beautiful but ubiquitous tree the Paper Bark Maple (Acer griseum). Most street trees should be installed in a “standard” form. That is a single trunk where branching is limited to 5′-6′ above soil level. The city has yet to cotton to multi-trunked street trees but you can always ask. The two most popular cultivars as street trees as of now are ‘Natchez’ (white) and ‘Tuscarora’ (coral pink)- approximately 22′ + tall and eventually forming a spreading crowns respectively. In reality there are even better cultivars for this detail. 25’+ ‘Wichita’ would be a phenomenal street tree with an incredibly long season of bright lavender flowers. The robust shade tree ‘Muskogee’ with lavender pink flowers for almost three months in summer is also an ideal choice. ‘Dynamite’ (to 20’+) (brilliant cherry red) has already been used as a street tree and should be more often. Other candidates that fit the size and desired scale are ‘Sarah’s Favorite’, (white), ‘Osage’ (pink) ‘Zuni’ (rosy purple) ‘Pecos’- as a standard (pink) ‘Yuma’ (lavender) ‘Twilight’ (soft purple). All of these will eventually form respectable street trees. We will strive to grow more as standards to increase the home owners choice in this application. Make sure to water ALL street trees thoroughly and regularly through the first SEVERAL dry summers. This rapidly expands their root system and speeds growth dramatically. Build a basin around the base of the tree and mulch deeply with bark or compost to conserve soil moisture. Do NOT let grass or weeds grow up to the trunk of the tree (any tree that is getting established) these weeds will rob the surface of the soil of moisture and can result in drought stress and anemic growth for the tree. Water, water, water.