Texas Azalea


Posted by Julien Stern | Posted in Plants | Posted on 22-02-2013

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Texas azaleaAzaleas have a reputation of being quite exacting plants in their growing requirements – yet few vistas can surpass a garden or a flower bed of azaleas in full bloom. And, well, rumor may be exaggerated sometimes.

While modern horticulture has created hundreds of variations of this spectacular and delicate shrub (each with different tolerance thresholds to the various conditions that characterize a given garden), there’s this one among them that is especially fit for our Texas gardens – for the simple reason that it’s native to our area.

The name of this beautiful lady is Texas azalea, and, if taken care of properly (which is not at all difficult, as we shall see in a moment), she’ll be embellishing your outdoors – with her dainty white flowers, her lush deep green foliage, her lemonish, slightly spicy fragrance, her discreet yet powerful presence – like few other plants can. Yes, you can call me a bit prejudiced here…

So, let’s get down to exploring a few facts about Texas azalea and its optimal growing conditions:

Texas azalea (rhododendron oblongifolium)

The natural habitat of Texas azalea is the sandy, organically enriched, slightly acidic (pH 4.5-6.0) soil that can be found in pine forests, wooded stream banks, and boggy areas. This is a light soil, unlike the heavy clay that abounds in several Texas areas and can cause root rot (indicated by yellowing, wilting foliage and collapse of the plant) – but that can be amended with proper preparation of the ground.

Incorporating peat moss, bark mulch (especially pine bark), and compost rich in leaves down to a depth of 12” will increase acidity of the ground and improve aeration, so much needed by the shallow root system of Texas azaleas. Constructing raised flower beds will work fine with these plants, although it’s not a sheer necessity, if preparation is done correctly. Another way to make pH levels more suitable is to add agricultural sulphur.

Texas azaleas don’t like limy, alkaline soil either, as it can lead to iron deficiency and, subsequently, to chlorosis, characterized by yellow leaves with distinct, dark green veins. However, there’s a number of ways to treat chlorosis such as:

  • applying copperas (iron sulphate), which is a soil acidifier and will allow iron to return to an available form;
  • applying granular iron to the soil; some gardeners simply drive iron nails or iron shards into the ground, waiting for them to rust and release the substance;
  • applying a foliar spray of an iron compound – this method will have much shorter residual action, though, and it must be repeated frequently.

Sun exposure
Texas azalea’s natural habitats are very telling of the kind of sunlight it prefers: partial sun or filtered light beneath trees with high limbs. This means that azaleas do not fare well in places that receive excessive amounts of our hot Texas sun, especially during the afternoon hours. Excessive exposure to sun will initially bleach the leaves (due to the deterioration of chlorophyll) and then burn them, with brown spots and edges appearing on the foliage.
On the other hand, complete shade invariably leads to lanky growth and to insufficient blooming. Plant your Texas azaleas in a spot that receives afternoon shade – the east or north side of your home are usually the best picks. Another advantage of optimal sunlight conditions is that they will help increase the plant’s hardiness to low temperatures.

Texas azalea is generally spread in regions included in the USDA hardiness zones 7 to 9 – in other words, areas that manifest lowest temperatures of 0-25º F. It is also tolerant of high heat. The secret to always remember is to keep the plant’s “feet” cool, and this is accomplished by adequate mulching (2″-3″ deep).

Apply mulch in spring, just after the blooms fade. This will help lock moisture in the ground, and it will also protect the roots from summer heat. On the contrary, avoid mulching in fall, as this will hold heat in the soil, thus delaying the onset of dormancy and increasing the odds for winter damage.

Texas azalea

Texas azaleas love moisture, but need a well-drained soil to develop properly. Try planting them on a slope: besides seeing your shrubs thriving, you will have the additional advantage of preventing soil erosion.

Watering the azaleas is finding a delicate balance between keeping the ground moist, but not soggy, without letting it get too dry either. When the plant is new, check the soil around it every day to ensure it is slightly damp. Mature plants need about 1″ of water per week during cool seasons, and more during hot summer spells, as azaleas have shallow root systems that dry out quickly. Curling, twisting, or drooping leaves are a certain sign of water deficiency.

Prefer watering deeply and infrequently rather than in regular small amounts. Apply mulch to prevent evaporation, and amend your soil with compost to improve texture and water holding or draining capacity. Avoid drip irrigation, as it will benefit only a very restricted area of the widely spread roots.

Texas azaleas also absorb water through the foliage, which means that you can water both roots and leaves. In this case, prefer to water early in the morning in order to avoid leaving moisture on the leaves, thus preventing the onset of fungal diseases.

The best season for pruning Texas azaleas is during the first two to three weeks after flowering is finished, and definitely before budding begins around late July. Any pruning that takes place after that point must be done with major attention, as it will affect the overall shape of the plant and the flowers of the following blooming season.

Don’t be afraid of performing minor shaping of your plants throughout the growing season; this will help the shrub maintain its fullness and compact shape. Just pay close attention and be very selective with your cuts after budding, as they will significantly impact the display of flowers for the following season.

Texas azaleas are deciduous shrubs, meaning that during winter (and until March) they are dormant and leafless; this makes it also a good time to prune – always keeping in mind the above cutting restrictions.

The best time to fertilize Texas azalea is in spring, right after the blooms fade and the shrub is pruned. Use a slow-release, acidic fertilizer such as cottonseed meal or commercial azalea-camellia-gardenia dry fertilizer, applying it evenly around the roots. Fertilizing in a concentrated area will most probably cause fertilizer burn. At any rate, avoid lawn fertilizers; they are too high in nitrogen and they may burn or even kill the shrub.

Never fertilize late in the growing season, like after budding (July) or in the fall, as this can cause tender new growth to develop right before winter — with its chances of severe frost — sets in.

Texas azalea flowers

Other Considerations

A Texas azalea in full growth can reach up to 6 ft in height and 3 ft in width. Be sure to provide 36” to 48” spacing when planting your azaleas, thus leaving adequate room for the shrub to develop.

As mentioned above, Texas azalea has a shallow root system —the roots tend to spread horizontally near the surface rather than drive deep into the ground. When planting Texas azaleas, perform 2-3 vertical cuts in the root ball, so as to help the roots spread apart. In the opposite case, the plant won’t be able to hold fast on the ground, and the plant will be severely under-achieving in growth and appearance.

The family of Rhododendrons, to which Texas azalea belongs, has leaves and flowers containing poisonous substances that are dangerous when ingested by humans and animals. What’s more, honey made from these flowers may also be toxic.

Native plants are generally pest and disease free, or they wouldn’t have survived and propagated in the regions where we see them thriving today. It’s a law of nature, and it’s called adaptation. This doesn’t mean that these plants are plastic and invulnerable to natural enemies, pests, and diseases – and Texas azalea has its own share of this type of problems. One thing’s for sure, though: given the proper environmental and growing conditions, your native azalea shrubs will fare much better than rumor has it.

Photo credits:
– Clarence A. Rechenthin @ USDA-NRCS PLANTS Database
– treegrow in Flickr