How to Grow a Lavender Star Flower Tree

Close up of a lavender star flower

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Grewia occidentalis, more commonly known as the lavender star flower or crossberry, is a small tree that originates from southern regions of Africa. It thrives in habitats that include evergreen forests, wooded grasslands, and coastal dunes. In the United States, the tree can primarily be found growing in southern states like Arizona, California, Florida, and Texas.

The simple leaves of the lavender star flower are deep green, shiny, and a bit hairy in texture. When flowers appear, it becomes obvious where this species derives its name. Appearing in the summer, the star-shaped blooms are a beautiful lavender color with yellow, filamentous stamens at the center of the blossom.

Best planted in the spring, lavender star flower can be grown as a small tree, shrub, container plant, and even a bonsai tree. When left to its own devices, lavender star flower will grow quickly, reaching a maximum height of 9 to 10 feet. Contrast that with the plant's pruned bonsai form (usually no taller than 10 inches), and it's easy to see why this small tree is appreciated for its versatility.

Botanical Name  Grewia occidentalis
Common Name  Lavender star flower, cross berry, button-wood
Plant Type  Deciduous shrub, tree
Mature Size  9–10 ft. tall, 9–10 ft. wide
Sun Exposure  Full sun, partial shade
Soil Type  Moist but well-drained 
Soil pH  Neutral to acidic
Bloom Time  Spring, summer, fall
Flower Color  Purple
Hardiness Zones  9–11 (USDA)
Native Area  Africa

Lavender Star Flower Care

Lavender star flower is important to wildlife in its native habitat. Both livestock and wild animals graze on the tree's leaves and fruit, as do several species of butterfly. In some regions, the fruit is dried and later boiled in milk to create a beverage or make flavored yogurt—the ripe fruit may also be brewed into beer.

Lavender star flower does not have an aggressive root system that would cause problems with sidewalks, so it makes for a great option to plant near walkways and buildings. It's also a popular choice for butterfly gardens, where the foliage and nectar attract both butterflies and birds alike. The plant is relatively easy to care for, provided you supply it with enough sun and the proper soil conditions.

Light

Lavender star flower prefers full sun, which promotes the best growth and robust blooming. However, the plant can tolerate shade as well, especially in locations where the summer months are particularly hot or dry. Ideal planting locations are those with western or southern exposure that get at least six to eight hours of sunlight daily.

Soil

Plant your lavender star flower in soil that has a neutral to acidic pH level and drains well. The exact blend of soil is not super important, as the plant can thrive in a variety of conditions. That said, you'll see the most success with a mixture that is rich in organic matter and quick to drain—a blend of two parts peat moss to one part sand works particularly well. If you notice the leaves on your plant are yellowing, that's a good sign that the soil is too alkaline.

Water

It's important that you do not let the soil of your lavender star flower plant dry out completely—the plant does not tolerate even brief periods of drought well. Water consistently when the top 2 inches of soil have gone dry and do so deeply, making sure to saturate the plant so that the water penetrates the entire root ball.

Temperature and Humidity

True to its tropical nature, the lavender star flower tree likes warmer temperatures and slightly humid conditions. Though it can survive in temperatures below 55 degrees Fahrenheit, it will not thrive (and certainly not bloom) and should be brought indoors for the winter months if possible. If being kept indoors for the winter, place it somewhere warm and mist it periodically to maintain humidity levels.

Fertilizer

For optimal growth, fertilize your lavender star flower three times a year with a slow-release acid-based fertilizer. An annual iron supplement is also recommended to help boost the plant's natural chlorophyll and keep its leaves from turning yellow.

Pruning Lavender Star Flower

To maintain an aesthetically pleasing shape for your lavender star flower tree, you should prune the tree heavily as need. Unlike most plants, you can do this any time of the year. A once-yearly pruning in the fall is a great way to keep the plant's size in check; likewise, you can cut back the branches immediately after the blossoms have dropped in late summer to promote additional flowering the following year. Also, take care to remove any branches that appear to be diseased or broken. As a rule of thumb, never remove more than one-third of the plant's bulk at a time—otherwise, you risk stunting its growth.

Propagating Lavender Star Flower

Lavender star flower can be propagated in the spring using cuttings from a mature plant that has flowered for at least one to two seasons beforehand. Additionally, you can also grow the plant from seed. Seeds should germinate in about two to three weeks' time, as long as they're exposed to temperatures that are consistently about 70 degrees Fahrenheit.

Common Pests & Diseases

Lavender star flower plants are susceptible to a variety of typical garden pests, such as scale, mealybugs, and aphids. Additionally, because it's such a big hit with butterflies, lavender star flower may have slight issues with butterfly larvae that like to feed on the foliage—however, there will be no significant damage done. The plant does not respond well to the use of any insecticides, which can easily impact its growth or reduce its flowering significantly. To battle pest issues, remove any insects from the plant by hand or with a strong blast of water, and treat the plant using a horticultural oil like neem oil.