How to Grow Cape Plumbago (Plumbago Auriculata) Like a Pro

Cape Plumbago, Plumbago auriculata, belongs to that special group of plants that produce true blue flowers. Valued for its bloom color, this leadwort is versatile and can be grown as a shrub, vine, or potted plant.

A rapid grower, it works beautifully in hedges, trellised or cascading over walls and fences. Flowers attract pollinators and are popular additions to butterfly gardens. Hardy only in southernmost climates, cape plumbago is usually grown as an annual in more temperate zones but is easily overwintered as a potted plant.

Follow this guide to learn about Cape Plumbago and how to expand your garden's color palette with some elusive blue.

Cape Plumbago Care

Considered an evergreen shrub, Cape Plumbago has a sprawling growth habit and can be trellised and trained as a vine to climb or drape.

Whichever form you choose, some maintenance is needed to keep it looking its best. This ornamental isn't overly picky about conditions as long as it's planted in fertile, well-draining soil.

Light

Cape Plumbago performs well in full sun with six or more hours of exposure daily. It adapts easily to part shade but does require a minimum of two hours of direct sunlight. Potted plants, overwintered as perennials, should be kept in a brightly lit room.

Soil

This leadwort does equally well in all soil types provided they are organically rich and drain well. Planting in the garden or pots, aim for a sandy soil texture. Neutral pH either slightly acidic to slightly alkaline is adequate for plant health but too much alkalinity causes degradation of foliage.

Water

Once established, cape plumbago is drought tolerant, however regular irrigation supports the most vibrant flowers and the longest continuous bloom. Water needs are average with about one inch per week sufficient for peak performance.

Temperature and Humidity

Temperatures greater than 60°F establish a vigorous growing environment. Cape Plumbago is evergreen to 25°F and root hardy to 10°F.

Native to coastal regions of South Africa, it thrives in moist, warm climates and is salt tolerant. Periods of extremely high temperatures can cause flower colors to fade.

Fertilizer

Feed plant twice annually, in the spring and autumn, with a balanced NPK 10-10-10 slow release fertilizer.

Types of Cape Plumbago

• Plumbago auriculata 'Monott': Evergreen with the deepest blue flower color. Blooms year-round in large clusters of vivid blue and white phlox-like flowers.
• Plumbago auriculata 'Imperial Blue': Semi-evergreen with clusters of blue flowers on arching branches during summer months. Tender perennial.
• Plumbago auriculata f. 'Alba': Evergreen shrub with clusters of creamy white five-petaled flowers spring through summer or year-round in frost-free zones. Foliage is light green with spoon-shaped leaves.
  

Pruning

Pruning this rapidly growing plant is essential for a pleasing appearance. Well-branched stems tend to climb and plants are predisposed to produce suckers. Flowers form on new growth so cut back perennial plants in late winter or early spring and remove suckers. Be consistent about deadheading spent flower clusters throughout the growing season. Stems that cross along with any that are diseased or damaged can be removed anytime.

Grown as a vine, cape plumbago requires a support. Arching stems do not attach with tendrils and need to be tied to a stake or trellis.

Propagating Cape Plumbago

Cape Plumbago is propagated with cuttings during the growing season when plants are most vigorous. Gather a clipper, small pots with drainage holes, quality potting soil, and rooting hormone then follow these steps.

1. Clip off a green stem 4 to 6 inches in length. Make your cut below a set of leaves.
2. Cut away any terminal buds and lower leaves keeping the top one or two sets.
3. Dip the lower third in water and then in rooting hormone.
4. Fill a pot with soil and use your finger or pencil to make a deep, narrow planting hole in the center. Use a single pot for each cutting.
5. Insert the cutting in the hole taking care to retain the rooting hormone.
6. Water thoroughly and cover the pot with plastic.
7. Place in a location to receive bright, indirect light and keep the soil moist.
8. New shoots should appear above the soil in two to three weeks.
9. Allow plants to grow another two weeks before potting up into a larger container.

How to Grow Cape Plumbago From Seed

Cape Plumbago grows easily from seed, but it often takes two years to produce flowers. Here's how to grow it starting with seeds in early spring.

1. Mix together and moisten equal parts potting soil and sand, perlite or vermiculite.
2. Set seeds on top of the soil and cover lightly with 1/8- to 1/4-inch of potting mix.
3. Water and place in a warm location (72 to 75°F) in full sun to partial shade.
4. Keep soil consistently moist.
5. Seeds germinate in seven to ten days.
6. Grow out in pots until seedlings are several inches tall.
7. Harden off before planting outdoors once temperatures stay consistently above 60°F.

Potting and Repotting Cape Plumbago

Repot in spring every three years increasing the container by one pot size. Plants also can be repotted in autumn once they've entered dormancy.

1. Loosen soil around the root ball and remove the plant.
2. Shake off excess soil and go ahead and take care of any annual pruning tasks.
3. Fill the larger pot with quality, well-draining potting mix.
4. Set the cape plumbago in the center and fill in around roots keeping the root ball at the same level as in the original pot.

Overwintering

In USDA zones 8 and lower, cape plumbago can be overwintered in pots indoors as a perennial or in a sheltered location as a dormant plant.

Move plants indoors when temperatures drop consistently below 50°F. The challenge for wintering indoors is to give your plant adequate light. Keep it in a brightly lit room or consider adding a grow light if natural light is insufficient.

Reduce the watering frequency and withhold fertilizer until new growth starts up in spring. Plants can be returned outdoors at consistent temperatures of 50°F.

To overwinter as a dormant plant, prune back in late autumn and move pots into a cool dark location such as an unheated garage or basement. Cape plumbago foliage is hardy to 25°F with roots able to sustain temperatures as low as 10°F.

Foliage may die back but will quickly regenerate in spring. Reduce watering and return plants outdoors when temperatures stay above 50°F.

Common Pests and Plant Diseases

Cape olumbago is relatively free of both pests and plant diseases. If leaves begin to curl and appear stunted you may have a type of thrip called a "chili thrip."

Scale and mites can invade but don't affect the health of the plant. Organic pesticides are the best option for controlling a rare infestation.

How to Get Cape Plumbago to Bloom

Cape plumbago bears flowers on new growth and, because it grows rapidly, consistent pruning encourages prolific blooming.

Bloom Months

Grown in its USDA hardiness zone, Cape Plumbago may bloom year-round. In temperate zones below USDA zone 8, flowers first appear in May with continuous bloom through October in the right conditions.

What Do Cape Plumbago Flowers Look and Smell Like?

Flowers appear in clusters on each stem with five petals. Lightly aromatic blooms measure 1 to 3 inches across and attract butterflies. Depending on the variety, flower colors may be rich to soft blue, pink, or white.

How to Encourage More Blooms

Removing spent flower clusters is key to producing more blooms and extending the bloom period. Fertilize in early spring and again in autumn in hardiness zones and for potted plants overwintered as perennials.

Cape plumbago blooms best when kept well watered consistently throughout the growing season, but avoid soggy soil which can lead to root rot.

Deadheading Cape Plumbago Flowers

Clip off spent flower clusters at the stem base or just above the first set of leaves.

Common Problems With Cape Plumbago

Cape plumbago adds color and versatility to the garden with few problems. It won't look its best though if soil pH is too alkaline and if pruning is neglected. Here are a few issues that could arise.

Yellowing Leaves

Soil is too alkaline. A pH above 7.3 is too high for this plant which requires a more neutral pH of 6.1 to 7.3. Test soil and work in lime or sphagnum moss to lower pH.

Wilting Flowers and Foliage

Flowers and foliage may wilt following bloom if the soil drains too quickly or plants are underwatered. Add sphagnum moss or work in some vermiculite to help retain moisture. Develop a watering schedule to keep soil consistently saturated but not soggy.

Lack of Blooms

For plants overwintered in dormancy, prune stems back in autumn. Prune all others back in late winter or early spring to encourage the new growth that produces flowers.

Deadhead all spent flowers during the growing season and consider lightly pruning after a bloom flush to encourage additional growth and more flowers.