How to Grow and Care for Blue Tweedia

Tweedia plant with light blue and purple flowers and buds

The Spruce / Adrienne Legault

Finding a plant with blue flowers is rare, but finding one whose flowers are also fragrant and whose foliage is attractive is even rarer. Blue tweedia has all three, which makes it a popular choice for gardens, floral arrangements, container gardens, and even bridal bouquets. The attractive gray-green leaves are heart-shaped, and beautiful star-shaped flowers bloom from summer into fall. It generally grows to about 2 feet when planted as an annual, but as a perennial in warm zones, its stems may sprawl 10 feet or more.

Blue tweedia is best planted in the early spring as a nursery container plant after all risk of frost has passed, but as nursery plants can be hard to find, the alternative option is to buy seeds and start them indoors. It is a fairly slow, steady grower that will reach flowering size in 70 to 85 days after seed germination.

Although blue tweedia is not included on most official lists of toxic plants, some commercial seed packagers note that blue tweedia is in the milkweed family, with a mildly toxic sap that should not be ingested.

Common Name Tweedia, blue tweedia, blue milkweed
Botanical Name Oxypetalum coeruleum, also known as Tweedia coeruleum
Family Apocynaceae
Plant Type Herbaceous annual (perennial in zones 10–11)
Mature Size 2–3 ft. tall, 2–3 ft. wide (up to 10 ft. long when grown as a perennial)
Sun Exposure Full, partial
Soil Type Moist but well-drained
Soil pH Acidic to alkaline (5.0–8.0)
Bloom Time Summer, fall
Flower Color Light blue
Hardiness Zones 10-11 (USDA)
Native Area South America
Toxicity Sap is mildly toxic to humans and pets

Blue Tweedia Care

Tweedia is a tropical twining vine or subshrub native to Brazil and Uruguay, grown as a perennial in USDA zones 10 to 11, but in colder zones it can be planted as an annual that grows back to ground each winter.

Blue tweedia is a relatively new garden introduction, and you may have trouble finding a nursery that stocks the plant. Online retailers are often the best option, and you may need to purchase seeds rather than live plants. When choosing a spot in your garden to plant tweedia, select a location that is protected from the elements to ensure your blooms maintain their gorgeous petals throughout the whole blooming season. Its delicate sky blue flowers can be easily damaged by strong winds or intense rain.

Blue tweedia is a relatively easy plant to grow and does not require any special attention. As an annual in an ideal location, it may reach as much as 3 feet tall; as a perennial, it sometimes sprawls to as much as 10 feet. Grown as a perennial, it will need support for its twining stems.

Tweedia vines covering ground with small light blue flowers

The Spruce / Adrienne Legault

Tweedia vine with light blue and purple flowers closeup

The Spruce / Adrienne Legault

Tweedia light blue-purple flowers and buds with bee on top

The Spruce / Adrienne Legault

Light

Blue tweedia usually grows best if planted in an area that boasts full sun, especially in climates with cooler summers. In regions with particularly hot summers, it may prefer a partial sun location.

Soil

Blue tweedia can tolerate a wide range of conditions, including poor, infertile soils, but for best results, plant it in moist, well-drained soil. As with most plants, tweedia does not tolerate wet feet, so make sure the soil has adequate drainage. Adding perlite or sand to the mixture will help to increase drainage if needed. The plant does not have any special pH requirements, and can thrive equally well in acidic, neutral, or alkaline conditions.

Water

Blue tweedia plants require regular watering in order to thrive. Well-established plants are slightly more drought-tolerant than young plants, but will still do best when given regular soaking. If you live in an area that does not receive much rain, you will need to supplement rainfall with additional watering to help your tweedia thrive—about 1 inch per week should work well in most climates.

Temperature and Humidity

Tweedia is a heat-loving plant and requires warm temperatures in order to stay evergreen year-round. In most climates, tweedia is grown as an annual, or overwintered indoors as a houseplant and moved outside during the summer. Whether you're planting from seed or transplanting seedlings, wait until temperatures have reached at least 50 degrees Fahrenheit and all chance of frost has passed before moving your plant outdoors.

Fertilizer

Tweedia plants should not be fertilized until they are well-established, at which point they can benefit from fertilization during the growing season to help encourage new growth. Feeding with a standard all-purpose fertilizer in the spring and summer months will encourage more aggressive blooming from late summer into fall.

Types of Tweedia

The common name "tweedia" is applied to many species across several genera in the Apocynaceae family of plants. All are native South American plant species with a vining, sprawling growth habit. But of these many species, only Oxypetalum coereleum is commonly cultivated as a landscape plant, usually sold as blue tweedia. Don't be surprised, however, if you see this plant labeled by its previous botanical name,Tweedia coreleum. A number of named cultivars are available, including 'Heavenly Blue' and 'Heaven Born'.

Pruning

To help keep your blue tweedia plant looking full and bushy, pinch the stem tips in the spring to encourage branching. In climates where tweedia is hardy over the winter, regular season-end pruning will help to encourage new growth in the spring. Cut back tweedia as you would other shrubs, making sure not to remove more than one-third of the total mass at any single pruning.

Propagating Blue Tweedia

Tweedia can be propagated by taking softwood stem cuttings in early to late spring. This method can also be used to overwinter plants in colder climates. Here's how to do it:

  1. Take a stem cutting about 4 inches in length from a mature" plant, using a sharp knife or pruners. Make sure that at least one node is present on the cutting.
  2. Remove the leaves and flowers from the lower part of the cutting, leaving at least two leaves at the top.
  3. Make a fresh slice through the stem just below the bottom node, then dip the cutting in a rooting hormone.
  4. Plant the cutting in a small pot filled with seed-starting mix, water it, and place it in a location that receives bright (but not direct) sunlight.
  5. Roots should begin to grow within four to eight weeks; at this point, the plant can be planted in the garden, or transplanted in a larger pot that can be moved indoors for overwintering

How to Grow Tweedia From Seed

Blue tweedia can be easily grown from seeds, either by purchasing seeds directly or by harvesting seeds from an existing plant.

  • When growing blue tweedia as an annual, seeds can be started indoors in late summer and overwintered until outdoor planting time the following spring. These are fairly slow-growing plants that may not have time to flowering maturity if you sow the seeds outdoors. Heated seed mats are recommended for germinating blue tweedia seeds.
  • In warmer regions where you are growing blue tweedia as a perennial, seeds can be sowed directly into the garden, or they can be started indoors and then moved outdoors once the seedlings are well established. It can take three to five years for an outdoor plant to reach its full size—as much as 10 feet. Outdoor plants will require some form of support for the twining stems.

Potting and Repotting Blue Tweedia

Blue tweedia will grow readily in a well-draining pot filled with standard potting mix. In colder regions, a potted plant can be overwintered indoors, placed in a bright, warm location. Pots can also be wintered outdoors in a sheltered location where temperatures get no lower than about 37 degrees Fahrenheit. Plants should be repotted whenever they become root-bound.

Overwintering

In colder regions where blue tweedia is being grown as an annual, simply pull the plants from the garden at the end of the season and discard them.

In regions where you can grow blue tweedia as a perennial, cut back on watering as winter arrives. In areas with harsh winter winds, providing a wind shield may be helpful.

Common Pests and Plant Diseases

This plant is generally pest- and disease free—the only issue you may encounter is milkweed bugs (Oncopeltus fasciatus) during the tail end of their season. These insects rarely do any serious damage, but if necessary, they can be controlled with horticultural soaps. Avoid chemical pesticides, as these will also harm the butterflies and other desirable insects drawn to blue tweedia.

How to Get Blue Tweedia to Bloom

Mature blue tweedia plants will normally bloom well from summer into fall, provided the plants are getting enough sun. If blooms are insufficient, add an early summer feeding with a balanced fertilizer.

These plants like to be moist, and drought conditions may also cause reduced blooms. Make sure to water these plants well during the hot months.

Common Problems With Blue Tweedia

Outside occasional late-season problems with milkweed bugs, these plants are remarkably free of common complaints. If you are growing a blue tweedia plant as a perennial, it may gradually get a bit overwhelming, with stems reaching as much as 10 feet or more. Hard pruning can keep it under control; or, simply provide it with a trellis or other climbing structure to support the plant.

FAQ
  • How should I use blue tweedia in the landscape?

    As a part of the milkweed family, this plant attracts various types of pollinators and makes a great addition to a butterfly garden. Its long bloom season also makes it a fine addition to any border garden. Blue tweedia pairs nicely in gardens with other late-blooming plants such as lavender, sunflower, black-eyed Susan, and purple coneflower.

  • How long does blue tweedia live?

    When grown as a perennial in warmer climates, Oxypetalum coereleum is sometimes a relatively short-lived plant. It's common for plants to begin declining after five years or so. It's a good idea to propagate a mature plant in order to ensure the survival of the specimen.

  • Does blue tweedia make a good cut flower?

    Though the flowers are relatively small, they last well when cut for vase display. They are normally cut and displayed along with sprigs of the plant's gray-green foliage with heart-shaped leaves.

  • Does blue tweedia attract monarch butterflies?

    Unlike native North American milkweeds, this plant does not specifically host monarch butterfly larvae, but it is still attractive to a variety of butterflies who feed on the nectar of the flowers.