Petrea

( peh - TRAY - uh )

At-A-Glance Information

Commonly called Queen's Wreath, Purple Wreath or Sandpaper Vine, this evergreen vine needs full sun and regular water. The bright purple flowers will attract butterflies to your garden. It is a woody-based native of Mexico, Central America and the West Indies, and has deep green, rough-surfaced leaves. Clusters of blue-purple star-shaped flowers appear in warm weather in late spring and summer. Great when trained onto a pergola or trellis, and on high walls or along eaves. The genus Petrea is a member of the plant family Verbenaceae and includes 11 species. The only species commonly cultivated in gardens is Petrea volubilis. The best growing zones for Queen's Wreath are 19-24, H1 and H2 (to find your zone, click here: Zone Map).

Caring for Petrea Vines

Petrea vines do best in full sun to partial shade, and ideally should be receiving between 4 and 6 hours of direct light each day. They will flower and produce the best foliage the more sun they get. Some afternoon protection from sun is needed in particularly hot areas to avoid over-stressing the plant or foliage sunburn. Petrea vines are wind-resistant but frost-sensitive, so make sure that they are in a protected area, especially when young. They prefer well-draining soil with a pH of between 6.0 and 7.0. If local soils are compacted, do not drain well, or are particularly poor in nutrients, make sure to amend the planting area with plenty of organic matter or compost before installing. Apply a thick layer of mulch around the base of the plant after installation, ensuring that mulch stays at least a few inches away from the stems. This will increase soil moisture retention, suppress weed growth, and maintain a constant soil temperature. 

Keep the soil moist while plants establish a strong root system; mature plants are considered somewhat drought-tolerant, but they do appreciate consistent moisture during the growth and flowering season. Foliage can be trimmed back at any time of the year to control growth and remove dead, damaged and diseased stems and leaves. Doing so will keep the plant at its healthiest form. Pinch young plants to encourage a bushy habit to form. Fertilize plants yearly for the best show of blooms with a dressing of organic compost applied around the base of the vine. Work the compost into the soil a bit, and then replace the mulch around the base.

Propagation

Petrea vines can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Petrea, follow the instructions below:

Propagating Petrea by Cutting
  1. Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
  2. In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
  3. Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
  4. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Petrea by Seed
  1. Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
  2. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
  3. Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.
Petrea seed pods.
Petrea seeds.

Problems and Pests

Although generally pest and disease-free, these vines can suffer from issues with the following:
  • Aphids
  • Spider Mites
  • Whiteflies
For more information, see the following links:
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Gallery

These woody vines are perfect for adding color and interest to entryways.
If given adequate support, Petrea vines can look amost like small trees.
Here, Petrea vines are braided to form something like a tree trunk.
Petrea on an archway can provide privacy for front entrances.
Petrea is used in instances where Wisteria is not a good choice (or where Wisteria is considered invasive).
Here, Petrea vine is grown on a series of trellises.

Videos

All about these wonderful ornamental vines.
How to grow these vines in containers.

Resources

Petrea volubilis
Queen's Wreath Info - Learn About Growing Queen's Wreath Plants
Wikipedia: Petrea volubilis
Wikipedia: Petrea
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 496, Petrea volubilis
If you have any questions, comments, concerns, or photos you’d like to add to the gallery, please let me know by sending me a message using the button below!
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