Polygala

( pall - ee - GALL - uh )

At-A-Glance Information

This genus of evergreen shrubs commonly called Milkwort or Snakeroot includes species which need full sun to light shade and regular water to perform well in the garden. They are grown for their colorful, asymmetrical, bird-shaped flowers. Polygala shrubs are native to temperate and tropic zones worldwide as accents low hedges or screening plants, or in containers on patios or walkways. They are also sometimes used as filler in cut flower arrangements. Take care when planting these shrubs in the landscape, as ingestion of plant parts can be moderately toxic to humans and pets.

Polygala Species and Varietals

The genus Polygala includes between 350 and 730 species and is a member of the plant family Polygalaceae. Plants in this genus are related to The genus name is derived from the Greek term 'much milk', as the plant is thought to increase the yield of milk from cows that consume it. The genus was first described by Carl Linnaeus in 1754, and since then, many species of flowering shrubs have been added to the genus, possibly incorrectly, due to similarities in flower shape (which is why the species count in the genus varies so widely). Polygala ideal growing zones vary depending on the species; for more information, see the descriptions below. To find your zone, click here: Zone Map.

Polygala x daimaisaiana (Sweet Pea Shrub, Milkwort)
This species grows in USDA hardiness zones 8-11 or Sunset growing zones 8, 9 and 12-24; reaches 3-5 feet tall and wide. Leaves are grey-green and pink-purple flowers bloom throughout the summer and fall seasons. Cut back hard in late wintertime to create a more compact plant with bushier growth. Great as a filler in landscapes.

Polygala fruticosa (Sweet Pea Shrub, Dwarf Sweet Pea Shrub, Heart-Leaf Polygala)
This species grows well in USDA growing zones 9-11 or Sunset growing zones 8, 9 and 14-24 and is native to South Africa. It reaches 4 feet tall and 2-3 feet wide, with grey-green foliage. Blossoms are purple-pink, present almost year-round in mild areas. In other regions, blooms appear most profusely from spring through fall. Great near coastlines and to provide interest to cut flower arrangements. Cultivars include 'Petite Butterflies' (to 2-3 feet tall with rounded grey green leaves), 'Africana' (with rich purple blooms), and 'Southern Shores' (with coastal resiliencies and dense growth).

Caring for Polygala

Take care when planting these shrubs in the landscape, as ingestion of plant parts can be moderately toxic to humans and pets. Plant Polygala shrubs in full sun to partial shade. They should be getting at least 4-6 hours of sun each day for optimal growth and flowering. Check the requirements of the species before planting, however, as some varieties can take more shade. Soil should be well-draining and rich in organic matter with a pH of between 6.0 and 7.5 (acidic to neutral). Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water new plantings regularly as they establish a strong root system in their new home. At maturity, these plants perform well in consistently moist soils.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Polygala shrubs have a beautiful, rounded natural shape and do not need much in the way of pruning. Regular deadheading will encourage more blooms to be produced; these plants produce blooms on new growth. More extensive prunings to reduce the size or rejuvenate the plant should be completed in late winter to early springtime. Any damaged or leggy growth can be removed from the plant at any time of the year. Polygala plants can be annuals or perennials. Annual species are typically pulled at the end of the growing season or left in place to enrich soil, and replaced in the next year with new plants. Perennial species can be expected to survive for decades in the landscape before needing to be replaced.

Caring for Polygala in Containers
Polygala shrubs are wonderful in the ground, but can also be grown in containers. Choose a container that is at least a few inches wider and deeper than the nursery pot or root ball. Ensure that the pot has adequate drainage holes on the bottom to allow for excess water to flow away. Fill with a well-draining potting mix amended with organic material and perlite, and top with a layer of mulch to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water regularly as the plant establishes itself in its new home. Once established, waterings can be lessened. Polygala plants grown in containers will need more frequent irrigation than those grown in the ground. As a general rule of thumb, water whenever the top few inches of soil feels dry to the touch. Prune to remove dead, damaged, or diseased foliage at any time during the growing season. Every few years, check the bottom of the pot to ensure that the plant is not outgrowing its root space. If roots are growing through the drainage holes in the bottom of the container, it is a good indication that it needs to be potted up; choose a slightly larger container and repot.

Harvesting Polygala
These shrubs are sometimes harvested for cut stems of foliage and flowers. They are in bloom from late winter through summertime (or year round in warmer climates). The best time to harvest is in the morning, after dew has dried but before the heat of the day sets in. Using clean, sharp shears, cut stems at a 45 degree angle just above a node. Select stems that are in the budding stage or in full bloom. Drop the harvested flower stems into a bucket of cool water, and then bring them indoors to arrange them. Polygala stems have a vase life of between 7 and 10 days.

Propagation

Polygala 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 shrub, follow the instructions below:

Propagating Polygala by Cutting

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. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In spring or fall, 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.
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.
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 Polygala by Seed

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. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
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 14-28 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.
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.

Polygala shrubs produce small, two-celled capsules that hold two seeds each. They split open to release seeds when they are mature.

Polygala seeds are small, oval, and have a hairy surface. They can be brown to black in color, and have distinct two-lobed appendages at their base that aid ant or wind dispersal.