Horticulture Report — September 2019
By Sherrie Eoff
Ironweed: vernonia lettermanii-Letterman Ironweed: the narrow leaf or thread leaf ironweed is a plant species known only from Arkansas and Oklahoma. In its native range this species occurs on gravel bars and adjacent rocky outcrops in droughty, sometimes flooded sites. Ironweeds are members of the daisy family. Narrow leaf ironweed is typically two feet tall and three feet wide; a long-lived, tap-rooted herbaceous perennial with stems that originate from a dense crown. It has entire, 1/8th-inch-wide by 3-inch-long leaves that cover the unbranched stems from top to bottom. From early August through September the plant is topped with open clusters of purple disc florets joined into an inch-wide head. Ironweeds are favorites of a wide range of butterflies and are often covered with them. Allan Armitage, the University of Georgia plantsman who has introduced a number of fine plants, selected “Iron Butterfly,” a vigorous and floriferous selection from seeds obtained from Arkansas sources. The plant is named for George W. Letterman (1841-1913), a reclusive botanist said to have been famous amongst plantsmen of his day. Letterman had a one room cabin near St. Louis and collected plants from the Meramec River, the principle river system that drains the northern portion of the Ozark Highlands and enters the Mississippi River near St. Louis.
*The feathery foliage creates a soft texture that is a lovely addition to a perennial border, container or wildflower garden. In bloom it is covered with bright purple tassel flowers. Very tolerant of drought, it performs beautifully in a wide variety of soil types and seems to thrive in summer humidity.
*Full Sun, 24-30” tall, blooms late summer-early fall. Attracts butterflies.
Stachys: Stachys monnieri, ‘Hummelo’, Hummelo Alpine Betony was named after Piet Oudolf’s hometown. The low growing rosette of textured green leaves is topped by showy spikes of lavender-pink flowers in mid-summer for an extended period. Stachys ‘Hummelo‘ is a tough, carefree beauty. Easily grown in average, medium, well-drained soils in full sun. Appreciates some light afternoon shade in hot, humid climates. Soils should be kept evenly moist, but established plants have some drought tolerance. Spreads by creeping stems (stolons) that root as they go along the ground. Plant 12-18” apart for use as a ground cover. Cut back the flowering stalks to encourage re-blooming. Clumps will spread over time to form a dense ground cover. Although some species of Stachys are grown primarily for their gray woolly leaves (e.g., Stachys byzantina or lamb’s ears), this species is grown primarily for its vivid flowers which can provide a spectacular display, particularly when massed. Great addition to borders, cottage gardens, informal naturalized areas. Interesting edging plant.
*Full to part sun, great for cut flowers, 18-20” tall. Tolerates Deer, Black Walnut**
St. Johns’ Wort: Hypericum calycinum- Easily grown in average, medium, well-drained soil in full sun to part shade. Tolerates wide range of soils. Thrives on sandy soils in full sun. Less floriferous in part shade. Evergreen in warm winter climates. Usually dies to the ground or suffers some tip dieback in cold winter climates, but blooms on new growth and comes back nicely each spring. In areas where it does not die in winter, shear or mow plants in late winter or early spring every 2-3 years to renew and induce new growth. Spreads rapidly by underground stems and can spread aggressively in ideal growing conditions. Plant 18″ apart for use as a ground cover. Mass as a ground cover. Rock gardens, border fronts, naturalized plantings. Edger for open woodland gardens. Also effective massed on slopes, hillsides or embankments for stabilizing soils. Plant under trees where it competes well with shallow tree roots. Allan Armitage calls the species “one of the finest ground covers available”.
*Attractive evergreen groundcover with deep green foliage and 2” gold flowers with pincushion-like stamens in late spring and early summer. Plant in average, well-drained soil.
*Full sun, 15-18” height
Japanese Anemone: ‘Honorine Jobert’. Japanese windflower is easily grown in average, medium moisture, well-drained soils in full sun to part shade. Prefers fertile, consistently moist, humus-rich, neutral to slightly alkaline soils with good drainage. Best in part shade. Flowering stems tend to flop in too much shade. Prefers sheltered locations with protection from wind. Foliage tends to burn in hot, dry, sunny summer conditions. Soils must not be allowed to dry out. Avoid wet, poorly-drained soils, however, particularly in winter. Plants may not survive wet overwintering conditions.
*A timeless classic-this stately, clear white selection was made in the mid-1800s and is still beloved by modern gardeners. Add to a patio container or plant directly into flowerbeds for a dramatic late summer show of blooms.
*Use in perennial borders, cottage gardens, woodland gardens.
* Part shade, 3-4’ height, blooms mid to late summer, white blooms. Tolerates deer
Comfrey: Symphytum officinale herb, Comfrey is a tall, easy to care for perennial plant that is often grown simply for its beauty. However, comfrey was once grown as a popular medicinal herb. Unfortunately, we have recently learned that it can be carcinogenic when taken internally, but it is still used as a topical treatment for skin irritations, cuts, sprains, and swelling. It is also used as livestock feed and making compost. Comfrey plants shoot up quickly, early in the season. Comfrey is in the same family as borage, a smaller plant with a similar structure. Because of its deep taproot, comfrey is extremely drought tolerant and a useful clay-busting plant. It produces multi-colored flowers born on forked cymes.
*Beautiful foliage is outstanding all season. Nodding bell shaped flowers in blue, pink, purple, or white. A well-behaved ground covers that lights up shaded or woodland gardens.
*Blooms late spring to summer. Part sun to shade. 15” tall.
* Provides habitat for beneficial insects with its huge leaves, which helps to keep the garden pest-free.
*Fertilizes with nutrient-rich mulch. It is a nutrient accumulator, reaching its roots deep into the ground to mine the subsoil for nutrients (potassium, phosphorus, calcium, and more). The nutrients accumulate in the fast-growing leaves, which can be used as fertilizing green mulch.
**Toxic Juglone: black walnut trees are not always good companions in the garden and yard. In fact, they can be toxic to nearby plants. Very often, when sensitive plants are grown near the roots of black walnut trees, the plants die.
Black walnuts contain a chemical called juglone which can be allelopathic to other plants. According to Purdue University Cooperative Extension, “Juglone has experimentally been shown to be a respiration inhibitor which deprives sensitive plants of needed energy for metabolic activity.” What that means to gardeners is that many plants growing in the vicinity of a black walnut tree will either be killed or will struggle to live, with yellowing, wilting leaves.
Here are seven ways we can take advantage of comfrey’s goodness to enrich and condition the soil for healthier and more bountiful crops (for free!).
Activate Compost: Comfrey cuttings are high in nitrogen, making them an excellent bio-activator in the compost bin. If you have a large amount of dried brown material–such as fall leaves–layering it with comfrey cuttings is an efficient way to balance out the carbon-to-nitrogen ratio and jumpstart decomposition. To give the compost pile an immediate kick into high gear, collect comfrey leaves and crush them. Garden scissors can be used to quickly cut through the leaves roughly. Add a small amount of water and stir/crush for a minute or two to make a paste. Add more water to liquefy, and then pour the entire solution onto the compost pile. This quick little extra step is the equivalent of chewing food. The pre-digestion helps beneficial micro-organisms of the compost pile (like those of our stomachs) get to work faster. The finished compost will have a higher nutrient content with the addition of comfrey cuttings. Comfrey cuttings are ready to be used as green manure, green mulch, or crushed and added to the compost bin.
Comfrey Manure: Green manure is an alternative to—or supplement to—animal manures as a soil amendment. Green manure plants are simply cut back and turned into the soil. For those on city lots who may not have easy access to livestock manures, green manures are the way to go.
Manure sources are rated for their N-P-K values (nitrogen-phosphorus-potassium) since they are the primary nutrients plants need for healthy growth. When comparing comfrey manure (1.8-0.5-5.3) to chicken manure (1.1-0.8-0.5) for example, we can see that they are relatively close in value, with comfrey actually having higher nitrogen and potassium values. By comparison, the value of homemade compost usually falls around 0.5-0.5-0.5, highlighting the fact that the benefit of compost is in its beneficial microbial content and as a soil conditioner, rather than as fertilizer.
When using comfrey as a green manure, add chopped comfrey to garden soil in the fall. Gently mix it into the top layers of the soil using a digging fork. By spring, it will have mostly decomposed and enriched the soil. Comfrey cuttings and compost soil are added to beds in the fall as a green manure soil amendment.
Powdered Comfrey: the dried comfrey leaves are used to make a healing salve for cuts, scrapes, bites, bruises, sore joints, and all manner of external ailments.
Dried and powdered (root or leaf) comfrey can also be used to build and fertilize garden soil. Make your own by air drying comfrey or by using a dehydrator at 95 degrees until crisp. Remove the dried leaves from the stems and use a blender or coffee grinder to make a powder. Store in an air-tight container.
Simply mix powdered comfrey into the soil with a digging fork, about two weeks before planting. Remember that powdered comfrey is more concentrated than fresh leaves, so a little goes a long way. A sprinkle along each row should be plenty. The benefit of using the powdered comfrey is that it can be used in the late winter/early spring garden before the comfrey plants have woken up and produced leaves. The powder will also decompose more readily than fresh leaves, which is better for the spring garden.
Condition Soil: Comfrey’s roots reach 6-10 feet deep into the earth, breaking up heavy clay and creating channels for aeration and better water absorption. Over time, its decomposing leaves and roots will fertilize the soil. This dual action of decomposing leaves and roots can help improve marginal land. Since comfrey prefers rich soil, when planting it in poor or damaged soil, give it a head start by adding a shovel of manure or compost.
Boost Seedlings: Young perennials and fruiting vegetable seedlings will enjoy a nutritional jumpstart from comfrey. At the time of planting, bury a few comfrey leaves (not flowering stems) underneath each planting spot. As the comfrey leaves decompose, they will provide essential nutrients and help the young plants grow strong and free of pest and disease.
Compost tea is an excellent way to provide an immediate nutrient boost to established plants. It is made by steeping fresh plant matter in water for a certain amount of time, straining the liquid, and using it to water stressed plants for a mid-season boost. The extra nitrogen in comfrey compost tea will help overall growth, while the potassium will encourage better flowering and more vigorous growth in perennials and mature fruiting vegetable plants such as tomatoes, peppers, potatoes, cucumbers, etc. Comfrey compost tea is not recommended for young plants.
To make a strong comfrey compost tea: Fill any size container halfway with fresh comfrey cuttings. Fill with water, cover, and steep for 3-6 weeks. Warning: This will smell really bad! Strain off the liquid and dilute by half. Or if using a hose end sprayer, no need to pre-dilute.
To make a weaker (less smelly) comfrey compost tea: Add one gallon of water for every quart of fresh comfrey cuttings. Let sit for three days, stirring daily, and then strain and use full strength.
Comfrey Mulch—in general—is a great way to protect soil and prevent erosion. Mulching with comfrey—also called chop-and-drop—will help to retain moisture and protect beneficial soil organisms. Comfrey mulch is a slow-release fertilizer that is best used under perennials and fruiting vegetables. We grow comfrey underneath our cherry trees so that the fruit trees benefit from comfrey fertilizer.