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Flowers, Fruits, and Frass

Local and statewide information on a variety of current topics for home gardeners and market growers.
Extension Horticultur

Second Spring Package from University of Illinois Horticulture Educators

February 11, 2013

News source/writer: Rhonda J. Ferree, 309-543-3308,

Allergenic plants

URBANA -- If you are an allergy sufferer, spring often brings sniffling, sneezing, and watery eyes, said a University of Illinois Extension horticulture educator.

"One culprit is pollen from flowers of trees, shrubs, grasses, and weeds," explained Rhonda Ferree. "Though most of these bloom for just a short period, something is almost always blooming. In early spring, it's the trees and shrubs. In summer the main pollen source is flowering grasses. In late summer and fall, weedy plants from roadsides are the problem."

Pollen is an important part of plant reproduction and must be moved around from flower to flower. Showy flowers attract insects such as bees, which help pollinate the flowers, but not all plants use insects.

"Most plants that cause allergies use wind to spread their pollen," she said. "Therefore, these plants typically have abundant pollen and not very noticeable flowers."

Fortunately, not all pollen causes allergies. Ample research has been done in this area to determine which plants are the culprits. Allergenic trees are usually a problem from March through May and include the following (in flowering order): maple, willow, poplar, elm, birch, mulberry, ash, hickory, oak, and walnut.

Grasses are more powerful allergens than trees and bloom from May through summer. A few allergenic grasses include orchard grass, bluegrass, timothy, Johnson grass, Bermuda grass, and redtop.

"Late-summer and fall allergenic plants include many weeds such as ragweed, pigweed, lambs quarters, and wormwood," Ferree explained. "Common and giant ragweeds are serious hazards to hay fever sufferers. Both types of ragweed are included on the Illinois noxious weed list for municipalities. It is illegal to allow ragweed to grow on ground you own or work on within any municipality in Illinois."

The best way to manage these pollen producers in the landscape is through proper identification.

"You need to be able to recognize and identify plants that produce irritating pollen," she said. "Admittedly, you cannot completely eliminate allergies no matter what you do because airborne pollen travels great distances; but you can improve the immediate area where you live.

"Existing tree pollen is hard to manage, but if you are an allergy sufferer, choose non-allergenic trees. The greatest allergy offenders are grasses and weeds, so try to keep them from blooming through mowing and weed management programs. For some dioecious plants, you can plant the female instead of the male plants, because it's the males that produce pollen, but remember that female plants produce all those seeds."

Pollen (and mold) counts are routinely provided through the nightly news or on the Internet. Each provides counts for the local area and lists the allergen sources. Counts are usually ranked from low (1) to high (10) and indicate to allergy sufferers the potential for symptoms of hay fever or asthma.


February 11, 2013

News source/writer: Richard Hentschel, 630-584-6166,

2013: Another dry gardening season?

URBANA -- Gardeners were really glad to see the cooler weather and some rainfall at the end of the 2012 gardening season. The question is whether 2013 will be any better, said a University of Illinois Extension horticulture educator.

"For a lot of areas in Illinois, the usual fall rain did not materialize, and through mid-January snow has been scarce," said Richard Hentschel. In a more normal year, plants start the season by using the soil moisture available from the melted snow and spring rains. Later those plants will rely on the soil moisture farther down in the soil profile. This is why, after a landscape plant is established, gardeners tend not to worry about watering.

"As we approach spring, not only is the deep soil moisture lacking, but any upper soil profile moisture available will be quickly used unless there is adequate rainfall," he explained. "If this weather pattern continues, it will mean another gardening season requiring lots of water and close attention to the condition of all landscape plants."

Hentschel said that gardeners can do some things out in the yard that benefit the landscape even if snow and rain from late winter through spring is not adequate.

"If you have a compost bin or pile, adding organic matter does more than just feeding your plants," he said. "Garden soil that contains 1 percent organic matter holds one-third of a gallon of plant-available water per cubic foot. Soil that contains 3 percent organic matter will provide one gallon of available water."

Compost can be incorporated easily into a bed of flowers or vegetables either in the fall or early spring before planting. In perennial beds, it is best to add compost between plants and let it decompose, working itself into the soil profile. On more permanent landscape plantings, the compost can be applied as if it were a mulch layer, much like using bark mulch. Like the bark mulches, the compost will break down and find its way into the soil profile.

The third advantage that compost provides is the beneficial change in soil structure. This change allows root systems to grow deeper into the soil, finding more soil moisture as they do. "When you combine the availability of nutrients, the water-holding capacity of organic matter, and the change in soil structure, it is easy to see how this will help plants, drought or not," he said.

Plant selection will also be an important part of redoing a planting or bed that lost plants due to the drought, disease, or insects.

"If there is a location that has historically been dry in your landscape, plants that have a strong drought tolerance will perform much better than a high-water-use plant," he said. "Dry sites typically have a western or southern exposure or are those parts of the yard that are on a slope or in soils having a high percentage of sand. Sand is just a very small rock that does not have any nutrient- or water-holding capacity and promotes very rapid drainage after a rain."

Many local native plants have root systems that can take advantage of soil moisture several feet into the soil profile. Lawn grasses have roots that go down 8 to 10 inches in good soil; native grasses will have roots 6 feet or more into the soil.

"How we water will likely be different in 2013," Hentschel said. "Watering restrictions are almost certain and are, for many gardeners, something that has been in place already for a number of years. By respecting those restrictions, a ban on watering altogether can be avoided or at least postponed."

Water properly so as not to waste water, and place it to the best advantage of the plants. Watering at the base of a plant or using a drip hose rather than using a sprinkler prevents water loss into the air or off-target areas. Allowing the water time to soak in deeply will encourage plants to send roots deeper into the soil, making them more drought-tolerant. This may mean watering once, letting it soak in, and coming back a second time to thoroughly moisten the soil.

If watering is restricted to even or odd days, it is not necessary to water on the appointed day if the soil is moist enough, he added. Frequent shallow watering will not promote a good root system for the plants.

"Always water deeply when you do water and then wait until the soil begins to dry out before watering again," he said. "Do not use the plants as an indicator and wait until you see them wilting."


February 11, 2013

News source/writer: Rhonda J. Ferree, 309-543-3308,

Spring wildflowers

URBANA – A University of Illinois Extension horticulture educator said that spring walks are very enjoyable.

"Many of us look for morel mushrooms, but there is much more to see at the same time," said Rhonda Ferree. "Woodland wildflowers are beautiful and a welcome sign of spring."

A common woodland wildflower is the spring beauty (Claytonia virginica). This is a low plant with loose clusters of pink or whitish flowers striped with dark pink. The flowers are one-half to three-fourths of an inch wide with five petals. Leaves are long, linear, and grass-like. These flowers bloom from March to May in moist woods and clearings. This spring perennial is spectacular in large patches and grows from a potato-like underground tuber.

"At my former residence near Champaign, I had beautiful large patches of these across the lawn," she said.

A more noticeable native wildflower is Virginia bluebell (Mertensia virginica). This 8- to 24-inch erect plant has smooth gray-green leaves and nodding clusters of light blue trumpet-shaped flowers. The individual flowers start as pink buds and open to about 1 inch long. Virginia bluebells flower from March to June in moist woods, and it is also a popular shade garden plant. Grown in masses, this flower is hard to miss.

There are several flowers from the poppy family that have spectacular spring showings: Dutchman's breeches (Dicentra cucullaria), Corydalis (Corydalis sp.), and bloodroot (Sanguinaria canadensis).

"Dutchman's breeches and Corydalis have delicate, fern-like leaves and grow to about a foot tall," she said. "Dutchman's breeches are more common. The name comes from the clusters of fragrant, white, pantaloon-shaped flowers.

Corydalis flowers are pink or yellow, tubular, and must be appreciated up close. Bloodroot has a solitary white flower, with a golden-orange center that grows beside a lobed leaf. Roots and stems have an acrid red-orange juice, thus the name bloodroot. Flowers last for a very short time and may be hard to find after March.

Two more woodland flowers you are sure to see are wild blue phlox and wild geranium. Wild blue phlox (Phlox divaricata) has loose clusters of slightly fragrant light blue flowers above creeping oval leaves. Also called wild sweet william, it will bloom from April to June.

"I remember seeing these as a child while walking Central Illinois woods with my dad," Ferree said.

Wild geranium (Geranium maculatum) is easily recognized by its typical geranium leaves and loose clusters of lavender flowers. It grows 1 to 2 feet tall and is found from April to June.

"These are just a few of the flowers to look for while exploring our woodlands this spring. Take lots of pictures, but please leave the wildflowers," she said. "Although the ones mentioned here are numerous, some of our wildflowers are becoming rare. Leaving them ensures that they'll remain for others to see in the future."

Photos of these wildflowers and more are on Ferree's Facebook page at For more information on this or other horticultural issues, contact U of I Extension at


February 11, 2013

News source/writer: Martha A. Smith, 309-756-9978,

2013 Perennial Plant of the Year

URBANA -- Polygonatum odoratum 'Variegatum,' also known as variegated Solomon's seal, striped Solomon's seal, fragrant Solomon's seal, and variegated fragrant Solomon's seal, is the Perennial Plant Association's 2013 Perennial Plant of the Year, said a University of Illinois Extension horticulture educator.

"This all-season perennial has greenish-white flowers in late spring and variegated foliage throughout the growing season," said Martha Smith. "The foliage turns yellow in the fall and grows well in moist soil in partial to full shade."

The name Polygonatum comes from poly (many) and gonu (knee joints) and refers to the many-jointed rhizome from which the leaves arise. "There are several explanations for the common name, Solomon's seal," Smith said. "One is that the scar that remains on the rootstock after the leaf stalks die in the fall resembles the seal impressed on wax on documents in the past. Another, proposed by the English plantsman John Gerard, is that the powdered roots were an excellent remedy for broken bones. Solomon's seal thus refers to the perennial's property of sealing wounds."

The plant is native to Europe and Asia and is a member of the Asparagaceae family; it was formerly in the Liliaceae family. Regardless of its classification, members of Polygonatum are excellent perennials for the landscape.

Polygonatum odoratum 'Variegatum' grows to 18 to 24 inches tall and will spread by its rhizomes to form colonies. The oval-shaped leaves are carried on upright, arching, unbranched stems. Pairs of small, bell-shaped white flowers with green tips are borne on short pedicels from the leaf axils underneath the arching stems. The flowers appear in late spring and have a sweet fragrance. Bluish-black berries sometimes appear in the autumn.

"Variegated Solomon's seal is a classic beauty for the shady woodland garden or the part-shade to full-shade border," said Smith. "It is a great companion plant to other shade lovers, including hostas, ferns, and astilbes, offering vivid highlights that echo the color of many neighboring plants. Flower arrangers will find the variegated foliage to be an attribute for spring floral arrangements. And, finally, this all-season perennial offers yellow fall foliage color."

Polygonatum odoratum 'Variegatum' is a very easy perennial to grow and will enhance any shade garden, especially a more natural one. There are no serious insect or disease problems associated with it. Plants may be divided in the spring or fall. The white rhizomes should be planted just below the soil surface.

"This is a tough plant that survives where many dare not grow," she said.

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