What Grows There :: Hugh Conlon, Horticulturalist, Garden Advisor, and Photographer

Nuts About Acorns

Posted by Hugh on October 10th, 2017

Acorn germinating into soil

Acorns are nuts that form on mature oak trees (Quercus spp.). Acorns come in many shapes, sizes and colors, depending on the species. An acorn is a single nut encased in a hard shell by a cap (used to identify what oak species it is). For example, Northern Red Oak (Q. rubra) tree produces egg-shaped acorns and are supported by shallow, saucer-shaped cup. White oak (Q. alba) produce acorns that are stubby and covered with warty cups.

Some oak species produce acorns almost every year, while on others acorns two years to mature. Older mature oaks, usually past 20 years old, produce many more acorns, and 70 or 80 year old trees can potentially produce thousands of nuts.

Many animal species rely on acorns as a food staple, such as squirrels, woodpeckers and deer (termed “mast”). Humans consume roasted acorns; right off the tree acorns are full of tannins, which can be toxic if eaten in high amounts. Acorns from the white oak group are low in tannin and have a nutty flavor when lightly roasted before grinding. Many acorns, cached away by squirrels and bluejays, will eventually germinate and become the next generation of oak forest.

Within its hard shell, an acorn contains one seed. The oak seed must not dry out or it will not germinate. To prevent drying, tree growers will collect and store acorns in plastic bags in the refrigerator for planting late next spring. Acorns need 1,000 hours of dormancy in low temperatures (33-37 º F). The larvae of some moths and weevils also live in acorns, consuming the kernel as it develops. These pests may consume more than 95% of all acorns in some years.

Acorns are rich in large amounts of proteins, carbohydrates, fats, vitamins, as well as the minerals such as calcium, magnesium, phosphorus, and potassium. Do not permit grazing animals to eat large amounts of acorns from specific Quercus species, especially red oak group and English oak (Q. robur).

Acorns of the white oak group typically start rooting as soon as they come in contact with the soil (in the fall). For example, bur oak (Q. macrocarpa) acorns fall from the tree from August to November. Germination usually occurs rapidly after seed fall, and favors root growth first. The taproot penetrates deeply into the soil. Contrarily, acorns from the northern red oak group drop in late fall, remain dormant through winter, and germinate in the spring.

These oaks are designated as “State Trees”:

White oak (Q. alba) – state tree of Connecticut, Illinois, and Maryland

Live oak (Q. virginiana) – Georgia state tree

Northern Red oak (Q. rubra) – New Jersey state tree

Bur oak (Q. macrocarpa) – Iowa state tree

Scarlet oak (Q. coccinea) – District of Columbia tree

Comparing Heritage® Vs Duraheat® River Birch

Posted by Hugh on October 6th, 2017

‘Duraheat’ at the NC Arboretum in Asheville, NC

Summer chlorosis caused by high soil pH

In general, most species of our native birches (Betula spp.) grow best in cool, northern areas of the U.S. They are found growing along the sides of rivers, lakes, streams, and mountainous areas (USDA Zones 4-9). Most birches (not all) are recognized for their distinctive gray to white bark. Birch species with the whitest of bark are not heat tolerant, insect and disease prone, and usually are short-lived in zone 6 and points south.

Compared to other species of birch, river birch (B. nigra) is more heat tolerant and is highly insect- and disease-free (USDA hardiness zones 3-9). Heritage® and Duraheat® are two exceptional cultivars of river birch that have changed our overall view of the species. Both grow almost identically at 40 feet high and 30 feet wide. Catkin-like flowers swell over the winter months and open in early spring.

Both cultivars are mostly purchased multi-trunk with a broad pyramidal architecture. Summer foliage is medium green and glossy and turn bright yellow in the fall. Heritage and Duraheat were selected for their lighter colored bark and medium green glossy leaves. To date, Heritage is the more popular, but Duraheat is preferred in southern climes. The mottled peeling bark exposes patches of cream, orange and pinkish tan colors within. Both are highly resistant to bronze birch borer.

River birch prefers a moist slightly acidic soil, and once established, it adapts to moderately dry ground. Mulch with pine needles or pine bark to favor an acidic soil. Otherwise, leaves may turn chlorotic (yellow) in summer if soil pH runs slightly alkaline. Feed with a slow release fertilizer such as Osmocote™ or Nutrikote™ in early spring. If soil pH becomes alkaline, apply elemental sulfur or chelated iron (follow precise package directions). Birches are bleeder species and are best pruned in summer.

River birch trees grow rapidly and require minimal annual care. Tree exhibits 4-season landscape interest. They are often planted in parks, golf courses and other public areas. Homeowners plant clump-growing river birches around deck and patio areas. Fall leaves decay rapidly and are an easy clean-up.

Halloween Pumpkins And Gourds

Posted by Hugh on October 3rd, 2017

Swan Gourds

American Tondo gourd

It’s Pumpkin Time!…celebration of Halloween across America. A local pumpkin farm had over 60 kinds of pumpkins to choose from.

According to the Missouri Botanical Gardens website: “the term pumpkin really has no botanical meaning”. Pumpkins and gourds are classified as squashes in the Cucurbitaceae family along with cucumbers and melons.

If you want to grow pumpkins and gourds, they require fertile soil and lots of fertilizer to support the vines and fruits. Apply 2-3 lbs. of 19-19-19 (N-P-K) per 1000 square feet at planting time followed by an additional 1-2 lbs. per 1000 sq. ft of bed of actual nitrogen (N) or ammonium nitrate at 3 – 6 lb. per 1000 sq. ft. rate in mid-summer. Irrigate as needed and keep vines mulched.

Pumpkins and gourds are threatened by several potentially serious diseases (anthracnose, downy mildew, powdery mildew, and alternaria) and insects (striped and spotted cucumber beetles, vine borer, and aphids). Crop rotation is very important. Grow on new ground each year. Consult your local Extension office or state university for the latest Pesticide Recommendations to manage pests and diseases on gourds. Luffa types are generally tolerant to insects and diseases. Be “Bee Aware” and other important pollinators of vegetable crops.

Wagon full of ‘Casperita’

Proper harvesting is just as important as growing pumpkins and gourds. Fruit skins are sensitive to injury. Luffa gourds are thick skinned and are harvested when the fruits turn brown. Cut gourds with a sharp knife or pruning shear. Leave some of the stem remaining, as stemless gourds are not as ornamental for decoration.

Wash fruits with a mild non-bleaching detergent and with a soft brush. Space gourds apart (not touching) in a dry place with good ventilation and out of the sun. Once thoroughly dry and hardened, gourds can be waxed and/or decoratively painted.

Saving Seeds – this is a common practice. However, many types freely inter-pollinate and their progeny may not look the same. The saved seeds are collected, dried, and stored in a cool, dry spot for 3 to 4 years.

First Days Of Fall…. Bring In Your House Plants

Posted by Hugh on September 30th, 2017

Schefflera

Norfolk Island Pine

The final days are summer are over. It’s time to move your tropical plants indoors before night temps in the low 40°F arrive. These plants thrive outdoors in summer temperatures and high humidity, but cannot survive being left outdoors. Container plants such as Ficus (rubber) trees, orchids, Norfolk Island pines, scheffleras, bromeliads, gardenias, palms, and lots more should be brought indoors. Cacti and succulents have probably doubled in size in the humid summer air and may need to be repotted.

Inspect and eliminate all bugs and diseased leaves before bringing plants into your home. Apply an insecticide labeled for houseplants. Insecticidal soaps are quite effective both inside and outside the home. Do not spray pesticides like malathion and diazinon indoors. Target aphids, mites, mealy bugs, and scales. Also inspect for freeloaders or nuisance pests such as earwigs, boxelder bugs, sowbugs, ants, and squash bugs which often hide on the bottom of pots. Some of these bugs multiply like crazy once they get inside your home.

If you have a garage or breezeway that receives filtered sunlight, move the plants into this halfway shelter for a week or two to acclimated to the lower light conditions indoors. Once inside, a room with a south- or east-facing window is ideal for most tropicals, although desert plants like cacti are best set in a west-facing window.

Put your plants on a diet, e.g. from fertilizer and water. Light levels are reduced and room temperatures are cool (65 to 72°F) through fall and winter seasons. Water plants every 7-10 days and mist tropicals every day to raise room humidity.

Winter Planting –Why Not!

Posted by Hugh on September 27th, 2017

Needle scorched Arborvitae after cold dry winter

Healthy Mix of Evergreens

For those who live in northern regions where winters are cold and snowy (USDA hardiness zones 3-6), many (not all) gardeners can still plant many kinds of trees, shrubs and perennials in late fall and winter if the ground is not frozen. Deciduous plants are in their natural period of rest or dormancy. This does not include evergreen trees and shrubs.

Deciduous vs Evergreens

Fall planting of deciduous trees works better because their need for water is a lot less in winter. Evergreens retain their leaves/needles all winter. Leaf metabolism is a lot less than in summer. Once the ground freezes, roots have trouble foraging for water, and by late winter, leaves/needles may become scorched along the edges, turn brown or die. Fall planting can be more difficult for broad-leaved evergreens like rhododendrons or hollies (Ilex). Mulch around evergreens before the ground freezes to trap in soil warmth and stimulate root growth.

Soil -Water Availability

Across the U.S., winter weather is very different. In the upper Midwest, the fall season is short, and winter is usually long and frigidly cold. The ground freezes early and stays through early spring in most years. Here, spring planting is more reliable with plentiful rainfall.

Along the Pacific coast (Washington, Oregon, and California), fall-winter planting makes sense. Summers are hot and very dry. Fall and winter are long cool periods with lots of rainfall that is ideal for root growth. The ground rarely freezes along the coastal areas.

Plant availability is a significant concern. Generally, garden centers and nurseries do not holdover huge inventories of trees and shrubs. Finally, in regions where winters are cold, magnolia, dogwood, tulip tree, sweet gum, red maple, birch, hawthorn, tulip poplars, cherries, plum and many oak species are more susceptible to winter injury (Purdue University study).

Sizing Up Crape Myrtles (Including Most Recent Introductions)

Posted by Hugh on September 24th, 2017

Delta™ Jazz crape myrtle at UNiv. of Tennessee Gardens, Knoxville

Delta™ Flame crape myrtle

Hybrid crape myrtles (Lagerstroemia fauriei x indica) have undergone significant makeovers over the past quarter century. Several new cultivar series continue to arrive garden centers, including: Black Diamond™ series, Enduring Summer™, Delta™ series, and Magic™ series.

In landscape terms size is very important and gardeners often make a serious error when not calculating the size of crape myrtle for the planting space. Crape myrtles fall into four size categories. Included here are a sampling of the major cultivars based on popularity in the mid-South region (Northern Atlanta thru Eastern Maryland):

Four Height Groups and Flower Color

Dwarf (less than 5 feet)
‘Pocomoke’ – rose pink
‘Berry Dazzle’ – fuchsia
‘Cherry Dazzle’ – vibrant red

Semi-dwarf (5 to 12 feet)
‘Acoma’ – pure white
‘Dwarf Centennial’ – lavender
‘Hopi’ – light pink
‘Tonto’ – fuchsia (red)
‘Zuni’ – medium lavender

Intermediate (13 to 20 feet)
‘Apalachee’ – light lavender
‘Dynamite’ – cherry red
‘Lipan’ – medium lavender
‘Osage’ – light pink
‘Sioux’ – dark pink

Tree type (23 feet and higher)
‘Carolina Beauty’ – dark pink
‘Muskogee’ – light lavender
‘Natchez’ – white
‘Tuscarora’ – dark coral pink
‘Tuskegee’ – dark pink, almost red

New crape myrtle series:

Black Diamond™ Series – 10 to 12 feet high and 8 feet spread with almost black foliage. Currently there are 9 cultivars ranging from red shades, pink shades, white, purple, and lavender.

Magic Series™ from First Editions® is a selection of intermediate size crape myrtles with glossy disease-free foliage; they bloom all summer into fall and hold their leaves until late. Currently there are 8 cultivars in the series of various sizes and color range.

Delta Series™ are part of the Southern Living Plant Collection (USDA hardiness zones 7-9); there are currently four cultivars in four colors: white, red, lavender, and light pink; foliage- unique burgundy, cupped leaves; grow between 6-10 foot tall.

Enduring Summer™ are part of the Garden Debut Plant Collection (USDA hardiness zones 7-9); there are 6 cultivars and grow 4-5 feet tall and wide

Eliminating Messy Fruits From Large Landscape Trees

Posted by Hugh on September 21st, 2017

Ginkgo fruits littering area

Walnut cleanup at Chanticleer Gardens, Wayne PA.

Messy fruit from yard trees are dreaded by property owners as well as park and city employees. Some notorious culprits are sweetgums, sycamores (planetrees), oaks, mulberries, persimmons, and (female) ginkgoes. Fruits include hundreds of hard nuts or pulpy, smelly, and potentially hazardous covering sidewalks, driveways, and parking lots.

Foliar sprays are available to reduce or eliminate undesirable fruits from developing on trees. Timing of application(s) are critical and environmental factors make absolute control impossible. Results also vary by each chemical labelled to retard or eradicate fruit development.

For example, preventing acorns on your oak tree is to chemically burn male catkin and female flowers. No registered product is effective for all plants. Florel® is only growth regulator labeled to reduce acorn formation. Application time can often be pure guess work and may be successful less than 50% of the time. Multiple applications may be needed. Spraying your tree can be costly and time-consuming. Hand-removing flowers or small fruits may work on a small tree, but is impractical for large shade trees and for large properties.

Fruits numbers can vary from one year to the next. A mature walnut or oak tree may produce a heavy crop one year and a light one the following 1-2 years. Diseases, pests, and spring weather factors may injure flowers and reduce fruit production.

For large trees you should hire a licensed pesticide applicator or tree professional to achieve adequate results.

Timing of application: Spraying before or after flowers results in wasted time and money and time of application should be between 60 and 95°F. Follow label directions closely.

Chemicals are available to reduce or eliminate fruit set on ornamental trees and shrubs. Follow specific label directions for application rates and safety information.

Florel® Fruit Eliminator (ethephon)

Fruitone® (Naphthalene acid (NAA))

Sevin™ (Carbaryl) – warning: harmful to bees and other pollinators

One final option is to plant landscape plants that are not messy. Yes, lots of beneficial trees produce fruits, but birds and other wildlife usually consume most of them. Male cultivars of large landscape tree include honeylocust (Gleditsia), ash (Fraxinus), fringetree (Chionanthus), redbud (Cercis), and others. Avoid planting hollies and other fruit producing plants adjacent to walkways.

Pest Alert – Emerald Ash Borer Update

Posted by Hugh on September 18th, 2017

Fringetree- Potential host for EAB

EAB Diagram (from Dr. Frank Hale, Univ. of TN Extension Entomologist, Nashville)

Recent news about Emerald Ash Borer continues not to be good. Almost weekly, state officials report the spread of this pest in their state. Emerald ash borer (EAB) is an invasive metallic wood boring or flat-headed wood boring beetle that is killing all species of North American ash trees (Fraxinus spp.). Since 2002, EAB has killed tens of millions of ash trees.

In the botanical world, European olive (Olea europea) and native fringe (Chionanthus virginicus) trees are ash relatives. White fringetree is native to the United States and grows wild from New Jersey south to Florida and west to Oklahoma and Texas. It is also a popular landscape tree in other parts of the country. Some fringe trees in the Midwestern U.S.have been found EAB infested.

Scientists at Wright University in Dayton, OH report the innate potential of EAB to use European olive trees as an alternate host under laboratory conditions. In the field conditions, EAB has not been found in olive trees—at least not in North America. Also,numbers of EAB infested fringetrees in the Midwest and Northeast are still low.

Community readiness is the key. EAB continues to expand its range across the U.S. In preparation for the arrival of EAB, the location of newly infested ash trees is first determined and the trees protected with systemic insecticides. Bio-control efforts are ongoing, and parasites may be released in attempts to reduce numbers of emerald ash borers. Ash trees in poor health are quickly removed and destroyed.

Quarantine procedures should be followed. In particular, potentially infested firewood should not be transported outside of quarantine areas.

Information and Photo Credits: Louisiana State University Ag Center in Hammonds and University of Tennessee Plant Diagnostic Lab in Nashville.

Robb’s Spurge (Euphorbia)

Posted by Hugh on September 15th, 2017

E.-amygdaloides-robbiae at Atlanta Botanical Garden

E. amygdaloides robbiae spring bloom at Atlanta Botanical Garden

Robb’s wood spurge at Virginia Tech’s Haun Garden, Blacksburg, VA

I always been a fan of spurges, but some have not perform well in my garden. One that does not disappoint is Robb’s spurge (Euphorbia amygdaloides var. robbiae), aka “Mrs. Robb’s Bonnet”. This evergreen spurge grows equally well in either sun or shade, including dry shade (USDA hardiness zones 6-8).

This carefree slowly spreading groundcover displays shiny, dark green, leathery leaves. The vegetative clump grows 12-18 inches high. Robb’s spurge looks fantastic in either a pot and in the garden. In its northern range, it should be planted in a wind protected location for best winter foliage.

In very early spring the chartreuse flowers of Robb’s spurge unfurl in dramatic fashion, presenting 18-inch tall stalks of flowers last for months. By mid-spring the yellow green “flowers” are glorious. They are actually colored bracts which arise independently from the base of the plant in clusters. Bracts remain colorful long after the flowers have passed. Pruning cuts reveals the milky sap, which is usually poisonous. Deer and rabbits stay away, but you should also keep way from small children.

Euphorbias make up of one of the largest and most diverse plant families in the world. The milky sap of many herbaceous Euphorbia species have traditionally been used as a purgative or a laxative, hence the common name “spurge”.

Robb’s spurge is a carefree plant, almost too easy to grow. However, beware of what you ask for. Over time the clump spreads via rhizomes which is “containable”. It spreads quicker if the soil is moist and loose with organic matter. It tolerates more shade than most other Euphorbias.

Robb’s spurge is easily propagated by division or cuttings. Useful as a dry shade ground cover or along wooded paths interwoven with more ephemeral plants.

‘Sunshine’ Privet: A Great Accent Shrub and It’s Not Invasive

Posted by Hugh on September 12th, 2017

‘Sunshine’ Privet (photo credit: Ball Horticulture)

‘Sunshine’ privet in Kingwood Center in Mansfield, OH

For generations ligustrum (privet) had been a landscape plant in East Coast and Southern gardens. However, in several states, privets have become declared as an notoriously invasive species . Unfortunately, you should never brand all privet cultivars the same way.

Sunshine privet (Ligustrum sinensis ‘Sunshine’) is likely to change your mind (USDA hardiness zones 6-10). This privet is sterile, e.g. this privet produces no viable flowers or fruits.

It is a long-lived evergreen shrub exhibiting 4-season interest. Its compact nature makes it an ideal choice in small urban gardens. Its golden foliage also tolerates foul city air. Along coastal areas, Sunshine privet is also salt tolerant.

Sunshine privet is a terrific accent plant. Its foliage is strikingly golden year-round. Utilize it in containers, set some out for low hedging, or mass several around as edging along walkways. Again, it will not re-seed into other areas of your landscape.

Unpruned mature plants reach 3-6 feet high and 3-4 feet wide in 10 years. For best color, the golden foliage shines in full sun; it grows in average soil that is adequately drained. Feed in early spring with a slow release fertilizer such as Osmocote® or Nutrikote® at package directions. This shrub is also highly drought tolerant after its first season. Freshly installed dark colored mulch makes the Sunshine privet planting a standout.

If you are handy with a hedge trimmer, Sunshine privet can be maintained as a short formal hedge, as low as 1 foot tall. I’ve seen it utilized in a garden railroad scene where it was clipped every 2-3 weeks. How about including it in a formal knot or quilt garden.

Sunshine Privet is not troubled by disease and insect problems. In general, privets are not a favorite food of deer, but they will damage plants where population are high.