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

Bedding Geraniums Excel In Cool Weather

Posted by Hugh on March 24th, 2016

Bedding Geranium at Disney Epcot in mid-January

Bedding Geraniums in Containers at Disney Epcot in mid-January

Zonal Geraniums at Disney Epcot

Over the past decade, the zonal or bedding class of geraniums (Pelargonium x hortorum) have become summer favorites in northern gardens (USDA hardiness zones 3-7). Geraniums thrive in cool weather, but are also widely planted in zones 9-10 gardens where winter temperatures are moderate. Increasing numbers of colorful varieties beautify flower beds and container gardens.

Leaves are marked by distinctive bands or “zones” of dark markings. Single or double blossoms are clustered into ball-shaped heads. Most zonal geraniums are seed produced and color choices include red, pink, salmon and white. Plants are compact in habit.

Geraniums should be planted in a compost-rich, well-drained garden soil or peat-based media for containers. Plant in full day sunlight to attain maximum blooming potential. Space plants 8 – 12 inches apart. Mulch to moderate soil temps and reduce weed infestations. Feed a granular fertilizer such as 10-5-10 at planting time and supplement with any water soluble fertilizer such as Miracle-Gro®, Peters®, or Schultz® every 3-4 weeks up to the first days of autumn.

When purchasing plants at garden center, choose those that are compact in habit, with blemish-free foliage, and full with flower buds. Zonal geraniums do not require constant deadheading, but monthly removal of seed heads will increase bloom numbers.

Zonal geraniums are disease and pest resistant when properly sited in the landscape. Geraniums prosper with summer irrigation. Geraniums need good air circulation, but need protection from strong winds. Over dry summer intervals, geraniums require weekly watering. Do not over irrigate geraniums as it will increase fungal leaf spots and dreaded botrytis diseases.

Three Easy Care Native Woody Plants

Posted by Hugh on March 15th, 2016

Red Buckeye in Flower in Early May

Plumleaf azalea in July

Red buckeye (Aesculus pavia) is a nearly perfect small native tree for either a full or part sun site. Decorative 5 to 9 inches long reddish flower candles form on tips of branches in late April and May (USDA hardiness zones 6 – 8). Hummingbirds will seek out the dark orange to scarlet tubular blooms.

Lustrous, dark green, palmately compound leaves cover branches from spring thru most of summer. Leaf diseases and summer drought may scorch or mar leaves in late summer. Most years, leaves drop prematurely by September ahead of other landscape trees.

Virginia sweetspire (Itea virginica) shrub flowers in late spring and has dark green, pest-free summer foliage that turns brilliant red in fall (USDA hardiness zones 5-9). It thrives in full sun to partial shade, and in moist, mildly acidic soils. Once established, it is also highly drought tolerant. Fertilize with a slow release fertilizer in early spring.

Virginia sweetspire grows 4 to 6 feet tall and wide, depending on cultivar. Pruning is rarely needed except to remove unwanted suckers after flowering is finished. Selected cultivars include: ‘Henry’s Garnet’ @ 5-6 feet; ‘Little Henry’ @ 4 – 5 feet; or ‘Merlot’ @ 3 – 3 ½ feet

Plumleaf azalea (Rhododendron prunifolium) is an Alabama/southwest Georgia native shrub that blooms in late July (USDA hardiness zones 6-9). Orange-red flowers brighten up its garden spot. A dark red flower selection is also available. Flowers are not fragrant, but do attract numerous butterflies and bees.

Plumleaf azalea grows in average well-drained soil and in part day sun or high shade. Irrigate weekly during summer dry spells. Shrub seems insensitive to soil pH; likely it prefers an acidic range between 5.5 to 6.5. No diseases, pests or deer trouble it. Pruning is rarely necessary. Plumleaf azalea grows 8-10 feet tall, but may be maintained to 5-6 feet in height and width.

Note: These wonderful natives are rarely sold at local garden centers. Find them at native plant or at e-commerce nurseries on-line.

Virginia sweetspire flowering in June

Slow Release Fertilizers Save Money

Posted by Hugh on March 3rd, 2016

Organic Fertilizers On Shelf Of Garden Center

On garden center shelves in the spring are slow-release fertilizers. Trade names include Scotts®, Osmocote®, Fertilome®, Hi-Yield®, and Vigoro®. Many are formulated for lawn use. Cost for these products are more than traditional granular fertilizers but prices have dropped over the years and they are better to use environmentally.

How do you compare and choose slow-release fertilizers? First, find the product in the proper ratio based either on your soil test analysis or crop needs. A 1-1-1 ratio fertilizer (10-10-10 or 19-19-19) is standard for flower and vegetable gardens. If phosphorus levels are high or very high, look for a no- or low- phosphorus fertilizer such as a 20-1-20 or 4-1-4 ratio.

For landscape trees and shrubs, a ratio of 3-1-2 or 3-1-1 is more appropriate than a 1-1-1. Turf fertilizers such as 18-6-12 or 24-8-16 are examples of 3-1-2 ratios which can be used for trees and shrubs as well. Fertilizer for bulb crops (tulips, lilies, gladiolas, etc.) should be high in phosphorus.

The benefits of a slow-release fertilizer is they slowly supply a steady supply of nitrogen to plants all season long at a time when they can use the nutrients. Nitrogen is absorbed by the plant and not lost by leaching. Slow release fertilizer is rated more environmentally-friendly. They are heat sensitive. Less nitrogen is released when the soil is cold in early spring, and more goes to plants when they’re actively growing in summer.

Natural organic fertilizers are a separate class of slow release products. Milorganite™ (5-2-0) is a safe organic fertilizer manufactured from municipal waste. Blood meal (12-0-0), rock phosphate, muriate of potash, and cotton seed meal (6-2-1) are other examples.

Timing Critical For Applying Crabgrass Preventive

Posted by Hugh on February 24th, 2016

A Weed-free Lawn Is Possible

Crabgrass in lawn before mowing

To control crabgrass and other lawn weeds, 1. maintain a vigorous healthy turf so weeds can’t get established, and 2. apply the proper pre-emergent herbicide at the right time. Pre-emergent herbicides do not kill weeds; they prevent weed seeds from germinating. It’s that simple.

Timing is important! In many states (USDA hardiness zone 5), apply pre-emergent herbicides to lawns against summer weeds by March 15 or winter weeds by September 15. If you live south of the Mason-Dixon line (Delaware and Maryland is south), this means a week earlier. In Atlanta and further south, subtract another week or March 1 on your calendar

Crabgrass seeds germinate when spring soil temperatures warm to 50 °F and higher. What! don’t have a calendar hanging up? If forsythia starts blooming where you live, rush to apply any of following products listed below. All give excellent control of summer crabgrass; fall applications control annual bluegrass in winter:

benefin (Balan, many products labelled “Crabgrass Preventer”)
bensulide (Betasan)
oryzalin (Surflan, Weed Impede)
pendimethalin (Halts, Pendulum)
prodiamine (Barricade, Prodiamine 65 WDG)
Surflan + Balan (XL 2g)

The key is timing of application. Pre-emergent herbicides must be applied before crabgrass seeds germinate. Early fall application should reduce numbers of most winter annual weeds. Lawn and grounds should be irrigated for a minimum of 2 hours within 48 hours after herbicide application.

Date of second application (in Tennessee, southwest VA and Western NC) is usually September 15 for annual bluegrass, henbit or chickweed; these nasty weeds germinate in your lawn and garden in fall and winter months.

Caution: Always read all herbicide labels thoroughly before applying the product. Know what grass species (bluegrass, fescues, ryegrasses, burmuda, zoysia, St. Augustine, centipede) makes up your lawn and what weed(s) you are trying to suppress.

Little Girl Hybrid Magnolias

Posted by Hugh on February 18th, 2016

Magnolia x ‘Ann’

Magnolia x ‘Susan’

Star (Magnolia stellata) and tulip (M. soulangeana) magnolias are early flowering magnolias. Early spring frosts destroy open flowers. In the mid-1980’s the U.S. National Arboretum released 8 shrub-type cultivars as a series called the “Little Girl Magnolias”. They are hybrid crosses between M. liliiflora and M. stellata. Four cultivars- ‘Ann’, ‘Betty’, ‘Susan’, and ‘Jane’ – became the popular choices in the series (USDA hardiness zones 4-8).

These hybrid magnolias turned out to be great leaps forward in developing a late flowering magnolias that avoided frost injury. Each Little Girl cultivar blooms in early spring (some places in late spring). Large goblet-shaped flowers are comprised of 6 to 9 inches long strap-like tepals (petals and sepals) and are real eye-catchers.

Flower colors vary by cultivar, in pink to purple shades: Ann (pinkish-red), Betty (reddish-purple), Jane (dark purple), Susan (purplish red). They often surprise with occasional blooms in the summer and early fall. Plants are commonly multi-stemmed large shrubs, but can be trained as small trees. Over ten years these deciduous shrubs will measure 10- 15 feet height and spread.

Little Girl magnolias grow in moist, well-drained soil, preferably an acidic pH, and in full to partial sun (4 – 5 hours minimum sunlight). Roots will not tolerate soppy wet ground. Prune spring flowering magnolias soon after the spring flowering flush is over. Prune to remove basal suckers and to maintain the desired form of the shrub or tree magnolia.

The deciduous leaves are thick and leathery and cope summer heat and drought. With proper care and in the right planting site, these hybrid magnolias are generally long-lived and disease and pest problems are rare.

Changing Bigleaf Hydrangea Flower Color

Posted by Hugh on February 14th, 2016

‘Endless Summer’ Hydrangea

Bigleaf Hydrangea at pH 6.4 or higher

Bigleaf hydrangeas (Hydrangea macrophylla), aka “hortensia” hydrangeas, bear pink flowers in low acidic and alkaline soil and blue flowers in mildly acidic soil. Some tips about regulating soil pH and flower color in bigleaf hydrangeas follows.

First, a short review about soil pH. Soil pH measures soil acidity/alkalinity on a scale of 0-14, with 7.0 being neutral. Numbers above 7.0 indicate alkaline soil while numbers below 7.0 indicate acidic soil. Bigleaf hydrangeas flower blue if the pH is between 5.0 and 6.2. Flowers are pink if soil pH rises to 6.4 and higher.

Flower color is an expression of the amount of aluminum ions (Al+++) in the soil. Aluminum is most available to the plant in acidic soil, and less available in alkaline soil. Gardeners typically purchase aluminum sulfate to lower soil pH. Unfortunately, aluminum toxicity to plants is a big concern because hydrangeas need only small amounts of Al+++.

Garden and shrub beds near cement or concrete foundation walls, sidewalks and driveways, often exhibit low acidic or slightly alkaline soil pH. Over many years limestone leaches from the cement or concrete. While limestone is ideal for most vegetables, flowers or lawn grasses, bigleaf hydrangeas will bloom pink instead of blue.

Pink Flowered Hydrangeas: Gradually add hydrated or dolomitic lime to raise soil pH above 6.2. Be careful on the amount of lime that you add. Above pH 6.4, the quantity of available iron in the soil may become deficient or unavailable to the plant. The hydrangeas take up aluminum best at lower (more acid) pH levels. By raising soil pH, Al+++ is less available to the plant.

Blue Flowered Hydrangeas: For bigleaf hydrangea to flower blue, add aluminum sulfate to garden soil or garden container. Distribute even amounts of aluminum sulfate into soil around the drip line of each shrub. Use of pine needle or bark mulch aids to keep soil slightly more acidic.

Directions: Apply 1/2 oz (1 Tbsp) aluminum sulfate per gallon of water be applied to plants monthly. Irrigate plants immediately following application to prevent burning roots.

Caution: using high amounts of phosphorus fertilizer may result in pink flowered hydrangeas. Soils low in phosphorus and high in potassium bloom more.

List Of Dioecious Trees And Shrubs

Posted by Hugh on January 29th, 2016

Kentucky coffeetree (Gymnocladus diocus)

Ginkgo or Maidenhair tree (Ginkgo biloba)

Some tree species are dioecious, that is produce single sex flowers (either male and female). Male flowers produce pollen and no fruits. Female flowers bear seeds or fruits. You may purchase male clones to avoid picking up messy seed pods or capsules in the fall. If you are allergic to certain tree pollens, avoid planting dioecious male trees.

Most popular of dioecious landscape shrubs are the hollies (Ilex spp.). In holly world many cultivars (varieties) seem to be specially “married” to one another. Gardeners may select female plants for their colorful fruits in fall and winter. Holly fruits may be red, yellow or white colored depending on the cultivar. Be certain that the correct pollinating variety has been planted nearby the specific female cultivar(s). For example, the male clone ‘Apollo’ will pollinate primarily ‘Sparkleberry’ female hollies.

Over the years male clones of several landscape trees have come to dominate our yards and gardens. Male fruitless types do not litter the ground with messy pulpy fruits and seed pods. Ginkgo is one such example. Female ginkgoes produce foul smelling apricot looking fruits. When the ripened fruits fall on sidewalks, the area around them reeks a horrible odor. Male ginkgoes produce no fruits and male clones are grafted by nurseries.

You may run into a third, slightly confusing group are “Polygamo-dioecious” species. This means the male and female flowers grow on separate trees, but occasionally produce perfect flowers on each tree as well. Best examples are certain species and varieties of Maples (Acer spp.), Honeylocust (Gleditsia triacanthos) and Spicebush (Lindera benzoin). These maple types produce few or no fruits in most years.

List of Dioecious Species:

Certain maples -example: boxelder maple (Acer negundo)

Tree of Heaven (Ailanthus altissima)

Japanese aucuba (Aucuba japonica)

Bittersweet (Celastrus scandens)

Plum yew (Cephalotaxus harringtonia)

Katsura tree (Cercidiphyllum japonicum)

Fringetree (Chionanthus spp.)

Smoke tree (Cotinus coggygria)

Persimmon (Diospyros virginiana)

Hardy Rubber Tree (Eucommia ulmoides)

Ash tree (Fraxinus spp.)

Ginkgo, maidenhair tree (Ginkgo biloba)

Honeylocust (Gleditsia triacanthos)

Holly (Ilex spp.)

Juniper (Juniperus spp.)

Spicebush (Lindera benzoin)

Osage orange (Maclura pomifera)

Mulberry (Morus spp.)

Bayberry (Myrica pennsylvania)

Amur Cork Tree (Phellodendron amurense)

Podocarpus (Podocarpus macrophyllus)

Poplar or Aspen (Populus spp.)

Willow (Salix spp.)

Yew (Taxus spp.)

Stinking Cedar (Torreya taxifolia)

Soil pH- What’s It All About

Posted by Hugh on January 18th, 2016

Rhododendron

Azaleas at Callaway Gardens

Soil pH is an indicator of the relative abundance of hydrogen (H⁺) ions and hydroxyl (OHˉ) ions in garden soils (Table 1). These ions play a very important part of soil fertility and a plant’s ability to absorb nutrients from the soil. The pH scale runs from 1 (highest acidity) to 14 (highest alkalinity). Soil pH of 7 is neutral.

Fourteen (14) of seventeen(17) essential plant nutrients are obtained from the soil. Most nutrients that plants need are readily available when the pH of the soil solutions ranges from 6.0 to 7.5, or slightly acid to neutral. Phosphorus is a major plant element that becomes less available below pH 6.0 and above 7.0.

Plants drink (absorb) nutrients that are dissolved in the soil water. Some minerals are more soluble in the company of H⁺ ions, and other minerals are more soluble in the company of OHˉ ions. Acid soils hold more H⁺ ions, and iron, manganese and phosphorus are more soluble in these soils. Alkaline soils have more OHˉ and calcium, magnesium, potassium, and molybdenum are more soluble in these soils.

Table 1: pH range and Nutrient Availability

Acidic Soil (below 7) Neutral = 7 Alkaline Soil (above 7)

More H⁺ Distilled (Pure) Water More OHˉ

Key Nutrients Most Available below pH 6: Key Nutrients Most Available above pH 7:

Iron Calcium

Manganese Magnesium

Aluminum Potassium

Molybdenum

Most (not all) nutrient elements are available between pH 6.0 to 7.0. As soil pH changes up or down, some elements becomes more soluble and available to the plant. Extremes in soil pH range, below 4.5 or above 7.7, may contain toxic nutrient levels and injure plant roots.

Certain plants have specific nutritional needs. Acid-loving plants (in the Ericaceous family) such as rhododendrons, azaleas, and blueberries are some examples. These plants don’t “love” acidic soil, but absorb higher amounts of iron compared to other plants. Ericaceous plants can not find enough soluble iron in neutral or alkaline soils where it is scarcer. They are also very efficient in absorbing phosphorus at a lower acidic pH.

What’s In Your Garden Soil

Posted by Hugh on December 10th, 2015

Tilled Garden Bed

Choice of 10-10-10 or 6-12-12 Blended Fertilizer at this garden center

There are two basic rules in gardening:

1. the right plant in the right place, and

2. properly feeding the soil that nourishes the plants.

Many problems in lawns and gardens can be avoided if the gardener knows what the fertility and pH of the soil is.

What is soil pH? It is a measure of the soil acidity or alkalinity. A pH meter will accurately measure this. Soil pH range varies from 0 – 7 – 14. Readings from 0 to 7.0 are acidic, 7.0 is neutral, and above 7.0 is alkaline. Most (not all) garden flowers, vegetables, and landscape plants (shrubs, trees and vines) grow best in the mild acidic range between 6.0 and 7.0. Outside this pH range, some minor nutrients like iron (Fe) and manganese (Mn) may become unavailable above 7.0 or in over supply below 5.0.

Soil tests are available from a number of sources: DIY kits sold at garden centers, on-line, or through mail order sources. The results obtained from these test kits are “ball park”. Soil testing from university soil labs or private labs is more accurate. For information about soil testing from university soil labs, contact your local Extension office in your state or county. For an extra fee, the lab may also determine your soil type: sand, silt, or clay.

Results from a soil lab should list: soil pH and suggest amounts of fertilizers and lime to apply to each area of your garden. Blended fertilizers contain nitrogen (N), phosphorus (P), and potassium (K). The analysis may suggest adding only nitrogen. Lawns may benefit from extra calcium and/or magnesium by liming. Dolomitic limestone (Dolomite) contains magnesium (Mg) and hydrated lime supplies calcium (Ca). If you need to lower soil pH, say for growing blueberries or azaleas, how much sulfur (S) should you apply per 1000 square feet.

Frequently, autumn through mid-winter period is the best time to test rather that in the spring. Labs are very busy at that time and a report may take 4-6 weeks to process.

Stop Inviting Critters to Your Property

Posted by Hugh on November 27th, 2015

Haven for Unwanted Critters?

Landscaping practices can influence pest populations. Old landscape timbers, particularly those that are partially rotted, may provide food for termites. powder post beetles, and carpenter ants. Numbers of millipedes, earwigs, crickets, sowbugs, and clover mite larvae may be greatly reduced if piled up old branches and boards are properly disposed of.

Mosquito populations rise in wet summer weather when buckets, plugged up eaves, old tires lay around filled with stale rainwater. Mosquitos carry serious health risks such as the West Nile virus and malaria.

Never distribute organic based mulches near house wood siding and low window sills. Watch wood chip mulch and other wood products on or in the soil (lumber scraps, boards, firewood, pallets, etc.) for signs of activity if termites are present in your area. Keep wood-based mulches several inches away from the house foundation. Bark-based mulches are permitted. Never allow soil or mulch to contact wood- made windowsills or house siding. Periodically inspect mulched zones around your home and garage for signs of termite activity.

Remove old fallen branches to discourage rodents and snakes from nesting. Firewood can also harbor large cockroaches, carpenter ants, wood-boring beetles, termites and others. Clean leaves and debris from gutters.

Overgrown weeds and grasses on abandon properties and vacant lots become the major weeds in the entire neighborhood. Noxious weeds gain a foothold in residential areas by one neighbor who does not take ordinary care of his or her property. In a short time invasive plant species such as multiflora roses, ivies (adult forms), honeysuckles, Johnson grass, and thistles cost muncipalities tens of thousands of dollars to eradicate.