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

Princess Flower Excels Where Summers Are Hot

Posted by Hugh on May 1st, 2018

Princess Flower in container

Closeup of flower

Princess Flower or Glory Bush (Tibouchina spp.) is a tropical shrub (from Brazil) that produces beautiful showy purple flowers. It blooms over a long time span (USDA hardiness zones 9-12). The most popular species in cultivation is T. urvilleana. A well-tended plant can be trained into a miniature tree in a large container for patios and decks.

This fast growing tropical needs an organic-rich, moist, well-drained soil. Sunlight and proper soil moisture are key components for nurturing a strong healthy plant. Under partial shade, shoot growth tends to be leggy and flower numbers are a lot less. Plant requires frequent (bi-weekly) pinching to increase branching.

Plant should be fed every 3 weeks with a water soluble fertilizer such as Miracle-Gro™ or Jacks™. An alternative nutrition program is to feed a controlled-release fertilizer such as Osmocote™ or Nutrikote™ to soil or container media.

Princess Flower produces 3-inch wide violet or purple flowers, particularly all summer long in southern climes. With proper care a plant in soil may reach 10- 15 feet tall and 6-10 feet wide. In a large container, expect less than half that size. Heaviest blooming happens in summer and falls of as air temps cool in the fall. In zones 8 (winter low temps around 20-25°F), Princess Flower may flourish through the Thanksgiving holiday. Further north move plant(s) into a greenhouse or sun room. Holdover plants should be cutback hard, repotted, and fed every 4-5 weeks from December thru February.

Popular cultivar is ‘Athens Blue’ with deep purple flowers. Scale, nematodes, and geranium budworm are occasional problems.

Warning: if you live in a warm region where Princess Flower is hardy, remove seed pods to prevent Tibouchina from becoming invasive.

Erosion Control – Try Weeping Lovegrass

Posted by Hugh on April 28th, 2018

Weeping Lovegrass (Eragrostis curvula) at Biltmore Estate in Asheville, NC

Weeping Lovegrass (Eragrostis curvula) is a warm season, perennial bunchgrass. It grows to a height of 2-4 feet and the long narrow 1/4 inch wide leaves (10 to 20 inches in length) suggest the grass is “weeping”. Seed heads may be erect or drooping and produce small very numerous seeds (1.5 million per lb.). Weeping Lovegrass is easily established by seeds and spreads by tillering. Over a years time a single plant can colonize an area 12-15 inches in diameter. Lovegrass was first imported into the U.S. from South Africa in the late 1920’s.

Weeping Lovegrass grows best in the dryland agriculture of Texas, Oklahoma, Arizona, New Mexico, Nevada and California (east of mountains). Weeping lovegrass is also used along roadsides and for hillside stabilization in the Mid-Atlantic States. The species establishes rapidly, produces a deep rootsystem, a key feature for erosion control. Unlike its native cousin, purple lovegrass, weeping lovegrass is commercially available at reasonable cost.

Weeping lovegrass can be an aggressive competitor in ecosystems and is considered an invasive species in some states. It thrives on soils of low fertility. Fertilizer applications should be made in April for first seed crop and in August for second. Weeping lovegrass produces taller plants than purple lovegrass (E. spectabilis), but can still be considered a low-maintenance grass. The root system of weeping lovegrass is fibrous as well as deep and is utilized on steep embankments for erosion control.

It grows on almost any well-drained soil, but prefers the sandy loams. Lovegrass responds well to fertilization. Used for pasture (early spring / fall), hay, erosion control, and for steep bank areas throughout Western Plains and also used in transition zone of Eastern USA primarily for forage and erosion control.

Seeding Lovegrass: Weeping lovegrass is easy to establish from seed between May 1 and June 15. Seed are planted with small seed drill. At this time weed competition is less, seedling emergence is more uniform Rainfall is a lot less compared to early spring. Seed alone at a rate of 3 to 5 pounds per acre, or 1 to 2 pounds per acre in mixtures with other species. Fertilizer containing nitrogen (N), phosphorus (P), and Potassium (K) should be applied prior to seeding. A second N feeding may be applied in mid-summer.

‘Alleghany’ Viburnum Is A Four Season Gem

Posted by Hugh on April 25th, 2018

Viburnum ‘Alleghany’

Large shrub

Alleghany viburnum (Viburnum x rhytidophylloides ‘Alleghany’) aka lantanaphyllum viburnum, is a large easy to grow semi-evergreen (USDA hardiness zones 5-8). It will grow to about 10-12 feet tall and a spread of 12 feet at maturity. This low maintenance shrub is a hybrid cross between V. rhytidophyllum and V. lantana ‘Mohican’. The cross was made in the Netherlands in 1925 and released by U.S. National Arboretum in 1966.

Its leathery dark green leaves are resistant to bacterial leaf spot. Its stiff upright branches are coated with woolly gray-brown hairs on stems and on the undersides of leaves. Its semi-evergreen foliage makes it an excellent choice for privacy screening. Foliage is evergreen in the South.

In most years leaves turn purplish in winter and persist through ice and snow through late February. In mid-spring, showy creamy white flat-top flowers open at the ends of branches. Upclose, flowers emit an unpleasant stale fragrance. When adequately pollinated from other viburnum species planted nearby, spectacular clusters of dark red fruits are produced from late summer to early fall that look great against the coarse green foliage. Red fruits ripen to black and attract numerous birds.

Alleghany viburnum grows well in any soil as long as it is drains adequately. Sun to part shade sites are preferred. Flowers are more plentiful in full sun. Feed with a slow release fertilizer such as Osmocote™ or Nutrikote™ in early spring as leaves emerge.

Alleghany viburnum is rated a four-star landscape shrub, with multiple season assets including beautiful semi-evergreen leathery foliage, dependable flowering, and showy fruits in fall and winter. Established shrubs are highly drought tolerant. In early spring rake away old leaves and mulch viburnums for a clean appearance. This viburnum has no serious insect or disease problems.

Prune as needed immediately after flowering because next year’s flower buds form in summer. Best fruit set occurs with cross pollination from parents or clones of the within hybrid.

Benefits Of Mulching

Posted by Hugh on April 22nd, 2018

Trunk filled with compost

Mulching benefits garden soil and enhances the landscape appearance.

Here is how:

Pine needle mulch at Biltmore Estates in Asheville, NC

Prevents weed seeds from germinating, thereby reducing hand weeding.
Mulching keeps plant roots moist and cool in summer.
Fall mulching acts like a thermal blanket and aids newly set plants to establish their roots quickly.
Reduces the need to water the garden as often.
Conservation measure via soil runoff protection.
Reduces soil compaction which permits rainfall and irrigation water to penetrate the soil surface.
Encourages beneficial insects and microorganisms.
Mulch decomposes and improves the organic level of the soil.
Offers a tidy appearance to the garden.
Certain kinds of mulch increase or decrease soil pH over time. Decomposition of oak leaves, holly leaves, and pine needles will lower pH over time. Mulch derived from hardwood bark tends to raise soil pH slightly over time.

Acid-loving plants such as blueberries, rhododendrons, azaleas, mountain laurels (Kalmia), and many evergreen shrubs benefit from low pH soils. To raise soil pH, apply hydrated lime (contains calcium) or dolomitic limestone (contains magnesium). Mulches derived from fresh sawdust or wood chips may tie up available soil nitrogen and plant foliage turns yellow (chlorotic). Do not over apply uncomposted mulches around landscape plants.

Typically, spring mulching entails adding 3-4 inches of composted mulch which may be purchased from garden centers or big box stores. Your city may sell or giveaway partially decomposed yard waste, a mix of cut tree/shrub prunings plus lawn clippings and leaves which have been ground up and composed for 3-6 months.

When not to mulch: do not mulch fall-planted fruit trees and shrubs the first year. Vole and other critters make their winter homes in the mulch and gnaw on the sweet soft bark of these plants. After the winter is over, fruiting plants may be permanently mulched.

Uniquely Different Spider Azalea

Posted by Hugh on April 19th, 2018

R. stenopetalum ‘Linearfolium’ at Biltmore Estates in Asheville, NC

Although rarely seen, spider azalea (Rhododendron stenopetalum ‘Linearfolium’) will be a pleasing addition to your woodland garden (USDA hardiness zones 6-8). Few people would ever guess that it is an azalea. This airy shrub grows 3-4 feet tall and a whole lot wider. It is slow growing, but is worth the wait. This unique semi- evergreen azalea hails from Japan.

April blooming spider azalea.

The very narrow (ribbon-like) leaves of spider azalea are mostly deciduous, nearly 3 inches long, and crinkly textured. The pink April/May flowers are very spider-like and appear in terminal clusters of three. Flowering may last 4-6 weeks in a dappled shade garden locale and are lightly fragrant up close.

Flowers are unique in that the 1 1/4 inch-long pink sepals tend to be slightly larger than the pink petals. Flowers are borne on tips of branches. The overall shrub is finely textured and will catch the attention of friends and visitors to your garden.

Spider azalea thrives in cool shade, best in partial day sun, preferably in the morning. Roots demand a moist, humus-rich, well drained, acidic soil and high shade that permits filtered sunlight. Do not plant in deep shade. The foliage is easily harmed by dry winds.

Feed spider azalea at the same time as you fertilize other azaleas and rhododendrons — once annually in late winter or early spring. Use a slow release fertilizer such as Osmocote™ or Nutrikote™. Maintain a 2-3 inch layer of an acidic based mulch comprised of pine needles or pine bark chips. Pruning is rarely needed and performed to shape the plant or to remove a dead or broken small branch. Irrigate as needed the first year to establish new shrub. Disease or pest troubles are rarely seen.

A number of sources, including Niche Gardens in Chapel Hill in North Carolina and Woodlanders Nursery in South Carolina, NC, list the variety ‘Seigai’.

Growing Celosia In The Summer Garden

Posted by Hugh on April 16th, 2018

Celosia ‘Arrabona Red’

Cutflower celosias sold at a Brooklyn, NY market

Celosias (Celosia argentea), aka cockscomb, feather, and plume amaranths, are summer flowering annuals in most of the U.S. (USDA hardiness zones 10-11). Mature plant height varies by cultivars, generally between 6 inches and 3 feet in height, taller types grown for the florist market. Celosia plants are classified into three groups: a crested type (C. cristata), plume type (C. plumosa), and spike or wheat type (C. spicata).

Celosias prefer full-day sun, although a minimum of 6 hours of direct sunlight is adequate. A compost rich, mildly acidic, well-drained garden soil is ideal. Plants are set outdoors in the garden when spring daytime temperatures stay above 60 °F. Add 2-3 inches of an organic mulch after planting and deeply water newly set plants. Mulching aids to suppress weed infestation and in soil water loss from evaporation. Celosias are not water hogs, but need irrigation during long summer dry spells.

At planting time apply a slow release granulated fertilizer such as Osmocote™ or Nutrikote™ according to package directions. Over the summer months, if plants need additional feeding, use a water-soluble fertilizer such as Miracle-Gro™ or Jacks™ every 2-3 weeks through mid-September. With taller cockscomb varieties, tie flower stalks to stakes to keep them from falling over; or simply pinch back shoots by one-half to develop a bushier plant. In addition, remove spent flowers to promote new blooms.

Celosia is rarely troubled by disease and insect problems. Inspect plants for mites over a hot dry summer. Good soil drainage is absolutelyessential to avoid root rot problems. Leading plumosa varieties: ‘Arrabona’, ‘Fresh Look’, ‘Dragon’s Breath’, ‘Prestige Scarlet’. ‘Intenz’, Century® series, and ‘Flamingo Feathers’ are spike type celosia. Cristata types include Bombay® and Kimono® series. Floral color range is purple, deep red, wine red, gold, and yellow gold.

Simple Care of Crape Myrtles

Posted by Hugh on April 13th, 2018

‘Muskogee’ crape myrtle

‘Acoma’ crape myrtle on City Street in Charlotte, NC

Crape Myrtle Hardiness: Know how hardy the cultivar is. USDA hardiness zones 6 to 9).

Site Location: Crape myrtles love sunlight. Flower numbers decline in light to medium shade. Plant in average soil that is well-drained. Select the right cultivar that fits the allotted planting space. Mulch plant and water as needed the first growing season.

Planting Time: In most regions plant in early- to mid-spring. Summer and early fall will also work in southern areas. Water newly planted crape myrtle deeply at planting time and mulch around them to conserve soil moisture and prohibit weeds. Apply a granular fertilizer such as 10-10-10 or equivalent in early spring. Keep plant(s) irrigated through the summer months.

Pruning crape myrtles: grow naturally as small upright or vase shaped trees with multiple trunks (except small shrub types). Late winter (late February thru March) is the best time to prune crape myrtles. Crapemyrtles generally require only minimum pruning annually. STOP THE CHOP! –do not prune back crape myrtles to the same point every spring as you often see landscapers doing at shopping malls and industrial buildings. This is “crape murder.” Removing seedpods is an optional activity.

Avoid Disease / Insect Problems
In general, crape myrtles contact few disease and insect problems if you select the best cultivars for the area where you garden. In southerly regions (zones 7-9) inspect newly emerging spring foliage for crape myrtle aphids, particularly on the leaf underside. Sooty mold fungus usually follows. Leaves and stems turn black, that is clear evidence of aphid feedings. Aphids are rarely seen in northern areas (zone 6).

Aphid Resistant Cultivars: ‘Muskogee,’ ‘Natchez,’ ‘Tuscarora,’ ‘Acoma,’ ‘Tuskegee,’ ‘Hopi,’ ‘Zuni,’ ‘Biloxi,’ ‘Miami,’ ‘Wichita,’ ‘Apalachee,’ ,’Lipan,’ ‘Osage,’ ‘Sioux,’ ‘Yuma,’ ‘Tonto,’ and ‘Fantasy.’ Target aphids using any of the following insecticides: malathion, diazinon, or summer horticultural oils. Read and follow package directions.

Crape Myrtle Bark Scale is becoming a significant problem in the deep South.

Powdery Mildew Resistant Cultivars: ‘Hopi’, ‘Lipan’, ‘Osage’, ‘Regal Red’, ‘Sioux’, ‘Tonto’, ‘Tuscarora’, ‘Tuskegee’, ‘Apalachee’, and ‘Fantasy’. For susceptible cultivars, spray leaves at first sign of disease with Funginex™, Immunox™, Bayleton™, or Strike™ to reduce the spread of powdery mildew; repeat spraying as necessary.

Cercospora Leaf Spot Resistant Cultivars: ‘Fantasy,’ ‘Tonto,’ ‘Tuscarora,’ ‘Tuskegee’, among others.

Credit: South Carolina Extension for listing of disease and insect resistant cultivars.

Landscape Ideas Using Crape Myrtles

Posted by Hugh on April 10th, 2018

30 feet tall ‘Natchez’ crape myrtle

‘Cherry Dazzle’ crape myrtle

If you live in zone 7 and points southward, you are likely growing crape myrtles (Lagerstroemia indica x fauriei). Additional hybrid cultivars (varieties) are hardy in zone 6. Crape myrtles are loved for their spectacular summer flowers, colorful fall foliage, and exquisite peeling bark over trunks and branches. Cultivars range in size from dwarf selections that grow less than 5 feet tall to several that reach upwards of 30 feet plus. Know the mature height of the cultivar before you purchase it.

Landscape uses: Planted several together to create a large deciduous hedge or privacy screen; utilize low shrub types in the front foundation. Plant 1-3 specimen trees as a distinctive focal point near the patio. Select the right size for your needs. Larger types should not grow into power lines. Medium-size cultivars (12 to 15 feet) are a perfect choice in a narrow side yard or a small urban garden. Dwarf selections are suited for large containers in zone 7 and points south.

Dwarf (less than 5 feet height) – ‘Cherry Dazzle’, ‘Berry Dazzle’, ‘Chickasaw’, ‘Centennial’, ‘Victor’

Semi-dwarf (5-12 feet) – ‘Hopi’, ‘Zuni’, ‘Tonto’, ‘Caddo’

Intermediate (13-20 feet) – ‘Acoma’, ‘Lipan’, ‘Osage’, ‘Sioux’

Tree type (21-33 feet) – ‘Muskogee’, ‘Apalachee’, ‘Tuskegee’, ‘Natchez’

Crape myrtles perform best in full sun and are not finicky regarding type of soil, as long as it’s well drained. Soil pH may be acidic to mildly alkaline. Keep them properly mulched and irrigated over the first summer. Feed crape myrtles with granular 10-10-10 or equivalent in early spring just before budbreak. Young trees benefit from one additional feeding in early summer. Do not fertilizer crape myrtles after mid- August. Mature trees do not benefit from annual fertilizing and frequently draw off adequate nutrition from a nearby lawn area that has been fertilized.

When To Cut Back Foliage Of Spring Flowering Bulbs

Posted by Hugh on April 7th, 2018

Tulip planting

Narcissus + hyacinth

Once your tulips, daffodils and other spring flowering bulbs have bloomed, don’t be in a hurry to cut off the stems and leaves. Plant foliage serves an valuable role in the health and growth of bulbous plants. The green leaves absorb sunlight and carbon dioxide as a part of the process of photosynthesis.

The spent blossoms are no longer needed and should be removed as soon as the flowers fade. Leaving the old flowers may encourage seed formation which further exhausts the food supply in the bulbs. Unless you are interested in growing daffodils or tulips from seed, the old blooms should be pruned off. Bulb growth, including the formation of new bublets is promoted.

It is not unusual to see garden workers at large public and private gardens pulling up bulbs right after they have bloomed. Several hours later, they may be planting annuals and perennials for spring – summer garden displays. In this instance the bulbs are considered annuals and are dug up and discard. These bulbs are mostly depleted of food material and most will not re-bloom next year without new carbohydrates being produced. In fall, garden staff will plant new bulbs.

Most home gardeners want their bulbs to perennialize, e.g. come back every spring. For small gardens the following suggestions should help minimize the impact of spent foliage in your garden. About a month after the flowers have faded, the leaves will turn yellow. At this time cutback the all stems and leaves about an inch above the ground. If there is space, at least 3-4 inches between the bulbous stems, plant bedding plants between. For this purpose, I attach an augur bit to my power drill to set summer annuals. Add a layer of an organic mulch to the bed and you’re ready for a summer of dazzling color. Feed bulbs and new annuals in spring and summer. Your bulbs will be back again next spring.

Another idea is to interplant spring blooming bulbs with winter hardy pansies, wallflowers, diascias, dianthus, et.al. in the fall. Bulbs and pansies will offer a full bed of color. Once the pansies have finished flowering in the heat of late spring, you may fill the void with summer annuals

Bugleweed (Ajuga) Groundcover

Posted by Hugh on April 3rd, 2018

Bugleweed (Ajuga)

A. reptans ‘Catlin’s Giant’

Bugleweed, aka carpetweed (Ajuga reptans), is low-growing semi-evergreen groundcover that offers almost year-round appeal (USDA hardiness zones 3-9). It develops a low prostrate habit and spreads by runners that root into the soil. Attractive vertical spikes of flowers arise in mid- to late- spring. Cultivars abound with multi-colored flowers. Foliage variants range from light green, dark green, bronzed, purple, or variegated leaves.

Vegetatively, ajuga grows 2 to 5 inches tall, depending on cultivar. Attractive flower stalks rise 6 to 10 inches above the foliage. Small flowers come in blue, purple, pink, or white, depending on cultivar. Flowers are covered by bees and skipper butterflies. Tiny brown seeds follow on the persistent fruiting stalks.

After flowering you may raise your mower height to clean off spent flowers and seed heads, and to renovate old winter beaten foliage. Ajuga grows best in partial sun to full shade and thrives in humus-rich soil; it will grow in average, well-drained soil. Utilize ajuga to cover large flat areas and minor slopes, to edge walkways, and for rock gardens.

Feed with spring application of granular 10-10-10 or equivalent fertilizer and irrigate regularly during the hot and dry summer intervals. It is susceptible to crown rot under extremely wet conditions. Ajuga is easily propagated from daughter plants (runners) and from crown divisions. Over the years ajuga will intrude into lawn areas and flower beds.

Leading cultivars:*

‘Bronze Beauty’ – bright green-bronze foliage turns glossy deep purple in fall and winter; lilac-blue flower spikes.
‘Burgundy Glow’ (aka ‘Burgundy Lace’) – pink, white, and green variegated foliage; blue flower spikes.
‘Catlin’s Giant’ – vigorous growing, glossy, bronze purple/near black, crisp foliage; deep blue flowers.
‘Chocolate Chip’ – compact growing, small, glossy, bronze-maroon and green foliage; 2 inches tall lilac-blue flower spikes.
‘Metallica Crispa’ (also known as ‘Cristata’) – bronzed foliage is small and crinkled, resembling dark spinach, but is not as vigorous as other cultivars; blue flower spikelets

*Note: some variegated forms may revert to green or bronzed foliage.