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

Preventing Disease Outbreaks In The Garden

Posted by Hugh on November 21st, 2015

* Hand pruners to remove dead or diseased wood

Viral leaf spot on hosta. Dig up and destroy

When a sick plant has been diagnosed with a viral or bacterial disease, your only option is to remove the diseased branch by pruning or destroy the entire plant. You should start out by practicing prevention.

Prevention is adopting good cultural and sanitation practices. Consider the following measures:

Start with disease-free plants. Inspect plants before purchase for any kind of symptoms. This includes the roots as well.
Use new or clean pots when planting pots and large containers.
Minimize outdoor irrigation or reduce the time interval that foliage remains wet. Keep plant foliage as dry as possible.
Don’t take cuttings from weak or sickly plants.
Don’t crowd your plants. Increase air circulation between them. This is particularly true for disease organisms such as botrytis, and powdery and downy mildews.
Routinely disinfect tools such as propagation knives and scissors with bleach, alcohol or disinfectant solutions. A 15% bleach solution (1 part bleach to 15 parts of water) will sterilize tools. Wash used pots in a mild disinfectant.
Discard any plants showing symptoms — no questions ask. At the garden center, if a flat of tomatoes or pansies contains a few weak or sickly plants, do not purchase. Don’t replace sickly plants in each cell with healthy looking ones from another flat. The tray cells could also be contaminated.
If a friend gifts a cutting or plant from his/her garden, isolate a minimum of 2 weeks before adding it to your plant collection. Daylily rust and hosta X disease frequently get started this way.
Similar measures should be followed for insect prevention.

What You Should Know About Herbicides

Posted by Hugh on November 18th, 2015

Weedy Patch in Garden

Winter annual weeds

By definition a weed is any plant that you don’t want in your garden. Herbicides are vegetation killers and classified as a pesticide that kills weeds. When used incorrectly, herbicides may injure good plants as well. Always read and understand the package directions before using.

In a lawn or garden, you may be trying to control (manage) three different kinds of weeds: grasses, broadleaves, and sedges. Broadleaf weeds including dandelions, spotted spurge, buckthorn, purslanes and thistles. Fall and late winter (before new leaves emerge) are safe times to spray broadleaf herbicides. Most deciduous shrubs and trees are shedding their leaves and are less susceptible to the spray drift. Some herbicides are labelled to kill sedges only or grassy weeds only such as yellow nutsedge, dallisgrass, or quackgrass.

Check the weather forecast before spraying herbicides. Avoid spraying on windy days or on hot days over 85 °F as herbicides may drift or volatilize, injuring nearby garden plants. Hot summer temperatures increase chances of lawn injury from herbicides. It should not rain for 8-12 hours following an application.

For a herbicide to work, outside temperatures need to be 60 °F and higher over a 6 hour interval for contact broadleaf herbicide spray to be adsorbed inside the plant. Regardless the time of the year, weeds need to be actively growing for herbicides to work.

Don’t mow a few days before and 2-3 days following an application. Greater leaf coverage is important here. Don’t spray newly seeded areas and wait 3-4 mowings before treating a new lawn with additional herbicides.

Spring and early summer herbicide applications do not control perennial and woody vegetation such as brambles, poison ivy, and invasive species. Wait until mid-summer to start tackling these tough weeds; multiple applications are usually necessary.

Heavy weed invasion in lawns may be evidence of poor mowing practices, low soil fertility, or too much shade which favors the weeds more than the grass. Presence of knotweed and spotted spurge usually indicates bad soil compaction.

Stylish Boulevard Cypress

Posted by Hugh on November 15th, 2015

PomPom Boulevard Cypress

‘Boulevard Cypress’

A twist here…a turn there, that’s the unique growth of Boulevard Cypress (Chamaecyparis pisifera ‘Boulevard’). It is a popular medium-sized evergreen shrub for home and commercial landscapes (USDA hardiness zones 5-9). Boulevard cypress exhibits a twisted pyramidal form with soft, silvery blue foliage that also grows in a slightly twisted manner. The fine, texture feathery needles take on a slight purplish tint during the cold winter months.

Boulevard cypress grows to mature heights of 8 to 12 feet and 4 to 6 feet wide. Its annual growth rate averages 6 to 10 inches. It thrives in full sun to light partial shade. In warm Southern climes it enjoys a break from extreme hot midday summer sun. Boulevard cypress should be planted in moist, compost-rich, well-drained, slightly acidic soil. Mulching newly planted shrubs is highly recommended. Fertilize with granular 10-10-10 or an equivalent product in late winter – early spring.

Boulevard cypress is relatively free of serious problems although Phomopsis needle blight and root rot problems may occur when poorly sited. Older mature specimens often show up interior needle browning, which is blown away with a leaf blower if the buildup becomes excessive or unsightly. Seed and fruit formation are unimportant.

Utilize Boulevard as a specimen shrub, or 5-12 foot high clipped hedge or privacy screen. Garden centers may sell pompom forms. Plants should be spaced minimum of 6-8 feet apart to avoid overcrowding and eventual decline due to disease and pest problems. During the summer, inspect all off-colored evergreens for a buildup of mites; hose them down with water weekly.

Winterberry Holly Brightens Winter Scene

Posted by Hugh on November 12th, 2015

Winterberry Holly at NC Hwy Rest Area

‘Winter Gold’ holly in early fall at Atlanta Botanical Garden

To escape from dreary days this winter, brightened up your landscape with deciduous hollies. Among a long, long list of deciduous holly species, winterberry holly (Ilex verticillata) is the superior choice (USDA hardiness zones 3-9). Inconspicuous white blooms in spring are followed by red, orange, or yellow berries in fall. Compared to their evergreen kin, winterberry hollies shed all foliage in the fall, revealing the colorful berry fruits.

Winterberry holly is native to swampy areas in the eastern half of North America. Winterberries prefer full sun and a moist, acidic soil (at home in wet soil). Well established after two years, shrubs are drought tolerant; berry production is highest on swampy or boggy ground. Feed with granular 10-10-10 or equivalent or with Holly-tone® in late winter or early spring.

In spring bees pollinate the tiny holly flowers, and birds consume the vibrant fruits in winter. Cut berry-filled branches in fall and bring indoors to decorate. In early spring prune deciduous hollies partially and back to the ground every 4-5 years. Disease and insect problems are rare and deer leave hollies alone.

Deciduous hollies are excellent for massing, for hedging, for wet soils, and for attracting wildlife to your landscape. Plant one “matched” male selection nearby 8-10 female plants to boost fruit numbers. Mature plant size depends on cultivar planted. Some of the better selections of deciduous hollies include:

Berry Heavy® – 6 to 8 feet tall shrub and abundant bright red berries.

Berry Nice® – 6-8 feet tall shrub and bright red berries.

‘Bonfire’ (I. verticillata x serrata) – 8 by 8 feet holly and bears small red berries at young age.

‘Red Sprite’ – compact 3 to 5 feet tall with large, bright red berries and lustrous dark green leaves.

‘Sparkleberry’ (I. verticillata x serrata) –upright branched, 12 feet tall, and brilliant red fruit.

‘Winter Gold’ – matures to 7 by 7 feet with lovely salmon colored berries.

Winter Red® – matures to 8 by 8 feet with lustrous dark green leaves and bright red berries.

Male Pollinators:

‘Apollo’ ( I. verticillata x serrata) – pollinator for ‘Bonfire’, ‘Red Sprite’, and ‘Sparkleberry’.

‘Jim Dandy’ – pollinator for Berry Heavy®, Berry Nice®, ‘Red Sprite’.

‘Southern Gentleman’ – pollinator for Berry Nice®, ‘Sparkleberry’, ‘Winter Gold’, Winter Red®.

Five Summer Perennials You Will Love

Posted by Hugh on November 10th, 2015

Phlox paniculata ‘Shortwood’

Echinacea x ‘Cheyenne Spirit’

In the past few years several great performing perennials have caught my eye. Some are exceptional landscape performers exhibiting long bloom period and exceptional disease resistance. All are hardy in Zones 4-9. Here are five of the best:

Echinacea Cheyenne Spirit coneflower mix (Echinacea purpurea ‘Cheyenne Spirit’) offers a spectacular floral show of many colored ray flowers from mid-summer to early fall. This hybrid purple coneflower comprises a delightful mix of bright red, orange, golden yellow, purple and white ray flowers with a large brown button center. Stems are strong and well-branched. Coneflowers attract butterflies and blooms are excellent for cutting. Deadhead (remove) faded blooms to encourage re-blooming.

‘PowWow Wild Berry’ coneflower (Echinacea purpurea) is an outstanding multi-year performer. From late spring to early fall, it produces large 3-4 inch wide deep rose-purple ray flowers with orange-brown button centers. Stems are sturdy and well-branched, 18-24 inches tall and 12-18 inches wide. Plants re-bloom without deadheading.

‘Pardon My Pink’ beebalm (M. didyma) is a self-branching, compact, 10 to 12 inches tall (and wide) beebalm or bergamont. Clear pink flowers measure 2½ to 3 inches across and attract bees, butterflies, and hummingbirds. It blooms from midsummer to late September along with dark green foliage that is highly mildew resistant.

‘Shortwood’ Garden Phlox is a garden phlox (P. paniculata) that is highly touted by Stephanie Cohen, the perennial diva herself. ‘Shortwood’ boasts full-size bright pink blooms with deeper pink eyes and are wildly fragrant. Flowers are superb for cutting, and attract lots of butterflies and hummingbirds. Plant is also highly mildew resistant.

Dazzleberry® sedum is groundcover type from sedum breeder Chris Hansen that grows only 8 inches tall and 18 inches wide. It is a strong grower with attractive dusty blue foliage. In late summer Dazzleberry is covered with clusters of vibrant raspberry colored flowers.

Echinacea purpurea ‘PowWow Wild Berry’

Fall Leaf Gathering Turns Into “Black Gold”

Posted by Hugh on November 7th, 2015

Compost in rose bed at Biltmore Estates, Asheville, NC

Compost on rose bed at Biltmore Estates, Asheville, NC

Leaf pile ready for composting

In autumn the cool crisp air paints the land with a colorful array from tree and shrub foliage. As days turn into weeks, leaves fall away and pile up on rooftops, walkways, lawns and gardens. Instead of just raking and tossing them curbside, gather and put them to good use.

Fallen leaves (and grass clippings) can be easily composted, turned into “black gold” and spread as leaf mulch over garden soils or around trees and shrubs, including roses. Leaf mold enriches the soil, locks in moisture, and protects plant crowns and roots from the frigid winter temperatures. You save money by not buying bagged mulch or compost at garden centers.

To speed the composting process, shred leaves and small twigs and branches with a mulching mower, shredder or leaf blower set on vacuum setting. Start with a thin layer of shredded leaves to compost. It decomposes rapidly, usually within a few months. Small twigs and branches decompose more rapidly. Heaping up thick heavy layers garden debris will block air and water from penetrating the pile.

Leaf mold (sometimes spelled mould) is essentially a soil conditioner. It improves soil water retention and soil structure, and creates a living habitat for beneficial organisms such as earthworms and bacteria that nourish the soil.

Distribute only a few inches of leaf mold. Thick layers of composted mulch locks in too much moisture, and smother plant roots that require well-drained soil. Roots become susceptible to rots and other fungal diseases.

The decomposition process for leaves takes at least 6-12 months. It takes very little work on the gardener’s part. To speed up decomposition, mow over the piled leaves once or twice. A few handfuls of nitrogen-rich fertilizer will speed up the rotting process. Turn the pile with garden fork or heavy rake to aerate. Throw a plastic tarp over the pile to keep leaves warm and moist.

Add leftover leaf mold to a compost bin or store remains in plastic bags for later use.

Selecting Japanese Maple Varieties For Winter Hardiness

Posted by Hugh on November 4th, 2015

Acer palmatum ‘Tamukeyama’ at NC Arboretum, Asheville, NC

Palmatum leaf type

Japanese maples (Acer palmatum) and (A. japonicum) are among the most picturesque of trees and shrubs. Their star-shaped leaves are comprised of 5-7-9 pointed lobes, depending on variety (cultivar). Trees exhibit layered branching, cascading form, lacy foliage (dissectum types), and stunning fall color. There are countless numbers of cultivars… those with green, yellow, purple, red, bronze, or variegated leaves. Tree/shrub sizes vary from 3 feet to 50 feet in height. Many cultivars are slow growing their first two years, particularly the dissectum types.

Select a variety based on its winter hardiness. Many Japanese maples are rated hardy in Zones 5 and 6 (-10 to -20 °F). You need to protect newly planted trees against winter sun scald, related to cold injury to tree bark on the south or west side.

Protect the trunk of a newly planted tree with special tree wrap, usually kraft paper or fabric, to prevent sunscald over the first two winters. The wrap swells as the trunk diameter expands; it should be totally removed after two winters. Maintain a 2-3 inch organic based mulch layer under the tree to keep roots moist and cool.

Other Japanese maples must cope with summer heat and humidity in Southern climes (Zones 7 and 8). Leaves may scorch and require shelter from midday sun. Planting them on the east or north side of the house is ideal. Green-leaf varieties tend to be more scorch resistant than red, purple, or variegated leaf types. Providing irrigation during the hot summer months is a practical step.

Rated among the cold hardiest cultivars for zone 5:

Dissectum class: Inaba Shidare, Tamukeyama, Crimson Queen, Red Dragon, and Viridis.

Palmatum class: Bloodgood, Emperor I, Sango Kaku, Atropurpureum, Osakazuki, Heffner’s Red, and Oshio Beni.

Additional species (other than A. palmatum): Acer japonicum (full moon maple) and A. aconitifolium (fernleaf maple).

Tips On Sowing Milkweed Seeds

Posted by Hugh on November 1st, 2015

Perennial Milkweeds at Chanticleer Garden in Wayne, PA

Closup of Ascelpias tuberosa flowers

Milkweed (Asclepias tuberosa), aka butterfly weeds, are tuberous rooted perennials native to the Eastern and southern U.S. (USDA hardiness zones 3 to 9). It grows in dry/rocky open woodlands, prairies, farm fields, and along roadsides. A clump of milkweed plants grow 1- 3 feet tall and spread 1 ½ feet wide. Unlike other milkweeds (Asclepias spp.), the sap is not milky.

For nearly six weeks, from late spring to early summer, 3 inch wide clusters of vibrant orange to yellow-orange flowers (umbels) cover the plant canopy. Narrow lance-shaped leaves are attached to the hairy stems. Flowers are an important nectar source for many butterfly species and leaves are a key food source for the caterpillars (larvae) of Monarch butterflies.

Butterfly weeds self-seed freely in the landscape. Prominent 3 – 6 inch long spindle-shaped seed pods break ripen, open and release multitudes of silky-tailed seeds which carry long distances by wind. Seed pods may be utilized in dried flower arrangements.

Butterfly weeds are prairie survivors. They grow in average well-drained soils in full sun. Two-year established plants are highly drought tolerant. Shoots emerge late in the spring and grow rapidly. Gardeners frequently include some in butterfly gardens, meadows, prairies, or other plantings. Do not attempt to dig up plants in the wild; they rarely survive transplanting due to their deep taproot system.

New plants are easily started from seed. Collect seed capsules from wild populations before they burst open. Dried capsules should be stored in a plastic bag. Autumn is a good time to direct sow seeds in a prepared garden bed. Most (not all) seeds will emerge by mid-summer next year, and plants will bloom for the first time in 2 – 3 years. Seeds may be sown into deep containers, but overall success is better in garden beds.

Few disease and insect problems trouble butterfly weeds when they’re grown in full sun open garden spot. Wet, poorly-drained soil leads to rot rots and eventual death. Leaves are susceptible to rust and leaf spots, particularly if the planting is too crowded or partially shaded.

‘Hello Yellow’ is a yellow-flowering milkweed cultivar. It possesses the same qualities of its orange-blooming cousin, including being a butterfly magnet.

Crocus: A Fine Start To Spring

Posted by Hugh on October 29th, 2015

Fall crocus at Atlanta Botanical Gardens

Fall blooming crocus at Atlanta Botanical Gardens

Spring flowering crocus planted around stewartia

Crocus (Crocus spp.) can be your wake-up reminder that winter is coming to an end (USDA hardiness zones 3- 8). They bloom in late winter (in the south); fall blooming varieties are also available. Bulbs (they’re actually “corms”) are available in flower colors from blue, purple, white, yellow, and mixed shades.

Choose from large and small flowered types. Six petal, cup shaped flowers stand tall above the foliage which emerges as bright green blades of grass with a center white stripe. The grassy foliage grows taller after flowers wither away.

Crocus thrive in full sun and tend to bloom earlier than those planted in partial shade. They prefer a well-drained soil with pH of 6.0 – 7.0. Crocus generally fail sown in soggy ground. Flower buds open to warming early morning sunlight, and close up in cloudy weather and in the evening. Crocus bloom and easily naturalize where winters are cold. Sow corms in mid-fall because they require 12-15 weeks planted in cold soil (35 – 45 °F) to initiate blooms.

Crocus grow 3- 8 inches high depending on variety. Sow drifts of crocus in several places around the garden, under trees, sprinkled in the lawn, in alpine and rock gardens, and in containers. Interplant crocus with short growing narcissus, hyacinths and tulips, and pansies and violas. Plant them where perennials emerge in mid-spring and crocus foliage has died back.

Crocus grow carefree for many years. They may become susceptible to virus diseases which cause leaf distortions and streaking; bloom buds fail to open. Dig up and dispose of virus infected plants to prevent spreading diseases. Crocus may be menaced by deer, chipmunks, rabbits and squirrels which eat the corms, leaves and flowers. Voles feed on the corms.

The ancient Greeks collected and dried the stigmas from autumn-flowering crocus (C. sativus) to make saffron herb used in food dishes.

Crocus may be purchased at most garden centers in the fall. For wider choice of varieties, including hard to find fall crocus, buy from a mail order supplier like Brent and Becky’s Bulbs in Gloucester, VA.

Avoid Crape Myrtle Woes In Winter

Posted by Hugh on October 25th, 2015

Lagerstromia faureii in UT Gardens in Knoxville, TN

Lagerstromia faureii at UT Gardens in Knoxville, TN

It’s no secret that in many areas with cold winters (USDA hardiness zones 6-9), hardy crape myrtle cultivars are now available. In northern areas like eastern Maryland and northern VA, crape myrtles have been prospering for two decades and more. However, there is one rule regarding winter care — “Don’t Touch”. Hold off all pruning of crape myrtles until March 1 or later.

Removal of seed capsules is ok, but not totally necessary unless you demand a litter free garden. All other pruning should wait until early spring. A common practice around shopping malls and public areas is “crape murder”; this drastic pruning should be outlawed. A landscaper lops back crape myrtles to 5-6 feet so that they don’t block the view of store signage. This practice is not recommended as it greatly limits the plant’s lifespan and branch wood hardiness.

Landscapers committing crape murder during the traditional frigid months of January and February wind up killing the plant to the ground. Likely, plants will suckered from the base and flowered the subsequent summer about a month or more later. Yes, hardy crape myrtles are tough plants despite human error.

If you must move an established crape myrtle to another location, wait until early spring. Transplanting a crape myrtle should not be necessary as replacement cost is low. It’s a lot easier to start over with a new shrub or tree form. Yes a new plant starts off smaller, but how quickly they size up.

In northeastern cities such as Boston, New York, Philadelphia, Wilmington or Baltimore crape myrtles are rated as hardy perennials. Expect an occasional winter when they will dieback to the ground. Some of the hardiest cultivars were developed at the U.S. National Arboretum. If you want to start out with just 3 or 4 cultivars, ‘Natchez’ and ‘Muskgoee’ are among the hardiest tree and ‘Acoma’ and ‘Osage’ shrub types.