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

Better Choices Than Leyland Cypress For Privacy Screen

Posted by Hugh on November 12th, 2014

Cryptomeria Privacy Screen near Chattanooga TN

For homeowners in a rush to establish a tall green privacy screen from the neighbor(s), perhaps a 12-foot tall green fence may be your better option. Among the choices of evergreens to plant, Leyland cypress (x Cupressocyperus leylandii) is fastest growing, but is plagued by any of three serious disease problems. An established leyland cypress planted 12 feet apart completely occupies its place and stands 12 plus feet tall within 10 years if adequately fertilized and irrigated.

Foliage disease problems usually do not infect leyland cypress until 10-12 years after planting. No disease cure-alls (fungicides) are presently available. Pruning off diseased branches on tall ladders is the best cure-all which can be a highly expensive and a dangerous chore for diyers to take on.

In northerly zones (USDA hardiness zone 6 and 7), Japanese cryptomeria (Cryptomeria japonica) and ‘Green Giant’ arborvitae (Thuja plicata x T. standishii) may be the evergreen privacy screen that you’re looking for. Within 1-2 years after planting, their growth rate is moderate, 16-20 inches annually. They may not be as vigorous like leyland cypress, but without the disease threat that may destroy a privacy screen within 20 years. Two-year established arborvitaes and cryptomerias exhibit better drought resistance than Leyland cypresses.

An occasional pest of all three evergreen species are bagworms which can devour new soft spring foliage. Inspect evergreens in late winter and treat with any of a number of pesticides previously listed in my “bagworms” blog. The winter foliage of all three usually bronzes off, but quickly recovers (greens-up) in the early days of spring.

‘Gyokuryu’ Japanese Cedar -Privacy Screen For Small Gardens

Posted by Hugh on November 9th, 2014

Photo credit: Dr. Susan Hamilton, University of Tennessee

Gyokuryu Japanese cedar (Cryptomeria japonica ‘Gyokuryu’) is a dense, broadly pyramidal evergreen shrub (USDA hardiness zones 5-8). It has short stiff needles that tend to be a slightly darker green than other cryptomeria cultivars. Gyokuryu holds its dark green color through most winters in zone 7 and further south. Expect winter bronzing when Gyokuryu is planted on high windy sites. Branches are pliable and release heavy snow to prevent limb breakage.

Spring/summer growth rate is moderate. Gyokuryu starts out as a short ball-shaped shrub, flattened on top. After 3 to 4 years it develops a dominant upright leader and takes on a pyramidal form. Gyokuryu grows 15 to 20 feet high and 5 to 7 feet wide in 20-25 years. Growth rate ranges from 6 to 9 inches per year. Over the years it becomes a handsome stand alone specimen plant, or you can group several together as a hedge or privacy screen.

Cryptomerias are planted in full sun and in an average well-drained, moderately acidic pH soil. One to three year old plants benefit from mulching. Disease and pest problems are minimal when plants are properly sited and not overcrowded. It is best to plant them 5-6 feet apart and allow them to gradually to fill in on their own. Two year established plants exhibit better than average drought tolerance. Supplemental irrigation during prolonged dry spells over 3 or more weeks is recommended for total optimum growth.

Deer generally stay away from cryptomerias. Feed in late winter and repeat in late spring with water soluble fertilizer (Miracle Gro™, Jacks™, or equivalent); or a granular fertilizer such as 10-10-10 or equivalent. Hollytone™ is a reliable evergreen plant fertilizer.

Carolina Buckthorn Attractive Native Shrub/Tree

Posted by Hugh on November 6th, 2014

Rhamnus carolinana (Photo from Southeastern Flora website)

Many native plant enthusiasts consider the Carolina Buckthorn, aka Indian cherry (Rhamnus caroliniana), one of our most underutilized native shrubs or small trees. It suffers with a bad common name as it has no thorns or spines. This open, slender branched shrub grows 12 to 15 feet high and 10 to 15 feet wide. (USDA hardiness zones 5-9).

Bright green leaves remain on long into autumn before eventually turning a blah yellow-green color. In southern areas much of the yellowed foliage holds through most of the winter. Spring flowers, mostly inconspicuous, are followed by 1/3 inch diameter green berries (drupes).

High point for this shrub is its brightly colored red fruits starting in late summer and eventually ripen to black in late September into October. Birds and other wildlife will devour the edible black fruits in the fall and early winter. Main trunk(s) and branches flaunt a smooth gray bark.

Carolina Buckthorn should be grown in full sun on well-drained soil, acidic or alkaline. Specimens reaching 25-30 feet can be found on moist woodland sites. It will tolerate moderate dry spells.

Buckthorns are rarely troubled by insect pests, but individual plants may be severely setback by a crown rust and by leaf spot diseases. Carolina buckthorn is easily trained into a small tree suited for planting under power lines. Training a young shrub into a small tree is not difficult. Plant several to form a hedge or thicket to shelter wildlife and provide them a feeding station.

Bee Bee Tree (Tetradium) Rarely Seen In U.S. Landscapes

Posted by Hugh on November 3rd, 2014

Beebee Tree (Tetradium daniellii) at Brooklyn Botanical Gardens, NY

Smooth Gray Trunk of Beebee Tree

Native to Korea and southwestern China, bee bee tree (Tetradium daniellii) is a deciduous tree with a spreading umbrella-shaped habit and rounded canopy (USDA hardiness zones 4-8). It was formerly named Evodia daniellii.

Bee bee tree typically grows to 25-30 feet tall and wide. In July-August small white flowers (sometimes tinged with yellow or pink) are flattened clusters (corymbs) up to 6 inches wide. Flowers are highly fragrant and quite showy. Summer blooming bee bee tree flowers when few other trees do so and is frequented by honey bees and many other pollinators

Flowers give way to reddish-purple seed pods that split apart when ripe. Each pod contains 2 shiny, buckshot-like, black seeds. Pods are highly ornamental and remain on the tree from late August to November. The red to black fruits are eagerly consumed by birds.

Lush opposite, pinnately compound leaves resemble ash (Fraxinus spp.). Individual leaves may be 18 inches long, comprised of 7-11 leaflets, each 2-5 inch long glossy dark green leaflets. Autumn leaf color is lacking; leaves typically fall when green to yellowish-green. Trunk bark is light gray and very smooth.

Bee bee tree thrives in moist, reasonably fertile, well-drained, mildly acidic soil. Plant it in full sun where it grows best, but it does tolerate moderate light shade. A newly planted tree grows rapidly and would make an ideal small lawn tree sited near a deck or patio. It is pest and disease trouble-free and grows rapidly in its early years.

Current availability of bee bee tree is from on-line specialty nurseries only.

The Last Mowing Of The Year

Posted by Hugh on October 31st, 2014

Beautiful Manicured lawn At Longwood Gardens in Kennett Square, PA

Well Manicured Lawn At Longwood Gardens’ Amphitheater in Kennett Square, PA

Within many garden circles, conventional wisdom says that you should mow lawns very close heading into winter. Mowing height should be adjusted by seasonal and current weather conditions. Mowing height also sets the shoot to root ratio of specific grass species. In cooler northern areas bluegrass and tall fescue are the lawn grasses of choice. In the mid-South (called the “transition zone”) tall fescues and warm season bermudagrass and zoysia are favored.

Cutting height changes with the season. During a hot dry summer mowing height should be raised an additional 1/2 to 1 inch from the spring cut. Just an increase of 1/8 inch inputs more light to individual grass plants and deeper rooting depth. The result: your lawn becomes more drought tolerant.

Turf scientists at the University of Tennessee recommend raising the cutting height for the last three fall mowings. This increases cold tolerance within the grass crown. Winter weather can be brutal on your lawn. Dr. Tom Samples, Extension Turfgrass Specialist recommends starting a month ahead to gain insulation value. In most areas this means the last 3 mowings of the year.

Recommended fall cutting height by species:

Bluegrass 2 inches

Tall fescue (wide blade types like K-31) 2 to 3 1/2 inches

Tall fescue (fine leaf cultivars) 2 -3 inches

Zoysia 1-2 inches

Common bermudagrass 1-2 inches

Are Your Trees Hazardous?

Posted by Hugh on October 28th, 2014

Mature Tree Removed By Certified Arborist

Silver Maple tree rotted at base

Is a hazardous tree lurking in your yard, ready to fall on your house or car? Take a few minutes to inspect trees on your property. Peek over the fence at your neighbor’s trees as well.

Some property owners have an unnatural fear of trees. Well-shaped landscape trees with no dead wood, good growth rate, and a full canopy (top) are rarely a risk. Yes, it’s true that the healthiest of trees are likely to be injured in a “category” hurricane or tornado.

Tree care goes along with tree ownership. Tree health, like people health, changes as they age. Middle-aged trees are less hazardous than mature trees. Age plus a category storm may inflict enough damage to render a tree hazardous.

Location is another factor. A tree deemed hazardous, but not growing near people, houses, and autos, is unlikely to inflict serious injury when it falls. Your insurance company may never hear from you. Trees in a public park, along streets, or in residential zones should be inspected, then pruned or removed.

Trees may show decay or cavities along the main trunk(s) and branches, and timely pruning usually cures most ills. It’s like going to a dentist. A cavity represents wood decay and branch weakness. Decay can be slowed by cleaning out the wound and spraying a pesticide to prevent wood boring insects from habitating.

Different tree species possess different mechanical strengths and decay mechanisms. Weak wooded species considered potentially hazardous include silver maple (Acer saccharinum), cottonwood and hybrid poplars (Populus spp.), willows (Salix spp.), boxelder (Acer negundo), ornamental pears (Pyrus calleryana), and tree-of-heaven (Ailanthus altissima).

A certified arborist can measure the extent of the tree decay using a Resistograph®. A hollow tree cavity is not always hazardous. Tree cavities that are surrounded by at least one inch of solid wood per six inches of tree diameter are unlikely to fail.

Hire only a certified, licensed and insured arborist. Certification is awarded through the International Society of Arboriculture (ISA) following extensive study and testing.

Rebuilding A Storm Damaged Young Tree

Posted by Hugh on October 25th, 2014

Same Sweetbay Magnolia 4 years later

Magnolia virginiana cutback

An enormous 60 foot white pine toppled over several smaller trees. The aftermath was a severely damaged 3- year old sweetbay magnolia (Magnolia virginiana). Replacing the 3 1/2 inch diameter tree would have cost the homeowner over $300. My recommendation to the homeowner was to cut back the magnolia trunk to approximately 12 inches from the ground in late winter or 6 inches above the graft union. While not much remained above ground, the grafted tree still retained 100% of its root system. Nearly 4 years later and after considerable timely pruning, the tree has completely regrown.

A few tree facts: Inside the trunk wood are several latent (adventitious) buds. Survival is what the tree is trying to do. Several multiple shoots pushed out in the spring from above and below ground. All growth below the graft union is from its seedling rootsystem and must be promptly removed, as to not compete with the preferred cultivar.

To create a new tree, prune off short or weak shoot growth, favoring the tallest, thickest, and straightest 1, 2 or 3 new shoots by mid-June (year one). You are deciding whether your new tree will be single or multi-trunk. All energy (growth) will be pushed into the selected shoots. No staking should be needed. Your “new tree” should be 3-4 feet by mid-September.

In early spring feed the stubbed tree with 10-10-10 or equivalent fertilizer; repeat that practice over the first 5 years. Mulch around the tree base, but do not pile mulch against the trunk. Over the next 2-3 years continue to prune off new shoots and root suckers which may form around the trunk base.

Prep Garden Soil In The Fall

Posted by Hugh on October 22nd, 2014

Pine bark amendment at a nursery

Often, spring arrives with too many gardening chores to handle. Some work can be shifted to the fall. Since a garden is only as good as its soil, fall is a good time to till your garden or to construct new beds. Add soil amendments such as deciduous leaves and pine needles which nature is providing for free. Till amendments into the soil with a shovel, multi-tined garden fork, or rototiller.

You may add organic nitrogen sources such as blood meal, animal manures (either packaged or fresh from a nearby farm). Fresh manure may be too hot to use in the spring, but will lose its hot urea properties over the winter. Incorporate digested (decayed) compost pile(s) into your garden soil. Soil microbes do most of the work decaying the organic additives over winter.

Shredded leaves, eggshells, coffee grounds, and fruit peels are all great soil additives; most will break down before spring planting season arrives. Caveat: huge quantities of undigested materials can rob the garden plants of nitrogen next summer. In such cases, you may need to add lots more fertilizer to feed both the garden plants and soil microbes.

The final step before spring is test the garden soil at a state soil lab operated by your state land grant university. Some full-service garden centers may also provide soil testing. Collect the soil sample before the lab’s mad spring rush begins. The local county or area Extension agent will interpret the diagnostic results for you.

The amended soil will be a lot easier to plant into next spring. Fall tilling also buries weeds and weed seeds to reduce this chore next summer.

Evergreens For Wet Soggy Soils

Posted by Hugh on October 19th, 2014

Emerald™ arborvitae at Daniel Stowe Botanical Garden, Gastonia, NC

Most needle evergreens falter in moist soggy soils. These sites usually have a heavy clay or fine particle sand content. Some arborvitaes (Thuja spp.) and Atlantic white cedar (Chamaecyparis thyoides) tolerate temporary wet soggy conditions better than most evergreens (USDA hardiness zones 3-8). An assortment of shapes, sizes and colors are available. All are U.S. natives.

Eastern arborvitae (T. occidentalis) tolerates dry to boggy wet sites. Emerald™ and ‘DeGroot Spire’ is two popular favorites, growing 12-15 feet or 8 feet tall respectively over 15-20 years. The scale- like foliage is uniquely twisted and spiraled. ‘Hetz Midget’ or ‘Tiny Tim’ are dwarf globe or ball forms that grow 12 inches tall and 16 inches wide. The light green scaly foliage turns bronze over winter.

Western arborvitae (T. plicata)) also tolerates tight wet soils. It grows tall and is fast-growing with a tightly pyramidal growth habit. Most popular is the hybrid ‘Green Giant’ (T. plicata x T. standishii) cultivar. Summer foliage is dark glossy green and bronzes over winter. Green Giant grows to a mature height of 50-60 feet tall and 8-10 feet wide. For something very different, ‘Whipcord’ is a dwarf cultivar with unusual thread-like branches and an arching plant habit. It grows to only 2 feet tall by 3 feet wide in 10 years.

Atlantic white cedar (C. thyoides) (zones 5-9) is often observed growing on soggy sandy sites, but dislike clay soils. Winter foliage turns a deep plum color and back to green by the start of spring.

Three popular selections of C. thyoides include:

‘Rubicon’, aka ‘Red Star’ – upright dense form with star-like foliage (6 feet tall by 2 feet wide).

‘Heatherbun’ – compact, globe-shaped form (6 to 8 feet tall by 4-5 feet wide).

‘Shiva’ – dwarf multi-stemmed form with upright spreading branches and silvery lacy foliage (5 feet tall by 4 feet wide) .

Bird’s Nest Spruce

Posted by Hugh on October 16th, 2014

Picea abies ‘Nidiformis’ at Boone County Arboretum in Kentucky

Bird’s nest spruce (Picea abies ‘Nidiformis’) is a dwarf cultivar of Norway spruce and is native to northern Europe (USDA hardiness zones 3-7). This slow growing compact shrub will attain 4 feet in height and 5 to 6 feet spread over 15 – 20 years.

The shrub grows in a round form with a distinctive flat depression or “bird’s nest” cavity on top. Lush, dark green needle foliage has a medium to fine texture and deer stay away from this sharp needle conifer. Short ½ inch long needles radiate along the slightly uplifted branches.

Bird’s nest spruce grows in average acidic, well-drained soil; it is best planted in full sun to partial shade with good air circulation. In the mid-south, this shrub conifer tends to struggle during periods of extreme heat and drought. Best specimens are seen in gardens from northern Virginia and northward and through the Midwest U.S. where summers tend to be less humid and a bit cooler.

When needles appear pale or off color, feeding spruce and eriophyid mites may be the problems. Pesticide controls are very effective; also hosing down the shrub with a coarse spray of water will wash away most mites. This naturally dwarf plant rarely requires pruning, other than to remove any damaged, discolored and/or diseased twigs.

Bird’s nest spruce has year-round appeal. It is frequently included in foundation or low border plantings. It is exceptionally winter hardy and may be planted in a large container.

Extra: Picea abies ‘Maxwell’ exhibits a similar form except its top is flat but not depressed.