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

Dwarf Southern Magnolia Cultivars

Posted by Hugh on June 1st, 2012

Small Tepal Flower of 'Little Gem' Magnolia

: Small 5-6 Year Old ‘Little Gem’ Magnolia

Southern magnolia (Magnolia grandiflora) is remarkably hardy in USDA zone 6. This evergreen magnolia prefers a moist well-drained, slightly acidic soil, and planted in a partial to full sun location. It is a long-lived large 70-80 feet tall tree, best suited to large commercial and residential properties, golf courses and public parks.

Four dwarf cultivars are available at garden centers:

‘Little Gem’ and ‘Hasse’ (35-40 feet in height)
Teddy Bear® and ‘Kay Parris’ (25-30 feet in height)

Little Gem is most popular and grows very shrub-like. Little Gem may encompass 20 or more feet of ground area. Hasse exhibits a tree-like habit and branching is primarily upright. Teddy Bear and Kay Parris grow slowly and are better selections for small landscapes.

Regarding the dwarf cultivars, the leaves and flowers are proportionally smaller that the species. The glossy foliage is thick and leathery, and dark green over both the upper and lower surfaces. Kay Parris foliage is reddish brown on the underside.

Goblet shaped flowers open intermittently from late spring through summer and are very fragrant. On trees ten years and older, one to several blooms open almost every day from May until late September. Ornate cone-like seed pods form after flower have shed their creamy white tepals (petals).

Pruning is rarely needed unless you desire to limb up the lower branches (for mowing under and such). Evergreen leaves drop through most of the year, most noticeable in late winter and early spring.

‘Helene Von Stein’ Lamb’s Ear Is More Behaved

Posted by Hugh on May 30th, 2012

Messy Floral Heads of Lamb's Ears

Stachys byzantina is a dense gray woolly perennial ground cover, which earns it the common name “lamb’s ear”. ‘Helene Von Stein’ is the single best cultivar, displaying larger leaves, and is more heat and humidity tolerant. Sometimes listed as ‘Big Ears’, it rarely produces flowers which may tarnish its lovely silvery gray foliage appearance.

Lamb’s ear grows approximately 12-18 inches tall and wide. High humidity, long exposure to moisture on the foliage, and poor soil drainage all lead to its decline and ultimate death. Do not irrigate lamb’s ear overhead.

Lamb’s ear grows in any average well-drained soil. After a short 6 month establishment period, it exhibits exceptional drought tolerance. It grows best in full sun in USDA zones 4-6 and under light afternoon shade further south. Leaves are evergreen in areas with mild winters, but will deteriorate under harsh winters. Excessive shade may invite foliar disease problems.

Common lamb’s ear spreads aggressively by runners. Erect, small-leaved spikelets of small purplish flowers appear from late spring thru the summer, rising several inches above the foliage. Gardeners may choose to remove the floral shoots to tidy up this ground cover or switch over to grow ‘Helene Von Stein’.

Lamb’s ears is a great choice in the front of a flower border or in a rock garden.

Stachys 'Helene Von Stein'

Add Hardy Begonia To Your Shade Garden

Posted by Hugh on May 28th, 2012

Hardy begonia

Hardy begonia (Begonia grandis) is the only species of begonia which is winter hardy in USDA zones 6-9 (zone 5 with protection). This shade-loving perennial grows 18 -24 inches high and wide, and displays a well-branched mounding habit. Foliage is medium to olive green above and reddish green with red veining beneath. Leaf shape is similar to angel wing begonia. Sprays of pink ¾ to 1 inch flowers rise above the foliage from early summer to fall.

Hardy begonia grows best in open shade. It thrives primarily in moist, humus-rich, well-drained soil where it mixes among other leafy shade garden favorites such as hostas (Hosta spp.), lungworts (Pulmonaria spp.), brunneras (Brunnera spp.), and ferns. A back-up irrigation plan in the hot summer weather is a must. Mulch generously around clumps in late fall for winter protection in zones 5 and 6. Hardy begonia dies back to the ground each winter, leaving little evidence that it was ever there.

Deadheading spent flowers will extend its blooming time and reduce the probability for self-seeding. Hardy begonia also spreads by tiny bulblets which can be dug up and transplanted in the late fall to increase the bed size. Hardy begonia has no serious insect or disease problems and is rated as rabbit proof. ‘Alba’ is a white flowering form.

Unfortunately, availability of plants through nursery and garden center sources is not plentiful, but can be purchased on-line.

Northern Maidenhair Fern Appear Delicate But Grow Tough

Posted by Hugh on May 23rd, 2012

Maidenhair fern (Adiantum pedatum)

Their leaves (called “fronds”) appear delicate, but maidenhair ferns (Adiantum spp.) are reliable long-lived perennials. Northern maidenhair (A. pedatum) thrives in most gardens within USDA zones 3-8, while the Southern counterpart, (A. capillus-veneris), predominates in warmer USDA 7-10. Unfortunately, planting of maidenhairs are not utilized in the Southern Appalachian gardens (USDA zones 6-8).

Fronds average 18-24 inches in length and form 12-15 inch wide colonies. Northern maidenhair flourishes in zones with a humid, warm summer its soil rhizome network as the only clue of its presence. Spritely green fronds emerge in the spring. Utilize them in partially- to fully- shaded landscape areas. In a container, permit the dainty fronds to spill over the edge of the planter.

Choose a dense moist woodland spot and generously amend the well drained soil with compost. Maidenhair prospers around ponds and other water features. A neutral to slightly alkaline soil is perfect. Gradually add limestone to adjust soil pH higher as needed and maintain good air circulation around plants.

When planting most ferns, set the roots in the hole so the crown is at or slightly shallow with the soil surface. Avoid planting deep! Lightly cover with 1-2 inches of an organic mulch such as bark chips, pine needles or leaf mold.

Most ferns are light but constant feeders. Feed bi-monthly from March thru August with a water-soluble fertilizer such as Miracle Gro®, Schultz™ or Hollytone® for optimum growth.

Protect Autos and Home Siding From Artillery Fungus

Posted by Hugh on May 20th, 2012

Mild Case of Artilery Spores on Home Siding

Artillery fungus (Sphaerobolus stellatus) deposits small tar-like specks on the siding of your house or on your car finish in early spring or fall. Artillery fungus is a wood-rotting organism living in the mulch around your home foundation. The fungus shoots its sticky, black spore masses as far as 20 feet out away. The tar spots adhere tightly to the paint or siding and are difficult to wash off.

No fungicides are labeled for control of the artillery fungus in mulch. Cellulose is the principal component of wood mulch and the primary food source for this wood-rotting fungus. Instead, select a bark mulch which contains lignin that decays more slowly.

Adding a fresh layer of a large nugget bark mulch over an existing mulch each year may reduce the sporulation of the artillery fungus. Do not apply more than 4 inches of mulch, as plant roots into the soil may become smothered. Covering existing mulch with a layer of pine needles may prevent sporulation of the artillery fungus. Mushroom compost, mixed with bark mulch, @ 40% by volume, will also suppress artillery fungus.

Another approach is to remove the contaminated mulch and replace it with a synthetic mulch, such as shredded rubber mulch and artificial pine needles. Synthetic mulches last much longer and not provide a growth medium for the artillery fungus. Planting groundcovers instead of mulching is another option.

Favorite Mountain Laurel Cultivars

Posted by Hugh on May 17th, 2012

'Carol' - dark pink buds / light pink flowers

Shopping for mountain laurels is like sampling sweets at a candy shoppe or ice cream parlour. There are so many great choices. Most plants grow 4-5 feet tall and wide. Most have plant foliage which is lustrous, dark green and leaf spot resistant. All cultivars need minimal pruning and fertilizing once a year. In great apprehension I have weaned my lengthy list of favorites down to ten:

‘Bullseye’ features a purple banded tint inside the floral corolla; exhibits a vigorous, upright growth habit and new foliage has reddish hue.

‘Carol’ features dark-pink floral buds, open light pink, and fade to white. Plant habit is dense, low and compact.

‘Carousel’ features flowers with a purplish-cinnamon inner corolla and a white edged border; shrub is a vigorous grower.

‘Heart’s Desire’ has red flower buds which open to reveal cinnamon-red colored corolla. Shrub has a dense, well-branched habit.

‘Minuet’ has light pink buds that open to stunning cherry-red banded corolla within. Minuet is a dwarf 3 foot tall mountain laurel.

‘Olympic Fire’ possesses deep red flower buds that open light pink.

‘Pink Charm’ has dark pink flower buds that open to luscious pink.

‘Pinwheel’ features cinnamon-maroon flowers with white centers and scalloped edges. Plant exhibits a compact form.

‘Sarah’ has flowers that are red in bud and open pinkish red.

‘Snowdrift’ displays pure white buds and white-flowers.

Growing Mountain Laurels in Your Landscape

Posted by Hugh on May 14th, 2012

Hybrid Mountain laurel

Mountain laurel (Kalmia latifolia) is a U.S. native evergreen broadleaf shrub (USDA hardiness zone 5). Mature sizes range from 5 feet (dwarf cultivars) to 12 feet in height and with equal spread. Over the past 30 years, mountain laurels have so improved, thanks to breeding efforts of Dr. Richard Jaynes*. He has released several dozen cultivars to date, including those with dwarf forms and with highly colorful flowers.

Flowers open over a two week period beginning in mid-May here in the Southern Appalachian region (USDA hardiness zones 6 and 7). In the wild, mountain laurel tends to grow near a woodland clearing. In the garden, plant in an open area for full or partial sunlight. Mountain laurel prospers a cool, moist, acidic (pH 6 or below preferred), compost rich soil which is well drained. Flowers and foliage are best protected from direct wind.

Pruning is best performed within a few weeks after flowering is finished. Prune to shape, to limit shrub height and width, and to remove dead or diseased twigs and branches. Pruning and feeding with an acidic water soluble fertilizer such as Miracle-Gro®, Hollytone® or Schultz® invigorates new growth and flowering the next year. Mountain laurel tolerates droughty soils once established for two years.

Mountain laurels tend to perform more reliably than rhododendrons. While several plant maladies are possible, gardener should be most aware of phytophthora root rot in poorly drained soils and lace bug damage on the spring/summer foliage.

*Dr. Jaynes’ book: “Kalmia: Mountain Laurel and Related Species”, 3rd ed.(Timber Press).

Next blog: list and descriptions of ten favorite kalmia cultivars.

Evaluating Weeping Bald Cypress Cultivars

Posted by Hugh on May 9th, 2012

‘Cascade Falls’ weeping baldcypress

Bald cypress (Taxodium distichum) is a large 75 -80 foot deciduous conifer tree. They are long-lived, often 100 years or more. Bald cypress is incredibly hardy from the warm humid Florida swamps to the cold winter temperatures and loamy soils of central Michigan. Bald cypress is tolerant of a wide range of soil and moisture conditions. It grows in full sun and in any average acidic (not alkaline) soil type.

‘Cascade Falls’ (CF) and ‘Falling Waters’ (FW) are two dwarf cultivars which are better fits in most gardens. Both exhibit a strong weeping habit. Their fern- like foliage is light green in spring and summer months, and finishes burnt orange to brown in the autumn. The small leaves fall and compose rapidly around the tree. Both are real standouts as small weeping trees. Their exfoliating bark is an added winter feature.

Cascade Falls grows to about 20 feet tall and 20 or more feet in width. FW has a graceful arching form which is 15-20 feet tall by 8-12 feet in width (after 20 years). FW grows taller with less staking and holds its narrow tree profile.

In the early years, staking is a must for both cultivars. CF grows as tall as you stake it. It arches down, eventually forming a mound. Bend up and stake the leader until the desired height is achieved. If not staked, CF tends to grow like a ground cover.

Bald cypress requires little other maintenance, possessing few disease and insect issues. It is deer resistant.

Firethorns Make Good Utility Shrubs

Posted by Hugh on May 6th, 2012

6 Feet Tall Firethorn (Pyracantha) Hedge

Firethorn (Pyracantha spp.) is an old- fashion shrub that is making a comeback. Its white flowers makes a lovely presence in spring, followed by dark green leaves in summer, and bright orange or red fruits (berry clusters) in fall and winter. Firethorn tolerates close clipping and is often utilized as a short 6-8 foot tall privacy screen.

White clusters of foul smelling flowers cover the shrub in the spring. Fragrance is not detected from a few feet away. Fruit color depends on the cultivar planted. Firethorn prefers full to partial sunlight (6 hours minimum) and a well-drained average soil. Fertilize in late winter, but do not overfeed. Firethorn is susceptible to bacterial fireblight and scab leaf spot, but disease resistant cultivars are available.

Firethorn creates an effective 8-10 feet barrier or hedge. Sharp ½ – ¾ inch long thorns keep people and pets behind the sharp barrier and unwanted guests on the outside. The short stiff spines are mostly hidden among the foliage.

Firethorn tolerates close clipping and is easily pruned into an espalier against a wall or fence. You should wear leather or heavy canvas gloves to protect your hands during pruning.

Firethorn performs almost evergreen in the Southern Appalachian region (USDA zones 6 and 7), some years defoliating in mid to late winter. The leaves drop pale yellow, rarely catching your eye.

Here are 5 new hybrid cultivars are scab and fire blight resistant:

‘Apache’ grows to 5 feet high and 6 feet wide and forms large, bright red berries that last well into winter.

‘Fiery Cascade’ grows to 8 feet tall and 9 feet wide, and bears orange berries in the fall that turn red in winter.

‘Mohave’ grows to 12 feet tall and wide and develops many big orange-red berries which last well into winter.

‘Rutgers’ bears orange-red fruits on a low spreading 3 feet x 9 feet shrub. It demonstrates better winter hardiness than ‘Mohave’ and ‘Navaho’, writes Dr. Michael Dirr in the Manual of Woody Plants (6th ed.).

‘Teton’ has a tall upright growth habit (12 feet high and 4 feet wide) and is very cold hardy. Berries turn golden yellow in the fall.

Variegated Tapioca Plant Thrives In The Summer Heat

Posted by Hugh on May 3rd, 2012

Variegated Tapioca Plant (Manihot)

Add some tropical flair to your garden with variegated tapioca plant (Manihot esculenta ‘Variegata’), aka Cassava. Variegated tapioca is a spectacular foliage plant (zone 8 – 11) which excels as summer’s heat and humidity arrives and lingers.

Tapioca plant is not likely to be sold in every garden center and you’ll likely need to order one or more on-line. Young 12-18 inch tall plants grow to 5-6 feet tall and wide by late summer in full sun or partial sun (6 hours minimum). The first hard frost in autumn will kill this tropical plant.

Set out plants in mid- to late spring when all danger of frost has passed. Once temperatures climb into the seventy (70°F) plus degree range, plants will shoot up quickly. Tapioca plant thrives in poor soils and needs little attention once it becomes established after 4-5 weeks. Plant growth does excel with backup irrigation during long dry spells. Feed with a slow-release fertilizer at time of spring planting.

Its striking creamy yellow splashed foliage is a real eye catcher. It looks good in containers or in garden beds. Here in the Southern Appalachian region (USDA hardness zones 6 and 7), it is grown as an annual as it will not overwinter outdoors. Tapioca plant can be grown in large outdoor containers and brought indoors in early fall. Plants are cut back severely to fit inside a room to re-sprout.

Cassava is native to South America but is cultivated in tropical and subtropical zones throughout the world. It is one of the most important tropical food crops in the world. It requires at least 8 months of frost-free weather to produce usable roots. Cassava (tapioca) roots are poisonous and must be properly cooked to become edible.