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

Summer Blooming Trees

Posted by Hugh on July 30th, 2023

Other than crape myrtles, few trees bloom in July and August. Here are four exceptions: Chaste tree, Sourwood, Golden Raintree, and Franklinia.

Chaste Tree (Vitex agnus-castus) is a 10-15 feet tall, vase-shaped, deciduous shrub or a small 15-20 feet tree. The species is native from southern Europe and Asia. It is often mistaken as a purple-flowering crape myrtles which are so common locally. Its grayish green foliage is palmately compound and aromatic if you crush the leaf. Airy panicles composed of tiny, fragrant, lavender to pale violet flowers (to 12″ long) appear in early to late summer and attract numerous bees and butterflies.

Ben Franklin tree (*Franklinia alatamaha*)

Sourwood (Oxydendrum arboreum), aka lily of the valley tree, is a deciduous native tree found in the TN, VA and NC woodlands. A member of the Heath plant family, which includes azaleas, rhododendrons, and mountain laurels, sourwood prefers an acidic soil. The tree (or multi-branched shrub) grows 20-25 feet tall (50 feet or higher in the wild). Finely-toothed, 5-8 inch long, glossy green leaves produce one of showiest red fall hues. Terminal 4-8 inch long panicles of white lily-of-the-valley flowers drape off branch tips in early summer. Flowers are slightly fragrant. Long-lasting dried flower panicles are present through September, and attract many bees. Sourwood honey is a tasty result sold at local gift shops.

Goldenrain Tree (Koelreuteria paniculata) is a medium-sized, open-branched, deciduous tree with a rounded crown. Native to China, it grows 30-40 feet tall and almost as wide. Its pinnate or bipinnate compound leaves, up to 18 inches across, are comprised of 7-17 irregularly lobed leaflets. The bright green, blemish -free summer foliage turns yellow in fall. Bright yellow flowers (each 1/2 inch wide) appear in early July as part of terminal 12-15- inch panicles. Flowers give way to brown lantern-like, papery seed capsules in fall. Caution: the non-native tree produces many seedlings and is listed “invasive” in some states.

Franklinia (Franklinia alatamaha) is known as the “Ben Franklin tree”. This small native tree is finicky to establish. It produces showy 2 – 3 inch pure white camellia-like flowers with showy golden yellow stamens from mid-August thru September. The blooms are sweetly-fragrant. Narrow, oblong-obovate, glossy dark green 3-5 inch long leaves turn multi-shades of orange, red and purple in autumn. Branching is upright and spreading to create an open airy. Franklinia is extinct in the wild and sold by native plant nurseries.

General care recommendations: all four trees prefer a moisture, mildly acidic, well-drained soil and full sun (morning sun for franklinia).

Vintage Large-Growing Oakleaf Hydrangeas

Posted by Hugh on July 24th, 2023

‘Snowflake’ Oakleaf hydrangea at JC Raulston Arboretum in Raleigh, NC

Oakleaf hydrangea (Hydrangea quercifolia) is an upright, broad-rounded, suckering, multi-stemmed, deciduous shrub that typically grows 4-6 feet (less frequently to 8 feet) tall. It is a wonderful flowering shrub with multi-season interest. It is native to the Southeastern U.S. and tolerates hot, humid weather. Oakleaf hydrangeas aren’t quite as cold-hardy as other hydrangea species (USDA hardiness zones 5-9).

In recent years most attention has been directed to the compact varieties (cultivars) which have flooded the nursery marketplace over the past twenty years. Yes, they are sensational and are ideal fits in small gardens. For gardeners with space to enjoy the larger cultivars, here are three “oldies”, — still sensational oakleaf hydrangeas.

‘Snow Queen’ is one of the most popular oakleaf hydrangeas. It grows 6-10 feet tall and wide and bears 4- to 12- inch-long panicles of creamy white double flowers in early summer. Its floral display is long-lasting into early fall. Fall leaf color turns gradually to red to burgundy to purple. It was introduced by the former Princeton Nursery in NJ.

Fall Color of ‘Snow Queen’ oakleaf at Longwood Gardens

‘Snowflake’ is noted for its double white flowers. It typically grows 5-8 feet tall and wide (less frequently to 12 feet tall under optimum growing conditions). Snowflake struts large pyramidal flower panicles consisting mostly of showy sterile flowers with multiple bracts or sepals which give the panicle a double-flowered appearance. It blooms in June for 6-8 weeks, gradually fading to pink and then brown in late summer. Distinctive, deeply-lobed, coarse, deep green, oak-like leaves (to 8 inches long) acquire attractive shades of maroon and purple in autumn. Snowflake was introduced in the early 1970s by Aldridge Nursery in AL.

‘Alice’, largest of the three cultivars, struts large 10 to 14-inch white arching floral panicles, the blooms later turning rose color. Additionally, enormous deep green, oak-like foliage, some up to 8 inches long and usually disease-free foliage and its superior fall color. Alice was introduced by Dr. Michael Dirr. The shrub averages 6 to 8 feet in height but can achieve 12 feet tall and wide in the South.

Oakleaf hydrangeas grow in moist, fertile, well-drained soil in sun to part shade. Shrubs appreciate a 3–4-inch layer of organic mulch to conserve soil moisture. They bloom on old wood. enerally, little pruning is usually needed. If pruning is needed, do so immediately after flowering. Winter damaged stems may be pruned in early spring.

In cold parts of USDA 5, set plants in a sheltered location or protect with a burlap blanket. Otherwise, flower bud numbers may be a lot less or shrub will die to the ground in harsh winters below -10°F. A winter mulch blanket will also help. Attractive peeling cinnamon-color bark adds interest in the winter after the leaves have dropped.

2023 Carex Evaluation From Mt Cuba

Posted by Hugh on July 18th, 2023

Pennsylvania Sedge (*Carex pensylvanica*)

The native plant research team at Mt Cuba Center in Hockessin, DE has recently published the results of a 3-year Carex (sedge) study in which they evaluated 70 species and cultivars. The study included a number of under-planted Carex species and varieties.

One grouping was grown in full sun and a second planting was tested under 60% shade cloth. Sedges were grown in clay soil that had a high moisture retention and high moisture retention. The study determined the optimum environment for each variety. Ratings took into account many factors including habit, floral display, disease resistance, hardiness, and foliage quality.

In a separate one-year study, sedges were evaluated as a sustainable alternative in lawn and turfgrass areas. Some were mowed or others not. Some low-growing species needed mowing only one or twice annually.

Carex varieties that grew much like traditional grass and could be mowed for improved aesthetics and foot traffic included: Carex woodii (Wood’s sedge), Carex eburnea (bristle-leaf sedge), Carex socialis (low woodland sedge), Carex pensylvanica (Pennsylvania sedge), and Carex jamesii (James’ sedge).

An underutilized species, Wood’s sedge (C. woodii) was the top performer in the entire study. Wood’s is similar to the popular C. pensylvanica also with a low-growing slow-spreading habit. Wood’s sedge is superior to C. pensylvanica from both garden utility and ornamental standpoints. Wood’s sedge forms a denser mat of foliage than C. pensylvanica and is better at suppressing weeds. Wood’s fine-textured foliage emerges an attractive blue-green hue in spring, changing to green in late spring and summer. A bonus eye-catching feature is a carpet of straw-colored flowers provides the perfect complement to other spring wildflowers.

Wood’s sedge is found in forests in the midwestern and eastern U.S. and performs equally well in both shade and sun. It was a top performer in the mowing evaluation, developing an attractive dense mat, and could be a suitable lawn substitute.

Mt. Cuba’s Top-Performing Carex:

Carex woodii (Wood’s Sedge)
Carex cherokeensis (Cherokee Sedge)
Carex bromoides (Common Brome Sedge)
Carex haydenii (Hayden’s Sedge)
Carex stricta (Upright Sedge)
Carex emoryi (Emory’s Sedge)
Carex sprengelii (Long-Beaked Sedge)
Carex pensylvanica (Pennsylvania Sedge)
Carex pensylvanica ‘Straw Hat’ (Straw Hat Pennsylvania Sedge)
Carex muskingumensis ‘Little Midge’ (Little Midge Muskingum Sedge)
Carex albicans (White-Tinge Sedge)
Carex jamesii (James’ Sedge)
Carex muskingumensis ‘Oehme’ (Oehme Muskingum Sedge)
Carex crinita (Fringed Sedge)
Carex leavenworthii (Leavenworth’s Sedge)
Carex plantaginea (Plantain-leaf Sedge)

Read the complete report which includes descriptions of all 70 Carex species and varieties @ https://mtcubacenter.org/trials/carex-for-the-mid-atlantic-region/

Mountain Hydrangeas

Posted by Hugh on July 9th, 2023

Mountain hydrangeas (Hydrangea serrata) look very much like big leaf hydrangea (H. macrophylla) except shrubs are smaller, more compact in growth habit with smaller flowers and leaves. They are native to the cool moist woodland valleys in Japan and Korea mountains. (USDA hardiness zones 6-9). These unique hydrangeas fare better in cool climates in zones 5 (protected) and 6 than bigleaf hydrangeas (H. macrophylla).

Current cultivars are listed below. Currently, Tuff Stuff™ series from Proven Winners (PW) is available through local garden centers. Currently, five cultivars have been introduced and are ideal compact hydrangeas for a small garden. Plant breeders are also crossing Mountain hydrangeas with other species.

Mountain hydrangeas begin blooming in early summer on old wood and continue to produce lacecap flowers on new wood from late June into October for a long bloom display. Utilize them as foundation planting, low hedging, front bed edging, or as a single specimen.

Leaves are toothed, ovate, dull green, up to 6 inches long) and their summer lacecap flowers are long-blooming. Most of the florets are fertile and attract pollinators. Smaller numbers of showy sterile florets form along an outer marginal ring around the tiny fertile florets. Mountain hydrangeas bloom on both old and new wood.

In alkaline soils (above 6.5 pH) pink florets are likely and blue florets in acidic soils. To achieve bluer blooms, lower the soil pH for 5.5 or lower feeding an acidic type fertilizer like Miracid™ or Hollytone™ or one specifically labeled for hydrangeas, one containing aluminum sulfate. Mulch beds with pine needles.

Mountain hydrangeas should be grown in partial shade or in and out all day filtered sun. The soil should be humus-rich, moist and well-drained. Plants will handle more sun if soils are adequately irrigated. Little pruning is necessary if properly sited. Deadhead old spent flowers and prune out weak or winter-damaged stems in early spring.

Diseases are rare with some susceptibility to bud blight, bacterial wilt, leaf spot and mildew. Aphids are occasional visitors. Because of its compact mounding habit, annual pruning of Tuff Stuff™ hydrangeas is minimal other than to remove some broken branches.

Tuff Stuff® is a small reblooming hydrangea that bears pink lacecap flowers with creamy centers in alkaline soil; they are lavender-blue in acidic soil. Its serrated leaves turn burgundy in fall. At maturity Tuff Stuff often reaches 3×3 feet tall and wide.

Tuff Stuff Aha® grows 2-3 feet tall and wide. Tuff Stuff Ah-Ha^® hydrangea will bloom pink or blue, depending on soil chemistry. Flower buds are more cold-tolerant, which ensures good blooming even in USDA zones 5 and 6.

Tiny Tuff Stuff® bears similar flowers to ‘Tuff Stuff’ but grows more compact shrub @ 2 feet high and wide.

Tuff Stuff Red™ is the newest addition to the Tuff Stuff series. Large, lacecap flowers are a deep pink-red color which is set off by lustrous, deep green foliage.

Tuff Stuff^™ Red Mountain has improved bud hardiness and is a reliable rebloomer. This dwarf hydrangea grows 24 – 36 inches high and wide with blue or red lacecap flowers.

Other varieties with a H. serrata bloodline include: ’Blue Bird’, ‘Blue Billow’, ‘Pink Dynamo‘, ‘Diadem’, and ‘Preziosa’.

Colorful Bugleweed As A Groundcover

Posted by Hugh on June 29th, 2023

Bugleweed (Ajuga reptans), aka “carpetweed” and “carpet bugle”, is a fast-growing evergreen perennial ground cover in the Lamiaceae (mint) family. The species name “reptans” means creeping. It is native to Europe, northern Africa, and southwestern Asia. Cultivars are hardy in USDA hardiness zones 3-9 (unless otherwise noted).

Most bugleweed cultivars demonstrate aggressive plant vigor that helps to control erosion on a bank or hill or to simply add color to shady spots. It performs well planted underneath shrubs and trees. Their leaf color and stay attractive almost all year-round, and they flower from spring into early summer.

Depending on the cultivar, bugleweed produces glossy, dark green scalloped leaves and clusters of blue, purple, or white flowers that may reach 6-10 inches in height. Several cultivars strut variegated foliage colors and patterns. Floral spikes generally stand above the foliage although some cultivars are shorter.

Early spring flower spikes attract bumblebees, hummingbirds and songbirds. Generally, rabbits and deer do not trouble bugleweed.

Plants form dense mats of glossy foliage in sun to partially shady areas, although the foliage color of some cultivars is most vibrant in full sun. Bugleweed grows best in moist well-drained soils; it struggles in heavy clays and periods of drought exceeding two weeks, particularly in its establishment year.

Bugleweed spreads aggressively via stolons and often creeps into nearby lawn and garden areas. Plant bugleweed in mid-spring thru summer, spacing plants 8-15 inches apart. Every 3-5 years divide plants when they grow too crowded in the spring or fall to prevent overcrowding.

Crown rot can be a problem in very humid conditions and in heavy clay soils. Space plants for good air circulation and avoid overfertilizing. Ajuga is listed as invasive in some U.S. states because it may spread aggressively.

Bugleweed doesn’t require pruning but clip off spent flowers for a neat appearance; for rapid cleanup, raise the cutting height of your mower and make a quick pass.

Great Ajugas to Grow:

‘Catlin’s Giant’ – 8 to 10-inch spikes of deep blue flowers are held atop bronze-blue foliage. The plants grow 3 to 6 inches high and 12-24 inches spread.

‘Blueberry Muffin’ – vigorous, fast-spreading (6 inches tall/ 18 inches spread), deep blue flowers. (zones 5-9).

‘Black Scallop’ –blue flowers and purple-black leaves with scalloped edges.

‘Toffee Chip’ –spring leaves start out light brown, later turn grayish-green with creamy gold margins (zones 3-10).

‘Chocolate Chip’ – dwarf variety with chocolate-burgundy leaves and bluish-purple flowers.

‘Burgundy Glow’ – exceptionally hardy cultivar, 6 to 10 inches high, with blue flowers and tricolored foliage in shades of pink, cream and white.

‘Purple Brocade’ – hardy non-aggressive variety, 6-8 inches high, with bluish-violet 6-inch flowers and deep green leaves with purple markings

Goatsbeard

Posted by Hugh on June 19th, 2023

Goatsbeard (Aruncus dioicus) or “goat’s beard” is a North American perennial that produces feathery plumes of cream-colored flowers in late spring or summer. Goatsbeard is also indigenous to western Europe. This clump-forming woodland plant is hardy in zones 3-7a (?) and appears to flounder under the intense summer heat in Georgia and the Carolinas. The arching plumes are densely covered with small florets in 20-inch branched clusters.

Goatsbeard is often mistaken for Astilbe and both have dark green pinnately compound leaves. The perennial is dioecious (separate male and female plants); flowers on male plants are showier on female ones.

Flowers are at their peak for about 10 days and make good cut flowers. Female plants produce tiny brown seed capsules, which are poisonous. After flowering the plumes turn tan or light brown above the 3-4 feet mounds of finely dissected foliage. Each leaf has 20 or more toothed oval leaflets.

In the garden goatsbeard grows slowly the first few seasons. It grows best in moist, rich, well-drained soil in partial shade, although it will do fine in full sun if given consistent moisture. Set in multiples of 3-4 plants, spacing them 2-4 feet apart. Within 3 years, plants should fill-in and offer a spectacular floral show.

Goatsbeard is a relatively low maintenance plant. Keep the soil moist during dry spells. Cut back old stems in fall to just above ground-level and mulch with leaf compost.

Goatsbeard has no significant insect or disease problems and is reported to be deer resistant. Propagate by division or grow from seed.

Over 3-5 years goatsbeard looks shrub-like in a sunny perennial border or in a woodland landscape area. Over time plants will self-seed freely.

Addendum: “Dwarf Goat’s Beard” (Aruncus aethusifolius), native of Korea is a good choice in a smaller garden. It produces short spikes of cream-white flowers in June. Utilize as edging along a woodland path or grow in a front border; at its best in moist soil and in sun to partial shade. Deadhead faded flowers to encourage repeat blooming.

Bergenia Or Pigsqeak For Sun Or Shade

Posted by Hugh on June 9th, 2023

Bergenia (Bergenia spp), aka “pigsqeak”, is a herbaceous perennial with distinctive glossy, rounded leaves. Bergenias are native to the forest and alpine zones of China and Siberia. Eight species are available including heartleaf Bergenia (B. cordifolia), leather bergenia (B. crassifolia), and fringed bergenia (B. ciliata). Hybrid selections are also available. (USDA hardiness zones 4-8).

Bergenia’s colorful bloom spikes rise 12 – 16 inches tall in the early spring garden. Depending on the variety, the showy bell-shaped flower clusters come in white, pink shades, or purple colors.

‘Peppermint Patty’ bergenia — new from Walters Gardens (WG photo)

The key reason for growing Bergenia is for the huge, round, brassica-like leaves which are deciduous in the north and evergreen in the Southern areas of the U.S. In a shady garden, its bold textured almost leathery foliage standout among perennials with finely textured leaves, such as ferns, bleeding hearts, and astilbes or broad-leafed hostas and brunneras.

Bergenias are rated as good shade plants, although they also perform well in sun. Set plants in humus-rich soil and mulch annually in late spring with well-rotted compost. In northern areas they thrive in almost any amount of sunlight (zones 4-6) and preferably in afternoon shade in the Southern U.S. (zones 7-8).

Whenever you spot bergenias growing poorly, the soil probably drains poorly or holds to much water over the winter months. Plants spread slowly via rhizomes (underground stems). The best time to divide rhizomes is in spring (after flowering) or in the fall. Dig up the whole clump, discard the old woody center and cut the remaining rhizomes into several sections, making sure each one has at least one leaf attached.

Bergenia leaf spot and anthracnose are fungal diseases that trouble this perennial. Deer are not rarely troublesome. Clip off and discard diseased leaves promptly. Avoid overwatering and water mainly in the morning hours. Slugs and snails can lurk under the leaves and disfigure the foliage.

Native Catalpa Trees

Posted by Hugh on June 2nd, 2023

Catalpa Tree

Northern catalpa or cigartree (Catalpa speciosa) overpowers most private landscapes by their enormous presence (USDA hardiness zones 4-8). This 40-60 feet large native tree commonly grows along roadsides, particularly on bottomlands from Illinois and Missouri south thru Arkansas and Tennessee. Catalpa is not a tree seen planted in most residential neighborhoods because of its fast growth rate, messy behavior, and enormous size.

Without question catalpa is treasured for its showy fragrant white flowers in late May into June. The orchid-like blosoms are surely beautiful. Numerous two-inch long white flowers are borne on large terminal spikes, many unfortunately hidden beneath the enormous catalpa leaves. Each flower are marked with small gold spots within its frilly edged corolla. Narrow long cylindrical cigar fruits, 8 – 15 inches in length, are easily visible in the fall and winter months.

In summer catalpa’s huge heart –shaped pale green leaves measure 8 – 12 inches in length and width and provide excellent summer shade. Small birds often seek shelter within their dense tropical-like foliage cover.

The bad news is their spent blooms turn into a soggy, slippery, smelly mess when they drop onto a sidewalk, deck, patio, driveway, or pool side. In the autumn months add their trashy dried seed pods to your raking list; their sharp points may result in pin-point skin pricks incurred during fall cleanup.

Even mild winds can leave your yard covered with sticks and twigs that fall from this brittle-wooded tree. Wide-ranging, invasive roots can infiltrate foundations, sewer lines, collapse retaining walls, or penetrate underground swimming pools.

Catalpa trees are often visited by the catalpa sphinx moth whose larvae (caterpillars) are prized for bait by fishermen. Hummingbirds are a major pollinator that are attracted to its floral nectar. There are no listed cultivars of northern catalpa (C. speciosa).

Southern catalpa (C. bignonioides) is another native species native to the Gulf Coast region from northern Florida across the Mississippi. It grows smaller, averaging 35-50 feet in height (zones 5-9). Both species self-seed readily.

American Beautyberry

Posted by Hugh on May 28th, 2023

American beautyberry (Callicarpa americana) is a deciduous shrub native to open meadows, fence rows, or woodlands in the southeastern U.S. and northern Mexico (Zones 6-11). This vigorous shrub grows to 4-8 feet high and wide and belongs in the Lamiaceae (mint) family.

American beautyberry, also called French mulberry, has an open growth habit and arching branches. The ovate to elliptic, oppositely arranged leaves are coarsely toothed; they range from 3-8 inches in length and 1-3 inches in width. The small, light pink to purple or blue tinged flowers are arranged in dense, axillary clusters along main branches in early summer and develop bright, lavender to violet ¼ diameter fruits in September. White-berried varieties are available.

Beautyberry is widely adapted to moist, well-drained soils containing lots of organic matter. It is not finicky as to soil type as long as drainage is adequate. Mulch first year planted shrubs to conserve soil moisture. Irrigate during prolonged periods of hot, summer drought to prevent early fall defoliation.

Optimum fruiting occurs in full sun, although beautyberry does tolerate moderate shade and be less fruitful.

Prune in late winter to encourage more bushy, compact growth. Plants can be cut as far back as 1-2 foot from the base. Or shrub(s) can also be left to favor a more natural habit. Remove deadwood in spring. Propagate from cuttings or seed.

An unusually cold harsh winter may result in stem dieback, but pruning back shrubs will regenerate vigorous new shoots from the shrub base. Summer flowering and autumn fruiting will be unaffected.

Beautyberry is relatively disease and pest free. Leaf spots are possible but not usually a serious problem. Green leaves emerge in mid-spring on upright arching stems. Clusters of small lavender pink flowers bloom during the late spring and early summer. Clusters of purplish to bluish berries size and color-up in August through October. A pink-fruited and several white-fruited forms are available (see below). Fruits may persist into early winter and are a good food source for songbirds and small mammals.

Shrub size and its loose open form relegates American beautyberry to the back of a shrub border. In large landscapes mass several beautyberry shrubs together for a maximum fall berry show and winter wildlife habitat.

Cultivars

‘Welch’s Pink’ blooms in late spring into early summer and form beautiful pink berries in September that last into winter; grows 4-6 feet tall and wide, smaller than the species; initially found in east Texas and rated winter hardy in zones 7-11.

Var. lactae produces white berries in the fall.

Factoid: the sap from crushed leaves of American Beautyberry have proven to repel mosquitoes and biting bugs both on livestock and humans.

Watering Newly Planted Trees And Shrubs

Posted by Hugh on May 21st, 2023

Tree “gator bag” for irrigation

Tree watering

Proper watering of a newly planted tree or shrub starts the day it is planted. This is the final crucial step! Dig a wide shallow hole that will accommodate the roots of the new tree. Adding soil amendments is generally not necessary unless the shrubs are moisture-loving, acidic-loving types such as azaleas (Rhododendron spp.), blueberries (Vaccinium spp.) or mountain laurels (Kalmia spp.). Treat the original topsoil removed from the hole as “gold” as it contains some humus.

Water deeply after planting. For a 3-4 feet wide hole, add a minimum of 5 gallons of water. Add 2-3 inches of organic mulch such as shredded pine bark, pine straw (needles) or lawn grass clippings.

Under- or over-watering may kill the tree. Too much water drowns tree roots; it takes oxygen out of the soil around the roots. Yellowing or sudden leaf loss are common symptoms of overwatering, usually first noticed on the interior leaves.

Most tree roots grow in the top 6 to 12 inches below the soil surface. To water a newly transplanted tree, you might opt to using a soil needle, aka “root feeder” which is attached to a garden hose. Water goes deeply to the root zone. A root feeder is a valuable tool for watering older trees and shrubs as well.

Water newly transplanted trees thoroughly through September (in most states), then gradually cut back watering in autumn to allow plants to “harden off” as cold weather sets in. After the leaves drop, continue watering if natural moisture is significantly below average.

Newly planted trees and shrubs need adequate soil moisture to become established, especially through the first hot dry summer. Naturally shallow rooted trees such as Japanese maples (Acer palmatum), spruces (Picea spp.) and azaleas require more frequent watering than tap rooted species such as oaks, ashes and walnuts.

Drip irrigation system or soaker hose is common methods of timely supplying water. Treegator™ bags, available in 15 and 20 gallon sizes, slowly release water (and nutrients) to a newly planted tree. They’re available through garden centers, hardware and box stores across the U.S.

Additional facts:

Newly planted trees need more frequent watering than those established 3 years or more. Larger trees demand more soil moisture than smaller species.
Evergreens do require watering during the fall-winter period in areas with a rainfall deficit.
Clay and silt loams retain more soil moisture than porous sandy soils.
Weekly rainfall amounts of one inch per week during the growing season is rated satisfactory.