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A bit of garden housekeeping in February and March can literally help clear the way for the floral exuberance of April and May. With that in mind, here are some spring cleaning projects for late winter, on days when the Polar Vortex isn’t visiting.
Winter offers a lot in the way of stark clarity – including a clear view of dead twigs and branches. Now’s the perfect time to pull on some warm clothes and work gloves and have a go at any twigs and branches that have passed their expiration date. Pay special attention to bigleaf hydrangeas (Hydrangea macrophylla), spiraeas, mock oranges (Philadelphus spp.), and other prolifically sprouting shrubs that tend to develop a central snarl of congested stems. Entirely dead growth can often be yanked out by hand, but you may also need pruners or a pruning saw.
Broken and wayward limbs (such as “crossing” branches) are also relatively easy to spot (and prune) during the dormant season. You might want to save this job for late winter or early spring, to minimize the risk of cold damage to pruning wounds.
Garden phlox (Phlox paniculata), bee balm (Monarda spp.), mallows (Malva spp.) and quite a few other ornamental plants are plagued by leaf-disfiguring diseases and pests that winter over on plant debris. If you haven’t already removed said debris to some place far away from potential host plants, now’s the time to do so. Late winter is also an excellent time to stage a horticultural-oil attack on numerous pests, including hemlock adelgids and soft scales. (Click here to read an article about using horticultural oils to manage pests.)
Matted leaves, winter mulch, and the like provide ideal cover for voles as they nose their destructive way through your garden, devouring the roots of perennials and shrubs and girdling the bark of trees. Check your garden regularly for their furrowed surface runways – and be prepared to take action if you discover damage. Siberian irises, daylilies, ornamental grasses, and other perennials that produce ground-smothering mats of spent leaves are especially vulnerable to infestation (and destruction) by voles. The best way to control voles in the perennial garden is to trim mat-prone foliage (preferably before winter). Which brings us to….
Ornamental grasses are one of the glories of fall and early winter, their gossamer seed heads and papery leaves shimmering and ruffling in the November and December breeze. Most of them are considerably less glorious by February, however. A mild, dry late-winter day might be a good time to break out the hedge clippers and shear back your vortex-shredded Miscanthus (or Pennisetum or Panicum).
Shear the tattered foliage of hellebores, Christmas ferns, epimediums, and other semi-evergreen perennials in late winter to clear space for their newly emerging growth. The tail end of winter is also the ideal time cut back the stems (to 4 inches or so) of semi-woody sub-shrubs, including Russian sage (Perovskia), butterfly bush (Buddleia × davidii), and blue mist (Caryopteris × clandonensis). They’ll respond by pushing vigorous new shoots and clouds of summer flowers. Apply an inch of Fafard® Garden Manure Blend in spring to give their fresh growth an extra boost.
Oil-based insecticides have come a long way in the last few decades. Lighter and more versatile than the “dormant oils” of yesteryear, today’s horticultural oils can be used at most times of the year and are effective against a wide variety of insects. They’re also among the most benign pesticides, decomposing within a few days of application and causing minimal harm to beneficial insects and other untargeted organisms. Accordingly, many brands of horticultural oils are OMRI LISTED for organic gardening.
Most new-wave horticultural oils derive from petroleum, although an increasing number are vegetable-oil-based. In all cases, they’ve undergone several rounds of processing to remove impurities, such as sulfur that can damage leaves and other soft plant tissues. Their relatively high purity (92 percent or greater) and low viscosity allows them to go places – such as directly on foliage – that are largely off limits for old-school “dormant oil sprays.”
Almost all horticultural oils work not by poisoning pests but by mechanically coating and smothering them. Consequently, they’re an excellent remedy for infestations of slow-moving, soft-bodied arthropods, such as aphids, mites, and whiteflies. They also control a number of plant diseases, including powdery mildew and aphid-transmitted viruses.
Neem oil departs from the norm by disrupting insects’ feeding and development via several biologically active compounds. Virtually non-toxic to humans and other mammals, it’s effective against a relatively wide range of pests, including some that are resistant to other horticultural oils.
Horticultural oils come with a few provisos. First, they lose their effectiveness in rain, drought, cold (sub-40 degrees F), heat (90-degrees-plus), or high humidity. Additionally, even highly refined horticultural oils can sometimes cause minor damage to flowers and tender new plant growth. Horticultural oils are also said to be mildly toxic to a number of plant species including ferns, Japanese maples (Acer palmatum), and smoke trees (Cotinus spp.), although this may not apply to the highly purified oils currently in use.
Of course, horticultural oils are effective and ecologically friendly only when they’re properly used on visible pests at vulnerable points in their life cycles. A thorough, targeted coating of oil at the right time will put a serious dent in a susceptible pest infestation. Conversely, indiscriminate spraying will likely do more harm to beneficials and foliage than to pests. It’s always good horticultural practice to know your enemy and to read the label.
The horticultural oil season begins in late winter, as temperatures moderate and overwintering pests begin to shake their slumber. Hemlock woolly adelgids (pest info here), euonymus scale (pest info here), and spruce spider mites (pest info here) are among the insects and mites to look for and treat at this time.
Use horticultural oils from mid-spring to fall to control the likes of aphids, lacebugs (pest info here), spider mites (pest info here), powdery mildew (pest info here), and sawfly larvae such as “rose slugs” (pest info here). Mild days in late fall are a good time to spray scales, mites, and other pests that survived early spring treatment.
Indoor plant pests are also fair game, whatever the season. Your spider-mite-infested weeping fig and all your other insect-plagued houseplants will welcome a quick visit to the back porch for a spritz of death-dealing horticultural oil. Or you can give your plants (and their insect pests) a bath by inverting them into a bucket filled with highly diluted horticultural oil. Outside or in, horticultural oils are an environmentally friendly solution to a host of insect problems.
Camellias have been known to trigger acute plant envy in Northern U.S. gardeners. If only those voluptuous blooms came on hardier shrubs that could withstand sub-zero temperatures.
As a matter of fact, in some cases they do. Although most camellias trace their origins to mild subtropical and maritime areas of East Asia, a few hail from chillier regions. These cold-hardy camellias have contributed their genes to the development of new varieties that are as happy in Newport, Rhode Island as they are in Newport News, Virginia.
Many of these winter-ready camellias owe their toughness to arguably the hardiest species in the genus, Camellia oleifera. Widely cultivated in China for its seed oil, it occurs in the wild as far north as Shaanxi Province, where winter temperatures resemble those in south-coastal New England and the upper Mid-Atlantic. In American gardens, it’s grown chiefly for its fragrant, white, 2- to 3-inch-flowers, borne in fall on large, shrubby plants furnished with oval, evergreen leaves that taper at the tips. The handsome gray-brown bark makes an eye-catching winter feature.
Camellia oleifera proved its hardiness in a series of bitterly cold winters that clobbered the eastern U.S. in the late 1970s. Of hundreds of decades-old camellias at the National Arboretum in Washington, D.C., only a dozen or so survived – including several selections and hybrids of this rugged species. Subsequently, horticulturists have used Camellia oleifera to produce a number of comely cultivars that flourish into USDA Zone 6 (0 to minus 10 degrees F minimum temperatures). Most of them produce pink or white, 3-inch-wide, single to double flowers in early to mid-fall (the earlier the better, so as to escape damage from Arctic spells).
Camellia oleifera and its progeny are not the only hardy camellias on the block, however. Recent introductions of Camellia japonica from Korea and northern Japan are also blessed with USDA Zone 6 hardiness. Handsome year-round, they typically form dense 6- to 12-foot shrubs with lustrous, leathery, evergreen leaves and early-spring flushes of rich-red, 2- to 3-inch-wide flowers accented with yellow stamens.
Thanks to these two species, gardeners in Zone 6 can now do the formerly unthinkable: enjoy a fall and spring garden display of showy camellias.
Combining the showy flowers of the cold-tender Camellia sasanqua with the Zone 6 hardiness of Camellia oleifera, this highly prized hybrid bears zingy, double rose-pink flowers in early to mid-autumn, well before freezing weather threatens. They’re lovely planted in combination with Colchicum ‘Waterlily’. The dense, 8-foot plants have relatively small, dark green leaves.
Two of the hardiest white-flowered camellias (‘Plain Jane’ and ‘Frost Princess’) teamed up to produce this beautiful, tough-as-nails cultivar. Frilly white pompons appear in early to mid-autumn on a fast-growing shrub that takes well to early spring pruning and winters reliably through Zone 6. Combine it with Anemone japonica ‘Whirlwind’ and Ilex glabra ‘Ivory Queen’ for a fall symphony in white.
Single white flowers open in mid-fall on vigorous 10- to 20-foot plants. A hybrid of Camellia oleifera, it lives up to its name by consistently showing superior hardiness in cold-winter climates (to USDA Zone 6).
Named for the shape of its single, lavender-pink flowers, ‘Winter’s Star’ actually commences bloom in October, well before the onset of winter weather in Zone 6 (where it’s perfectly hardy). It forms an open, conical, 10- to 12-foot shrub.
No cold-climate camellia produces anything more luscious than the 5-inch-wide, semi-double, creamy-pink flowers of this remarkably hardy 1996 introduction from Camellia Forest Nursery. It rapidly forms a vigorous, 6- to 10-foot shrub with large rich-green leaves. If you garden in USDA Zone 6 but want bodacious Southern belle camellias, ‘April Remembered’ is the place to start. And yes – it does bloom during the first warm days of April, or sometimes March.
Brilliant red flowers, lush foliage, and a large, dense, rounded habit make for one of best all-around camellias for Zone 6 gardens. The single, 3-inch-wide blooms occur in flushes during mild spells in late winter and early spring. The original plant – grown from Korean seed at Morris Arboretum in Philadelphia – is more than 12 feet tall and 6 feet wide.
Smoldering-red, six-petaled, 2-inch-wide flowers repeat from late winter through early spring, weather permitting. Perhaps the hardiest camellia variety introduced to date, ‘Korean Fire’ is well worth trying in favorable microclimates into USDA Zone 5. Plants grow to 10 feet tall and 6 feet wide.
All camellias grow best in acid, friable, humus-rich soil, with protection from north winds and strong sunlight. If you garden in sandy or heavy soil, give your camellia an extra-wide planting hole (at least 3 times wider than the root ball), and amend the backfill with Fafard Premium Natural & Organic Compost. Spring planting and a yearly application of an inch or two of compost are also advisable, whatever the soil.
Salt can be a winter lifesaver for cars and pedestrians. It can also be murder on the garden, sometimes literally. Most de-icing salt contains sodium, which is toxic to many plant species. Even when used sparingly, it can find its way onto the leaves and roots of nearby plants, disfiguring or killing them.
One of the best ways to prevent salt damage to your garden is to use plant species that can handle some sodium. The five shrubs described below are a great place to start. They’re perfect for framing and sheltering gardens in salt-exposed sites, such as roadsides and seashores.
Brilliant foliage in fall, attractive clusters of white flowers in spring, and adaptability to a wide range of soil conditions are among the many merits of these handsome, disease-resistant shrubs from wetlands and uplands of central and eastern North America. Red chokeberry (Aronia arbutifolia) doubles down on the fall color by covering itself with bright red berry-like fruits that persist into winter. Happiest in moist soil, it slowly expands into suckering, 8- to 10-foot-tall clumps that are at their most luxuriant in full sun. Its abundantly fruiting cultivar ‘Brilliantissima’ is particularly showy. Smaller in size and less flashy in fruit, black chokeberry (Aronia melanocarpa) typically forms a thicketing, 3- to 5-foot shrub with glossy, rich-green leaves and edible black fruits. Varieties of this exceptionally drought-tolerant shrub include the compact growers, ‘Autumn Magic’ and ‘Iroquois Beauty’, as well as ‘Viking’, which is cultivated for its relatively large, tasty fruit that’s excellent for juices, preserves, and baked goods. The fruits of all chokeberries are favorites of birds. Aronia arbutifolia is hardy to USDA Hardiness Zone 4; A. melanocarpa to Zone 3.
The suckering, upright, 3- to 8-foot-tall stems of this eastern North American native are lined with lustrous, serrated, dark green leaves and topped in midsummer with fuzzy steeples of white or pinkish, root-beer-scented flowers. The leaves turn bright yellow in fall, and the persistent, peppercorn-like fruits make a pleasant winter garden feature. Sweet pepperbush comes in numerous varieties, including low-growing ‘Hummingbird’, pink-flowered ‘Ruby Spice’, and late-summer-blooming ‘September Beauty’. All forms do best in moist soil and full to partial sun in USDA Zones 5 to 8.
Its leathery, salt-tolerant, evergreen leaves and rounded habit would recommend inkberry for eastern North American gardens, even if it weren’t native to much of the region. Most varieties become leggy 6- to 8-footers with age, so you might want to opt for a compact, densely leaved cultivar such as the 4-foot-tall ‘Shamrock’. Female inkberries produce small, black, relatively inconspicuous fruits in fall, although white-fruited ‘Ivory Queen’ is a notable exception. All cultivars are hardy in USDA Zones 5 through 8.
Recently redubbed Morella pensylvanica, bayberry will no doubt continue to be known to gardeners under its former botanical name, Myrica pensylvanica. A signature species of salt-sprayed coasts from the Maritimes to the Carolinas, it’s literally a natural for salt-tolerant plantings in the eastern U.S. (and an excellent choice for other locations in USDA Zones 3 to 7). All of its parts – from the leathery, deciduous or semi-evergreen leaves to the waxy berries (on female plants) – possess a silver-gray cast and a pleasingly pungent fragrance, made famous by the candles that bear its essence and its name. Mockingbirds, yellow-rumped warblers, and other songbirds feed on the fruits in winter.
Almost all Syringa species boast moderate to high salt tolerance, reflecting their origins in arid regions of Asia and eastern Europe. Although best known in the form of the ever-popular common lilac (Syringa vulgaris), the genus includes numerous other garden-worthy species and hybrids, many of which are relatively scarce in gardens. Among the best of these for hedging and screening are littleleaf lilac (Syringa pubescens ssp. microphylla ‘Superba’), well worth growing for its aromatic, pale pink flowers that appear in late spring and summer on dense, dainty-leaved, 6-to 8-foot plants; cutleaf lilac (Syringa protolaciniata), distinguished by its deeply lobed leaves, compact arching habit, and pale lilac-purple spring flowers; and Chinese lilac (Syringa × chinensis), which in its best forms (such as ‘Lilac Sunday’) weights its stems with armloads of pale purple flowers in mid-spring, a few days before common lilac hits its stride. Any of the above would make an excellent screen or hedge in a sunny site in USDA Zones 5 to 8.
Whatever their salt-tolerance, all your plants will do better if you take measures to build their soil and to reduce their exposure to sodium. Apply an inch or two of Fafard Premium Natural & Organic Compost or several inches of shredded leaves in fall or spring to boost and maintain the levels of sodium-neutralizing organic matter in your soil. In addition to its many other benefits, mulch also lessens surface evaporation, thereby increasing soil moisture and lowering salt concentrations.
You can reduce the amount of incoming salt by screening planting areas with structures and salt-tolerant plants, by grading the soil to divert salt-laden surface water, and by using sodium-free de-icers, such as magnesium chloride, on your driveway and paths. The right plants and the right care can go a long way toward making your garden safe from salt.
Fall and winter – when most of the vegetable garden is slumbering – is a great time to get a jump on next year’s onion, scallion, and shallot crop. Most members of the onion tribe (known botanically as Allium) are hardy perennials and biennials that tolerate winters in most areas of the U.S. Garlic (as discussed elsewhere on this site) is one well-known and often-grown example – but winter onions and shallots are also ideal winter-growing crops for USDA Hardiness Zones 6 through 9 (in zones 4 and 5 they need winter protection).
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The “perfect lawn” – that oft-celebrated but all-too-rarely achieved carpet of unblemished turf grass – is a seductive concept. It’s also impossible to grow in most areas of the United States without major inputs of pesticides, fertilizer, water, and labor (as well as cash). This is not to mention the significant secondary costs that come with chemically supported lawns, such as damage to beneficial soil microbes and the neighboring environment. What’s good for that velvety green carpet is often not good for other forms of life.
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Commonly known as “magic lily,” plants in the genus Lycoris are, in fact, much more closely related to amaryllis than to their namesake. But they do bring plenty of magic to the landscape when they open their large funnel-shaped flowers on tall naked stems in mid- to late summer. Several are winter-hardy to boot, creating all sorts of delicious possibilities for gardens in USDA Hardiness Zone 5 and warmer. With their showy amaryllis-like flowers and their tolerance of bitter winters and partial shade, these bulbs from East Asia make marvelous (and miraculous) subjects for cold-climate gardens.
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Most gardens can use a visual lift in the dog days of late summer. This is where late-blooming lilies come in. When their voluptuous, often deliciously scented blooms make their grand entrance in July and August, it’s like a royal fanfare in the landscape. Goodbye, garden doldrums.
Nitrogen is one of the most essential plant nutrients, and one of the best ways to boost nitrogen in your soil is to grow nitrogen “fixing” plants. This amazing group of plants naturally add nitrogen into the soil by taking nitrogen from the air and converting it into a usable form in the soil. And many are common garden plants that you may already grow, like peas, beans, bayberry, or clover. Read the full article »