Baby, it’s cold outside. Console your green thumb by tackling some February garden projects.
Veggie Planning
Grab a sketch pad or some graph paper and plan your vegetable and flower beds. You can work out crop rotation, placement and successive crops without getting your hands dirty.
Beginning gardeners – and those that want a refresher – might appreciate this reference from our Seed to Supper webpages that take you from seed to harvest (hence the name!) Guides are also available in Spanish! ¡Las guías también están disponibles en español!
Weeding
Okay, if you want to get your hands a little dirty, pull a few weeds. Winter weeds pop up here and there and many can be vanquished with a quick dig or tug in our soggy soil.
Here’s a nice reference for weed ID and management:
Common groundsel is a winter annual weed you can manage now by pulling or digging. Photo credit: Betty Marose
Garden Bones
While you’re scouting for weeds, look at your garden’s basic structure – its bones. Without the distraction of leaves, it’s easier to identify areas that could use an arbor, trellis or hardscaping.
You’ll probably spy opportunities to liven up your winter landscape, too. How about a sweep of native grasses, a winterberry pop of red, or bright yellow and oh-so-fragrant wintersweet?
Carry a notepad to capture all your ideas. Wouldn’t a big container make a marvelous focal point there? And that downspout is crying out for a rain barrel, isn’t it?
January to mid-March is prime time for pruning most trees and shrubs. Make sharp cuts at an angle. Remove no more than a third of the plant. And step back often to avoid overdoing it. Here’s a good pruning guide.
February also marks the season for grapevine pruning. My collection of grapevine wreaths from trimmings ranges from petite 3-inch rings to 2-foot whoppers.
Starting Seeds
Get a jump on spring by starting some plants from seed under grow lights. Now is a good time to start peppers, onions, broccoli, cabbage, cauliflower and Brussels sprouts.
Growing plants from seeds gives you more choices for plant varieties, organic growing options, and the satisfaction of growing your own food from start to finish. Plus, you can save money. Learn how on our Staring Seeds Indoors page.
I enjoy the glow of a friend’s grow lights as I drive by her home each winter. I can see the tidy rows of sprouts in my mind regardless of the amount of ice and snow piled around me.
Starting seeds indoors jump-starts your growing season. Photo credit: Home & Garden Information Center
Ice and Snow Damage
Deal with that ice and snow gently. To remove snow from tree branches without damage, brush up, not down. If ice coats the branches, let it melt naturally.
Should winter’s worst snap off a branch of a tree, make a clean cut now or in early spring. Clean cuts heal faster. Call on an arborist for jobs too big to tackle on your own.
Make a clean cut on winter-damaged branches to minimize health impacts. Photo credit: Home & Garden Information Center
Feeding Birds
Wintertime can be a tough time for birds, too. To ensure their springtime birdsong and bug-eating services, keep their feeders clean and well-stocked.
Tool Maintenance
Are you looking sharp? How about your tools? If you didn’t sharpen your garden tools in the fall, do it now to have them ready for spring. Here’s a reference that includes tool care tips.
See? I told you there were a dozen different ways to keep your green thumb happy this winter. Grab some graph paper, seed catalogs, notepad and pruners and get going!
By Annette Cormany, Principal Agent Associate and Master Gardener Coordinator, Washington County, University of Maryland Extension. Read more by Annette.
Okay, gardeners. We can see the finish line. It’s been a busy gardening season, but we are almost ready to wrap things up for the year. Almost.
October and November are the wrap it up, clean it up months. Now’s the time to give the last of your withering vegetable plants the heave-ho.
I know there is still one tomato out there, but it’s a brick. Let it go. Toss healthy plants on the compost pile and bag and trash the rest.
Are you one of those garden daredevils who cheat the season with late plantings of cool weather crops? Good for you. Just be ready with frost protection such as floating row covers or a deep layer of straw.
Floating row covers extend the growing season. Photo: UME/HGIC
Cut back any perennials that had serious disease or insect problems, but leave the rest standing to provide food and shelter for birds and overwintering pollinators and beneficial insects.
Mums have sensitive crowns – the part where the roots and stems meet– so treat them gently. After their fall show, leave them standing to increase their chances of coming back. Not all hardy mums are hardy.
Use leaves as mulch around trees and shrubs and in your vegetable and flower beds. Use a fine layer on your lawn and toss the rest in your compost pile.
Collect fallen branches to start a brush pile for wildlife. Put larger pieces on the bottom and smaller ones on the top to create cover and resting places for creatures great and small.
Yes, you can still sneak in some bulbs. Remember to plant them three times as deep as they are wide. In other words, a 1-inch daffodil bulb goes into a 3-inch hole.
You can plant trees and shrubs until the ground is frozen, too. Earlier is better to give roots a chance to get established. Just make sure you water them deeply every week.
There’s still time to plant trees such as this native black gum (Nyssa sylvatica) with brilliant fall color. Photo: T. David Sydnor, Bugwood
Here’s a fact sheet that tells you how to plant trees and shrubs and lists plants that are best planted in the spring.
Also deep water any tree or shrub you planted earlier this year to send them into the winter well-hydrated. Water until we get a ground-penetrating frost, usually around Thanksgiving.
Water any newly planted trees and shrubs to help them overwinter. Photo: M. Talabac, UME
Want a live Christmas tree? Save yourself some colorful language by digging the planting hole now before the ground freezes. Drop in a few unopened bags of mulch to avoid losing Bowser or any holiday guests in there.
We’re almost to the cuddle up with cocoa season. Taking care of these few last-minute garden tasks will let us smile and sigh under the afghan, reveling in a job well done.
By Annette Cormany, Principal Agent Associate and Master Gardener Coordinator, Washington County, University of Maryland Extension.
Blue Atlas Cedars on the American University campus in Washington, D.C. Photo: M. Talabac
Q: I have always loved the look of blue spruces, and I see many Maryland nurseries stocking them. I’ve heard that I should consider alternatives, though. Why?
A: Although every plant has something it can be vulnerable to (pests, diseases, environmental stress) and nothing is risk-free, Colorado spruce (Picea pungens), the species with the popular blue-needled cultivars, struggles in Maryland growing conditions. As such, it is at risk for several problems that cause dieback and significant aesthetic damage. Overall, spruces as a group are not well-adapted to high summer heat and humidity, or compacted or clay-dominated soils common to urban or suburban landscaping.
No spruces are native to the state except for the tip of western Maryland, where the locally rare red spruce grows in the mountains. (Maryland Biodiversity Project notes that prior logging and wildfires reduced this already limited population.) You can see from the spruce species range maps on the Biota of North America Program website that no other spruce species grows wild anywhere near Maryland.
Due to the particularly damaging nature of the issues spruces can develop here, primarily from fungal infections — drastic needle browning and shedding, plus branch dieback — I suggest using alternatives if you want a large-statured, pyramidal, and/or blue-leaved evergreen specimen tree. This spruce decline issue is prevalent enough that it has its own University of Maryland Extension web page, “What’s Wrong with my Colorado Blue Spruce Tree?”
A substitute plant won’t necessarily look the same (it might have broader or looser branching, or won’t have blue foliage), but it can have a better chance of thriving. Your options will depend on the site conditions, including how much space you have for the plant to mature, though your best range of choices will be for a location in full sun (in summer) with good drainage and no deer browsing pressures.
Few locally native species are evergreen and large-statured, but they include American holly (Ilex opaca), Eastern redcedar (Juniperus virginiana), and Atlantic whitecedar (Chamaecyparis thyoides), the latter of which is rare, unfortunately hard to find for purchase, and limited to the coastal plain in the wild. Several species of pine grow wild throughout Maryland, but their mature habit is quite different from spruce.
Left: Eastern redcedar (Juniperus virginiana), Right: American holly (Ilex opaca). Photos: M. Talabac
Non-native candidates include other holly species or hybrids, Japanese cedar (Cryptomeria japonica), true cedars (Atlas Cedar, Cedrus atlantica, and Deodar cedar, Cedrus deodara), and Western arborvitae (Thuja plicata). Arizona cypress (Cupressus glabra) and atlas cedar come in silvery-blue forms if you want a foliage color similar to blue spruce. While leyland cypress (Cupressocyparis leylandii) is commonly planted, it suffers from some serious shortcomings that can make it short-lived and prone to fungal branch dieback.
Smooth Arizona cypress (Cupressus arizonica glabra). Photo: M. Talabac
Whichever plants you try, use a mix of species if you’re growing them in a group, like a screen or living fence, rather than mass-planting only one species or variety. This helps the planting to resist future pest, disease, or weather stress problems, since different species have different tolerances and vulnerabilities. That way, a future issue won’t be likely to impact them all equally severely, like a fungal needle cast infection wiping-out a row of blue spruce.
By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.
Have a plant or insect question? The University of Maryland Extension has answers! Send your questions and photos to Ask Extension. Our horticulturists are available to answer your questions online, year-round.
Arborvitae (Thuja sp.). Photo: Jason Sharman, Vitalitree, Bugwood.org
Q: I need to reduce the height of an arborvitae…. I might take around 5 feet off the top because it’s too big. When should I prune?
A: While late winter or early spring is generally a good time to prune conifers (needled evergreens), in this case timing won’t matter much, because the amount you want to remove is more than the plant can handle. Instead, it may be better to replace the plant with a smaller-growing option.
Most conifers, including arborvitae, do not regrow foliage when it’s lost due to heavy pruning, deer browsing, or crowding from being planted too close together or too close to a wall or fence. Unlike broadleaf evergreens (boxwood, holly, euonymus, etc.), they don’t have dormant buds along the older stems, lying in wait to grow if the branch or foliage beyond them is removed.
Once the foliage is gone and bare wood is visible, it’s not coming back on that part of the plant. This is the reason why deer-browsed arborvitae are easy to spot, developing a shape sort of like a stemmed flute glass, because the parts the deer can reach become stripped of foliage and never fill back in again, even as the out-of-reach tops get wider.
As conifers age, it’s perfectly normal for the innermost branches to become quite bare, as those older leaves shed over time. They are deliberately jettisoned by the plant because they are being progressively shaded by the outer shell of live growth, so they cost the plant more to keep alive than the meager photosynthesis energy they get back. This will be exacerbated if the plant is sheared, where the foliage tips are lightly trimmed to give the plant a more manicured look, because that makes the layer of foliage casting shade on the plant’s interior even denser.
Pruning cuts that take off that outer layer or shell of younger growth on the branch tips will result in permanent bare areas. Once the foliage is gone from that inner wood, it will not regrow, even if sunlight now reaches the interior due to pruning cuts. This also applies to the main leaders. Reducing the height of a tall arborvitae will stunt the top growth and give it a permanent gap or flat-looking top. If this isn’t really visible from where you typically view the plant, then it’s not necessarily a problem (assuming the pruning cuts seal-over well and don’t develop wood decay). Otherwise, nothing will give the plant its former shape back.
Fortunately, there are lots of compact and dwarf conifer varieties on the market these days. A couple conifer types, like yews, will be able to rejuvenate after heavy pruning. Even so, it’s still best practice to select a plant that should fit in a given space in the yard without relying on pruning to make it fit.
I acknowledge that there are many gardeners that inherit poorly-chosen plants in their new yards, but if or when it comes time to replace them, research your options to make sure you won’t run into the same problem down the road. Plants never really stop growing, though older specimens can slow down. Due to a reduced growth rate, dwarf and miniature cultivars will stay much smaller over the same amount of time as their full-size counterparts, even though some dwarf cultivars can also get larger than you’d expect a few decades after planting.
By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.
Have a plant or insect question? The University of Maryland Extension has answers! Send your questions and photos to Ask Extension. Our horticulturists are available to answer your questions online, year-round.
Each year, the spring and summer seasons seem to go faster and faster, and 2024 is no exception. If you have a lilac shrub, you can probably still imagine the sweet fragrance and beautiful flowers from a few months ago. I get several questions each year about lilacs, so the blog today is going to answer some of those inquiries!
A few years ago, we decided to begin excavating for our new garage in late summer, and unfortunately, had to move a lilac shrub. The transplanting was not as high of a priority as it should have been, and the shrub suffered tremendously the following year. We gave it a season to see if it would recover, but ultimately, it was too damaged. At that point, we decided to try rejuvenation pruning and cut everything back to 6” above the soil line in hopes that the shrub would come back and have a better overall shape and appearance. We had nothing to lose as the plant was suffering, not growing, and not flowering.
A lilac that was transplanted at the wrong time of the year and damaged. Photo: A. Bodkins, UME
Question: What is rejuvenation pruning?
Answer: Lilac rejuvenation pruning involves cutting the entire woody shrub back to a few inches above the soil surface. This can be done if a shrub is really scraggly or if you want to change its shape entirely. Last summer, my parents had to do a construction project behind their very large, 20+-year-old white lilac, and they had to cut it back to the ground. It seems to be rebounding just fine, though!
March 8th: First sign of life on the rejuvenation pruning. Photo: A. Bodkins, UME
June 4th: Regrowth progress. Photo: A. Bodkins, UME
Question: My lilac has not bloomed for the last several years. What could be wrong? It used to be beautiful each spring!
Answer: Lilacs need full sun to bloom. Often in people’s landscapes, as trees mature, lilacs get less sun than they once did, leading shrubs that once produced abundant, full blooms to have limited to no blooms.
Question: Why did my lilac bloom in the fall?
Answer: Environmental stress can cause out of season blooming. Some examples include drought, excessive heat, defoliation from pests, heavy pruning, insects, or diseases.
Question: What time of year should I prune my lilac?
Answer: Many spring-blooming, woody shrubs will set the flower buds for the next season’s growth in late spring or early summer, so be sure to prune for shaping and maintenance purposes as soon as the shrub is finished blooming for the current growing season.
For more information on lilacs, see the Home and Garden Information Center’s page, Lilac: Identify and Manage Problems — particularly the sections on diseases, insect pests, and heat-tolerant and powdery mildew-resistant varieties.
‘Emerald Green’ Arborvitae screening a property line. Photo: Miri Talabac, University of Maryland Extension
Q: I have limited space in a tiny city front yard and would like to block some of my view of the street. What types of evergreens would work well but not get too wide?
A: The width of the mature plants is the tricky part, since many upright evergreens mature at least 3 to 5 feet wide at their base, and not many are trimmable to keep them smaller. Plant options will depend on whether you have full sun or some shade from nearby trees or the house itself. Few city yards have issues with deer (though some do), so I’ll assume for now that browsing is not a factor.
Soil compaction is a common challenge, and poor drainage (is a roof downspout nearby?) can exacerbate root stress and cause plants to fail. If the site drains reasonably well and receives full sun in summer, your choices include slender-growing cultivars of widely-used evergreens. (Alas, there are very few native options to fit these criteria.) Examples include arborvitae (Thuja), juniper (Juniperus), yew (Taxus), Japanese plum yew (Cephalotaxus), boxwood (Buxus), and holly (Ilex).
Yew as well as broadleaf evergreens like the boxwood and holly can be pruned relatively easily to manage size, since they rebound well. Even so, it’s best to select cultivars that will mature close to the size you can accommodate without having to prune, both to save yourself the task and to reduce plant stress.
For the rest of those listed plants, especially other conifers (needled evergreens), pay close attention to expected mature size on the plant tag and make sure you have room, taking into account overhead utility lines. Take that stated size with a grain of salt too, since older plants keep growing and will not plateau at a set height forever.
Yew, Japanese plum yew, boxwood, and holly will handle a fair amount of shade and still look good, though the less sun they get, the less dense they might stay (or growth will slow). None of these species are super fast-growing (otherwise they’d get much too large for the space), but boxwoods and the upright yew varieties are among the slowest in pace. Even so, planting small, young specimens will be easier on both you and the plants (especially if shade tree roots are infiltrating the area), and they will catch up.
By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.
Have a plant or insect question? The University of Maryland Extension has answers! Send your questions and photos to Ask Extension. Our horticulturists are available to answer your questions online, year-round.
Tree planting efforts are picking up as Maryland’s 5 Million Trees Initiative moves forward in 2024. Getting these trees – any landscape trees – off to a good start at planting time and through their first few years of establishment is important for their long-term growth and benefits to the environment.
At Ask Extension, we often receive photos of newly planted trees and older specimens with signs and symptoms of trouble. One of the things we do in our diagnostic process is look to see if there is a “root cause.” Is a girdling root present at the base of the tree trunk? Is the tree planted too deeply? Can we see a root flare? Today I want to bring these questions to the surface and explain why an exposed root flare can help prevent the formation of girding roots and why it matters for tree health and pest management.
A beech tree with normal, healthy root flare. Photo: Miri Talabac, University of Maryland Extension (UME)
What is a root flare?
The root flare is the area at the base of a tree trunk where the topmost roots emerge outward. This area is sometimes referred to as the trunk flare or root crown. In many species of trees, the trunk widens and curves outward (“flares”) like the base of a wine glass. This is illustrated nicely in this brief video by the University of Maryland Arboretum and Botanical Garden’s Outreach Coordinator, Meg Smolinkski.
What is the root flare of a tree?
When thinking about the trunk and root system of a tree, it is important to keep in mind: Roots need to be in the soil to get a steady supply of moisture and nutrients. The trunk (stem) portion should be out of the ground where exposure and good airflow help to keep the bark dry.
In our landscapes, we have many trees that are planted too deeply and the root flare is not visible at all. The trunks go straight into the ground like telephone poles. This can result in lower bark rotting, reduced oxygen supply to the roots, disease and pest problems, and girdling roots.
We have an epidemic of planting trees too deeply
At the University of Maryland Extension Advanced IPM Conference for the commercial horticulture industry last month, Jacob Hendee, an arborist for the Smithsonian Institution Gardens, talked about how common it is nowadays to see trees planted too deeply. Burying the root flare has reached “epidemic” proportions in our landscapes, he noted – and it is killing trees.
The main problem he addressed in his talk was that buried root flares can set the stage for stem girdling roots to develop unnoticed. Stem girdling roots (SGRs) grow around the tree’s base, rather than pointing outward away from the trunk as normal roots should. As girdling roots grow and enlarge, they compress the water- and nutrient-conducting tissues in the tree. This interrupts normal plant functions and can lead to symptoms such as leaf yellowing (chlorosis), smaller-than-normal leaves, leaf scorch (browning), branch tip dieback, and bark cracking. SGRs can and do result in overall tree decline and eventual failure.
An example of girdling roots. Photo: M. Talabac, UME
Looking at a cross-section of a tree trunk, the light-colored portion is the water-conducting sapwood (xylem). Source: Jacob Hendee, Smithsonian Gardens
When a stem girdling root forms around the trunk of a tree (represented in orange in the diagrams), it compresses and kills the water-conductive sapwood, which can result eventually in a dead tree.Source: Jacob Hendee, Smithsonian Gardens
Trees under moisture stress due to stem girdling roots become more susceptible to pests and diseases.Scale insects are significant pests of some landscape trees, as are some types of beetles and other insects. If a tree develops a pest issue, the pest may be secondary to the problem that made the tree vulnerable to the pest in the first place – stress.
Hendee emphasized that maintaining a visible root flare and preventing SGRs are practices of Integrated Pest Management (IPM). IPM involves using physical, cultural (plant care), and biological methods to manage pests and diseases, leaving chemical pesticides as a last resort. In the example of tree care, correct planting and monitoring to prevent stem girdling roots are key steps to preventing tree stress. Instead of thinking about killing secondary pests that show up on trees, think about how to prevent stressful growing conditions from the beginning and during the life of a tree. Trees with minimal stress are more resilient to insect pests and less likely to be overwhelmed by them or need intervention to recover.
How do stem girdling roots get started?
Hendee noted that plant care practices, both before planting (at the nursery), during planting, and afterward (over-mulching) contribute to this problem.
1. Many trees are grown too deeply in the nursery. Girdling roots can start to form inside nursery pots when the roots hit the container and start circling. This issue can worsen when young trees are moved into larger containers as they grow (such as saplings being transplanted into a bigger pot as they mature) and their roots are not loosened or pruned to correct deformities. Larger trees are sometimes planted too deeply in the nursery field and come to the customer in “ball and burlap” form with the root flare already covered in soil.
2. Many trees are planted too deeply at the time of installation. If the planting hole is dug too deeply, the root flare gets buried when the soil is filled back in, and often then further covered with mulch. In that situation, stem girdling roots can develop and worsen undetected.
3. Tree flares are often buried deeply in mulch. Too often we see huge piles of mulch – sometimes one foot high or more “mulch volcanoes” – around trees. This will keep the bark moist and can encourage new roots to sprout from the trunk above the main supporting roots (the flare). Those adventitious roots will grow upward for oxygen and may begin to girdle the flare and trunk. They will also be more vulnerable to moisture stress since the mulch does not retain water in the same way soil does. There is absolutely no horticultural basis for putting a big mound of mulch around a tree like this!
An example of incorrect mulching. Photo: Dr. David L. Clement, UME
Here fresh mulch was incorrectly placed on top of a girdling root and up against a tree trunk. Photo: C. Carignan, UME
What can you do? “Free the Flare”
1. Check the roots at planting time. If you purchase a container-grown tree, ensure it is free of circling roots inside of the pot. If you do find roots that are circling the root ball, cut through those roots with a pruner or other sharp tool. Set the roots in the planting hole so that they are pointing in an outward direction.
Prevent girdling roots when planting a container-grown tree
2. Keep the top of the root flare visible. Root flares should be above the soil line. Plant so the root flare is 2 to 4 inches above grade. When purchasing a container-grown or burlapped tree, you may need to wash away some of the soil to see where the root flare begins. If a landscaper is installing a tree for you, make sure they set the tree at the correct depth.
A hose was used to wash away the soil from a container-grown tree, revealing the top of the root flare. The difference in the lower bark color (on the trunk) indicates that the plant was several inches too deep in its container. Photo: M. Talabac
When a root flare is visibly present, it can help deflect any stem girdling roots that begin to grow, forcing them away from the trunk. It also makes it easier to see where girdling roots begin to form. Monitor the root flare area of your tree(s) regularly and cut through any circling roots that begin to grow. It is easier to cut wayward roots when they are small. The process of locating and remediating stem girdling roots on older trees can be very expensive.
Also note that some species of trees are more prone to developing girdling roots (e.g., maples), and sometimes girdling roots develop below the soil surface where they are not easily detectable except by above-ground clues. If you see symptoms of water stress in the canopy of an otherwise sufficiently-irrigated tree (e.g. leaf scorch, smaller-than-normal leaves), consult with a certified arborist for a tree assessment.
3. Don’t overdo it with the mulch! Keep a mulch-free buffer zone around the root flare. Hendee suggested leaving a 3 to 12-inch area bare around the base of the tree. Think of it as a donut hole: mulch should be laid down in the shape of a wide, shallow donut rather than a big heaping mound. The total depth of the mulch should be only about 2 to 4 inches.
Mulch applied correctly. 1 Free root flare, 2. Mulch-free buffer around the root flare, 3. 2 to 4 inches mulch depth, 4. Broad mulch width. Infographic by Smithsonian Gardens
For further exploration of these topics and correct tree-planting procedures, I recommend the following resources:
By Christa Carignan, Certified Professional Horticulturist & Coordinator, University of Maryland Extension Home and Garden Information Center. Read more posts by Christa.
Illustrations used with permission from Jacob Hendee, Smithsonian Gardens
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