evergreens – Maryland Grows

Q&A: Reduce the Height of an Arborvitae?

July 16, 2024July 16, 2024Maryland GrowsLeave a comment

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.

Q&A: What Screening Plants Fit in a Small Space?

March 18, 2024March 14, 2024Maryland Grows1 Comment

a row of small evergreen arborvitae shrubs near a brick building — ‘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.

Look out for wintercreeper

February 22, 2023February 22, 2023Maryland Grows5 Comments

wintercreeper vines climbing up trees in a forested area — Wintercreeper euonymus (*Euonymus fortunei*) overrunning a woodland floor and climbing tree trunks. Photo: Ryan Armbrust, Kansas Forest Service, Bugwood.org.

Q: I realize English ivy is widespread in Maryland, but there are some evergreen vines clinging to trunks that look a bit different than typical ivy leaves. Are they native, or should they too be removed?

A: An evergreen climber I see covering tree trunks in parks which might be confused for English ivy at a distance is wintercreeper (sometimes written winter creeper; Euonymus fortunei). This non-native invasive acts like English ivy in that it’s a groundcover when no support to climb is present, and a clinging vine when trunks or walls are available.

wintercreeper vine — Wintercreeper vine. Photo: Chris Evans, University of Illinois, Bugwood.org

wintercreeper flowers — Wintercreeper vine. Photo: Chris Evans, University of Illinois, Bugwood.org

This species also has negative impacts on the trees and our ecosystem and should be removed if growing on your own property. Parks manage invasives as best they can, but with limited resources, we can do our part by not cultivating the species likely to spread into them, even if we don’t live immediately next to parklands. Weed Warrior volunteer programs exist, such as in Montgomery County, if you wish to be trained in invasive plant ID and to help with their removal on public lands. While wintercreeper has been banned for sale by the Maryland Department of Agriculture since 2018 as a Tier 1 invasive plant, established plants in the region can still mature enough to produce fruit (berries) that wildlife then inadvertently spreads into natural areas. Long a popular landscaping groundcover due to those vibrantly green leaves (and the variegated forms for their color), I always recommend removal and replacement with alternatives, preferably a medley of native species instead.

As with English ivy, it’s safest for the tree to simply sever the climbing wintercreeper stems’ connection with the roots in the ground and let them slough off the trunk on their own as they dry out and disintegrate. Even though they attach via root-like structures, those aren’t functional roots and no moisture or nutrients are absorbed by them. Pull up, smother (deny them light), or spray any running stems covering the ground. As with any tenacious weed, eradicating an established patch of this species may take time and repeated efforts at removal before finally being successful. Be vigilant, because birds could always re-introduce it in a future year. (Invasive plants…the gift that keeps on giving.)

Tips for using garden evergreens for holiday décor

December 10, 2021December 9, 2021Maryland Grows2 Comments

Using evergreen cuttings to decorate the home offers an easy way to incorporate different textures, shapes, and aromas. Evergreens add a touch of simplicity, elegance, and nostalgia to holiday décor. They can be used easily on doors and entryways, as garland, or centerpieces. Cutting materials from your own landscape can provide a thrifty option.

Here are a few tips for making evergreens a beautiful addition to your holiday décor.

mixed evergreens with pinecones and a bow

If cutting from your own landscape, be cautious not to cut too much. Pruning in the early winter is generally not recommended unless it is to remove diseased or damaged material. It won’t hurt a well established plant to trim off a few branches, but try not to cut anything from newly installed plants. Check out this factsheet for additional information on pruning evergreens.
Caution! Several critters are overwintering on evergreens so once they get warm in your home, they will become active. These uninvited guests can cause surprise and panic from those not expecting them this time of year. If you find spiders, etc., you can put them outside.
Keeping evergreens cool and hydrated will extend how long they stay fresh and beautiful. Place the ends of cut branches into water.
Often mixing different types of evergreens is a fun way to add unique smells, shapes, and texture to your home.
Shorter needled (hemlock/spruce) plants tend to lose their needles faster than longer needled species.
Evergreen boughs are easy to stick into seasonal planters before the soil freezes. Be warned that if the branches freeze in the soil, they will be impossible to remove until it thaws.
Don’t forget to gather interesting seed pods, ornamental grasses, pine cones, etc. These add additional interest and natural beauty.

Some favorite cuttings include Junipers, Arborvitae, Holly, White Pine, Rhododendron, Boxwood, Lavender, and Rosemary. If you have a live Christmas tree, be sure to repurpose those trimmings as well.

wreath made with grasses, seed pods, evergreens, and a bow — Here is a wreath base made from dried ornamental grass. Also, ornamental grass seed heads, Monarda seed heads, pine cones, and mixed evergreen cuttings are included. Photo: A. Bodkins

wreath made with Juniper and lamb's ear leaves — This wreath uses cuttings of native Eastern redcedar and leaves of lamb’s ear. Photo: C. Carignan

door swap made with evergreens, pinecones, and a bow — Door swag. Photo: A. Bodkins

As you gather your materials and get ready for crafting, remember that:

Sharp pruners give a clean cut that will help increase the life of your branches and prevent premature needle drop. Guidance on sharpening pruning tools can be found here.
Use green floral wire to put cut branches together. It blends in well and is easy to work with. It is widely available at craft stores and low in cost.
Repurpose metal clothes hangers for inexpensive frames for swags/wreaths/garland.
Swags are often simpler and easier than a wreath to make and require less material, but provide a nice garnish for your entryway. Think of making a bouquet and then turn it upside down to get an easy door swag.
If you’re placing cut evergreen stems into a container, use clean water and clean containers to prevent fungal and bacterial growth.
Keep arrangements out of direct light and as far away as possible from the heat source.
Misting cut evergreens can help extend their beauty.
Using cut evergreens outside the home will help them last the entire season.
Ribbon with wired edges is easier to work with for beginner bow makers.

You can create many beautiful decorations by working with nature! Be creative and enjoy the gifts that your garden continues to give all year round. And it’s never too early to start thinking about garden plant additions for 2022! Think about items you could use in future holiday decorations or another season’s decor.

By Ashley Bodkins, Senior Agent Associate and Master Gardener Coordinator, Garrett County, Maryland, edited by Christa Carignan, Coordinator, Home & Garden Information Center, University of Maryland Extension. See more posts by Ashley and Christa.

What’s Wrong with My Blue Spruce Tree?

January 8, 2018April 12, 2021Maryland Grows11 Comments

blue spruce with cytospora — Blue spruce with symptoms of Cytospora canker.

Dr. Dave Clement, University of Maryland Extension Plant Pathologist, explains two common diseases of this popular evergreen tree.

Colorado blue spruce trees, although not native or adapted to Maryland, are commonly planted in landscapes for their attractive color and shape. There are, however, two plant diseases that commonly infect and disfigure them. Both diseases also can occur simultaneously and progressively speed up the decline of this popular tree.

Continue reading →