3 Arborvitae Browning/Half Dead Trees - Can I save them?

Question: Hello, we bought a home in Harford County with 3 in-ground Arborvitae ornamental trees that were seemingly in excellent condition as of Aug-Oct 2022.  By Feb 2023 I realized they were heavily browning and it has only gotten worse & more extensive.  I don’t know what the cause is so wanted to ask for advice before trying any heroic measures.  I’m not seeing any obvious fungal spores on the needles.  I have not watered or fertilized them at all yet and there is no drip irrigation lines either.

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied April 07, 2023, 12:05 PM EDT
response: This appears to be classic deer browsing damage, and if the plants are fairly new (if the prior owner or developer installed them before you purchased the home), that could explain why the damage seems recent and not chronic. Plus, deer can alter their browsing habits in winter when their food source dwindles, and they often feed at night when we don't notice them as readily. This may be why the damage appeared over this past winter. Eastern Arborvitae (Thuja occidentalis), which is the type in the photos, is quite palatable to deer and is a common victim of browsing throughout Maryland.  We do not think any of the browned foliage is due to infection or pest activity, and the comparatively few pest or disease issues Arborvitae can develop generally produces different symptoms than what we see here. When plants that are still establishing (as these probably are at this size) they tend to succumb to environmental stressors more often than a pest or disease issue. Environmental stressors include soil that is too compacted, roots that were not adequately loosened upon planting (or burlap root ball wraps that were not removed), and soils that are over- or under-watered either through irrigation practices or poor drainage. (Is there a roof downspout outlet near their roots?)  Arborvitae and many evergreens naturally shed their oldest, innermost foliage as they age, because the outermost layer of younger leaves/needles blocks too much light from these older layers and the plant no longer needs them. Normally, the dense outer growth hides this bare interior (and any foliage in the process of shedding since it browns and dries before falling) and it's not a great aesthetic concern. However, when the outer leaves are removed or thinned due to pruning or deer browsing, then the unappealing interior becomes visible. Few evergreens, Arborvitae included, are capable of replacing lost foliage, so deer browse or excessive pruning damage is permanent since there are no dormant leaf buds lying in wait on that inner growth that can fill back in, the way it can on hollies, boxwoods, yews, and a few other species.  Aside from the current aesthetic issue or problem of poor establishment (it's possible both deer and struggling roots are contributing to the plants' current state), you may want to move/remove the Arborvitae anyway given their current location. The variety 'Emerald Green', which these appear to be as which are very, very commonly planted, mature in the neighborhood of 15 to 20 feet high and about 5 to 7 or so feet wide when mature (granted, they don't grow super fast) so would eventually wall-in this area completely. They also need lots of sun to thrive (6+ hours of direct light in summer) so if the house shades them for a substantial part of the day (hard to tell here) then they might not remain vigorous.  If this is a suitably sunny spot and you like Arborvitae as an evergreen accent there, then perhaps a dwarf cultivar of a different species (if deer are around) might be a better choice. (If deer are not around, there are dwarf forms of Eastern Arborvitae also.) Western Arborvitae (Thuja plicata) looks similar in texture but does not appeal nearly as much to deer and is often ignored. A few cultivars of this species exist that mature into either compact rounded globes or slender (but shorter then full-size 'Emerald Green') upright spires. Additionally, Junipers (Juniperus) are a group of needled evergreens for sunny spaces that deer almost always avoid, and several species and dozens of cultivars exist with varying mature sizes, shapes, and needle colors (golden, green, blue-gray) that can be considered as well.  Miri

responder: The Question Asker Replied April 07, 2023, 4:44 PM EDT
response: Hi Miri,Thank you so much for your prompt and thorough response!  We do in fact have deer AND there are unfortunately 2 downspout outlets right near these Arborvitae (see photos attached).  How can I figure out if there’s an over-/under-watering or drainage problem affecting the roots?  Additionally, you’re also right to suspect that the house does shade that area so I don’t think they’re getting the requisite 6+ hours of sun.If I understand correctly, any of the Arborvitae cultivars and Junipers you mentioned are still going to require 6+ hrs of sun, so it sounds like I should move the existing 3 trees out of that spot altogether.  Do you have any recommendations for a deer-resistant plant that might thrive better in that shadier spot and won’t eventually wall off the area completely?  What is the best way to transplant a tree of this size?Lastly, I am a newbie gardener trying to learn how to design some beautiful gardens (floral + greenery) in our backyard that receives heavy afternoon sun and has some shaded areas with mature evergreens.  I’m interested in native plants and organic practices since we have well water and I’m hoping to attract pollinators.  Do you have any recommended resources that might help get me started?  (I could easily email you all very frequently but I don’t want to abuse your service and goodwill!)Many thanks,Mary BethOn Fri, Apr 7, 2023 at 12:05 PM Ask Extension <<personal data hidden>> wrote:

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied April 10, 2023, 5:03 PM EDT
response: Hi Mary Beth,  Yes, the Arborvitae and Junipers would be best in full sun, so if a site is semi-shade or more shaded during the mid-afternoon hours then a more shade-tolerant species would be better to try in their place. The shrubs that look like Azaleas below them in the photos are fine with part shade but, as seems to be exemplified here, are quite palatable to deer, who will not only eat foliage but at least tend to consume the buds so they won't flower. (They also detest poor drainage and over-watering, so it might be easier to deal with them at the same time.)  The proximity of the two downspouts is a concern and it would be best for any future plantings (and for the home foundation too, really) to extend their outputs further from the house. Most gardeners do this by burying them via an extension tube that empties either closer to the property line or, ideally, into a rain garden which can help capture and filter that rainwater before it enters the stormwater sewer system or nearby streams.  If you want to keep the Arborvitae and move them to another part of the yard, be mindful of periodically treating them with deer repellent (at least from about autumn into early spring or so) to discourage more browsing. Although the deer can only reach so high (so at some point the browsing will end), any area they browse will not regrow, so the form of the plants will permanently take on a slender vase-like shape. If this is not too bothersome, you can plan to hide some of this with low-growing shrubs if you prefer, since crowding the Arborvitae foliage at that point will no longer be a concern. As for transplanting the Arborvitae, how far the roots may have spread depends partly on how long ago they were planted. You'll have to experiment with digging around the root ball wider than you think the original roots extended so see where the bulk of the root system is; then, dig as wide of a root ball as you can manage given they will be fairly heavy to move. Replant right away so the roots don't dry out too much and then water-in the plants in the new location.  As for what shrubs to consider for this location, we'll list some ideas below (though it's not an exhaustive list). Nothing is really deer "proof" but these will be species they rarely bother. Sometimes all bets are off in winter when deer are at their most hungry, but other than using a physical barrier or repellent spray there's not much that can be done about this. We'll assume for now that the location receives a mix of sun and shade and that the soil drains reasonably well aside from the downspout contributions. Botanical names are in parentheses.Leucothoe (Leucothoe axillaris or Leucothoe fontanesiana) evergreen; arching foliage so not very amenable to pruning to a more exacting shape; almost native (occurs near MD but not in the state, despite being sufficiently hardy here); some varieties have cream-marbled foliage, white-edged foliage, or green foliage which blushes burgundy-maroon in winter Anise-shrub (Illicium, many species and hybrid cultivars) evergreen, looking superficially like a Rhododendron but with different flowers that may or may not be showy; similarly not amenable to regular pruning but there are dwarf forms that should not grow too tall if left to their own devices; sometimes hard to find because they are closer to the northern edge of their cold hardiness tolerances in MD, though our average winter is not too threatening; might be easier to find online or in Northern VA nurseries than local nurseries, but it may depend on what wholesale suppliers the nursery usesFalse Holly / Holly-leaf Osmanthus (Osmanthus heterophyllus) spiny foliage like that of hollies but will not produce the same berries; can have fragrant but tiny flowers in autumn; several varieties on the market maturing at different sizes and with different foliage colors (plain green, purple-tipped new growth, creamy-marbled leaves, solid yellow-green leaves, etc.); easy to trim and not a fast growerJapanese Plum Yew (Cephalotaxus harringtonia) not to be confused with their "true" Yew (Taxus) cousins which are quite palatable to deer, these have slightly longer (but still soft) needles and grow relatively slowly; mature sizes and shapes depend on the variety, with some being upright and proportionately slender while others are squat and wider than tall; most are deep green but a few forms have golden needlesInkberry Holly (Ilex glabra) native and evergreen but naturally has a more bare interior or lower limbs with age than other holly species; spineless foliage; prefers full sun but will tolerate a decent amount of shade, though this might exacerbate any "leggy" tendencies so a planting of shorter shrubs or perennials like ferns to hide the bare stem bases might be preferable; might produce small black berries if plants are female and get pollinated by male Inkberry selections (the latter are not easy to find)Summersweet (Clethra alnifolia) deciduous and late to leaf-out in spring compared to some shrubs; very fragrant summer flowers that attract pollinators; some cultivars stay shorter than othersAdam's-Needle Yucca (Yucca filamentosa) native and evergreen; clumping, so not very tall and useful as a foreground accent, but a sturdy and nearly indestructible perennial that can flower in summer on a tall spike (no leaves on the flower stalk so it won't block a view); some varieties have striped foliage for added interest but the wild-type coloration is a bluish-greenFothergilla (Fothergilla major or Fothergilla gardenii and their hybrids) native a bit to our south but hardy here; deciduous; some varieties have blue-green foliage in summer; showy blooms with mild fragrance; good fall foliage colorsSweetbox (Himalayan, Sarcococca hookeriana humilis, or Shrubby, Sarcococca confusa) evergreen with small, fragrant late-winter blooms; the former species spreads like a tall groundcover while the other remains upright and shrubby; slow-growing An array of perennials and other deciduous shrubs could work well in this space, so we suggest deciding on which will be in the rearmost row and determining how much space they need to mature with minimal crowding before choosing plants to fill-in as much of the remaining space as you wish. Ferns as a group are good filler plants while being unpalatable to deer; there are many species and their mature heights vary considerably; some creep and spread while most clump and remain where you put them. Sedges (Carex) are grass-like perennials that would also add texture while generally being left alone by deer. Many are native but there are a handful (often striped forms) that are non-native but non-invasive. Here too, a few spread but many are clumping and remain a tidy tuffet of foliage.  We have web resources about native plants that you can explore (here again, not exhaustive since there are thousands of native species, but an introductory sampling of a handful of the recommended species) as well as information about pollinator gardening that includes many links to plant lists and helpful references. Fortunately, for a full-sun location you have many options among native and (non-invasive) non-native species that attract butterflies, moths, bees, hummingbirds, and other pollinators. The candidate list will be shortened a fair amount by what deer will usually avoid, but if you are able to shield the planting by fencing-in part of the yard you will be able to grow more species. We have a deer-resistant native plants list, but it probably does not include everything they tend to leave alone (it really depends on the individual deer as to what they skip over or sample). In any case, using a mix of species suitable to the site's growing conditions as-is (since making alterations to suit certain plants is challenging and not always successful) will help ensure the planting as a whole is as resilient as it can be in the face of a potential pest or disease issue or temporary damage from extreme weather. Plus, the more diverse the plantings, the more diverse a range of pollinators you can support.  As for organic practices, we maintain an organic lawn care page but not other pages specific to organic options for gardens like flower beds or habitat plantings. That said, though, we do list non-chemical methods for pest or disease management where appropriate on our web pages for particular pests or diseases. Native plants can contract as many pests or diseases as non-native plants can, but fortunately many of them are more temporarily and cosmetically damaging than actually threatening to long-term plant health.  Miri