Avocados can be tricky. You buy them green, and the next day they’re still not ripe. The day after that they’re still not ripe. Then, the day after that they’ve all gone bad! To be clear, avocados don’t come from conifers. But I’m often reminded of avocados when homeowners contact us regarding concerns they have about their conifers. Conifers, like ripening avocados, can also be tricky. A row of ‘Emerald Green’ Arborvitae can appear to be fine, and then seemingly overnight, half of them are DEAD! A mature white pine can appear to “almost die” every second or third year. These issues can be understandably frustrating and can give us the false notion that these plants are hard to grow. Understanding the ways in which they’re different from other plants in the landscape can help in successfully caring for conifers and allowing them to thrive.
Understanding conifers should begin with a few simple definitions to clarify and classify. A conifer is a plant that bears its seeds in cones. When we hear the word cone, we likely think of pine and spruce trees, two types of coniferous trees that are widely found throughout Central Ohio and beyond. Their cones are obvious when they fall and scatter on the ground surrounding the tree. But did you know that yews (Taxus) and junipers are also conifers? Both bear their seeds in a fruit-like structure that is often incorrectly referred to as a berry. These berry-like fruits are actually cones, botanically speaking. Some other common conifers in Central Ohio include arborvitae, hemlocks, and firs. Because the foliage of most conifers is evergreen, meaning it does not fall off each year with the cycle of the seasons, the terms evergreen and conifer are often used interchangeably. Doing so, however, is not completely accurate. It’s important to understand that the term evergreen also refers to some broadleaf plants like rhododendron, holly, boxwood, and others. These plants are evergreens, but not conifers.
Conifers belong to a very ancient classification of plants and are different from non-coniferous plants in a number of ways. Below are a few of their key characteristics that often confuse homeowners (and sometimes even otherwise qualified arborists!). Knowing what to expect and how to care for conifers is the first step in successfully maintaining them in your landscape.
Seasonal Needle Drop
Japanese White Pine experiencing fall foliage
Even though most conifers are evergreens, their evergreen foliage still eventually falls off. Some very common conifers in Central Ohio, like pines, yews, and arborvitae, will drop a significant amount of their inner foliage every 2-3 years as part of a natural occurrence of cyclical needle drop. This can be alarming if you’re not familiar with the process. When it happens, the important thing to recognize is that it’s happening uniformly throughout the entire plant, and all of the browning/yellowing foliage is further back on the branch. These are the needles that are 2-3 years old and have reached the end of their life cycle. You might also look around your neighborhood to see if the same tree or shrub in other landscapes is doing the exact same thing, and at the same time. This process will never occur on the tips of the branches. If you have needles that are discoloring and falling off from the very tip or end of the branch, it is likely due to other factors and may indicate a disease, insect, or watering issue.
Delayed Response to Stress
A dead ‘Emerald Green’ Arborvitae due to drought stress
Perhaps the most challenging thing about conifers, specifically evergreen conifers, is that they do not give immediate feedback from water-related stress or injury. Herbaceous annuals like impatiens and petunias will let you know almost immediately when they are low on water by wilting excessively. Many deciduous trees, when first planted, will also show signs of wilting foliage relatively quickly when their roots become dry. This type of visual feedback is often what reminds us to get outside and water our newly installed landscape trees or shrubs. Coniferous evergreens, on the other hand, can have a delay of weeks or even months before they show obvious signs of drought stress. The reason this is an issue is simple; by the time we see it, the damage may be too extensive to reverse. It’s important to thoroughly and properly water any newly planted trees or shrubs. Don’t over-rely on in-ground irrigation, which often does not water for a long enough span of time to properly soak the ground, or may not thoroughly cover an area, leading to “dead zones” that receive little to no water at all. Proper watering regimes should be followed for the first season, and supplemental watering may be beneficial in subsequent years during very dry months. Watering in the fall is important too. This helps to keep roots moist once the ground freezes. Inadequate levels of water in the soil during freezing temperatures can rob a plant’s roots of water and lead to winter desiccation. Oftentimes we see this show up late winter or even early in spring.
Limited Regrowth with Pruning
The proper pruning of conifers varies from that of their non-coniferous counterparts. Many landscape shrubs and even a few tree species can be pruned aggressively to maintain a certain size or habit without adversely affecting the health and longevity of the plant. Many conifers, however, are not tolerant of heavy pruning that removes the majority of the foliage from a stem or branch. Junipers provide a classic example of a plant that cannot be pruned back to bare wood. Once this is done, the exposed area will not fill in with new growth. Pine, spruce, and fir are also examples of conifers that will not produce enough new growth on over-pruned parts of the plant. One example of a conifer that is an exception to this rule is the yew. When cut back aggressively, yews can and do generate enough new growth (slowly) on old, bare branches. Knowing how to properly prune conifers requires a good understanding of each plant species’ characteristics and habits, and may be best left to a professional arborist.
Healthy Dawn Redwood trees in the fall
Finally, it’s worth noting that a few types of conifers succeed in inciting worry and confusion whenever a home changes hands and the new owners are unfamiliar with the trees in the landscape. These are of course the deciduous conifers. Two deciduous conifers can be found commonly throughout Central Ohio landscapes- the dawn redwood and bald cypress. These trees will naturally lose their needles every year just like a Maple or Ash loses its leaves. As mentioned previously, most of us equate conifer with evergreen. So to see this occur for the first time and not understand what’s happening, one might assume the tree is dying for some unknown reason.
Conifers do things a bit differently, which can make them a little harder to understand. Answers to your coniferous questions are always just a phone call away at Russell Tree Experts. The unique characteristics mentioned above are just a few of the many reasons you should entrust your trees, all of them, to a qualified professional tree care company. Otherwise, your new neighbor, though his intentions are good, might just tell you to cut down that dawn redwood that keeps “dying” every year.
Walter Reins | Regional Manager, Russell Tree Experts
Walter has been an ISA Certified Arborist since 2003. He graduated from Montgomery College in Maryland with a degree in Landscape Horticulture, and has called Columbus, OH his home for nearly 20 years. Walter appreciates trees for their majesty and the critical role they play in our world.