9 Reasons Your Lemon Cypress Tree is Dying and How to Save It
Fragrant, bright, and beautiful, lemon cypress trees are true stars in the garden. Their foliage remains golden yellow all year. If your tree turns brown or grows slowly, it may face diseases, pests, or cultivation issues. Join former nursery tree grower Jerad Bryant in solving these nine common lemon cypress problems.
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No one wants to deal with a sick tree! You expect your landscape plants to thrive for years without issues. It can be heartbreaking when your favorite lemon cypress tree begins to suffer and die off, especially if it’s an older specimen.
The good news is that most conditions are preventable, and some are treatable. We’ll discuss what you can do to keep these problems away and how to address them when they appear.
One solution all growers should start with is taking cuttings. Once you suspect something’s wrong with your tree, take semi-hardwood cuttings from healthy lemon cypress branches. That way, if your treatment solutions fail, you’ll have backup trees to plant in its place.
After taking cuttings, it’s time to analyze your lemon cypress tree and see what’s happening inside it. Here are nine problems you may see, and solutions for treating each one.
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Root Rot
Damp, moist winter conditions create the perfect breeding ground for fungi that target weak roots. They spread throughout soggy sites, invading the trees through wounds on their roots. Root rot often took out large swaths of lemon cypress trees at the nursery where I worked.
Root rot is hard to diagnose because the pathogens reside underneath the soil. You’ll see symptoms aboveground as the tree suffers. Look for brown leaves, dead branch tips, and dying foliage. Root rot is initially difficult to discern; monitor your tree closely after you suspect it.
How to Save It
Root rot is nearly impossible to cure once it infects your tree. It’s best to start over with a new tree. You may take cuttings from high branches to try propagating new specimens. Ensure they’re from branches up high to avoid spreading the root rot pathogens from lower stems.
Although rare, some cypresses survive root rot! Start by pruning off any dead or dying branches. Move the sick tree somewhere it can dry out with full sun or partial shade. Letting the soil dry hurts the root rot fungi and allows your tree to heal.
Freezing Temperatures
Lemon cypresses are cultivars of the famous Monterey cypress from the California coast, and they’re cold-hardy to an extent. They tolerate cool, coastal winds that are common in their native habitat. Below-freezing temperatures can kill or severely damage them when they grow outside of coastal California.
Two common cultivars exist. ‘Goldcrest’ is a medium-sized tree that reaches 40 feet tall and survives winters from USDA hardiness zones 7 through 11. ‘Goldcrest Wilma’ is a dwarf cultivar that stays lower than six feet tall and it’s hardy from zones 7 through 10.
How to Save It
Growers in zones 7 and lower can protect their tree outdoors or consider bringing it indoors. This cypress thrives as a potted plant, especially the dwarf cultivar ‘Goldcrest Wilma.’ Bring it outdoors for spring and summer, then place the tree in a cool, bright room for winter.
Offer outdoor specimens winter protection with frost cloth and mulch. Add compost to the soil around the roots to protect them. As temperatures warm in spring, the mulch decomposes into a humus-rich amendment for your growing specimens.
Frost cloth works best as a temporary solution for the aboveground parts. You put it over the tree’s branches when you expect a hard frost, and take it off after temperatures warm the next day. It keeps cold air out and hot air in.
Not Enough Water
Low water levels can shock sensitive roots no matter the time of year. Dry soil cultures during winter are especially deadly, as they allow frost to penetrate the ground and shock sensitive roots. Lemon cypresses tolerate short periods of drought in the summer, although they prefer a consistently moist culture with cool temperatures throughout the year.
How to Save It
Cypress trees require different levels of moisture depending on the season. Potted plants indoors prefer low water levels during the winter when they grow slowly. Actively growing specimens in spring and summer drink lots of water to stay cool under the heat.
Two things help with soil moisture: well-drained soil and proper watering. Lemon cypress prefers sandy or gritty soil that drains freely and prevents excess moisture from building up. After using the right soil, ensure you’re watering as often as necessary to keep the soil moist, but not soggy.
Insufficient Lighting
These sun lovers prefer full sun or partial shade, with two to eight hours of daily direct sunlight. They’ll grow leggy under low light indoors or in the landscape. They may lose their leaves before dying completely after many days or weeks in the shade.
Indoor plants are more susceptible, as walls and windows filter light and prevent it from reaching their leaves. The only time shade is beneficial is if you’re growing cypresses in warm regions outdoors. They’ll appreciate afternoon shade during the hottest hours of the day.
How to Save It
Save shaded trees by moving them where they receive sufficient sunlight. Whether they grow inside or outside, ensure they’re under full sun or partial shade. Choose the brightest room in your house for overwintering. These cypress trees prefer bright, cool conditions during the cold months.
Some homes are especially dark and lack ample natural sunlight. Consider adding grow lights to dark rooms—they’ll boost your cypress tree while it grows indoors.
Pot-Bound Roots
Mature lemon cypress trees grow thick, woody roots that swell as they age. This allows them to grow strong and resilient in the wild, although it can cause issues for container specimens. They’ll need repotting every so often to ensure the roots have ample fresh soil to grow into.
You’ll know your cypress is pot-bound if you see roots poking out of the drainage holes, and if the container dries more frequently than usual. Circling roots may poke out of the soil surface.
How to Save It
Save a root-bound lemon cypress specimen by transplanting it into a larger container. The best time to transplant is early spring after the danger of frost passes, or in fall at least two months before the first frost. Prepare the new container with well-drained soil, then remove your tree from its pot.
Inspect the roots, ensuring they dangle downwards. Prune off thick, woody roots that circle the pot, and remove any that grow up or across instead of down. After loosening the roots, place the tree in its new pot, fill it with soil, and water it well. Explore more transplanting tips in this easy-to-follow guide.
Honey Fungus
Honey fungi, or Armillaria, are mushroom-growing pathogens that target woody trees and shrubs. They infect wounded roots or trunks and spread throughout the soil, colonizing the tree. They’ll wound and kill it after a few years.
Look for a white, fungal growth that appears between the bark and inner heartwood. The bark may be mushy or weak and pull off easily. Mature infections sprout mushrooms in the fall with brown, honey-colored caps.
How to Save It
This fungus is deadly. There aren’t any treatment options for an existing infection. The best thing to do is to dispose of the infected tree and start anew with a fresh one. Wait to plant a new one in the same location for a few years; this lets the honey fungus die out.
Cypress Aphids
Cypress aphids are tiny insect pests that target weak trees. They reproduce quickly and in large numbers, meaning a single bug can turn into hundreds in a few days. Hungry aphids target fresh growth, turning yellow foliage brown and sickly.
These pests are common in warm regions during early summer. Keep your specimen happy and healthy to prevent their arrival, as healthy trees can resist pest infestations before they spread out of control.
How to Save It
One easy way to remove aphids is with a strong stream of water. Spray your tree daily to remove the aphids, ensuring you hit every branch with the water. The bugs should disappear after a few days.
Aphids are a main source of food for other predators in the garden. Ladybugs, hoverflies, and small birds may eat aphids when they’re abundant. Leave small infestations for predators to find; they’ll typically take care of the problem before it hurts the foliage.
Phytophthora
Phytophthora is a nasty plant pathogen that targets shrubs growing in cool, wet conditions. It’s not a fungi or a bacteria. Some growers call it a “water mold” because it needs water to grow, although it lives for some time in the soil and on infected plant material.
This condition infects many common crops for food production and ornamental landscaping. Blueberries, cherries, and oaks are some other common hosts. The disease is common in nursery settings where damp, stagnant conditions sometimes exist.
How to Save It
Phytophthora is a fatal condition that kills its hosts. It’s best to destroy the infected tree, sterilize your tools, and start again elsewhere with a new tree to let the disease die out. It causes nurseries millions of dollars in lost sales and is easily spread through wet potting soil.
Cypress Canker
Canker is a troublesome, slow-killing disease affecting hardwood shrubs and trees. It’s a fungal condition spread through splashing water, dirty tools, or the wind. You’ll notice lesions on the trunk and branches that ooze sap. Sections above cankers often die after many seasons of restricted growth.
Mature infections create big, knobby growths on the bark. These attract moths that lay eggs in the soft tissue. Their larvae hatch, tunnel into the wound, and cause further damage to the tree.
How to Save It
Saving an infected specimen is sometimes possible. Low cankers may prove fatal, as they’re difficult to remove without harming the trunk. The upper ones are easier to take care of. Remove cankers and the wood above them to prevent their spread. Use sterilized tools, and dispose of the infected plant material far from your tree.
