It may be bacterial blight if the leaves of your lilac bush appear deformed, olive-green, or have water-soaked patches that turn yellow-ringed and brownish. Brown or limp blooms may also be symptoms. The curling and browning of the leaves on your lilac bush may be a sign of a fungus infection. By removing these leaves with a pair of garden shears and then spraying a copper fungicide to ward off the illness, you can rescue the lilac tree.
The most frequent fungus that afflicts lilacs is powdery mildew, and in addition to the browned edges, the leaves may also appear yellowish and powdery. To improve airflow, you can try thinnng out the interior of the bush. Additionally, you can get rid of any neighboring vegetation or try moving smaller lilac bushes to areas with more sunlight and space (but only make this move when the lilac is dormant).
Lilacs are also afflicted by verticillium wilt, which is brought on by two different fungus. Your lilac bush may appear to be withering as a result of this wilt, but it may already be beyond saving. According to University of Minnesota Extension, once the illness has entered the plant’s vascular system, it prevents it from receiving enough nutrients. Even if extra fertilization and watering can be beneficial, it might already be too late if the branches begin to die.
How can an ancient lilac tree be revived?
The common purple lilac is a hardy, dependable shrub that can grow up to 20 feet tall. Unfortunately, the lower, shady sections of lilac shrubs typically lose their leaves as they get older. Large, overgrown specimens as a result are frequently leggy and ugly. Pruning can restore or rejuvenate old, neglected lilacs. Home gardeners have two alternative pruning techniques to pick from.
Cutting the entire plant back to within 6 to 8 inches of the ground in late winter is one method of renewing a huge, overgrown lilac (March or early April). A significant number of shoots will sprout during the growth season as a result of this aggressive pruning. Select a few sturdy, robust shoots to construct the shrub’s framework, keeping a few of them, and cut off all the others at ground level in the late winter of the next year. To promote branching, head (clip) back the retained shoots to just above a bud.
Cutting back the overgrown shrubs over a three-year period is a second method for pruning mature lilacs. In late January, start the process by digging up and removing one-third of the big, old stems. The following year, trim out half of the remaining old stems (again in late winter). Additionally, trim out some of the recent growth. Keep a few healthy stems that are evenly spaced apart and cut off the rest. In the third year’s late winter, completely remove all of the old wood. It is also necessary to thin the fresh shoots more. This pruning technique should enable you to take pleasure in blossoms every spring because lilac wood must be three years or older before it blooms.
Within a few years, with the right pruning, an old, overgrown lilac can be converted into a robust, appealing shrub. Pruning should be a frequent component of the lilacs’ management regimen after they have been revived. By cutting a few of the oldest branches every three to five years, the shrub can be kept strong and healthy.
(This article, which first published in the Sunday edition of the Lincoln Journal Star Newspaper in February 2005, has since been amended. Consult the Terms of Use for details on how to copy this content and use any images or visuals.)
Can a dead lilac shrub be revived?
You might occasionally question if your bushes have survived after a particularly harsh winter as you scan your yard. Many Northerners lust after lilac plants for their early spring blossoms and fragrant scent. The lilac shrub might appear to be dead during its dormant period due of its straggly limbs. To ensure that it is alive, there are a few things you may do.
Use a pocketknife to scratch the lilac bush’s surface. If you detect green beneath the surface, there is a strong likelihood the lilac shrub is very much alive. Just make a small, 1/2-inch scrape to reveal the green tint behind the dark bark without injuring the plant.
- You might occasionally question if your bushes have survived after a particularly harsh winter as you scan your yard.
- There is a significant possibility that the lilac shrub is still alive if you can see green below the surface.
Hold off till spring. The first few weeks of spring are noted for the vigor with which lilacs flourish. Your lilac bush’s buds ought to be expanding by the time the snow has melted and you notice the birch trees are producing pollen. You might just have one dead branch, therefore be sure by checking multiple branches that it is still alive.
Trim the branches to check on the health of the root system. A lilac tree can be pruned all the way to the ground, and it can frequently grow new shoots from its extensive root system. As you chop, watch for greenery under the bark and for little shoots poking through the ground. You can wait a few weeks throughout the growing season to check whether there is any life if you have the patience. Otherwise, you might have to start over with a new plant.
- The first few weeks of spring are noted for the vigor with which lilacs flourish.
- Trim the branches to check on the health of the root system.
Fungal diseases
This season, the Lilac Pseudocercospora leaf spot, a fungus, was detected in lilac samples examined by the Plant Disease Clinic. The same symptoms have been recorded (yellowing then browning leaves, dieback).
The PDC places a strong emphasis on sanitation because it appears that Pseudocercospora spores can survive on plant detritus for a number of years (leaves, stems, dead flowers, bark).
- To assist lessen the possibility of reinfection the next season, remove fallen leaves.
- Consistent watering and renewal cutting to reduce density will sustain the stressed plant.
Several of the plants in our landscapes, including lilacs, are afflicted by verticillium wilt. Verticillium dahliae and Verticillium albo-atrum are the two fungi that cause it. For a plant with this fungus infection, there is no cure.
- As a result of the fungi clogging the branch’s vascular system and preventing the transfer of water and nutrients, individual branches turn brown and die quickly.
- To increase plant longevity, increase watering and fertilization.
- The disease can spread across all sections of the afflicted plant, thus the best preventive is to buy resistant cultivars and practice proper hygiene.
Insects
The Lilac Borer, sometimes known as the Ash Borer, is a clearwing borer moth that creates tunnels in lilac stems.
- Frass, sap, and sawdust are warning signs (excrement).
- Some plants can withstand this harm.
- Others see branch dieback, and occasionally the entire plant dies.
- They won’t likely catch anyone’s attention.
Jeff Hahn, an extension entomologist, confirmed that no lilac borer samples have entered his lab this year.
Herbicide damage
Broadleaf weed treatments on lawns may volatilize, changing to a gas, and float onto unintended plants if sprayed during periods of extreme heat and humidity.
Herbicide damage signs like cupping and browning would appear in patterns:
- along a hedge’s one side but not the other,
- bushes positioned in or close to lawn areas, at the same level throughout their bases,
- and most critically, away from the area’s predominant winds.
Lilac hedges next to agricultural fields or other sizable herbicide-treated areas may experience damage in this manner.
How can you assist a lilac in need?
Lilacs require full sun, or around six hours of sunshine each day. Make sure that no other trees are blocking your lilac’s sun so that it can thrive even in partial shadow.
Mulching around your lilac plant prevents the roots from drying out and aids with weed control. It’s crucial to routinely water lilacs in dry weather. Lilacs, however, prefer well-draining soil and dislike damp, moist roots.
Stop fertilizing your lilac if it isn’t flowering. Lilacs that have received excessive fertilization will produce an abundance of lush growth but not the desired amount of flowers. Lilacs don’t need a lot of fertilizer, perhaps only a modest feeding in the spring. Your lilac can be receiving more food than it needs if you routinely fertilize adjacent lawns or other plants. Your lilac’s soil will benefit from having phosphorus added, such as by using bone meal.
Scale insects and borers can harm lilacs. Check the leaves and stems of your bush to see if a renewal pruning is necessary. Usually, removing the problematic regions will solve the issue.
Why is my lilac acting strange?
Lilac frequently suffers with certain issues. On the majority of elder lilacs, powdery mildew is typical in the summer. When the rains become more frequent, the powdery covering that this fungal illness produces on the leaves is frequently washed away. However, at least for this year, powdery mildew is not to blame.
Lilac stem borer is another unwanted guest. The larva of this clearwing moth bores into the lilac’s stem after the female deposits her eggs near the plant’s base. Often, these moths exclusively select strained lilacs or very old stems as their prey. Near the plant’s base, sawdust, sap, and frass are indications. However, the Extension office’s samples do not show any signs of the lilac borer.
This year, leaf scorch may also be a problem that many lilacs are having. Excessive rainfall can smother and kill a section of the root system by causing saturated soils. The plant doesn’t have a root system capable of supporting the growth once the hot, dry summer weather hits. Frequently, leaves will quickly dry out and hang on the plant.
The real offender(s) might not even be there anymore. It seems that a bacterial or fungal illness was able to grow quickly in lilac plants during our period of cool, rainy weather. These illnesses can no longer be active in the sweltering summer heat as a result of the warming and drying of our climate. Still, the harm has been done. Spots on the foliage at first, then the entire browning of the leaves, then the branch death.
This year’s harsh freeze in the spring in Central Illinois is another meteorological occurrence that might have provided the ideal conditions for lilac foliar disease. Late spring frosts can harm delicate leaf tissues, allowing infections to infect them. Later in the season, when the plant is under additional stress from the summer heat, symptoms might not become obvious.
I am rather certain a foliar disease is the culprit, although I haven’t seen a lab test to support this. The two pathogens listed below are both potential candidates.
many illness symptoms on lilac Pseudocercospora leaf spot is a fungal infection that I have observed this season. The bacteria Pseudomonas spp. also has an illness that manifests remarkably similar signs and symptoms. Although these two infections affect lilac in a similar way, it’s vital to know that one is a fungus and the other is a bacteria. So how can you distinguish between the two? A lab test from a plant diagnostic lab like the University of Illinois Plant Clinic is necessary to determine the solution. Anything else is pure speculation. For instance, deciding to spray a bacteria with a fungicide could be wasteful.
How can a half-dead lilac bush be revived?
You might believe your lilac is dying if you see it becoming a little frail or worn out, or if it only produces a few little flowers in the spring. Often, all a plant needs to produce robust new growth and abundant, fragrant blossoms is some hard pruning and some feeding. Rejuvenate a lilac bush by working with it just after bloom, when the blooms have dried up and are spent.
To get to the grass or soil layer, rake away any debris, dead branches, or fallen leaves from the lilac’s base.
Pick three to five of the lilac’s strongest branches after surveying the entire plant. Follow the branches you’ve chosen to the plant’s base, where you can flag each sturdy branch by gently tying a rope or ribbon around its base.
Use hand pruners or a handsaw if needed to make a clean, horizontal cut across all of the unflagged branches that are about an inch off the ground. To prevent breaking off any limbs you want to maintain, carefully pull the trimmed branches away from the lilac.
- You might believe your lilac is dying if you see it becoming a little frail or worn out, or if it only produces a few little flowers in the spring.
From the remaining branches, take off your sting or ribbons. Fertilize the lilac around its base according to the dosage and application guidelines provided by the manufacturer.
Mulch should be applied in a ring around the lilac’s base that is no deeper than 3 inches and no wider than 3 feet. New sprouts won’t be able to emerge if the mulch is too deep.
If there is a drought or excessive heat in your area during the summer, make sure the plant is well-watered. Lilacs require good drainage, but they don’t fare well in dry soil.
The next spring, watch for buds to start swelling on the branches. Reapply fertilizer right before flowering and once more after flowering is finished. This is how you should fertilize each year.
- From the remaining branches, take off your sting or ribbons.
- The next spring, watch for buds to start swelling on the branches. Reapply fertilizer right before flowering and once more after flowering is finished.
Maintain your lilac by doing minimal annual pruning to remove wasted flowers and only every three to five years to remove old and dead branches.
Avoid letting the feed come into contact with the branches when applying fertilizer to the area around the plant, whether it be granular or water-soluble.
What does a lilac that is overwatered look like?
Overwatering your lilacs is one of the worst things you can do. If the soil around a particular lilac variety is always wet, then all lilac kinds are susceptible to fungal diseases including mildew, mold, and other sorts of fungi.
- If lilacs are overwatered, mold and fungus can harm them.
- Lilacs that receive too much water may have root rot.
- Your lilacs have received too much water if their leaves are yellow, pale, or withered.
- If your lilacs have been overwatered, let the soil dry to a depth of 34 inches (7.510 cm) before providing additional moisture.
Lilacs that receive excessive water risk developing root rot. A lot of the time, wilted, pale, or yellow leaves indicate an excess of water. Reduce watering to once every 14 days until these symptoms go away if any of these things happen or if the ground appears to be persistently damp. Remember that you might not need to water your lilacs at all if you are experiencing regular rains.