Medlars were once a highly popular winter fruit grown widely in England and other parts of Europe. Today they are rare and are relatively unknown in the US. Unfortunately, the medlar is perhaps one of the most misunderstood fruits, with many people considering it a curiosity as the fruit must be left to blet, meaning allowed almost to rot before it can be eaten! However, if you give medlars a chance, you may grow to love them just as I have as they really are a wonderful tree with delicious fruit. Here we will be looking at some of the more common problems experienced when growing Medlar.
What You'll Learn Today
Is There Only One Type Of Medlar?
First, we must start by clearing something up. There is a wide variety of Medlar trees available all with different qualities, and for a long time, it was thought that these medlar all derived from one species scientifically known as Mespilus germanica, which was commonly acknowledged as the only species in its genus.
However, there exists a proposed second species named Mespilus canescens or Stern’s Medlar, sometimes referred to as ×Crataemespilus canescens.
The origin of this alternate species can be traced back to Jane Ellenbogen Stern, an environmentalist from Pine Bluff, Arkansas. While conducting a bird-monitoring project in 1969, she stumbled upon an unusual plant resembling a hawthorn (Crataegus) with a shrubbier nature and white flowers.
After collecting a branch sample and notifying regional biologists and experts, news of the plant spread among other plant professionals who tried for nearly fifty years to provide a proper identification and name.
It is now officially recognized as a naturally occurring hybrid and still appears in some literature as a Mespilus.
The focus of this post is on Mespilus germanica.
Common Problems of Medlar Trees
The cultivation of medlar trees is relatively easy but there are several factors you must keep in mind to avoid running into problems.
Winter dormancy
Like other fruit trees in the same family such as pear or apple, medlar trees must be given an adequate cold period during the winter if they are to fruit during the next growing and fruiting season.
If insufficient winter dormancy is provided then a poor fruit set is likely.
To avoid this, ensure any medlar trees you grow in pots are placed somewhere cold, but where they can be protected from freezing during the winter.
If you live in an area where temperatures do not drop lower than 55°F for a prolonged period during the winter months, you may find your medlar trees do not thrive and produce good fruit yields.
Light
Medlars need full sunlight exposure for six hours or more a day during the growing and fruiting period. If the location you have installed your medlar tree is too shaded then growth and fruiting problems are likely to occur.
As the trees grow and develop, the canopy can become overcrowded due to its bushy growth habit. This reduces light penetration to lower branches. It’s important to maintain a tidy and open canopy.
To do this pruning is required to remove vigorous vertical branches in the middle of the tree to keep the center open.
Pruning is best done in late winter during dry and frost-free weather conditions.
Be cautious when pruning as medlar trees are tip bearers, therefore you must leave plenty of small lateral branches intact, as the fruit buds are usually located at the very tips of these branches.
Drainage
Ensure you plant your medlar tree in soil with good drainage. They are not particularly fussy about soil type providing it doesn’t become waterlogged.
If you do have a heavy soil type, it is likely that your medlar tree will suffer from root rot, which will result in the tree’s eventual death.
Pollination
All medlar varieties are self-fertile, which means they do not need a pollinator to produce fruit. However, like all self-fertile fruit trees, cross-pollination with other medlar varieties can increase fruit production and quality.
If you only have one medlar tree, consider getting another one of a different variety to help increase fruit yield.
Other pollination problems can occur if there is a lack of pollinators. To address this problem you have two options, firstly you can try attracting more pollinators to your garden such as solitary bees, honey bees, moths, and butterflies.
This can be done by creating attractive habitats for these creatures to live such as an insect house where solitary bees will nest.
Also try planting other plants and shrubs that draw the insects to your garden such as an early flowering milkweed variety such as Spider Milkweed – Asclepias viridis, which has large yellow/green flowers with a purple center.
Other problems that are common include disease and insect pests which we will look at next.
What Is The Disease In Medlar Leaves?
Fire blight is a disease that can have a severe impact on plants including medlars. It often results in the loss of limbs or even the entire tree or shrub.
Fire Blight is caused by the bacterium Erwinia amylovora, and it can cause cankers to form on branches, trunks, and twigs.
Symptoms
These cankers are areas where the pathogen has killed the bark, and they exude a watery, light-tan bacterial ooze that turns dark when exposed to air.
The ooze leaves streaks on branches or the trunk of the tree, and infections can cause flowers, shoots, and young fruit to shrivel and blacken. The amount of fruit loss depends on the severity of the disease.
Fire blight infections most commonly occur on open flowers and can cause them to wilt and turn black. Infections can also cause small shoots to wilt and form a crook-like appearance at the end.
Succulent tissues of shoots and water sprouts are also susceptible to infection. Dead, blackened leaves and fruit cling to branches throughout the season, which can give the tree an unpleasant scorched appearance.
Spread
Once a plant is infected, it can harbor the pathogen indefinitely. The bacteria may spread from blossoms into the wood, causing pink to orange-red streaks to form.
The bacteria can also spread into the wood surrounding overwintered cankers that become active in the spring. As the canker expands, the infected wood dies, turns brown, and dries out, often leading to sunken areas of dead tissue and cracks in the bark.
The bacteria can be spread to nearby blossoms or succulent growing shoots by splashing rain or insects. Honey bees pick up the pathogen from contaminated blossoms.
Typically, the progression of the pathogen is from the infection site toward the roots. In the fall, leaves on infected shoots often turn red and then black.
Fire blight bacteria invade young leaves and shoots that have been injured by wind, hail, or insect punctures.
Ideal conditions for infection and disease development include rainy or humid weather with daytime temperatures between 75°F and 85°F, especially when night temperatures remain above 55°F.
The pathogen doesn’t move uniformly through the bark but instead invades healthy wood by moving in narrow paths up to 1 1⁄2 inches wide in the outer bark ahead of the main infection.
The extent of fire blight damage depends on tree vigor and growth rate. Vigorously growing shoots are most affected, and trees are more susceptible when young.
How To Treat Fire Blight
Unfortunately, there is no cure-all for fire blight, but it can be managed. Monitor trees regularly and remove and destroy any infected wood.
- Fertilizer – Avoid excess nitrogen fertilization and heavy pruning, which promote rapid shoot growth.
- Watering – Don’t water older trees at all during bloom, and only water young trees lightly when the soil is completely dry.
- Spraying – Apply blossom sprays if fire blight has been a problem in the past. However, in years when weather conditions are very conducive to fire blight development, it may be difficult to control the disease.
- Pruning – During the summer or winter, when the bacteria are no longer spreading throughout the tree and infections have stopped growing, is the best time to prune affected wood from the tree.
The canker margins become clearly visible, so there’s no need to clean pruning shears after every cut, just leave a large enough margin.
However, if you notice a rapidly advancing infection, you should remove it as soon as it appears in the spring. At this time, it is advisable to dip the shears in a 10% bleach solution between cuts, but more important than cleansing the tools is the location of the cut.
Pruning cuts have not been observed to cause new infections but it’s important to avoid making a cut that doesn’t remove all infected tissue.
To find the correct cutting site, locate the lower edge of the visible infection on the branch and trace it back to the point of attachment. Cut at the next branch juncture down without damaging the branch collar to remove the infected branch and the one to which it’s attached.
If a fire blight infection occurs on a trunk or major limb, the wood can often be saved by scraping off the bark down to the cambium layer in infected areas (both outer and inner bark should be removed).
While scraping, look for long, narrow infections that extend beyond the margin of the canker or infection site. If any are found, remove all discolored tissue and an additional 6 to 8 inches beyond the infection.
It’s best to perform this procedure in winter when the tree is dormant and bacteria are inactive.
No dressing should be applied to the wound. If the limb has been girdled (the infection is all the way around the branch) scraping won’t work, and the entire limb must be removed.
- Chemical Control – Homeowners have limited options for chemical control of fire blight, and copper products are currently the only materials readily available.
However, multiple applications of weak copper solutions such as 0.5% Bordeaux mixture are often required but may not provide adequate control. Although this spray helps to prevent the incidence of new infections, it cannot eliminate existing infections.
The spray must be applied to open blossoms, and the number of applications required depends on the length of the bloom period.
The first application should be made when the average temperature (average of the maximum and minimum temperatures for a 24-hour period) exceeds 60°F, and subsequent applications should be made at four- to five-day intervals during periods of high humidity and until the late bloom is over.
It is important to note that copper products can cause russeting or scarring of the fruit surface, and this risk increases as fruits enlarge.
In this video you can see how to identify and treat fire blight:
What Other Diseases Affect Medlar Trees And How Are They Treated?
There are several other diseases to which Medlar trees can be susceptible including:
Brown Rot
A fungal disease that causes fruits to rot and turn brown. It also affects the flowers and leaves of the tree.
Where possible, it is best to prevent the disease. This can be done by improving air circulation as brown rot thrives in humid and moist conditions.
Prune your medlar tree to provide it with an open shape, removing any inward-growing, crossed, or crowded branches. This will help reduce humidity levels.
Fungicides can help prevent and control brown rot in medlar trees. Apply the fungicide according to the manufacturer’s instructions, and make sure you cover the entire tree. Repeat applications may be necessary depending on the severity of the infection.
Ensure your medlar tree is healthy by providing it with adequate water, nutrients, and sunlight. Healthy trees are less susceptible to brown rot and other diseases.
To remedy this you will need to remove any branches or twigs that show signs of brown rot. Do this by cutting several inches below the affected area to ensure you remove all the infected tissue. Burn or dispose of the pruned branches to prevent the spread of the disease.
You may also need to take off any mummified fruits. These are dry, shriveled fruits that remain on the tree and can harbor the brown rot fungus. Removing and disposing of them reduces the chances of the disease spreading.
Powdery Mildew
This is a fungal disease that creates a white, powdery coating on leaves, stems, and flowers. It can cause stunted growth and defoliation of the tree.
As for brown rot above, you will need to prune off any infected areas and safely dispose of them to prevent the disease from spreading. This includes any infected leaves, stems, or fruit. Pruning also improves airflow and reduces the humidity that promotes fungal growth.
Fungicides help control the spread of powdery mildew. Some effective fungicides for powdery mildew include sulfur, copper-based fungicides, and neem oil. Follow the manufacturer’s instructions for the proper application rate and frequency.
Remove nearby weeds or plants that may be blocking airflow or are showing signs of powdery mildew themselves. This helps reduce humidity and slows down the spread of the disease.
When watering, don’t water the tree’s leaves, but only the soil around the medlar to reduce the risk of creating humid conditions that promote powdery mildew.
Monitor the medlar tree for any signs of new powdery mildew infections, and take action quickly if any new infections occur.
Leaf Blight
This is a bacterial disease that causes dark spots on leaves and can lead to defoliation.
Cut off and safely dispose of any infected branches immediately to prevent the disease from spreading.
Clear away any fallen leaves or debris from around the tree to reduce the chances of the fungus spreading.
Apply a fungicide that is labeled for use on medlar trees and is effective against leaf blight. Follow the instructions on the label carefully, including the proper timing and application rates.
Provide proper irrigation, fertilization, and pruning. A healthy tree is more resistant to diseases.
Watch for any signs of recurrence. If the disease persists, you may need to reapply the fungicide or seek additional treatment options.
Canker
This fungal disease creates sunken, dead areas on branches and trunks and may lead to dieback of the tree.
Start by removing the affected branches by pruning them at least 6 inches below the infected area. Don’t forget to sterilize your pruning tools between cuts to prevent the spread of the disease.
Fungicides can be applied to the wounds to protect the tree from further infection.
Rust
The symptoms of rust on Medlar trees include small, yellow, or orange spots on the leaves that eventually turn into small pustules or blisters.
These pustules often rupture and release spores, which spread the disease to other parts of the tree and nearby plants. In severe cases, rust can cause defoliation and weaken the tree’s overall health.
Remove infected leaves and branches and dispose of them.
Use fungicides to help prevent the spread of rust.
Leaf Spot
Another fungal disease that can affect medlar trees and typically causes small, round spots on the leaves that are dark brown or black in color with a yellow halo.
As the disease progresses, the spots may merge and cause the leaves to turn yellow and fall off prematurely, which can weaken the tree over time.
Leaf spot is caused by several fungal pathogens, including Mycosphaerella and Entomosporium.
The disease spreads rapidly in wet and humid conditions and is often more severe in trees that are stressed or growing in poor soil.
Rake up and dispose of fallen leaves, and avoid overhead irrigation to prevent further spread. Fungicides can be applied to protect the leaves from infection.
Verticillium Wilt
This fungal disease attacks the tree’s vascular system, preventing water and nutrients from being transported throughout the plant.
Symptoms of Verticillium wilt in Medlar trees can include:
- Wilting leaves on one or more branches will die back, even if the soil is moist.
- Leaves may turn yellow or brown, and the branches may also show discoloration.
- The tree’s growth may slow down or it may produce smaller leaves.
- The leaves may fall off prematurely, especially during hot, dry weather.
- You may notice sunken areas or cankers, which can become infected with secondary pathogens.
Unfortunately, there is no cure for verticillium wilt once a tree is infected. Infected trees should be removed and destroyed to prevent further spread to other trees.
Phytophthora Root Rot
This is also a fungal disease that attacks the roots of the tree and can cause wilting, yellowing, and stunted growth.
Help to remedy its progress by improving drainage in the soil to prevent waterlogged conditions, and avoid planting in areas that are prone to flooding.
Fungicides can be applied to protect the roots from infection.
Look for any signs of disease regularly and take appropriate measures, such as pruning infected branches and using fungicides.
What Insect Pests Affect Medlar Trees And How Can They Be Treated?
There are several insect pests that affect medlar trees, among them are:
Medlar fruit fly (Ceratitis capitata)
These flies lay eggs in the fruit, which hatch into larvae that feed on the flesh, causing the fruit to rot.
To control this pest, fruit should be harvested as soon as it’s ripe, and any fallen fruit should be removed from the ground and destroyed. Insecticide sprays can be applied during the growing season, although are best avoided if possible.
Medlar sawfly (Hoplocampa brevis)
The larvae of this insect feed on the developing fruit, causing it to drop prematurely.
To control this pest, insecticide sprays should be applied during the flowering period and repeated after petal fall. Note that natural sprays can be made from neem oil.
Scale insects
These small insects suck sap from the leaves and stems, weakening the tree and causing stunted growth. They can be treated with horticultural oil sprays or insecticidal soap.
Aphids
Small, soft-bodied insects which feed on the sap of the tree, causing leaves to curl and become distorted. They can be treated with insecticidal soap or neem oil.
Follow the instructions given on pesticide products and use them sparingly, as they can harm beneficial insects and pollinators. In general, maintaining healthy trees through proper watering, fertilization, and pruning can help reduce the likelihood of insect pest infestations.
Why Is My Medlar Tree Not Fruiting?
There could be several reasons why a Medlar tree is not fruiting:
Age
Medlar trees don’t usually produce fruit for the first few years after planting. It can take around 4 or 5 years for the tree to reach maturity and begin to fruit.
Very old trees may also stop fruiting, which can sometimes be remedied by pruning.
Pollination
Medlar trees are pollinated by insects, mainly bees.
The flowers of the medlar tree are hermaphroditic, meaning that they have both male and female reproductive structures, and are capable of self-pollination. However, cross-pollination by insects is required for optimal fruit set and quality.
When bees and other pollinating insects visit the flowers, they transfer pollen from the male to the female reproductive structures, resulting in fertilization and the development of fruit.
Therefore, it is important to encourage bee activity around the medlar tree during the flowering period to promote pollination and fruiting.
Pruning
Excessive pruning can reduce the number of fruit buds that are formed, resulting in a poor fruit set.
Prune the tree during the dormant season to remove dead, diseased, or damaged wood. Thin out any overcrowded branches to improve air circulation and sunlight penetration. This will stimulate the tree to produce new growth and fruit buds.
Nutrient deficiencies
A balanced supply of nutrients is required to produce fruit. If the soil is lacking in essential nutrients, it affects the tree’s overall health and its ability to produce fruit.
Fertilize the tree in the spring with a balanced fertilizer that contains nitrogen, phosphorus, and potassium. This will provide the necessary nutrients for the tree to grow and produce fruit.
You may also wish to conduct a soil test so you can provide appropriate fertilizer that can help to address this issue.
Environmental conditions
Adverse weather conditions during flowering or fruit development can cause fruit drop or a lack of fruit set. Excessive heat or drought can also negatively impact fruit production.
Ensure the tree is receiving adequate water, especially during the fruiting season.
Pest Control
Manage any pest or disease problems that may be affecting the tree. This will help reduce stress on the tree and improve its ability to produce fruit.
Conclusion
Medlars were once a popular winter fruit in Europe but are rare and relatively unknown in the US. Despite this, they are a wonderful tree with delicious fruits and can be a great addition to any garden.
However, there are common problems to consider when growing medlar trees, including the need for sufficient winter dormancy, adequate sunlight exposure, proper drainage, and pollination.
Additionally, medlar trees are susceptible to various diseases such as fire blight, brown rot, powdery mildew, leaf blight, canker, rust, and leaf spot. These diseases can be managed by pruning infected areas, improving air circulation, using fungicides, and maintaining tree health.
Overall, medlars are a unique and delicious fruit that deserves more recognition.
Discover more about a wide variety of fruit trees including the medlar by looking at more of our articles!
