Fruits & Vegetables

Special Update: Fall Fruit Tree Care and Fire Blight Management

During this session, Statewide Fruit Outreach Specialist Josie Dillon provided a seasonal update for apple growers and home fruit gardeners as harvest season reaches its peak. Fire blight, a serious bacterial disease affecting apples, pears, and related plants was highlighted. Gardeners were encouraged to look for the characteristic “shepherd’s crook” appearance on infected shoots and to remove infected branches 12 to 18 inches below visible symptoms.

Pruning tools should be disinfected between trees to prevent spread of the disease. Josie also discussed common late-season fruit diseases including bitter rot, white rot, and black rot and emphasized fall sanitation. Removing fallen fruit, fruit mummies, and diseased leaves can significantly reduce disease pressure the following year.

• Apple Summer Rots – wisc.edu
• Bitter Rot – wisc.edu
• White Rot – msu.edu
• Black Rot of Apples – umn.edu
• Fire Blight – wisc.edu
• Cleaning and Disinfecting Pruning Tools for Orchard Crops – missouri.edu

Transplanting Rhubarb

Q-What are the best practices for transplanting rhubarb?
A-Fall is an excellent time to transplant rhubarb after foliage has died back. Plants should be dug with as much root structure as possible and divided if desired. Consistent moisture after transplanting helps improve establishment.

• Rhubarb – wisc.edu

Tomatoes

Q-Why does the center of a tomato stay green and fibrous?
A-Uneven ripening and green cores are usually physiological disorders rather than diseases. Environmental stress, especially fluctuating temperatures and uneven moisture, are common contributing factors. Nutrient issues may also play a role, but moisture management is generally the most important factor. Consistent watering helps reduce many tomato fruit disorders.

• Troubleshooting Tomato Problems – wisc.edu
• Homegrown Tomatoes for Wisconsin – wisc.edu
• Tomato Disorder: Physiological fruit problems – wisc.edu

Fruit Tree Companion Plants

Q-Do flowers and herbs help fruit trees?
A-Incorporating flowers around fruit trees, particularly species that attract pollinators and beneficial insects. Insectary plants such as sweet alyssum support natural enemies of pests. Greater plant diversity can strengthen ecosystem resilience and improve biological pest management.

• Plant Flowers to Encourage Beneficial Insects – wisc.edu
• Companion Planting: Adding Diversity to the Garden – udel.edu

Disease on Fruit Tree Branches

Q-Should diseased fruit tree branches be pruned now or during dormancy?
A-For most fruit tree diseases, dormant-season pruning remains preferable because trees heal more effectively and disease spread is reduced. The major exception is fire blight. Because it spreads rapidly, infected branches should be removed promptly during dry weather to limit movement into larger branches and trunks.

• Fire Blight – wisc.edu
• Tree Fruits – wisc.edu

Vegetable Roots in Soil

Q-Is it okay to leave vegetable roots in the soil after harvest?
A-Leaving roots in place can support soil health by reducing disturbance and contributing organic matter as roots decompose. While removing roots is sometimes necessary when replanting or preparing beds, leaving them in place generally poses no concerns and aligns with soil health practices that emphasize minimal disturbance and active root systems.

• Making and Using Compost in the Garden – wisc.edu

General Gardening

Effects of Drought on Perennial Plants

Q-What will happen to perennials, trees, and shrubs after this year’s severe drought?
A-Drought effects will vary depending on soil conditions, plant species, and supplemental watering. Most established perennials are expected to survive if they receive adequate deep watering, although flowering may be reduced next season. Evergreens were identified as the greatest concern because they continue losing moisture through foliage during winter. Deep, infrequent watering through fall before the ground freezes is especially important for arborvitae and other shallow-rooted evergreens. Drought stress may not become fully evident until next year through branch dieback, winter burn, insect problems, or canker diseases.

• Drought and Watering of Ornamental Plants – wisc.edu
• Gardening for Weather Extremes in Wisconsin: Extreme heat and drought – wisc.edu
• Keep Watering in Fall to Protect Evergreens from Winter Burn – wisc.edu
• Video: Best Practices for Watering Yards and Gardens – wisc.edu

Wood Aster

Q-Why have robust wood asters suddenly turned brown?
A-The most likely explanation is drought stress causing plants to go dormant earlier than normal. Also, there is the possibility of fungal leaf spot diseases causing browning and suggested diagnostic testing if symptoms appear unusual or continue worsening. Long-term drought effects may continue to surface in future seasons.

• Plant Disease Diagnostic Clinic (PDDC) – wisc.edu
• Wood Aster – ncsu.edu

Transplanting Peonies

Q-What are the best practices for transplanting peonies?
A-Fall is an excellent time to transplant peonies after foliage has died back. Plants should be dug with as much root structure as possible and divided if desired. Peony buds should be positioned only one to two inches below the soil surface. Planting too deeply is a common reason peony fail to bloom. Consistent moisture after transplanting helps improve establishment.

• Peonies – wisc.edu
• Why Iris & Peonies Fail to Bloom – wisc.edu

Arborvitae

Q-What grows well underneath mature arborvitae?
A-Growing plants beneath arborvitae is challenging because of dense shade and competition for moisture. Suggested options included Pennsylvania sedge, dead nettle (Lamium), woodland phlox, hostas, ginger, and certain hardy geraniums. Supplemental watering may improve success because the root systems of arborvitae are highly competitive.

• Arborvitae – ncsu.edu
• Alternatives to Lawn: Groundcovers – wisc.edu

Fall Cleanup for Hostas

Q-Should hosta and other perennials be cut back in fall?
A-It’s recommended to allow foliage to die back naturally so plants can move nutrients into their root systems. Hostas may be cut back after leaves decline. However, many perennials with hollow stems or seed heads provide valuable winter habitat for pollinators and food sources for birds. Leaving some plant material standing through winter can benefit wildlife while adding visual interest to the landscape.

• Hostas – umn.edu
• Pollinators – wisc.edu

Mums

Q-Will tightly closed buds on decorative mums still open?
A-Healthy decorative mums purchased with tight buds should continue flowering if they receive adequate moisture. It was cautioned that many retail “hardy mums” planted in fall do not reliably overwinter because they devote significant energy to flowering instead of root establishment. Native asters are an attractive fall alternative that often has better long-term survival and ecological value.

• Native Asters – umn.edu
• Mums for Fall Beauty – wisc.edu
• Mums the Word for Fall Flowers – wisc.edu

Houseplants

There were no questions on houseplants this month.

Insects

Praying Mantids

Q-Why are there so many praying mantids in the garden this year?
A-Warmer-than-normal temperatures likely accelerated development of praying mantids and their prey this season, resulting in higher visible populations. Mild winter conditions may also have improved survival of overwintering egg cases. Mantids are generalist predators that consume a wide range of insects and other prey, not specifically aphids. While they are fascinating insects, they are not considered particularly effective biological control agents because they eat both pest and beneficial insects indiscriminately. Lacewings are a better alternative for biological control.  

• Praying Mantids – wisc.edu
• Plant Flowers to Encourage Beneficial Insects – wisc.edu
• Lacewing – umn.edu

Q-How can gardeners protect praying mantis egg cases over winter?
A-Allen explained that overwinter survival of mantis egg cases depends heavily on winter conditions. Egg cases may be moved to sheltered but unheated locations to moderate temperature extremes. Gardeners interested in encouraging mantids can leave egg cases undisturbed outdoors or relocate them carefully. He stressed that while mantids are interesting and beneficial predators, they are not highly effective biological control agents because they consume a broad range of insects, including beneficial species.

• Raising Praying Mantis – osu.edu

Ground-Nesting Wasps

Q-How can gardeners prevent ground-nesting wasps from returning?
A-Yellowjackets and other wasps have been especially abundant this year. Ground nests can be difficult to predict or prevent. Keeping landscape areas maintained, reducing food attractants such as rotting fruit and exposed garbage, and monitoring sites where nests have occurred previously may help. The experts also reminded viewers that wasps are important predators and pollinators despite sometimes becoming nuisances.

• Outdoor Hazards Guide – wisc.edu
• Managing Wasps – wisc.edu
• Wasp and Bee Removal – umn.edu

Lawns

Overseeding Lawn

Q-When should lawns be overseeded?
A-September remains the preferred window for overseeding Wisconsin lawns because seedlings need time to establish before winter. Good seed-to-soil contact is critical for success and slit-seeding was recommended whenever possible. Gardeners are encouraged to overseed as soon as possible rather than waiting until later in fall.

• Timing Questions for Fall Lawn Care – wisc.edu
• Lawns – wisc.edu

Plant Diseases

There were no questions on plant diseases this month.

Trees & Shrubs

Fall Pruning

Q-Should Japanese Beetle damaged maples or overgrown Forsythia be pruned this fall?
A-Japanese beetle feeding was described primarily as cosmetic damage. The buds for next year are likely intact, so pruning affected maple branches is generally unnecessary. Regarding forsythia, light removal of stray shoots is acceptable, but extensive fall pruning should be avoided because flower buds for next spring are already present. Poor flowering may have been related to winter injury and weather fluctuations rather than improper pruning.

• Forsythia – wisc.edu
• Pruning Deciduous Shrubs – wisc.edu
• Japanese Beetles – wisc.edu

Weeds & Invasive Species

Quackgrass

Q-Is there an easier way to remove quackgrass from iris beds?
A-Quackgrass is one of the most difficult weeds to manage. Its aggressive underground rhizomes spread rapidly and often regenerate from fragments left behind. Hand removal can help but rarely eliminates infestations. Selective herbicide options may be limited depending on surrounding desirable plants. Long-term persistence and repeated management over several years are usually necessary.

• Quackgrass – wisc.edu
• Quackgrass Difficult to Deal With – wisc.edu

Wildlife

Wildlife Ecology Factsheets

• UW Wildlife Ecology factsheets – wisc.edu