Hello Marianna,

Thank you for your question. Unfortunately, without more information and photos, it is not possible to give a definitive diagnosis, but below are some general things to consider that could be causing the leaf wilt, crumbling and dying on the redbud and oak and decimation of the roses. 

If you would like a definitive diagnosis, you could submit more information long with detailed photos for review and/or submit samples to the CSU Spur Diagnostic Clinic. More information on how to do that is provided at the bottom of this response.

Watering:

First, the tree wilting, dry and crumbing leaves could very well be caused by drought stress. As you know we are in a drought and this past winter was unseasonably dry and warm. A primary, often invisible driver of summer tree decline in Colorado is a lack of winter watering. If the trees didn’t get sufficient water this past winter, you may just now be seeing the results.

Even when trees are dormant between October and March, their root systems remain active and require moisture to survive the cold, dry winter months. When Colorado experiences dry, sunny, and windy winter stretches without consistent snow cover, the top layers of soil dries out, killing off the fine absorbing roots. When spring and summer arrive, the damaged root system is physically unable to transport enough water to match the evaporation happening at the leaves, causing them to wilt, turn brown, and get crunchy.

You can perform a simple check of your soil moisture using a long, slender screwdriver.

• The Method: Push the screwdriver down into the soil beneath the tree’s canopy.
• The Result: If you cannot easily penetrate the soil to a depth of 6 to 8 inches, the soil is critically dry and the tree is experiencing moisture stress.

While you have a sprinkler system, it may not provide enough water for the trees. Sprinklers may be okay for shallow grass roots, but, depending upon run times and frequency, they may not be enough for trees, shrubs or other plants. If your soil is still dry with the sprinkler system settings, you can take immediate action by providing supplemental water.

Even with the current drought restrictions and watering system limits, you can still hand water to provide supplemental moisture. Denver Water Rules for Outdoor Water Use, explicitly state that trees, shrubs, perennials, and vegetable gardens are exempt from the designated days-of-the-week schedule if you use a hand-held hose or a low-volume drip system and water only before 10am or after 6pm.

For more on watering mature trees and on fall and wintering watering, see these articles.

https://extension.colostate.edu/resource/fall-and-winter-watering-of-plants-and-trees/

https://extension.colostate.edu/resource/watering-mature-shade-trees/

https://www.denverwater.org/residential/rebates-and-conservation-tips/summer-watering-rules

Diseases and Pests:

Second, drought stressed plants are more susceptible to disease and pest problems. Without photos and more information on your plants, it is not possible to know if those problems are present. Some common redbud and oak diseases include the following.

Redbud

Verticillium Wilt: A soil-borne fungus that enters the roots and clogs the tree's water-transport pathways. It typically causes sudden wilting and browning on just one side or a single branch of the tree. https://planttalk.colostate.edu/topics/insects-diseases/1400-6-verticillium-wilt-catalpa-trees/

Botryosphaeria Canker: A fungus that attacks stressed bark, forming sunken, dark, cracked sores (cankers) on the branches. The leaves above the canker will rapidly wither and die. https://extension.psu.edu/botryosphaeria-canker-in-the-home-garden

Oak

Oak Anthracnose: A fungal disease favored by wet spring weather that creates irregular, brown, paper-like blotches across the leaves, often starting in the lower and inner canopy where humidity is highest. https://planttalk.colostate.edu/topics/trees-shrubs-vines/1766-oak-anthracnose/

Oak Wilt: A lethal vascular fungus that causes leaves to rapidly turn bronze or brown starting from the outer leaf tips and moving inward. Leaves often drop cleanly while still partially green, and the disease can kill a tree in a single season. https://ohioline.osu.edu/factsheet/plpath-tree-02

Regarding your roses, they could also be suffering from drought stress. A diagnosis cannot be made without more information and photographs. With decimated roses and leaves, it could also be Japanese Beetles. They just came out again. These are easy to observe and remove by hand. They love roses and can decimate the flowers and skeletonize leaves very quickly. Have you seen them in your garden? Here is more information on Japanese Beetles. https://extension.colostate.edu/resource/japanese-beetle/

For a more definitive diagnosis, feel free to submit another request with more information on the plant or plants and photographs or submit a request to CSU’s Plant Diagnostic Clinic by going to their website (fee-based testing). https://agsci.colostate.edu/agbio/plantclinic/ The CSU Clinic offers both basic and advanced testing for fungal, bacterial, viral and abiotic plant health conditions. They also provide plant and insect identification services. For all diagnostic cases, they provide management recommendations when applicable.

Helpful information to provide for review:

• Plant ID: Type of plant and age.
• Symptom Onset & Timeline: Exactly when the problem was first noticed, and whether it developed rapidly overnight or gradually over months.
• Pattern of Damage: Whether the damage is localized to one side of the plant, confined to lower or upper branches, or widespread across the entire canopy.
• Watering Practices: The frequency, duration, and exact delivery method of irrigation (e.g., drip line, lawn sprinklers, manual deep-soak), as well as a history of winter watering.
• Chemical Exposure History: Any applications of fertilizers, pesticides, fungicides, or lawn-applied weed-and-feed herbicides within the past 1–2 seasons
• Environmental & Site Context: Soil type, proximity to sidewalks, streets, or home foundations, recent construction or root disruptions, and recent weather events like frost, hail, or severe heatwaves.
• Scope of the Issue: Whether nearby plants of the same or different species are exhibiting the exact same symptoms.

Helpful photos for review:
When diagnostic testing cannot be executed on a physical sample, digital photos are highly effective. However, close-ups of single dead leaves are rarely enough. A progression of 3 to 5 images from different perspectives is most helpful.

1. The Landscape / Wide-Angle View

• What it shows: The entire plant in relation to its immediate surroundings.
• Why it matters: This establishes environmental context. It allows the diagnostician to see if a tree is suffocated by nearby asphalt, competing with turfgrass for water, or situated right next to a reflective, heat-retaining wall.

2. The Whole-Plant View

• What it shows: The complete structure of the tree, shrub, or crop from top to bottom.
• Why it matters: It reveals the structural pattern of the symptoms. For example, a whole-plant shot quickly displays whether an entire side of a tree is flagging (classic vascular wilt) or if only the exterior margins are browning (classic environmental scorch).

3. The Problem-Area / Branch View

• What it shows: A mid-range view focusing on the transitional zone where healthy tissue meets dead or damaged tissue.
• Why it matters: On woody plants like redbuds and oaks, this perspective highlights the branch unions, trunk flares, or stems. It allows diagnosticians to check for sunken bark cankers, wood boring insect exits, or structural damage that cuts off water to the branches above it.

4. The Macro Close-Up Shot

• What it shows: Ultra-focused images of the symptoms or signs on individual leaves, twigs, or fruits.
• Why it matters: This captures fine details like the lacy "skeletonizing" patterns of Japanese beetles, the irregular blotches of fungal anthracnose, or the physical presence of fungal fruiting bodies and scale insects.

Happy Gardening!