Yellowing Knock Out Roses in St. Louis: Fertilizer, Pruning, and Organic Sprays

A St. Louis gardener's mother had new Knock Out roses yellowing/thinning from bottom up after Miracle-Gro time-release fertilizer 4 weeks prior. Asked about vinegar remedies.

Diagnosis: Normal Knock Out Habit + Fertilizer Timing

Knock Outs naturally have flexible canes, thin lower foliage. Miracle-Gro is excellent—unlikely cause. Yellowing = seasonal leaf shed or light penetration issue.

Solution: Spring Hard Prune (Same as VA Beach)

• Remove twiggy growth
• Keep thick canes
• Cut back 1/3
• Stimulates dense, healthy regrowth

Organic Spray Recipes (From Expert)

Mildew & Black Spot: 8 cups water, 1 Tbsp baking soda, 1 Tbsp vinegar, 1 Tbsp canola oil. Hose morning → spray daily (mildew) / weekly (black spot).

Bug & Fungus: 1 quart water, 1 Tbsp baking soda, 1 Tbsp canola oil, few drops dish soap.

Super Alfalfa Fertilizer: 32-gal trash can water, 25 cups alfalfa pellets, 1 cup 20-20-20, 2 cups Epsom salts, 2 cups fish emulsion. 1 quart/rose monthly. (Hold nose!)

Vinegar Note

Vinegar in baking soda spray = pH buffer. Straight vinegar damages foliage. Use recipes above!