Why does my broccoli have yellow leaves?
Written by
Paul Reynolds
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.Yellowing of the broccoli leaves is more likely to indicate a nitrogen deficiency than the presence of a disease. This condition is a common one. It is first noticed on the lower older leaves. I frequently see it in my garden as the active growing period approaches in spring. The plants are evidently using a considerable amount of nitrogen to build up their foliage. A little soil testing shows that the soil is wanting in this element.
Nitrogen Deficiency
- Apply blood meal fertilizer around plants
- Use fish emulsion every 10 days
- Add compost tea for quick absorption
- Test soil pH first (needs 6.0-7.0)
Overwatering Symptoms
- Check soil moisture with finger test
- Improve drainage with perlite or sand
- Reduce watering frequency immediately
- Elevate containers for better runoff
Temperature Stress
- Provide shade above 75°F (24°C)
- Use row covers below 40°F (4°C)
- Mulch heavily to regulate soil temp
- Avoid transplanting during extremes
Distinguish between deficiency and disease. For example, there is a yellowing due to a nitrogen shortage, with no black spots, no oozing, and no fuzzy mould. I examine the leaves with a magnifying glass... The healthy yellow leaves will recover on feeding, but the diseased ones will not.
Soil Moisture Test - A week after repotting: Stick finger into the soil surrounding the stems - push it in up to your second knuckle (about four inches deep). If it feels like a damp sponge, don't water. I utilize a moisture meter, to accurately gauge when my plants are thirsty. Overwatered soil will smell sour, and compact easily between your fingers. I let my plants go dry in the pot then water thoroughly.
"compacted soil. Remedy. Aerate. Gently push a garden fork around the plants, being careful not to injure their roots. Add compost to break up. I do this monthly in most seasons, of course. I am speaking of heavy clay soils. Proper aeration enables the root to get oxygen (known to be one of the causes of yellowing)."
Keep an eye on temperature fluctuations. Broccoli hates anything below 40°F and above 80°F. I use some wireless sensors in my garden. Try to get some shade cloth up before any heatwaves, and cover the plants with row fabric on those cold nights. A consistent range of conditions will minimize the stress yellowing in your plants.
Preventing recurring issues begins with seasonal soil preparation. Conduct nitrogen testing annually in the spring and fall. Compost is added before planting. Broccoli crops should also be rotated on an annual basis. Utilizing these methods will help sustain a nutrient balance, ultimately minimizing the occurrence of yellowing leaves.
Read the full article: When to Plant Broccoli for Best Results
