Beef Cow Manure

• Beef cow manure, sometimes referred to as steer manure, is often acquired from a local farmer who raises beef cattle. This method is not advisable unless you are familiar with the farmer and his practices. Beef cow manure can contain unwanted weed and grass seeds. Additionally, unless the beef cow manure has been well aged and rotted, fresh, green beef cow manure emits heat as it breaks down. Using green beef cow manure with your hydrangeas can heat the soil and the roots. This damages the roots so severely that the plant dies. Beef cow manure also contains a higher nitrogen content and should not be used after flower buds begin developing so the hydrangea grows flowers, not leaves and foliage.
  
  

Dairy Cow Manure

• Dairy cow manure is cleaner than beef cow manure. Dairy cows are usually fed a higher quality, no-weed, feed promoting more milk. Dairy cows process their feed efficiently and the nitrogen, phosphorus and potassium levels can be half that of beef cow manure. Like beef cow manure, dairy cow manure heats as it rots and breaks down. Dairy cow manure is a better, safer choice of cow manure for a regular feeding of your hydrangea, as long as it is well rotted.
  
  

When to Use

• Well-rotted, dry, cow manure is a recommended soil supplement for hydrangea plants. Working dry cow manure into the soil of your planting area two to three weeks before transplanting your hydrangea adds needed nutrients and aerates the soil, giving the roots needed oxygen to thrive. Place side dressing of cow manure, placing dry cow manure around the hydrangea's base, at the beginning of the growing season in the spring. Repeat it every three to four weeks until July when flowering begins.
  
  

When to Avoid

• As much as hydrangeas benefit from cow manure, placing any cow manure in the bottom of the planting hole, then placing the roots of the hydrangea directly on top can kill your hydrangea. This is because a hydrangea, like any plant, is in stress when transplanted. The roots must establish in the soil, and if cow manure is what the roots must grow into, the manure is too high in nutrition for the stressed roots. The same holds true when your hydrangea is in its dormant stage in winter. The cow manure's nutritional value cannot be absorbed, but builds up in the soil. When the roots finally begin gathering nutrients from the soil in the spring, the winter manure build up is too much, possibly at toxic levels, and harms or kills the plant.