Foliar Feeding: A Secret to Thriving Roses and Plants

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Summary: The article explores foliar feeding’s benefits for roses and other plants, emphasizing its potential to produce larger blossoms, vibrant foliage, and improved winter hardiness. It delves into the process, integration with pest control, and the role of potassium nitrate and other nutrients.

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Key Takeaways

  • Foliar feeding can result in larger, more vibrant blossoms, dark green foliage with a glossy sheen, and improved winter hardiness for roses and other plants.
  • Plants can absorb certain nutrients directly through their foliage, making foliar feeding an efficient method of nutrient delivery.
  • Fertilizer can be combined with pest control materials and applied through regular weekly spray programs for rose growing.
  • Potassium nitrate plays a crucial role in foliar feeding, providing a continuous supply of nitrogen and potassium without accumulating toxic residues.
  • Foliar feeding can be supplemented with spring and fall applications of a 5-10-10 or 6-12-12 fertilizer containing trace elements for optimal plant growth.

The Benefits of Foliar Feeding

Larger, more richly-colored blossoms, dark green foliage with a glossy sheen, and improved rose winter hardiness have been observed in 1200 roses grown in the Horticultural Gardens at Michigan State University under a foliar fertilization program.

Foliar Feeding Benefits include:

  • Larger, more vibrant blossoms
  • Dark green, glossy foliage
  • Improved winter hardiness

Nutrient Absorption through Foliage

Horticultural scientists know plants can absorb certain nutrients directly through the foliage. 

Foliar Feeding and Pest Control Integration

The practical application of this knowledge fits particularly well into the rose growing culture as the fertilizer can be included with pest control materials and applied in regular weekly spray programs.

Foliar Feeding Program Details

The foliar feeding program is carried out in the following manner. One handful of a 5-10-10 or 6-12-12 fertilizer containing trace elements is applied to each plant in early April after the soil hills are removed from around the canes. 

Only soil fertilizer applications are made in late fall, just before the roses are healed when the spring application is repeated.

The Role of Potassium Nitrate in Foliar Feeding

During the growing season, all fertilizer is applied through the foliage of the plants by adding one ounce (one rounded tablespoonful) of potassium nitrate to every eight gallons of all-purpose spray solution applied to the plants at weekly intervals. 

The foliar feeding program begins when growth starts in the spring and continues until growth ceases in the fall.

Benefits of Late Fall Fertilization

Many rose growers suspect fertilization in late fall results in weak, easily winter-killed growth. However, the experience with foliar feeding indicates the contrary. 

Rose fertilization until all growth stops results in improved hardiness of plants and reduced winter-killing.

Horticulturists have determined that fertilizer applied to foliage is absorbed within 30 minutes and can supply the plant with sufficient nutrients from one to two weeks.

Nutrient Supply and Plant Growth

Plants use nutrients at a slow, steady rate throughout their growing periods. As a result, foliar applications continuously provide nutrients at concentrations well below those which might cause injury. 

Soil fertilizers usually recommended for roses during the growing season have a wide fluctuation of nutrient supply.

Eliminating Trace Elements

Potassium nitrate has an analysis of 13-0-44, which gives about a one-to-two ratio of nitrogen to potassium. 

Because the plants utilize both nutrients in this fertilizer, there are no residues that might accumulate in toxic amounts. 

The omission of phosphorus fertilizer in this foliar feeding program is deliberate because phosphorus fertilizers in such a spray combination may inactivate certain insecticides, such as Malathion.

Further, it is also known that one or two soil applications of phosphorus and trace elements per year are sufficient to supply the needs of that plant for at least one year. 

Another reason for eliminating trace elements is that certain elements may not move throughout the plant if applied only to the foliage.

Calcium and Trace Elements in Foliar Feeding

Calcium, for example, can move only upward in a plant and cannot move down to the root system when applied only to the plant tops. 

Trace elements, applied to the roots, become effective nutritional agents.

Foliar fertilizer, with potassium nitrate as a supplement to spring and fall applications of a 5-10- 10 or 6-12-12 fertilizer containing trace elements, provides a continuous supply of the nutrients needed for growing fine roses. 

“These roses are first rate,” said a garden visitor from Reading, England, last June upon viewing the roses in the Horticultural Gardens at Michigan State University.

This remark from an Englishman steeped in the tradition of fine rose growing was taken as a sincere compliment. 

It is felt that the excellence of the growth he observed may be attributed largely to the fact that the plants had been foliar-fed. 

44659 by Prof. Richard F. Stinson