Topdressing Plants in Professional Ornamental Horticulture

What is Topdressing

Topdressing is an agronomic procedure where nutrients are applied on the surface of the substrate. It’s a technique suitable for both plants in pots or container and for plants grown in open field. It is important to avoid contact with plant collar. Plants are topdressed at a stage when incorporating the fertilizer into the substrate is no longer possible.

When crops remain in the nursery or greenhouse beyond their planned production cycle, topdressing fertilizers provide a targeted way to sustain uniform growth and maintain plant quality until sale or the next potting phase.

Topdressing with controlled‑release fertilizers (CRF) or slow‑release fertilizers (SRF), allows to:

• provide a steady nutrient supply
• support strong greening
• maintain visual quality

Why Topdressing Matters in Ornamental Horticulture

Topdressing is especially valuable for:

• Plants that were potted in the previous season
• Stock that will remain in production without imminent repotting
• Crops whose base substrate fertilization has exhausted its nutrient release
• Plants needing a nutritional boost to complete growth or holding periods

Topdressing fertilizer in a pot with Photinia

Topdressing Fertilizers for Ornamental Horticulture are Specific for Ornamental Plants

It is very important to remember that topdressing fertilizers for ornamental horticulture are engineered with specific characteristics that differ from those used in other sectors: the specific growing environment of potted plants and ornamental plants in general, requires specific longevity, NPK ratio, granule size, trace elements etc.

Choosing the correct topdressing product has measurable economic and horticultural impact because the appropriate controlled release formulation preserves uniform plant appearance and performance. On the other hand, the wrong fertilizer can lead to

• inconsistencies in growth
• salinity stress
• reduced marketability

How to Use Topdressing Fertilizers Effectively

Best practice ensures that nutrients reach the plant efficiently and safely:

• For salinity-sensitive crops, reduce standard doses by approximately 50%
• Apply topdressing only to well-rooted plants
• Delay topdressing if plants have been recently pruned (wait 2-3 weeks)
• Avoid application during the hottest part of the day
• Align topdressing with irrigation scheduling: growing media best to be well moisturized
• With overhead irrigation, distribute granules evenly across the pot surface
• With drip irrigation, place granules under drippers in multiple spots
• Avoid mixing fertilizers of different granule sizes to prevent segregation

These practices help maximize plant response and nutrient uptake while minimizing the risk of uneven distribution or root stress.

What Are the Best Topdressing Fertilizers

To meet the diverse nutritional needs of nursery and greenhouse crops, ICL offers a wide portfolio of topdressing fertilizers. From shorter to longer longevity products, this range covers multiple crop types, environmental conditions and production timelines, helping growers fine-tune nutrition without compromises.

Refer and/or download our Topdressing Comparison Table for detailed product specifications, release durations, and practical advice.

If you want to know which range is available in your area, in the top right corner of this page please select your country from the countries’ menu.