Author Archives: Bill Argo

About Bill Argo

Bill Argo is technical manager of Blackmore Co. You can eMail him at

Understanding Plant Nutrition: Managing Multiple Species

Multiple species are often grown in the same greenhouse section, or even in the same container.    Often, these species have different acceptable pH ranges and iron requirements (Table 1), which can lead to growing difficulties that affect plant quality. In this final article, we give tips on managing multiple crops in the same greenhouse.

Understanding Plant Nutrition: The Complete Series

An Introduction Read about the basics on essential nutrients for plant growth, uptake of nutrients and pH’s effect on nutrient solubility.  Nutrient Sources The authors take a look at the myth that cation exchange capacity is important to soilless media. Limestone And pH  Why does limestone need to be added to soilless media? It’s all

Understanding Plant Nutrition: Geranium Nutrition

View more images from this story here. Seed and zonal geraniums are iron-efficient crops that are prone to iron/manganese toxicity when the media-pH gets too low. Once plants show toxicity symptoms of necrotic spots and marginal burn (Figure 1), the affected leaves do not completely heal. The only options become shipping lower-quality plants–to take additional

Understanding Plant Nutrition: Calibrachoa

Calibrachoa are often described as a “high feed” or “high iron” requiring crop. This is not exactly true. Calibrachoa are an iron-inefficient crop and are prone to iron deficiency because they lack the ability to take up iron from the soil solution if the media pH is too high. Once iron deficiency sets in, calibrachoa

Understanding Plant Nutrition: Stock Plant Nutrition

Nutrient management for stock plants is similar to other long-term crops. We have worked with several leading stock plant growers both in the United States and overseas over the past decade. Together, we have found the keys for success are fairly straightforward: have an organized plan that includes media and fertilizer selection, organize crops into

Understanding Plant Nutrition: Poinsettias

Click here to see images and figures from this story.  Profit margins are extremely tight for poinsettias, so minimizing shrinkage that results from crop losses is essential. If nutritional stress occurs, you will be struggling from that point onward to produce a high-quality plant for sale. Poinsettias hang around your greenhouse for several months, much

Understanding Plant Nutrition: Low Media-EC

When growers talk about “lack of feed” or “hungry plants” (Figure 1), the issue is usually insufficient supply of fertilizer nutrients. The easiest way to measure fertilizer level in the root media is with an electrical conductivity, or “EC,” meter. What is Media-EC? Electrical conductivity (also know as conductivity, EC or soluble salts) is a

Understanding Plant Nutrition: High ph Problems

High media-pH (above 6.4) induced iron deficiency is the most common nutritional problem for certain iron-inefficient crops (Figure 1), including calibrachoa, diascia, nemesia, pansy, petunia, scaevola, snapdragon and vinca. Plants only take up dissolved nutrients through their roots. When the media-pH is too high, micronutrients (especially iron) are less soluble and unavailable for uptake by