January 23, 2010
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. Management Tips Organize greenhouse zones so plants are grouped by similar nutritional requirements. One of the most useful groupings is based on the plant’s ability to absorb iron from the soil solution (Table 1). For example, grouping all iron-inefficient species together and away from all iron-efficient species will simplify your nutrition program because all the plants in a specific group should be able to be treated the same. Other factors to consider when grouping plants include acceptable EC levels and fertilizer requirements, light requirements (both intensity and day length) and moisture requirements. If […]
January 16, 2010
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 about pH management. Limestone, Calcium And Magnesium Limestone provides calcium and sometimes magnesium to container media. This article looks at the nutrient content of different types of limestone and how it influences calcium and magnesium levels. Irrigation Water Alkalinity & pH Water alkalinity and pH are two different measurements. This article explains the difference, how to interpret testing results and how to adjust management strategies accordingly. Irrigation Water As A Nutrient Source Water rarely contains enough primary macronutrients, but can be rich in secondary macronutrients. Check out this article for tips on making the most […]
December 28, 2009
Understanding Plant Nutrition: Geranium Nutrition
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 time to produce healthy new growth that will cover the older damaged foliage–or throwing plants away. Therefore, the best approach is to prevent iron/manganese toxicity (and low media-pH) from occurring. Here are some pointers for growing geraniums: Pointers – With normal fertilization practices, the acceptable pH range for iron-efficient crops like geraniums is 6.0 to 6.6. – Pre-test your root medium to determine its acceptability for growing geraniums. Often, moistening the media to near container capacity and giving it three to seven days to incubate allows the limestone a chance to react and gives a more realistic starting pH measurement than […]
November 30, 2009
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 will often lose vigor and become susceptible to secondary problems like overwatering or root diseases. Therefore, to succeed with calibrachoa, you need to monitor media pH regularly and take the proper corrective actions when the media pH gets too high. Here are some pointers for growing calibrachoa. Points To Consider – With normal fertilization practices, the acceptable pH range for iron-inefficient crops like calibrachoa is 5.5 to 6.2. Once the media pH increases above 6.2, iron deficiency is likely (Figure 1). – Make sure the iron deficiency symptoms are being caused by high media […]
September 16, 2009
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 pH or EC groups, monitor nutrition regularly and ensure adequate levels of all nutrients are present in cuttings harvested from the stock. 1. Start with a quality growing medium. Some growers consistently produce excellent quality cuttings from stock plants grown in gravel, soil or locally produced compost to save costs. However, these locally produced substrates will often present the stock producer with challenges including inconsistent mixing, excess compaction or composting, limited root growth because of lack of aeration or excessive drying, and micronutrient toxicity (often manganese, depending on the rock type) when substrate pH decreases […]
September 1, 2009
Understanding Plant Nutrition: Poinsettias
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 longer than short-term spring crops. Therefore, a preventative approach that breaks the crop down into stages can help avoid the usual problems. Here are some pointers to consider at each stage. Pointers 1. Poinsettias have four stages in which fertilizer needs vary: propagation, initial growth, rapid growth and flowering phases. Figure 1 represents the goals in each stage. The amount of fertilizer taken up by plants varies depending on how quickly the crop is growing. 2. During propagation, avoid solutions that have a high electrical conductivity (EC) (above 0.75 mS/centimeter) or fertilizers containing phosphorus to avoid foliar damage (Figure 3). Rooting can be delayed as […]
July 24, 2009
Understanding Plant Nutrition: Environmentally Induced Plants
Most nutrients are actively taken up by the plant from the soil solution. With active uptake, the plant roots use energy to scavenge the root environment for soluble nutrients. For nutrients that are taken up actively (like nitrogen or phosphorus), their concentration in the root medium (as measured with soil tests) tends to correlate well to uptake by the plant. The exceptions to this rule are calcium and boron. Calcium and boron are taken up passively by the plant. With passive uptake, nutrients only move into the plant along with the water used for transpiration. No transpiration, no uptake, regardless of the concentration of those nutrients in the soil solution. The environment where the plants are being grown will directly affect transpiration rates, and calcium and boron uptake. The types of environments that suppress transpiration can include: – Hot, humid conditions, especially when light levels have been reduced with excess […]
June 19, 2009
Understanding Plant Nutrition: Common High Media-EC Problems
High electrical conductivity (EC) in the growing medium makes it harder for roots to take up nutrients and water–it is like trying to grow plants in sea water and can result in “salt burn” (damage to sensitive root tips) and toxicity symptoms in foliage (Figure 1). In this article, we will discuss the causes and corrections of high media-EC. What Causes High Media-EC? Media-EC is a measure of the total dissolved salt concentration contained in the soil solution and is often used as a measure of the overall nutrition status of the crop. You can think of the soil nutrient level as similar to a bank account. Our account balance (media-EC) is made up of deposits and withdrawals. The deposits are made with salts contained in the irrigation water, with water-soluble fertilizer, or by slowly soluble or controlled-release nutrients. Withdrawals are made through plant uptake or leaching. The account balance […]
June 4, 2009
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? What Causes Low Media-EC? The initial concentration of nutrients in a container media is provided by the pre-plant nutrient charge, which may include lime (providing calcium and magnesium), and other fertilizers such as superphosphate, gypsum or urea-formaldehyde. Part of the initial nutrient source is immediately soluble and therefore affects the initial media-EC. Other nutrient sources are bound to the soil particles or are in a slow-release form (e.g. limestone, resin-coated fertilizers), and only affect EC as nutrients dissolve into the soil solution. Most media components, such as peat, bark or perlite supply a small amount of nutrients, whereas compost can supply significant nutrients as […]
April 25, 2009
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 plant roots. High-pH induced iron deficiency can develop within one to two weeks, resulting in chlorosis of new growth and overall stunting. This problem is not occurring because plants need more “feed” or are “heavy feeders.” Instead, it occurs because the iron supplied in fertilizer becomes insoluble due to the high media pH. Getting Started We have undertaken considerable research and worked closely with growers to develop strategies to rescue crops that are stressed from high media-pH. If you think there is a problem, the first thing to do is test the pH and electroconductivity […]
March 23, 2009
Understanding Plant Nutrition: Correcting Low Media pH
Iron/manganese toxicity is a common problem when media-pH drops below the ideal level in certain crops, including geraniums, marigolds, lisianthus, and pentas. As media-pH decreases (meaning the pH becomes more acidic), iron and manganese become more soluble, resulting in higher concentrations in the soil solution. For each drop in media-pH by one unit, for example from pH 6.0 to 5.0, solubility of inorganic iron in the growing medium (and availability of this iron for uptake by plants) increases by a factor of 1,000. Geraniums, marigolds and certain other species are very “iron-efficient” at taking up the soluble iron and manganese into their tissue. These species evolved to grow in calcareous (low-iron, high-pH) soils and “harvest” extra iron by exuding acid or chelating agents from their roots into the soil, growing extra root hairs and other processes. When we place those plants into an iron-rich greenhouse media and fertilizer regime, they […]
January 6, 2009
Understanding Plant Nutrition: The Series
Understanding Plant Nutrition: An Introduction Read about the basics on essential nutrients for plant growth, uptake of nutrients and pH’s effect on nutrient solubility. Nutrient Sources: Media Cation Exchange Capacity 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 about pH management. Limestone, Calcium And Magnesium Limestone provides calcium and sometimes magnesium to container media. This article looks at the nutrient content of different types of limestone and how it influences calcium and magnesium levels. Irrigation Water Alkalinity & pH Water alkalinity and pH are two different measurements. This article explains the difference, how to interpret testing results and how to adjust management strategies accordingly. Irrigation Water As A Nutrient Source Water rarely contains enough primary macronutrients, but can be rich in secondary macronutrients. Check out this […]
December 16, 2008
Understanding Plant Nutrition: Managing Media EC
High fertilizer levels can be too much of a good thing, leading to excess growth, nutrient toxicity and potential runoff of nutrients into the environment. Conversely, low fertilizer levels can lead to nutrient deficiency symptoms. A basic goal for a nutrition program is to supply nutrients to the crop within an acceptable range for healthy and controlled growth. One way to ensure that nutrients are being supplied at adequate levels is with a soil test. So long as your irrigation water has salt concentrations within an acceptable range and you use a balanced fertilizer containing both macro- and micronutrients that doesn’t contain a lot of useless salts (like sodium or chloride), then there is a good relationship between the nutritional status of the root medium, and the media electrical conductivity (EC) measured using common soil testing methods (Table 1). This last article of our series discusses how to manage media […]
October 21, 2008
Understanding Plant Nutrition: Managing Media pH
Managing the pH of container media is a challenge in the greenhouse and nursery industry. Many growers face problems associated with their media pH either drifting up or down to levels that result in loss of crop quality and sales. In this article, we will discuss how the factors that we have discussed in previous articles (media, lime, water, fertilizer, etc.) interact to affect pH management. Balancing Factors Consider pH management as a balance (Figure 1). One side of the balance has the basic reactions commonly found in container media (i.e. the reactions that make the media pH increase). The four main basic reactions are: nitrate (NO3-N) fertilizers, irrigation water alkalinity, reactive lime and residual lime. On the other side of the balance are the acidic reactions (i.e. the reactions that make the media pH decrease). The three main acidic reactions are ammoniacal (NH4-N) fertilizers, media lime requirement and plant […]
September 17, 2008
Understanding Plant Nutrition: Controlled- And Slow-Release Fertilizers
Using controlled-release (CRF) and slow-release (SRF) fertilizers allows growers to supply nutrients for an extended duration without the specialized equipment needed to apply water-soluble fertilizers. These fertilizers are added to the media at mixing or applied to the media surface after planting. Nutrient runoff can be reduced using CRF and SRF, especially compared to applying water-soluble fertilizer through overhead sprinklers. Relying on CRF alone is not always the best solution for nutrient management. For example, even distribution of CRF prills from plant to plant is difficult when growing in cell packs or trays. The correct CRF should be matched to the crop and growing environment so that nutrients are released at the rate required for optimal plant growth – too rapid a release rate can cause media-electrical conductivity to climb too high and damage roots, or too slow a release can result in nutrient deficiencies. In some cases, a combination […]
August 25, 2008
Understanding Plant Nutrition: Fertilizers And Micronutrients
Micronutrient (iron, manganese, zinc, copper, boron and molybdenum) nutrition is different from managing macronutrients, such as nitrogen, in three fundamental ways. First, the solubility and plant availability of micronutrients is affected by media pH to a much greater extent than is macronutrient solubility. Second, the difference between acceptable concentrations of micronutrients and concentrations that are either too low (deficiencies) or too high (toxicities) is small compared to a broader range for macronutrients. Finally, while most macronutrients are mobile within the plant, most micronutrients are immobile, and so a constant supply is needed for the duration of the crop or growth and plant appearance may be affected. In this article, we will focus on micronutrient sources, and how they are applied to a crop. Preplant Sources In soilless media, preplant sources of micronutrients are often added at mixing. In general, the sources in starter fertilizers can include both soluble forms (sulfates) […]
July 24, 2008
Understanding Plant Nutrition: Fertilizers And Macronutrients
When you select a water-soluble fertilizer, the primary goal should be to supply plants with a sufficient amount of essential plant nutrients for good growth and flowering. In this article, we will focus on macronutrients (nitrogen, phosphorus, potassium, calcium, magnesium and sulfur) supplied by water-soluble fertilizers. We will discuss macronutrient sources, fertilizer formulations and the application of fertilizer to the crop. In subsequent articles, we will discuss other aspects of fertilization including micronutrients sources and formulations and controlled-release fertilizer. Fertilizer Formulations Water-soluble fertilizers come in two types, either individual fertilizer salts or blended fertilizers. Fertilizer salts are chemicals containing nutrients that can dissolve into a water-soluble form that are needed for plant uptake. For example, potassium nitrate (KNO3) will dissolve into separate potassium ions and nitrate ions. Blended fertilizers are combinations of two or more fertilizer salts that supply several macronutrients. For example, 13-2-13 is a blend of calcium nitrate, […]
July 8, 2008
Understanding Plant Nutrition: Fertilizers And Media pH
Choosing fertilizers can be one of the most important decisions you can make for managing the media pH of container grown crops. It is therefore important to understand how fertilizers raise or lower media pH, which results largely from the form of fertilizer nitrogen (ammoniacal, nitrate or urea). This article will help you understand why fertilizers are classified as acidic or basic and how the reactions produced by the fertilizer affect media pH. You Can’t Measure Fertilizer Acidity With A pH Meter! Here is a trick question: Which is the most acidic fertilizer in Table 1? The table shows the nitrogen (N):phosphorus (P2O5):potassium (K2O) ratio, the fertilizer label description in terms of potential acidity or basicity, along with the percent of nitrogen in the ammoniacal form (the rest of the nitrogen in these formulas is made up of nitrate). We prepared a solution of 200 parts per million of nitrogen […]
June 18, 2008
After water management, fertilization is the next most common problem with keeping large containerized plants alive through the summer. Most consumers do not fertilize their plants, or if they do, they don’t apply a sufficient amount to maintain the plants at good quality. In this article, we give specific recommendations about fertilizing of 10-inch baskets. For larger size pots and baskets, use these recommendations as a starting point for suggesting fertilizer rates. How much fertilizer does a 10-inch basket need? Assuming you start with a growing medium that contains preplant fertilizers, an additional 1.5 to 2 grams of nitrogen from a balanced fertilizer is sufficient to produce a 10-inch basket in 12 weeks with no leaching. That is equivalent to the application of 7 to 10 quarts of fertilizer with a concentration of about 200 ppm N. If you leach, you will need to use more fertilizer. Researchers at Michigan […]
June 18, 2008
Once mixed containers or baskets are sold to a customer, their subsequent watering greatly affects the “use by” date of the plant product and overall consumer satisfaction. How easily the medium rewets is a key to your consumer’s success. It may be unrealistic to educate all our customers to become expert irrigators. If water runs out through channels or flows off the media surface because of poor rewetting, customers are unlikely to water thoroughly. The choice of media components or the use of a wetting agent can improve rewetting. Understanding Rewetting Characteristics Rewetting ability refers to how rapidly a root medium absorbs water, and thus reaches its potential for maximum available water-holding capacity, with minimal leaching. Unfortunately, many of the components used to make container media do not absorb water easily. For example, organic materials such as peat or bark tend to be hydrophobic and may be difficult to rewet […]
December 18, 2017
California Growers Have a New Disease Control Tool
BASF’s Orkestra Intrinsic fungicide has been approved in California for control of several ornamental plant diseases.
December 16, 2017
Join the Emergent Group During a Reception at MANTS
“Emergent: A Group for Growing Professionals” will once again be hosting its Emergent Networking Event at MANTS in Baltimore, MD. The event will be held on Wednesday, Jan. 10.
December 15, 2017
Your AFE Donations Will Be Matched Between Now and the …
Between now and December 1, any donations made to the American Floral Endowment will be matched up to $20,000.
December 14, 2017
New Biofungicide Approved for Disease Control in Orname…
Certis USA recently introduced Carb-O-Nator, a new broad-spectrum foliar fungicide that works on contact to control powdery mildew, Alternaria, Anthracnose, Botrytis, Septoria leaf spot, and other diseases.
December 13, 2017
New Webinars Address Effective Propagation Techniques
e-Gro, an online clearing house for alerts about greenhouse disease, insect, environmental, physiological, and nutritional disorders, recently posted two new propagation-related webinars on YouTube.
December 12, 2017
New Products Designed to Protect the Quality of Plants …
The innovative technologies from Oasis Grower Solutions are aimed at ensuring that the supply chain delivers the best possible consumer plant experience.
December 12, 2017
Research Sheds Light on How to Manage Plant Stress With…
An innovative system developed by Chinese researchers uses rapid imagery to indicate plant health, enabling growers to respond quickly and automatically to plant stress.
December 11, 2017
Evaluating Robotic Transplanters for Plant Cuttings
There are several factors that might affect your decision to invest in transplant robots, based on initial observations and reported information about available equipment.
December 9, 2017
Southern California Wildfires Narrowly Miss Most Grower…
Here’s an update on horticulture businesses in the areas affected by the California wildfires.
December 9, 2017
Infrared Thermometers for Monitoring Plant and Substra…
Growers use many tools to monitor the greenhouse environment. Learn about the best practices for using an infrared thermometer to measuring plant temperature.
December 8, 2017
Spring Meadow’s New Logo Highlights Focus on New, Color…
In a move that highlights its commitment to developing new, colorful flowering shrubs, Spring Meadow Nursery has unveiled a new logo.
December 8, 2017
HortScholars Program Now Accepting Applications for 201…
Do you know any college students currently in a horticulture-related program? This unique program gives them a chance to connect with industry leaders and make new connections at Cultivate.
December 8, 2017
The Sustainability of the Peat Industry Looks Better T…
Despite talk about alternative products and differences of opinion over its sustainability as a resource, peat is here to stay.
December 7, 2017
Growing Tips From a Pro for SunStanding New Guinea Impa…
SunStanding New Guinea impatiens hybrids spruce up the landscape with vibrant blooms that explode with color in both sun and shade areas, and they hold up well in heat and humidity.