1. Growing Media pH: Harmonizing Peat and Lime

    3-1-14Drastic pH changes upset plant quality (figure 1), which is why growing media pH is a popular subject with growers. Peat mixes are not naturally well buffered against pH changes, and container growing exacerbates pH effects. Water, fertilizer regime, and even the species grown can affect pH, which is why it’s important to have a well-buffered mix. This blog explores research surrounding peat-based media pH and the effects of lime to help growers better understand liming and peat-based soilless mix performance.

    Peat moss is acid (~3.5-5 pH), which is why alkaline lime is added to help raise pH to a more neutral level (~6.5-7 pH) desired by most plants. Quality peat-based mixes always contain added lime, but the variable quality of peat and lime can cause variation in mix pH.

    The pH scale is logarithmic: a pH of 5 is 10 times more acidic than pH of 6 and 100 times more acidic than 7. Variation can be wide, so it is essential to create an effective mix buffer system. To do this, you must first know what causes pH variation in peat mixes. That’s exactly why Sun Gro R&D supported research at North Carolina State University aimed towards identifying and improving pH variation in peat moss and research at Martin Marietta Technologies aimed to improve horticultural lime performance. Research results allowed us to improve the performance of our professional and retail mixes.

    Peat Moss Variation

    Not all peat moss is the same. All fall under the genus Sphagnum, but there are several distinct species that perform differently, depending on the decomposition stage. The natural groundwater or rainwater of the peat bog can also influence pH. All these differences impact peat’s inherent acidity, but which predict peat’s lime requirement?

    3-1-2In late 2002, nearly 500 samples of three peat species (Sphagnum fuscum S. megellanicum, S. angustifolium) were collected from different bogs in Alberta. Alberta bogs naturally maintain the three major Sphagnum species and a hummock-hollow-type topography (figure 2). In each sample, species were tediously separated and their percentages estimated. Their decomposition rate was also determined.

    3-1-3We discovered that different species had pH differences. Sphagnum fuscum (hummock top) generally had a pH of 3.5 and is horticulturally the best because of its high water absorption and slow decomposition. Sphagnum megellanicum (hummock middle) also absorbs water fast and retains it well but decomposes quickly. Sphagnum angustifolium (hollows) has a pH of 4 to 5. There are also non-Sphagnum-like sedges or debris, which are generally low in pH and increase pH variability.

    Peats that are highly decomposed have high pH. When the naturally undulating bog surface is made flat for harvesting, each pass of harvester picks up variation in the species and decomposition, resulting in variation in peat pH (figure 3a).

    Lime Variation

    3-1-6Lime costs less than 1% of the mix price, yet it can cause lots of headaches. This is largely because of lime differences (figure 5) and that most lime companies don’t understand the horticultural industry and how to manufacture a product with uniform performance.

    Lime has to be water-soluble and dissolve to neutralize peat acidity. When it comes to lime in greenhouse growing, it needs to rapidly increase pH (in days if not hours) and the residual effect needs to last for 3 to 4 months. Creating a processed lime that does this is not straight forward.

    Many characteristics impact the performance of horticultural lime, including:

    1. Particle Size: Lime particle size impacts its solubility. Smaller particles dissolve faster, but research shows that particle size accounts for only half of the reaction rate of lime.
    2. Dolomite vs Calcite Lime: Research shows that dolomite lime (calcium and magnesium carbonates) exhibits tremendous variation, while calcite lime (calcium carbonate) exhibits little to no variation. This indicates it is difficult to change dolomite sources and easier to change calcite sources. Dolomite lime also takes four times longer on average to react than calcite lime.
    3. Magnesium Carbonate in Dolomite: Increased magnesium carbonate content increasingly slows the reaction rate, but again the lime reaction rate is not fully related to magnesium carbonate content.
    4. Surface Area: Lime surface areas vary (figure 6) Same-size lime particles with high surface area show an increased reaction rate.

    Particle size, lime type, and surface area account for 80% of the neutralization capacity of lime. These findings tell us that in addition to size and reaction rate, content and surface area must also be included in the specs to reduce horticultural lime variability. More data on other lime characteristics is being analyzed to account for 100% of the neutralization capacity.


    Predicting Lime Requirement

    You might expect a peat with a starting pH of 4.5 to reach a target pH of 5.8 with less lime than a peat with a starting pH of 3.5. You would think that some acidity would be already reduced by bases with the 4.5 pH peat, making the neutralization requirement lower. Surprisingly, the relation between higher starting pH and lower lime requirement is not strong, just 20%. Why? A peat with a pH of 4.5 can still have a much higher number of sites available for bases than a peat with a pH of 3.5.

    Confusing? Let me explain using an analogy of a large hotel (100 rooms) versus a small hotel (25 rooms). Knowing there are 25 rooms occupied in each hotel does not tell you how many rooms are vacant unless you know the total capacity of each. When 25 rooms are occupied in the large hotel, there is still a 75% vacancy while the smaller hotel is 100% full. The pH value of each peat is comparable. Even when bases like calcium and magnesium are extracted, a peat sample can yield a greater quantity of bases (equal to a greater number of guests) and still have a lower pH (equal to a lower percent occupancy).

    To predict the lime requirement of a peat, one must determine the total capacity for base saturation, and the percent saturated with bases. The correlation between increasing percent of base saturation and decreasing lime requirement is stronger (40%). The total capacity of a peat to hold bases is based on its cation exchange capacity, where cations (positively charged ions like hydrogen, calcium, magnesium) are swapped for one another.

    A high cation exchange capacity generally imparts a high buffer capacity. During growing, peat with high buffer capacity will have great ability to trade other cations for hydrogen ions that are coming from plants, fertilizers, microbial action, etc. Buffered peat resists pH drifts, which is a property we desire in a mix. Our research showed Sphagnum fuscum exhibited higher buffer capacity than the other species studied.

    Additionally, we generally believe that hydrogen is the source of acidity in peat. But, iron is also found in Alberta peat, and iron bonds with hydroxide in water, leaving acidic hydrogen ions in the solution. So, peat pH variations could also be due to differing amounts of iron.

    Matching Peat-lime

    So, what about the chemistry in creating a lime and peat match? What about pH drift during growing? The properties mentioned above give information to predict pH changes during growing. For example, different reaction rates of limes give information on balancing both the initial pH of a mix and pH maintenance during its use. Since the whole effect is a sum of its parts, we can select, add, or subtract relevant factors and evaluate their effects. This knowledge allows us to position the proper pieces in the pH jigsaw puzzle for the creation of great peat mixes with well-balanced pH that produce great looking plants.

    ~Adapted from an article by Shiv Reddy

  2. With Hydroponics, Don’t Guess…Test Your Plants

    recently matured leaves

    Always test the most recently matured leaves, in this case just below the flowers.

    “The plant is the final judge,” says Kathryn Lewis of Sun Gro Analytical Services, a branch of our company that uses rigorous testing and analysis to determine your crop’s needs. Even if a plant looks picture perfect, it may harbor a deficiency that could reduce flavor, oil content, and overall vigor.

    “It’s what the plant has taken up that matters,” stressed Lewis. “If you are having a plant growth problem, or you are trying to perfect your system, you must test the plants first.” At Sun Gro we test each sample to see if what you are doing provides your crops full access to all 16 essential nutrients needed for plant growth. Just testing soil or water will not necessarily tell you what’s available to plants. Other factors can be at play.

    Lewis knows the truth about nutrient uptake and how certain conditions can make nutrients unavailable. “Only by drying and crushing the plant’s tissues can we determine if it’s properly accessing nutrients, and whether or not there’s enough of all 16 essential nutrients for the plant to reach its full potential.”

    fresh cut material for sample

    Air dry samples for one day, place in the paper sack labeled Plant Tissue (drying and use of paper is very important).

    With today’s hydroponics, the mix-and-match approach to plant nutrition can be far from scientific. There is no way to determine if what you’re doing is working to its fullest advantage without scheduled testing. “Each plant should be producing at the highest level possible, but without analytic testing you can’t know if all nutrients applied are being utilized. Only with hard data can you fine tune individual micro and macro nutrient concentrations,” shared Lewis.

    Although Sun Gro offers an extensive list of analytical services, Lewis stressed that individual and commercial hydroponic growers are best served by first testing plant tissue. The requested sample size is 2 cups, or 1 oz. T collect one sample, collect every 2 to 4 weeks from the same variety. Collect recently matured leaves only, just below the growing point from at least 10 randomly selected plants. For unknown “problem” diagnosis, collect separate samples from both “good” and “bad” areas. This comparison often helps to determine corrective remedies. The data growers get from plant tissue analysis lets them know if they are on the right track or need to make adjustments in their feeding, light, watering, or media.

    The benefits to testing your plants are many, but above all testing allows a high degree of nutritional accuracy. Every grower has guessed at what plants need at one time or another, and sometimes you guess wrong. When you test your plants it eliminates guesswork to ensure that every crop you grow produces at its highest level. As you move into a new growth phase, there’s an opportunity to immediately correct deficiencies. Moreover, there’s less of a chance that you’ll add a nutrient that is already dangerously high just because it’s a component of your plant food product.


    Collect plant samples from the corners and center of your growing area for an accurate reflection of your growing space.

    Hydroponic horticulture is highly scientific, but there’s a lot of folk practice that can get in the way. When there’s a great deal of money on the line, or just a personal at-home crop, you can’t afford to guess wrong. If the desired result is a consistently good harvest time and time again, the cost of testing pays for itself.

    Click here to view a submission form for Sun Gro Analytical Services.

  3. NUTES: Nutrients and Indoor Growing

    Indoor-Plants-led-grow-lightOne of the common questions that customers ask is how to fertilize plants grown in Sunshine Advanced (SSA) mixes. Many are confused by all of the information about fertilization available on websites, in magazines, or product guidelines that may contain conflicting advice and opinions. The approach to fertilization should not be that difficult. We want customers to succeed when using our high-quality products, and part of that success relies on knowing the basics when it comes to ‘nutes’ (nutrients) and indoor growing with SSA mixes.

    Let’s start with some clarifying facts about Sunshine Advanced products—beginning with a summary from SSA Tech Sheets and Product Labels:


    Sunshine Advanced Mix #4 - OMRI-listedSunshine Advanced Mix #4:

    Ingredients: Canadian Sphagnum Peat Moss, Perlite, Coir, Dolomite Lime, Gypsum, Organic Fertilizer, Proprietary Blend of Endomycorrhizae, and Organic Wetting Agent. Plus RESiLIENCE®!

    Fertilization: Start your own feeding program within 7 days of planting or seedling emergence.


    Sunshine Advanced Rain Forest Blend - OMRI-listedSunshine Advanced Rainforest Blend:

    Ingredients: Bark, Coir, Perlite, Compost, Earthworm Castings, Organic Fertilizer, Proprietary Blend of Endomycorrhizae, and Organic Wetting Agent. Plus RESiLIENCE®!

    Fertilization: Start your own feeding program within 14 days of planting or seedling emergence. (14 days rather than 7; the earthworm castings give a little extra nutrient boost.)


    7106sunshine-mix4-myco-resilience-frontSunshine Advanced Mix #4 with Myco

    Ingredients: Canadian Sphagnum Peat Moss, Perlite, Dolomite Lime, Low Phosphorus Fertilizer, Proprietary Blend of Endomycorrhizae, and Wetting Agent. Plus RESiLIENCE®!

    Fertilization: Start your own feeding program within 14 days of planting or seedling emergence. (14 days rather than 7; the earthworm castings give a little extra nutrient boost.)

    Sunshine Advanced Ultra Coir - OMRI-listedSunshine Advanced Ultra Coir:

    Ingredients: Coir, Canadian Sphagnum Peat Moss, Perlite, Proprietary Blend of Endomycorrhizae, and Organic Wetting Agent. Plus RESiLIENCE®!

    Fertilization: Start your own feeding program within 7 days of planting or seedling emergence.


    Sunshine Advanced Mixes are formulated to have an acceptable pH and low level of all the necessary nutrients for plants or seedlings to get a great start. But these starter nutes are not for the long haul. After 7 to 14 days and at least 2 to 3 waterings (seedlings usually require more), the grower will need to begin a feeding program.

    When it comes to fertilization, it’s safe to assume that fertilizers will be dissolved in a grower’s irrigation water. These fertilizers can be bought in a liquid or powder form. Powder forms are often called “water soluble fertilizers.” So, let’s dig in by covering the five most common things that can go wrong with fertilization regimes, followed by ways to overcome these common problems.

    The five most common fertilization problems:

    1. Not considering the water quality (Poor water quality can derail even the best fertilizer choices.)
    2. Getting too wrapped up with ppm, EC and translation into percentage N (Electrical conductivity (EC) or parts per million (ppm) is usually a measure of the “strength” or the concentration of fertilizer put on your plants.)
    3. Thinking that all fertilizers have the same basic ingredients (Different fertilizers may have different ingredients, which is important.)
    4. Fertilizing with the wrong formulations
    5. Over-fertilizing or fertilizing too often

    Water Quality

    This is probably the most important issue in growing. Greenhouse growers are very aware of the impact of water quality on the success of growing crops. Water that has a high amount of dissolved lime (i.e. high alkalinity or bicarbonates) or a high amount of salt (i.e. high EC) will create a challenge for growing plants. Having water tested by a reputable lab, will tell a grower what he or she is dealing with.

    Once water issues are resolved, one can effectively choose what type of fertilizer to use. But it’s also smart to think about what type of mix is best for a given water situation. For example, at Sun Gro we usually recommend a more porous mix when dealing with poor water quality – like our Sunshine #4 Mix or our Sunshine Super Hydro where the built up salts at plant root zones can be “leached out.” This will be covered in more detail later in the article.

    EC or PPM 

    Forget about “ppm’s” and EC for right now.  There are so many methods used to figure out these two numbers, some right and some, well, not so right. This is where some growers make things more complicated than they need to be. They throw the baby plant out with the water by getting too analytical.

    The problem is that electrical conductivity (EC) or parts per million (ppm) is used to measure the amount of salts or specific nutrients in water, fertilizer solutions and soil (using some type of soil extraction method). They are not often interchangeable, but some growers treat them like they are, which leads to lots of misconceptions.

    Sunshine Advanced mixes have been formulated to achieve an acceptable starting pH and nutrient content, so growers should be okay with simply choosing a fertilizer. There are many fertilizers to choose from. We usually recommend using either a water soluble or liquid concentrate fertilizer for indoor growing – either will work. We don’t recommend slow-release prills because these are better for outdoor growing.

    Fertilizer Ingredients

    One very important thing that a lot of people don’t think about is the ingredients or actual compounds that make up a fertilizers. The first thing to know is that all fertilizer labels tell the makeup and ingredients in the product. This is called the Guaranteed Analysis. The major nutrients reported are nitrogen (N), Phosphoric acid (P2O5) and Potash (K2O), typically referred to as Nitrogen, Phosphorus and Potassium (N-P-K), and they correspond with the three numbers on a fertilizer label (e.g. 4-1-5). It’s always important to read the analysis.

    Nitrogen, the ‘N’ number, can be provided in various forms. The major nitrogen forms in most water soluble or liquid fertilizers are Nitrate (NO3-N), Ammonium or Ammoniacal (NH4-N) or Urea (NH2)2CO. Urea usually converts to Ammonium N in the soil, so most experts consider this an Ammoniacal source of Nitrogen. Plants respond differently to these different sources of N. Nitrate is much slower to assimilate, whereas Ammonium is the more readily assimilated in the plant. Too much Ammoniacal N is not necessarily a good thing, and for indoor growing it is best to have a “balanced’ ratio of nitrate to Ammoniacal Nitrogen or one that is higher in nitrate.

    What a lot of people don’t know is that using fertilizers high in Nitrate (NO3 – N) tends to increase growing medium pH, and high Ammoniacal (NH4 – N) fertilizers tend to decrease media pH. As mentioned, many fertilizers will have both types of Nitrogen in the right proportions so as not to affect the pH of the media. Bear in mind that this process is a slow one, taking weeks or even months.

    The lime charge blended into Sunshine Advanced mixes keeps the pH from dropping too low. Residual lime in media (if lime has been added to the mix at some point after planting) can also counteract the acidic effect of Ammoniacal Nitrogen.

    Choosing the Right Formulations

    Nitrogen is important to crops during their vegetative growth stage. When moving into the flowering and then fruiting stage, the amount of nitrogen can and should be lowered to avoid forcing vegetative growth. Phosphorus (P2O5) is necessary for the development of roots, and as plants mature Phosphorus moves into the flower bud and then into the fruit (seed). The key here is to provide an adequate amount of P. (Adding more P does not necessarily mean bigger or more flowers and fruit!)

    Most fertilizer formulations do not have a higher percentage of phosphorus as compared to Nitrogen or Potassium. In fact, we recommend a low percentage of Phosphorus. This is because the mycorrhizae in the Sunshine Advanced mixes do their best work (extending out into the mix to grab nutrients and water for the roots) when the Phosphorus level is low, providing an adequate amount of P to the plant. We recommend a middle number lower than 10, such as 4-1-5 for vegetative growth, or 1-4-5 for flowering.

    Potassium, usually expressed as K2O (soluble potash), is good for all stages of growth. It is usually added to increase a plant’s resistance to stresses and is essential to the development of chlorophyll. It also is integral in transpiration by regulating the opening and closing of plant stomata, which allows plants to make better use of light and oxygen.

    Secondary Nutrients (such as Calcium, Magnesium and Sulfur) and Micronutrients (such as Iron, Manganese, Zinc, Copper, Boron and Molybdenum) are also included in a good fertilizer, which means that no additional products are needed. You don’t have to break the bank once you find a well-formulated fertilizer. Generally speaking, very clean waters, or using reverse osmosis (RO) water, will usually require a fertilizer containing Calcium and Magnesium. The use of Dolomitic limestone as the liming source in Sunshine Advanced products helps provide needed Calcium and Magnesium.


    It’s always better to under-fertilize rather than over-fertilize. Never make the dilution stronger than recommended on the package. If deficiencies are noted along your growing timeline, have a media analysis done as well as a tissue analysis to get a clear picture of what is going on. Then the correct additional nutrients can be applied. Guessing almost always leads to mistakes!

    Bear in mind that plants get to a point where they can’t take up any more nutrients, and so the fertilizer is wasted. This can also cause problems, such as clubbing and the encouragement of unwanted microorganisms.

    Hopefully, this information will help indoor growers make better decisions when it comes to nutes and growing with Sunshine Advanced mixes. Those looking for even more good information should pick up the reference book Water, Media and Nutrition for Greenhouse Crops, edited by David William Reed. It’s a great resource.

  4. Wet and Dry Mixes: Pro Choices for Hydro Growers

    7106sunshine-mix4-myco-resilience-frontFor years hydroponic growers growing in media were forced to mix their own to create the ideal conditions for rooting. Through trial and error they sought to solve problems related to homemade media that retained too much or too little moisture at the root zone. Some growers sought the perfect mix for moisture retention while others wanted a mix with perfect drainage and aeration.

    The scientists at Sunshine® Advanced formulated two growing media products that take guesswork out of mixing your own wet and dry mixes. Sunshine® Advanced Ultra Coir retains moisture while Sunshine® Advanced Mix #4 with Mycorrhizae is a highly aerated, well-drained media with added mycorrhizae. Now indoor growers can choose the perfect mix for their growing needs.

    perlite-large_03 Sunshine® Advanced Mix #4 with Mycorrhizae uses only the finest peat and coarse perlite, lime, mycorrhizae and organic fertilizer to get your plants off to a good start. It is a premium mix for indoor growing mix that contains a higher amount of horticultural perlite for plants that prefer greater air porosity. By offering excellent drainage, it protects against overly saturated media, while also providing just enough moisture. What’s more, it is boosted with endomycorrhizae and a low phosphorus fertilizer  to better support mycorrhizae establishment and growth.  RESiLIENCE®, has been added, which may improve resistance to wilting.

    9570sunshine-advanced-ultra-coir-resilience-frontFor a drier greenhouse or outdoor growing conditions, Sunshine® Advanced Ultra Coir prevents dehydration that can slow and sometimes even stop growth.  Formulated much like our professional coir-based mixes. It is specifically designed for vegetables, herbs and other consumable plantings and is suitable for both indoor and outdoor growing. It is most recommended for indoor use for crops requiring a lot of water.

    Our soil scientists are devoted to creating media suited to a wide range of growing conditions. They eliminate the time-consuming process of fine tuning your own recipe. Whether you need a great mix for moisture retention or one with perfect drainage and aeration, Sunshine® Advanced has got you covered!

  5. Mycorrhizae and Sunshine Advanced Grow Mixes



    Mycorrhizal root tips (image by Thergathon)

    Mycorrhizae (pronounced My-cor-rye-zay) are fungi that form mutually beneficial relationships with the roots of certain plants. These fungi have mycelium that either grow either inside of a plant’s roots (Endomycorrhizae) or attach to root surfaces (Ectomycorrhizae). Both the fungi and plants benefit. The fungi benefits from the plant’s food and nutrients, and the fungi send out their hyphae (like small roots) out into the surrounding soil to absorb additional nutrients and water, which benefits the plants.

    So, mycorrhizae actually enhance a plant’s ability to take up nutrients and water. Because of this, research has shown that the presence of mycorrhizae helps plants better withstand drought and some diseases. Approximately 95% of the world’s plants have some form of mycorrhizal dependence. As far as growing is concerned, in many cases, increased root and top growth occurs when plants are treated with mycorrhizae. These benefits are not always evident, especially on short term crops, unless the crop is stressed or planted into a landscape where water and nutrients are less available.

    Read the full article »

  6. Give your Garden the Edge with Resilience™ Enhanced Mixes!

    SG  Retail 8 625x11 125 Jan15-page-001

    Sun Gro Horticulture® is proud to introduce Sunshine® Advanced Resilience™ mixes enhanced with silicon.  Available in Sunshine® Advanced Mix #4, Sunshine® Advanced Ultra Coir, Sunshine® Advanced Rain Forest Blend,  and Sunshine® Advanced Super Hydro, Resilience™ is Sun Gro’s brand name for growing mixes enriched with beneficial silicon—a patented technology developed by the company’s own research horticulturists.

    Read the full article »