African Violet Society of America May 31, 2013 Austin, Texas Panel: Barbara Pershing, Cedar Falls, Iowa Joyce Stork, Fremont, Nebraska Carolee Carter, Ocala, Florida
Understanding ph and Soilless Mixes to Grow Better African violets
What is wrong with these plants?
When diagnosing symptoms consider all culture problems Pests cyclamen mite infestations show small, tight, grayish centers. Light too much light will cause centers to become tight, lighter green foliage. Fertilizer too much or too little will affect growth of plant, color of foliage.
Diagnosis/causes of problems with African violets Rule out pests; disease Consider: Changes in environment: temperature, light, humidity Changes / inconsistencies in growing conditions (culture): Fertilizer Water source, quality, ph, method of watering Potting media ingredients, ph, amendments; any changes in the mix - source, components.
Culture break; new growth small; light in color; blossoms small & off color.
Suckering; older foliage dark and brittle
Leaf producing deformed, brittle plantlet.
New growth deformed; brittle leaves; culture break
Culture break; suckering; brittle foliage
Symptoms... Slow, stunted growth Culture break New growth small, light to yellowish green Crisp, deformed center leaf growth Older foliage dark and brittle Few blossoms which are small, off color, deformed Excessive suckering Eventually center growth stops
Potting mixtures may not produce good plant growth due to: Deficiency of essential plant nutrient elements Excessive acidity (low ph) or excessive alkalinity (high ph) Poor physical properties which cause poor drainage (porosity) or inadequate air spaces (aeration) Excess or deficiency of water and air. Source: Emory Leland, AVM, Nov. 1974
Prerequisite for Soilless Mixes Slightly acid 6.5 to 6.9 ph Good drainage and moisture retention Remains loose, porous; does not pack Has the capacity to buffer the ph and hold fertilizer nutrients Free of soil diseases, insects and contamination
Why worry about ph? ph controls all chemistry. ph has no DIRECT effect on plant growth. However, ph affects the form and availability of nutrient elements in irrigation water, fertilizer solutions and the growing medium.
WHAT IS ph? An arbitrary scale of values from 0 (strong acid) to 14 (strong alkaline) with 7.0 as neutral (neither acid or alkaline).
ph scale The ph scale is exponential and indicates the relative strength of the acidity-alkalinity of a substance.
ph Scale One unit change in ph represents a ten-fold change in the acidity or alkalinity A soil of ph 6.0 is ten times as acidic as one of ph 7.0. A soil of ph 5.0 is one hundred times as acid as one of ph 7.0. A ph of 4.0 is 1000 times as acid as one of ph 7.0. 1000x 100x 10x
ph scale comparisons Ideal range for African violets (6.5 6.8) Neutral (7.0)
Everyone who grows house plants should have a general knowledge of ph and how to turn it to his/her advantage.
Why is ph important? ph has a profound influence on many factors associated with plant growth. A slight change in ph is extremely important in its effects on availability of the mineral nutrients in the soil.
African violets require a growing medium of ph 6.5 6.9 in your potting mix/ water/ fertilizer. All essential nutrient elements are available to the plants when the ph of the soil/water/ fertilizer mix is in this range. IF A CORRECT ph IS NOT MAINTAINED, A PLANT CAN VIRTUALLY "STARVE" BECAUSE OF ITS INABILITY TO ABSORB WHAT IS NEEDED.
African Violets Depend on Soil, Water, Fertilizer and Light 16 Elements must be in proper balance Non-fertilizer elements: CARBON (C) from carbon dioxide (CO 2 ) (AIR) HYDROGEN (H) from WATER (H 2 O) OXYGEN (O) from carbon dioxide (AIR)
PRIMARY ELEMENTS Macronutrients From Fertilizer N = NITROGEN = GREEN LEAVES; needed for photosynthesis P = PHOSPHORUS = LARGE, NUMEROUS BLOSSOMS; needed for growth and development of all parts of plant K = POTASSIUM = ROOT DEVELOPMENT; promotes vigor; resistance to disease
SECONDARY ELEMENTS From Soil Sulfur from organic matter, decomposition of peat Calcium from dolomite lime Magnesium from dolomite lime
MICRONUTRIENTS Trace elements needed in small amounts from fertilizer Iron Zinc Boron Chlorine Copper Molybdenum Manganese
ph affects availability of Plant Nutrients Micronutrients Microorganisms The width of the bars indicates the ease with which an African violet s roots can absorb nutrients at different ph readings.
Beneficial Microorganisms To encourage a high microorganism population, a potting mix must: Have the ph in 6.0 to 7.5 range. Be porous and well aerated. Have adequate supply of organic matter. Moderately warm temperature in potting mix. Potting mix must be moist. Too wet or too dry greatly reduces microorganism population.
Micronutrients The availability of micronutrients is affected by other micronutrients and macronutrients in soilless mixes. The availability of micronutrients (Boron, Manganese, Copper, Iron, Molybdenum and Zinc) are reduced by high levels of phosphorus in the 6.5-6.9 ph range but are available in toxic amounts when phosphorus is locked up and unavailable below 6.5 ph.
ph and African Violets 5.0 5.5 6.0 6.5 6.8 6.9 7.0 7.2 MICRONUTRIENT TOXICITY PHOSPHATE LOCK-UP PLANT GROWTH SLOWS LESS BLOOM CULTURE PROBLEMS IDEAL ph FOR AFRICAN VIOLETS N E U T R A L IRON CHLOROSIS When the ph is below 6.0 and above 7.2, many important nutrients become locked up in the growing medium and the roots are unable to extract them for the plant s use. Nutritional starvation develops in the plants.
ph below 6.5 African Violets begin to develop micronutrient toxicity when the ph of the soilless mix is below 6.5. 5.0 5.5 6.0 6.5 6.8 6.9 7.0 7.2 MICRONUTRIENT N TOXICITY PLANT IDEAL ph FOR GROWTH AFRICAN SLOWS VIOLETS PHOSPHATE LOCK-UP LESS BLOOM E U T R A L IRON CHLOROSIS CULTURE PROBLEMS
ph below 6.0 Symptoms may not become obvious or severe until the ph is below 6.0 for a period of time. 5.0 5.5 6.0 6.5 6.8 6.9 7.0 7.2 MICRONUTRIENT TOXICITY PHOSPHATE LOCK-UP PLANT GROWTH SLOWS LESS BLOOM CULTURE PROBLEMS IDEAL ph FOR AFRICAN VIOLETS N E U T R A L IRON CHLOROSIS
ph and toxicity Some varieties show symptoms earlier; variegates appear to be the first to show symptoms of toxicity. 5.0 5.5 6.0 6.5 6.8 6.9 7.0 7.2 MICRONUTRIENT TOXICITY PHOSPHATE LOCK-UP PLANT GROWTH SLOWS LESS BLOOM CULTURE PROBLEMS IDEAL ph FOR AFRICAN VIOLETS N E U T R A L IRON CHLOROSIS
ph and phosphorus lock-up Phosphorus becomes locked up allowing micronutrients to accumulate in toxic amounts in the cells of the plant. 5.0 5.5 6.0 6.5 6.8 6.9 7.0 7.2 MICRONUTRIENT TOXICITY PHOSPHATE LOCK-UP PLANT GROWTH SLOWS LESS BLOOM CULTURE PROBLEMS IDEAL ph FOR AFRICAN VIOLETS N E U T R A L IRON CHLOROSIS
ph and soil bacteria Soil bacteria are less abundant below 6.0 ph. Soil bacteria changes fertilizer into nitrogen form that plants can use. 5.0 5.5 6.0 6.5 6.8 6.9 7.0 7.2 MICRONUTRIENT TOXICITY PHOSPHATE LOCK-UP PLANT GROWTH SLOWS LESS BLOOM CULTURE PROBLEMS IDEAL ph FOR AFRICAN VIOLETS N E U T R A L IRON CHLOROSIS
ph above 7.0 African Violets also develop toxicity at ph above 7.0 but because of the acidity of the peat this rarely occurs. 5.0 5.5 6.0 6.5 6.8 6.9 7.0 7.2 MICRONUTRIENT TOXICITY PHOSPHATE LOCK-UP PLANT GROWTH SLOWS LESS BLOOM CULTURE PROBLEMS IDEAL ph FOR AFRICAN VIOLETS N E U T R A L IRON CHLOROSIS
Cause of Micronutrient Toxicity 5.0 5.5 6.0 6.5 6.8 6.9 7.0 7.2 MICRONUTRIENT TOXICITY PHOSPHATE LOCK-UP PLANT GROWTH SLOWS LESS BLOOM CULTURE PROBLEMS IDEAL ph FOR AFRICAN VIOLETS N E U T R A L IRON CHLOROSIS When phosphorus is deficient and "locked-up" below 6.0 and above 7.0, micronutrients accumulate in excessive amounts in the cells of the plant. Micronutrient toxicity occurs when this accumulation of excessive levels of trace elements are absorbed into the cells of the plant over time.
PREVENTION IS ESSENTIAL African violets do NOT grow out of toxicity. All cells in the plant are affected. Suckers develop but do not root or thrive. Leaves do not produce healthy plantlets.
Prevention Understand soilless mix ingredients. Learn how to test the ph of soilless mixes and water. Check the ph of the mix before you use it.
ph of Water ACID ALKALINE 6.0 6.5 7.0 7.5 8.0 RAIN WATER WELL WATER REVERSE OSMOSIS CITY WATER NEUTRAL
Know the ph of the water you use on your plants Well water ph is usually alkaline; depends on where you live If alkaline (7.0-7.9) it will add to the buffering of the peat Hardness dissolved calcium and other minerals Rain water often slightly acid; no ph buffering Reverse osmosis water usually neutral or slightly acid; will remove all/most minerals; will not buffer ph of peat Municipal water check with city water department for ph and chemicals; will contain chlorine; may contain chloramines Distilled water neutral; contains no minerals; nutrients
Water testing Well water can be taken to an independent testing laboratory for analysis. In addition to testing for various chemicals and bacteria, a test for alkalinity (CaCO3) and an accurate test for ph is available. Check with the local city or rural water company for information on ph and alkalinity of the water and water treatments.
Alkalinity of water Do not confuse alkaline water (presence of minerals in the water) with alkalinity (ph above 7.0). Alkalinity is the concentration of soluble compounds including calcium, magnesium and sodium bicarbonate in the water that have the ability to neutralize acids. Do not use too much dolomite lime in your mix (more is not better!) and adjust the amount of dolomite if your water is alkaline. Alkaline water (well water) can raise the ph to toxic levels; this rarely occurs with peat-based soilless mixes.
Alkalinity and ph of Water Alkalinity is related to ph, because water with high alkalinity has a high "buffering capacity" or capacity for neutralizing added acids and has a big effect on potting mix ph. Alkalinity can be thought of as the "liming content" of water; alkaline water and limestone react very similarly when added to a potting mix. Do not use too much dolomite lime in your mix (more is not better!) and adjust the amount of dolomite if your water is alkaline.
Iron deficiency May occur at or above ph 7.2. Symptoms light green or white foliage. May first be noticed with plantlets and plants in small containers. Iron is needed for photosynthesis and may be locked up and unavailable to plant.
ph of Potting Mix Ingredients 0.0... 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0.... 14.0 ACID ALKALINE CANADIAN SPHAGNUM PEAT MOSS IDEAL ph FOR POTTING MIX NEUTRAL PERLITE VERMICULITE HORTICULTURE CHARCOAL DOLOMITE LIME
What is a soilless potting mix? A mixture of Canadian sphagnum peat moss, perlite, vermiculite and dolomite lime with other ingredients added.
A good soilless potting mix must: Drain rapidly and also have good water and air-holding characteristics, Be slightly acid 6.5 to 6.9 ph, Remain loose, porous; does not pack, Have the capacity to buffer the ph, Have the ability to hold the fertilizer nutrients and release them gradually as the plant is actively growing, and Be free of soil diseases, insects and contamination.
1947 Soil Recipe A soil formula: ( Mrs. Keller) 3 parts good black soil (gumbo) 1 part peat 1 part compost (about half manure) 2 parts sand To 1 bushel of this soil mixture add: 1 six-inch pot full of superphosphate 1 gallon of wood ashes containing bits of burnt wood or charcoal.
Cornell Mix Developed in the 1960s for commercial use at Cornell University. Two soilless media, sometimes called artificial soils, were developed through research at Cornell. These media have sphagnum peat moss and horticultural vermiculite and/or perlite as its main ingredients. Most soilless commercial mixes use the Cornell peat-lite mix as their base.
Commercial Peat-lite mix components Peat, vermiculite, perlite basic mixes Douglas fir bark, fine ground Ground dolomite limestone Wetting agent/surfactant Fertilizers Micro-organisms
Commercial soilless mixes Mixes differ in ingredients read labels. Mixes vary in different parts of the country. There are no standards for potting mixes. One test of 5 commercial mixes found ph of 5.0, 5.1, 5.6, 6.1 and 6.7. Buy quality products from local nurseries; buy what they use. ALWAYS TEST the ph BEFORE USING!
Soilless mix for African violets Cornell peat-lite recipe adapted to African violet mix recipes Most common adaptation: 1 part peat 1 part vermiculite 1 part perlite Dolomite lime to adjust the ph
SOIL(LESS) MIXTURE RECIPE 16 quarts Canadian sphagnum peat moss 8 quarts coarse vermiculite 8 quarts coarse perlite 8 tablespoons dolomite lime (to get ph of 6.5 to 6.9) 2 cups horticulture charcoal Mix thoroughly; add 2 cups hot water and mix again. For a lighter mix use equal parts peat, perlite, and vermiculite plus charcoal and dolomite lime. (Source: Marie Montague, African Violet Magazine, July/August 2005, p. 27)
Criteria to consider for ingredients in a potting mixture: Effective in producing good drainage and aeration Low in soluble salts Readily available in uniform grade Economical Capable of retaining moisture and nutrients to meet plant requirements Light in weight Easily incorporated into mixture Acceptable ph
Organic Ingredients Sphagnum Peat moss Spongy, fibrous texture, high porosity and waterholding capacity Low ph (ranges from 3.5 to 5.0) Decomposes; becomes more acid over time Base of most soilless mixes for African violets Canadian peat high quality; lighter the color the better the quality
Organic ingredients (continued) Coconut coir Derivative of coconut hulls; good water-holding capacity Has natural wetting agent; mix stays wet; add more perlite ph ranges from 5.5 to 6.5 Composted pine bark Finely ground Douglas fir bark; widely used in commercial media Native soil, garden or clay loam; leaf mold Not recommended must be pasteurized/sterilized Contains microbes; adds weight; compacts
Horticulture Charcoal Neutral ph (7.0) Used in soil mixes for drainage and to keep the soil and water fresh Has capacity for absorbing and holding nitrogen until plants can use it Varied opinions as to its usefulness in mixes
Inorganic ingredients Perlite Vermiculite Styrofoam beads Coarse Sand Horticulture charcoal Lime
Perlite Alumino-silicate volcanic material heated to 1800 F; explodes into closed, irregular cellular structures Adds space to mix for water retention; aeration; porosity; weight and density 75% porosity ph 7.0 to 7.5; has no buffering capacity Main use in mix improves drainage and allows water entry into mix
Vermiculite Manufactured from crushed mica ore, expanded by intense heat. ph varies from neutral (7.0) to alkaline (9.5). Will affect ph of the mix. 80% porosity holds lots of water Improves soil aeration while retaining moisture. Absorbs and fixes phosphate; holds fertilizer; makes it available to roots. Use coarse horticulture grade.
Inorganic ingredients (continued) Styrofoam Beads (Polystyrene Foam) Inexpensive substitute for perlite Helps aerate potting mixes and serves as space filler Lightweight; tend to float to surface Low density; high water capacity Neutral ph Lava Sand Source is volcanic slag; texture - full of holes; Increases water-holding capacity of mix Has the ability to make soil nutrients more available to plant roots Coarse Sand Not recommended for mixes for African violets
Dolomite Lime Calcium magnesium carbonate this is a big deal in soilless mixes. ph of 9 Buffers ph of peat Add to soil mix to adjust the ph higher Fine, powdery consistency (like gray flour) Dissolves rapidly; goes to work right away
Lime Agricultural Limestone Same chemical composition as dolomite lime Dissolves very slowly. May not affect the PH significantly until later; hard to determine ph of soil prior to use. Hydrated Lime DO NOT USE dissolves rapidly, leaches out May burn the roots.
Organic nutrients Worm castings Improve soil structure; improve aeration; drainage Provide Nitrogen, Potassium, Calcium, Magnesium, Iron and other trace minerals 100% natural; slowly release nutrients Not quickly soluble and has good residual; long term nutritional value Has high concentration of beneficial bacteria and microbes
Microorganisms Microorganisms require mix of ph 6.4-7.5 Mycorrhizal fungi A root bio-stimulant that increases the number of fine feeder roots a plant utilizes to take in nutrients. Natural bacteria Helps intake of nutrients by the roots All natural plant food 4-3-3
Organic fertilizers Bone meal (ph 6.8) Provides nitrogen and phosphorus Blood meal (7.4) Organic source of nitrogen and phosphorus
Nutrients commercial fertilizers NPK plus trace elements Superphosphate
ph testing Test strips Digital ph meters
ph test strips Phion Diagnostic ph Test Strips 4.5 to 9 Amazon.com $9 for 80 phydrion Vivid 5.5 to 8.0 Ph Test Strips Dispenser -.25 Intervals ph Test Strips -.25 increments 100 for $12 Online search for ph test strips Select strips with.25 intervals.
Using ph Test Strips Put 1-3 tablespoons of potting mix into glass container. Add distilled water. Stir vigorously for one minute. Let stand for at least 30 minutes. Filter soil using a coffee filter. Insert test strip into filtered solution. Compare color to the color chart provided with the strips.
Pour Thru Soil ph Test for container plants Ensure that plant has been watered several days ahead so it is moist, but not saturated. Pour a volume of distilled water (1/4 to 1 cup depending on size of the pot) through the pot, collecting what runs out. Wait 30 minutes to 2 hours. Measure the ph of this water using ph test strips or meter.
Slurry method Combine a 1:1 ratio of soilless mix and distilled water in a clean glass container. Mix well and let stand 30 minutes. With a digital electronic meter, the measure can be made directly in the slurry. For test strips, filter the mixture using fine mesh, cheese cloth or coffee filter and measure the ph of the filtered solution.
Digital meters Will not test water or loose, moist or dry mix. For moist, compact soil only. Can be used to check ph of mix in potted plants and garden soil. About $16 at garden centers or online.
Electronic ph testers Oakton Waterproof phtestr 10 $96.00 from Cole-Palmer.com (Model - YO-35634-10 )
Checking my recent mix Peat in distilled water @ ph 4.2 Vermiculite in distilled water @ 7.7 ph Well-water @7.6 ph Potting mix ¼ cup - 1:1:1 (3 qts. each peat, perlite, vermiculite) + 4 T. dolomite + ¼ cup well-water @ 6.7 ph YEA!!