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Articles by Dr. Francis Gouin

Catch Phytophtora quick and save the plant

A Bay Weekly reader recently complained that her magnificent large rhododendron was dying after it had produced a super abundance of blooms this spring. After examining the plants closely, I knew that the cause of death was Phytophtora cactorum. This disease is often the primary cause for rhododendron dieback. It kills the plants starting at the ends of the branches, and works its way down the stem. If you can prune out the dying branches as soon as you spot it, you can often salvage the plant.
    To identify the disease, look for chestnut-brown sunken cankers surrounding the stem immediately beneath the wilting flower. The stem just beneath the wilted flower or seed head will be green, but the lower part of that stem, where it had grown from the previous year’s stem, will be chestnut brown. You will note that the diseased stem originated near the stem that flowered the previous year.
    The disease-causing fungi entered the stem as the old flowers wilted and dropped. Sometimes one or two branches are first affected. When this occurs, prune away the branch as close to the main stem as possible, sterilizing your pruners with rubbing alcohol between each cut. To prevent the disease from spreading, spray the plants with a mild fungicide such as Phaltan or Captan as the blossoms begin to wilt. However, fungicides are only a temporary protection.  
    The occurrence of this disease has been associated with low levels of magnesium in the soil. If you have rhododendrons that exhibit any signs of dieback, I strongly recommend you have the soil tested.
    When taking soil samples from around shallow-rooted plants such as azaleas and rhododendrons, only sample from the upper three inches of soil. Ninety percent of roots from shallow-rooted species grow in that layer. Soil samples should be taken between the drip line of the branches and the trunk of the plant. Scrape away mulch before sampling.
    Where this disease has been a problem, I recommend applying Epsom salts at the rate of one-half cup dissolved in two gallons of water and applied over 100 square feet. Apply every spring just before the plants start blooming.
    To my knowledge, there are no rhododendron varieties that are immune to this disease. The best protection is frequent inspection of the new stems, pruning out diseased branches using sterile pruners, spraying infected plants as the blossoms are wilting and falling and proper nutrition following soil testing by a reputable lab such as A&L Eastern Agricultural Lab.


Ask Dr. Gouin your questions at DR.FRGouin@gmail.com. Please include your name and address.

Mountain laurel, blueberries and other acid-lovers, too

September is the best time of the year to transplant azaleas, rhododendrons, mountain laurel, andromeda, blueberries and other plants that thrive in acid soils. This is because these species have stopped growing new stems and leaves and are starting to generate and elongate roots.
    So take advantage of fall garden center sales. If your existing plantings are too dense or wrongly placed, now is a good time to dig and transplant.
    Here’s how to assure success in transplanting plants that prefer acid soils.
    First, make certain that the soil you will be transplanting into is adequate.  Acid soils are generally deficient in calcium and magnesium, but only a soil test of the area will correctly identify soil conditions. Each soil test should be made from a composite of five or more core samples. I rely on A&L Eastern Agricultural Laboratories in Richmond for all of my soil testing. 
    Plants like these also need well-drained, high-organic soils. Even if the soil test indicates an ample amount of calcium, I make it a regular practice to mix one-half cup gypsum (calcium sulfate) to the planting soil. To assure an abundance of organic matter, I also blend one-third by volume of compost or pine fines with the existing soil while blending the gypsum with the backfill. Compost adds not only organic matter but also slow-release nutrients.
    Never amend the soil with peat moss, especially when transplanting rhododendrons. Peat moss holds too much water, making conditions favorable for water-borne fungi that attack the roots of rhododendrons.
    All species that grow in acid soils are shallow-rooted. So never dig the planting hole deeper than the depth of the root ball. There is no need to place compost or back-fill under the root ball because of the shallow-rooting nature of these species.
    If you are digging plants that need more space to grow, the outside edge of the root ball you are digging should begin mid-distance between the drip line of the branches and the stem of the plant. If the soil is dry, irrigate the plant well at least two days before you dig.
    After digging, lift the plant by the root ball and not by the stem. If you are transplanting container-grown plants, after removing the plant from the container, use a sharp knife and slash the outside edge of the root ball an inch deep from top to bottom making the slashes two to three inches apart. Since most container plants are grown in soilless rooting media, slashing the root balls and pulling out some of the roots will hasten new root development.
    The top of the root ball should be visible at the surface of the finished grade. Before mulching, water the plants thoroughly to settle the backfill around the roots and eliminate air pockets. A good heavy watering helps to firm the soil in place.
    Apply no more than one inch of compost or pine bark mulch. Never use hardwood bark mulch because it is basic in nature and contains high levels of manganese.
    Azaleas, rhododendrons, mountain laurel, andromeda, blueberries and other acid-lovers will tolerate light to medium shade, but they will produce more flowers and be more cold-tolerant in full sun. In commercial nurseries, all of these species are grown in open fields and sometimes covered with light shade in late fall simply to give the plants a better appearance for sale in the spring.


Ask Dr. Gouin your questions at DR.FRGouin@gmail.com. Please include your name and address.

It’s a little late to start seeds but just right to plant seedlings

The best sauerkraut is made from fall-grown cabbage. The best kale and collards have been frosted a few times, growing sweeter with each frost. Fall-grown spinach and lettuce are more tender. Carrots, beets, turnips, rutabaga and kohlrabi are at their best when grown in late summer and harvested in the fall. Both cauliflower and broccoli form tighter heads in fall than in spring. I also harvest many more fall peas than spring peas. If you love Brussels sprouts as much as I do, you must get them started now to harvest a bountiful supply.
    There is more gardening ahead, and now is the time to start sowing seeds. If you planted onions this past spring, they should all be harvested by now — as well as the cabbage, broccoli, cauliflower and spinach. So you now have room to start planting your fall crops.
    I have stopped planting peas in the spring because I can make many more harvests from peas planted in August. The cooler fall temperatures promote continuous growth until the killing frost comes late in fall. Spring-planted peas stop producing pods as soon as the heat comes on.
    August is also a good time to make a planting or two of snap beans. If you make two consecutive plantings about two to three weeks apart, you will be harvesting snap beans until the frost kills the plants.
    If you sowed your seeds of broccoli, cauliflower, kohlrabi, Brussels sprouts and cabbage the first week of August, the plants will be ready to be transplanted into rows by the end of the month. Seeds of spinach, lettuce, kale, collards, turnips and rutabaga should have been sown by mid August. To grow the sweetest carrots this side of heaven, the seeds should also have been planted before the middle of August, as should a row of beets for greens as well as for the sweetest roots.
    If you haven’t started your seeds, check the garden centers for seedlings of these cool-weather crops.
    Your soil most likely still holds a plentiful supply of nutrients not utilized by the remaining summer crops. Since the soil is warm, the compost you added to the garden is also releasing nutrients. A fall crop allows you to maximize the uptake of the nutrients already added as well as those released during the decomposition of organic matter.
    If you are not going to plant a fall crop, sow a cover crop of winter rye to absorb all of those free nutrients into their roots and stems. Next spring when you plow the rye back into the ground, the nutrients will be there for that crop.


Ask Dr. Gouin your questions at DR.FRGouin@gmail.com. Please include your name and address.

Gardening in bales of straw

     As I prepare my fall garden, I’m walking in the footsteps of an Ohio gardener with poor soil who planted in bales of straw rather than install raised beds. He found his solution in a British gardening magazine on growing vegetables. Now I’m trying it, starting with four bales of straw that I placed in full sun along the edge of my vegetable garden.
    To minimize weed problems, use straw rather than hay. Straw is the residue after the grain has been harvested. Select bales tied with plastic string and not sessile. Both sessile and jute string will decompose and the bales of straw will fall apart. Those tied with plastic string will remain whole because plastic does not decompose. Place the bales of straw on either black plastic or non-woven geotextile ground cloth.  
    Before planting, prime each bale to initiate the composting process. Spread two and a half cups of high-nitrogen lawn fertilizer — not mixed with herbicide — over each bale. For organic preparation, spread three pounds of organic fertilizer over each bale. Next wet the bales thoroughly and insert a long-shank thermometer to monitor temperature changes within the bales. The fertilizers will initiate composting in the center of each bale, raising the temperature. Sprinkle the bales with water daily to keep them moist so composting will take place. When temperatures again equal ambient air, the bales are ready to be planted.
    Within five days after I applied the fertilizer on each bale, temperatures within the bales fertilized with Holly Tone Organic reached 120 degrees. The bales treated with 10-6-4 fertilizer increased to only 100 degrees. It took nearly three weeks for these bales of straw to achieve the Holly Tone temperatures.
    By the end of the third week of priming, the bales treated with Holly Tone Organic started producing inky-cap mushrooms; the bales treated with chemical fertilizer followed one week later.
    At the end of the fourth week of priming, temperatures dropped to between 95 degrees and 100 degrees in all of the bales of straw.
    When the internal temperatures are the same as the ambient air, I will plant the bales with broccoli, cauliflower, Brussels sprouts, kale and collards. My Ohio model claims to obtain at least two years of growth, sometimes three, from each bale.
    Regardless of the results, I will write about this new method of growing vegetables and share my results and photos. I write now in hopes that you will also try so that we can compare results.
    As my dad always said, “You will never know until you try.”

Outmaneuvering Stem Borers in Zucchini
    Every year, readers complain that stem borers have killed their zucchini plants only after a few weeks of production. I have had the same problem. To enjoy zucchini for most of the summer, I make repeated plantings.
    I’ve tried with no success spreading wood ashes around each hill as recommended by organic gardening magazines. I’ve had moderate success spraying under the foliage with the insecticide Sevin starting as soon as the leaves appeared and repeating weekly.
    This year I sprayed only the stems — not the leaves or petioles — with a jet stream of Sevin, starting under the flower bud farthest away from the roots. I am still harvesting zucchini squash from the original planting with no sign of borer injury. Protecting the stem with Sevin keeps the borer from gaining entry.  
    This year’s succession of plantings resulted in a surplus harvest, which I take to the SCAN food bank at St. James Episcopal Church on Rt. 2.

How to stop the Japanese beetles that cause the problem

     If you have brown patches in your lawn, I expect the cause is Japanese beetle grubs eating the roots of the grasses. Japanese beetles are out in full force, feasting on roses, linden trees and other favorite ornamentals, as well as puncturing and eating peaches, raspberries, blackberries and plums. Soon those same beetles will be landing on your lawn and depositing eggs in the earth. When those eggs hatch, hungry young larvae will begin feeding until fall when the soil cools and they burrow deeper in to survive the winter. Next spring those same larvae will crawl up closer to the roots of your lawn and resume feeding until they pupate and emerge as adults. The larvae are light gray with brown heads and curl into the letter C when disturbed.
    The brown patches you are now seeing are from last year’s larvae that survived the winter.
    Back when we lived in College Park, we did not have Japanese beetles. That’s because College Park was ground zero for the research that resulted in the development of the milky spore system of Japanese grub control. The developer was Dr. George Langford, chairman of the Department of Entomology. To test the effectiveness of the system, in the mid-1950s he treated all of the lawns within the city limits. A single treatment was highly effective.
    When Clara and I moved to Deale in 1990, the lawn was full of mole tunnels. Moles love to feast on. Realizing the mole problem was due to a large infestation of Japanese beetle grubs, I treated the entire lawn with milky spore powder the summer of 1991. It took three years before I had 100 percent control. I have never had to repeat the treatment. Japanese beetles are flying around and feasting on our little leaf linden, and they are laying eggs in my lawn, but the milky spore is digesting the larvae as they hatch. The milky spore system of control is self-supporting once it becomes well established. It has now been almost a quarter century since I first used milky spore, and I no longer have moles tunneling nor dead brown spots in my lawn.
    True, there are insecticides you can spread on your lawn that will kill the grub, but these insecticides have to be redone yearly. The use of them on lawns can also contribute to the pollution of the Bay. If you live near the Bay or its tributaries, do not use these insecticides; to be effective, they must be applied over the entire lawn.
    Milky spore is available in two forms, powder or granular. The powdered form is measured using one-quarter teaspoon at three-foot intervals. The granular form is applied using a spreader. One bag of granular milky spore will cover approximately 7,000 square feet. Milky spore must be thoroughly and promptly soaked into the soil soon after being applied. Applying it just before a predicted heavy rain is best unless you have an in-ground sprinkler system that covers the entire lawn.
    Milky spore can be used in the spring, summer or fall, but now is the best time because this is when the Japanese beetles are laying their eggs.
    Milky spore is a good, safe and effective grub control system, but it cannot be used in conjunction with any of the other harsh insecticides recommended for grub control. Having Japanese beetles laying eggs in your lawn every year keeps the milky spore population alive and well.

Organic matter adds ­hidden benefits to soil

Addition of organic matter does great things for soil. It works as a slow-release fertilizer and source of essential nutrients. It reduces the density of heavy silt and clay loam soils. It improves soil’s nutrient retention and increases water retention. All of these benefits redound to plant growth.

Retention of nutrients
    Adding organic matter to soils increases the retention of nutrients and makes them available to the roots of plants. This process is known as increasing the cation-exchange capacity of soils. You learned in the July 24 column how organic matter releases nutrients slowly through mineralization. In addition to supplying the major elements, compost supplies trace elements such as boron (B), iron (Fe), zinc (Zn), manganese (Mn), sulfur (S) and copper (Cu). These essential trace elements are important to the growth of healthy plants and to the quality of the crops they produce. But they’re not part of commercial fertilizer mixes.
    Increasing the cation exchange is especially important in sandy loams or loamy sands. Nutrients leach through these sandy soils quickly. Because sandy soils are well aerated, they do not retain organic matter. So to maintain productivity on sandy soils requires frequent applications compost or animal manure and the use of cover crops.
    On sandy loams or loamy sands, use no more compost or manure than six cubic yards per 1,000 square feet for the initial application. On silt or clay loam soils, make that four cubic yards as these soils are better able to retain nutrients than sandy loams or loamy sands. Repeated applications should be one-half or one-quarter.
Water-holding Capacity
    The addition of organic matter to sandy soils increases water-holding capacity.
    The addition of organic matter to heavy silt or clay loam soils increases water infiltration, thus increasing their ability to retain water while at the same time allowing excess water to drain.

Soil Density Reduction
    It won’t work to use sand to improve the drainage of heavy silt or clay loam soils. Short of 55 to 60 percent, the addition of sand will only result in making the soil like concrete.
    Adding 10 percent compost will increase both the organic matter concentration and the productivity of heavy silt or clay loam. Pine fines are one of the better organic materials to use to lighten heavy soils. Pine fines are a waste product from the manufacturing of pine bark mulches. Because pine fines contain high levels of lignins — a source of organic matter that resists decomposition — pine fines will persist in the soil for a long time.

Disease Control
    Another hidden benefit of amending soils with compost is its ability to control soil-borne diseases. Quality compost contains three naturally occurring fungicides and numerous beneficial microorganisms known to control common soil-borne diseases as fusarium, pythium and rhizoctinia. To get this bonus, use recently made compost. As the compost ages, these benefits are gradually lost as the biological activity of the compost decreases.

Lesson 3: Jumpstart your garden with compost tea

     Your organic garden will need a jumpstart. Organic gardening relies entirely on the release of nutrients from the decomposition of organic matter and the bodies of the microorganisms that digest the organic matter in the soil. In cold soils, nutrients are not readily available.
    Room temperature — a consistent 72 degrees — is the starting point for analyzing the situation. With 72-degree soil temperature, the rate of the mineralization of organic matter is approximately eight to 10 percent. If the soil contains three percent organic matter, it releases 24 to 30 pounds of nitrogen per acre per year. Producing a respectable crop takes between 80 and 100 pounds of nitrogen per acre.
    In summer, when soils are at room temperature and above, it takes a soil with five to 10 percent organic matter to produce a respectable crop. Even if soil temperatures increase above 72 degrees, the mineralization rate increases only a few percentage points. To grow a crop in soils containing less than five percent organic matter, you’ve got to add organic fertilizers, including compost. As the microorganisms that digest the carbon of the organic matter die, the minerals in their bodies and in the cells of the organic matter are released.
    The cooler the soil, the slower the process. Mineralization of nutrients from organic matter stops when the ground freezes. In spring, the mineralization rate of organic matter is not nearly up to summer’s eight percent. Even if the soil contained five to 10 percent organic matter, it would not supply sufficient nutrients to grow early spring crops such as cabbage, broccoli, cauliflower, celery and lettuce.
    Traditional agriculture uses starter fertilizers with early spring transplants. Starter fertilizers are made of water-soluble minerals that are instantly available to the roots of plants, regardless of soil temperature. Applying these fertilizers near the roots of new transplants helps establish them quickly in the soil and resume normal growth. 
    Compost tea can be used as starter fertilizer. Brew the compost tea at room temperature three or four days prior to transplanting. Partially fill a five-gallon pail up to half capacity with mature compost. To assure maturity, I strongly recommend using commercial compost. Top with water and stir vigorously. Stir the compost three or four times daily to provide adequate aeration for nutrient release from the compost. Or you can aerate the compost using an aquarium air filer as a substitute.
    When you transplant three or four days later, irrigate each plant with one to two cups of compost tea.
    A second batch of tea can be made using the same compost by filling the pail again with water and repeating the process. The second batch will not be as concentrated as the first unless you allow a week or more for it to release its nutrients into the water.

Part 2: How to supply nutrients organically

     In organic gardening, all nutrients are supplied through the process of mineralization. As organic matter is decomposed by the microorganisms that digest the cellulose and hemi-cellulose, minerals contained within the cells of the animal or plant tissues are released into the soil. After the microorganisms have digested all digestible cells, they die. Since their bodies consist mostly of proteins, the proteins are broken down by enzymes, releasing more nutrients, mostly nitrogen (N), into the soil. 
    The rate of mineralization is dependent on temperatures in the soil.
    Under laboratory conditions, mineralization rates are measured at room temperature, 72 degrees. Moist soil samples are held in temperature-controlled containers for several days, then the amount of available nitrogen in the soil is measured. This process is repeated until the figures are stable. Mineralization rates are faster at temperatures above room temperature and significantly slower at temperatures below room temperature. At 72 degrees, the mineralization of compost is between eight and 10 percent. Mineralization of organic matter stops when soil temperatures approach the freezing point.
    The rate of mineralization has a major effect on plant growth.
    Because soils are cooler in the early spring, the rate of growth is often reduced for early spring crops such as peas, cabbage, broccoli, cauliflower, lettuce and spinach. Cooler soils mean fewer nutrients becoming available. This problem can be minimized by selecting south-facing slopes for early spring and late fall crops. Planting the crops on ridges is another method of encouraging early warming of soils. A soil raised above a natural grade warms faster than a soil that is level on grade. Covering the area to be planted with a sheet of clear polyethylene several weeks before planting, followed by ridging and covering the ridges with black plastic mulch, is labor intensive but will stimulate early mineralization. Soils warm very rapidly under clear plastic due to the greenhouse effect. However, anticipate early growth of spring weeds, requiring light cultivation or spraying with horticultural vinegar. Ridging and mulching with black plastic will also provide weed control.
    Apply no more than four cubic yards of compost or animal manure per 1,000 square feet in any one year. Five percent is one year’s limit for organic matter added to the soil. Excessive applications of either can stimulate excessive vegetative growth and weak spindly plants. With the mineralization rate eight to 10 percent, 90 to 92 percent of the minerals remain in the soil’s organic matter. So repeated applications of compost and organic matter should be based on soil test results.
    If existing soils contain less than three percent organic matter, an initial application of four cubic yards of compost or animal manure the first year followed by repeated applications at two cubic yards in successive years (or on alternate years for sandy soils) can be adequate. In silt or clay loam soils, these levels may be excessive, requiring greater dependency on soil test results.
    Initially, compost or animal manure should be incorporated to a depth of six to eight inches, deeper if possible. Because organic matter reduces the bulk density of soils, deep incorporation promotes deep rooting, making crops more tolerant to drought. As deep incorporation of organic matter promotes deep rooting, the roots that penetrate this region will continue to maintain the organic matter concentration in that region.
    Repeated applications of compost or animal manure should be incorporated only in the upper three inches of soil. This results in concentrating the nutrients in the region where seed germination occurs and where roots of new transplants initiate growth. Leaching will move nutrients deeper into the soil as the growing season progresses.

Lesson 1: From the ground up

     Organic gardening is a science based on being able to supply nutrient needs and ideal growing conditions that will produce healthy plants that can resist diseases and pests. Fruit and vegetables free of pesticides are considered healthier because they are untouched by man-made chemicals with the potential to cause health problems.
    Success in growing plants organically begins with selecting land that can generate ideal growing conditions. Site and soil are of utmost importance. Establishing an organic garden on a slight slope facing south gives you soil that warms more rapidly in the spring and stays warmer in the fall than soil on a northern slope. A warmer soil will release nutrients from organic soil matter faster. Sandy soil will warm faster than silt or clay soil because there is less water present and the soil is denser. However, during drought, sandy soils will need supplemental irrigation and/or mulch to satisfy the water needs of the plants.
    Full sun also helps warm the soil, enabling the release of nutrients from organic matter and maximizing ­photosynthesis.
    Well-drained soils are essential to promote deep rooting of plants and early warming of soils. Avoid poorly drained soils. Good air drainage is essential for the rapid drying of foliage to minimize disease problems.
    Since the organic content of the soil is the primary source of nutrients for plants, the pH measurement of soil acidity should be monitored by regular soil testing at three-to-five-year intervals. Soil testing is also a guide to maintaining optimum levels of nutrients such as calcium (Ca) and magnesium (Mg) and to prevent phosphorus (P) and manganese (Mn) from accumulating in excessive amounts.
    The organic garden thrives on organic matter. To be successful, you need to increase the organic matter of the soil to five percent and above. For every percent of organic matter present in soils, 10 pounds of nitrogen (N) is generated per acre per year through a biological process known as mineralization. To obtain optimum yield, you must maintain the organic matter content of the soil at between five and 10 percent. Maintaining levels of organic matter concentration above five percent requires yearly applications of organic matter. Good sources include compost, animal manure and organic fertilizers such as fish emulsion, cotton seed meal, bone meal and compost tea.
    In choosing seeds, the organic gardener seeks varieties with vigorous growth characteristics and disease resistance. In planting, avoid over-crowding, which increases competition among plants for sunlight and moisture. Crowded plants are more susceptible to diseases because they tend to be weak and their foliage is likely to remain wet for prolonged periods of time.
    Healthy plants are more resistant to diseases than weak plants. However, healthy plants are equally susceptible to insect damage, though they are better able to tolerate limited plant damage before significantly reducing yields.

Can the Bay Gardener solve it?

About 30 years ago, I began to build up my garden with compost and leaves. Every few years, I would gather and put down about three feet of leaves to rot and be tilled into the 50-by-50-foot garden space. The garden now has a beautiful loamy soil. I have been planting with wonderful results for about 20 years.
    About six years ago, I collected the leaves and put them down but did not plant for two years. I gather the bags of leaves, mostly oak, from neighboring houses. Several mulched bags of grass were in the mix this time.
    When I next planted my garden in a six-by-30-foot area, all the plants, tomatoes and cucumbers withered and died over a 12-hour period. The plants had been in the ground for about three weeks and had begun to produce small vegetables.
    I immediately removed them. The University of Maryland Extension Service recommended I plant buckwheat and oats. This I did for two years in a row. It grew beautifully, and so did the weeds.
    This year I have once again planted the garden. In the very same area, all the vegetables withered and died over 12 hours.
    The garden has been tilled many, many times. This is the only area that has the problem. It has not spread to another section of the garden.
    Could I have gotten some chemical like Roundup in the collected bags? If that is the case, why has it not moved with all the tilling?
    I might add that the dead plants have perfectly healthy root systems, and there are no tunnels or holes from moles or voles.
    I am totally at a loss as to what is happening and as to what I can do to fix the problem. Any advice you can give would be greatly appreciated.
–Pat Fessler, Crownsville

The Bay Gardener’s Solution


    The problem is not Roundup. Glyphosate, as the Monsanto weed-killer is called, deteriorates into phosphorus once it enters the soil. It does not have weed control properties when it becomes a soil component.
    I suspect that the soil is infested with fusarium, which is a fungus, or possibly sodium or soluble salts. I suggest that you have the soil tested by A&L Eastern Agricultural Laboratories. Request the S3 test to include soluble salts and sodium. Submit one sample of soil from the affected area and a second soil sample from the surrounding area. Do not indicate crop or request recommendations. Each soil sample should include at least five core samples from each area. Air-dry the samples overnight before mailing them for fast results. Print submission form and instructions from the web page: www.al-labs-eastern.com.
    Have the lab send me the results at DR.FRGouin@gmail.com. We’ll get to the bottom of this.