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Articles by Dr. Francis Gouin

At Thanksgiving, this year’s garden continues giving

This year’s garden was one of my most productive in recent years, despite its late start as I recovered from a fall last November. With help from family members, including grandchildren, the garden was planted in mid-May.
    Even so, we harvested nearly a bushel of onions, which were braided and hung in the garage until recently. This year’s turkey stuffing will contain those garden-grown onions. The Crocket snap bean crop was outstanding, as was the harvest from the yard-long Gita pole bean plants.
    My 14 tomato plants were so productive that in addition to feeding the children and their families, I delivered many half-bushel boxes to the SCAN food pantry at St. James Parish in Lothian.
    I shared my ample okra crop with fellow Ruritans, who also enjoyed harvesting my Gita beans, tomatoes, cucumbers and melons while I vacationed in Maine in late August and early September.
    From six separate plantings of sweet corn, five harvests were better than expected. The last was not ready until early October; its ears were only partially filled and small.
    There were a few disappointments. Cabbage, broccoli and cauliflower were small due to being planted late. My garlic crop was thin because I was unable to keep up with the weeds. Peppers under-produced, too. A granddaughter came to help me transplant, but because I could not convince her to tear the roots of the transplants, the plants never fully established and produced only a few peppers each.
    This late in the year, the garden will bless our Thanksgiving table with fresh as well as frozen and canned vegetables. Fresh from the garden we’ll serve roasted Brussels sprouts, kale chips and raw salad of shredded carrots and kohlrabi — plus peas from the freezer and stewed tomatoes from the canning library.
    Leaves of kale will be spritzed with olive oil and baked at 400 degrees until crisp, approximately 10 to 15 minutes, then sprinkled with onion or garlic powder. This kale is the product of my successful experiment growing in the bales of straw, where both organic and chemical fertilizers did well.
    The Brussels sprouts will be cut in half, brushed with olive oil and baked in a covered dish for 15 minutes at 400 degrees, then baked uncovered for an additional 10 to 15 minutes or until the edges of the cut surface turn light-brown.
    The salad is made by shredding and blending together equal amounts of carrots and kohlrabi to be drizzled with real maple syrup made by my brother in New Hampshire.
    Peas harvested in October were blanched for five minutes in the microwave, chilled and bagged for the freezer. On Thanksgiving Day, they will taste as if they had just been harvested from the garden. We’ll put them in a Corning dish, microwave for five minutes and, as soon as they’re removed, sprinkle with Butter Buds.
    When tomatoes were plentiful in August, I peeled and processed 28 pints, each with a teaspoon of salt. On Thanksgiving Day, several pints of stewed tomatoes will be dumped into a large bowl with two tablespoons of light brown sugar per pint and a generous portion of fresh dill from the garden blended in, then microwaved for only three or four minutes before serving.
    Grow a garden, and you’ll eat this well at Thanksgiving and all year long.

If you’re not part of the solution, you’re part of the problem

Think again if you think shade trees pretty much care for themselves.
    In the forest, where trees care for themselves, fewer than one percent of seedlings grow to become marketable trees.
    What do you know about how the crotch angle, crossing branches and branch spacing affect tree health? Allowing narrow crotch angles on branches and stems to remain on young trees will result in premature tree damage. Rot is another common problem with narrow crotch angles. Branches that rub against each other result in early breakage. Young trees need to be trained to proper branch spacing.
    Nursery-grown trees raised in containers tend to develop girdling roots as they mature. Most girdling roots can be seen above ground or at the ground level. Look for roots circling or partially circling the trunk. Often the roots are embedded or being absorbed by the trunk. Cut such roots away with a sharp chisel or ax and remove them.  
    Parking your vehicles beneath the branches of the trees, do you consider the 800 to 1,500 pounds of pressure exerted by each tire? Ninety percent of trees roots can be found in the upper 10 feet of soil. The weight of cars and trucks compacts the soil, as do the tires of lawn mowers and the feet of people, including those who enjoy the shade of the branches during the summer.
    The roots of plants cannot grow in soil with 85 percent compaction or more. If you cannot poke a sharp dowel or digging shovel into the ground six inches or more, the soil is too compacted for roots to grow.
    Every year at this time, you rake away the leaves that fall to the ground. In the forest, fallen leaves return both organic matter and nutrients to the soil, hence to the tree.
    Nearly all fertilizer applied in the shade of branches is used by the turf. Very little nutrient from that fertilizer leaches down to the roots of the tree. Applying excessive amounts of fertilizer to satisfy the needs of the tree roots will result in fertilizer burn of the turf.
    Are you your shade trees’ friend or enemy?


Tree Help Needed

Q    In the spring I planted several fig trees. They  seem to be very slow growers and are now only maybe one foot high. I want them to live this winter. Any suggestions on what I should do?
    –C. Buchheister via email

A    If your fig trees are only a foot tall after growing for one year, your soil is deficient and poor. Your fig plants should be four to five feet tall at the end of the first growing season. Have your soil tested. With their limited root system, I doubt if the trees will survive the winter no matter what you do.

Q    Can you advise on how to eliminate the black soot or mold that is covering the leaves on my Nelly Stevens holly trees?
    –Lauren Avery, Millersville

A    The black on your Nelly Stevens holly is sooty-mold. I suspect your holly may be infested with scale insects. Inspect the undersides of the leaves and stems. The scale insects may be white or yellow-brown like small drops of wax. If your hollies are under maple or tulip poplar trees, it could be that the scale is feeding on the trees and the honeydew has drifted on the holly causing the sooty-mold to grow. Sooty-mold is best removed with a strong jet of water from a garden hose or power washer.



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

Now’s the season, so do it right

Mistakes made when planting shade trees grow up to haunt you.

Mistake 1: Choosing the wrong tree for the wrong place.
    Research the nature and habits of the species you want to plant. Do those qualities match the place you want to plant it and the job you want it to do?

Mistake 2: Planting too close to buildings, driveways, sidewalks or driveways.
    Plant the tree where it will provide shade in areas desired and as a backdrop for the landscape. Avoid planting trees where branches will rub against structures or interfere with traffic. Avoid planting shallow-rooted trees next to sidewalks, roads and driveways. As the tree roots expand away from the tree trunk, shallow-rooted trees will damage walkways and road surfaces. This result is commonest in heavy silt or clay loam soils.

Mistake 3: Planting in heavily compacted soils.
    If you are not able to dig the planting hole with a shovel, the soil is most likely compacted. If you need a crowbar, pick or jackhammer to loosen the soil to dig the hole, it is a waste of time and money to plant the tree. To solve the problem, you need to sub-soil the area and incorporate four to six cubic yards of compost per 1,000 square feet. Roots cannot grow in soil with 85 percent or more compaction.  

Mistake 4: Mistreating roots of bagged and container-grown trees.
    Trees grown in containers develop circling roots. Unless they are disturbed or cut, they will continue to grow in circles. As the trunk of the tree increases in diameter, it eventually makes contact with the girdling root, which has also increased in diameter. To prevent girdling and choking, cut roots near the surface of the root ball. When you see dead and dying branches at the top of a tree — or a tree growing lopsided — the damage is most likely caused by girdling roots. By then it is often to late to salvage the tree.  
    When transplanting trees grown in root-controlled bags, remove the bag. Unless all the fabric is removed from the root ball, the tree will not be able to develop sufficient roots to keep it upright.
    This is also true for trees that are sold as bagged and burlapped (B&B). If the burlap lining the wire basket has a green tint, it means that it is treated with a rot inhibitor. The rot inhibitor will prevent the burlap from decomposing, and the roots within the root ball will not be able to grow in the new soil. The burlap should either be rolled down below to the bottom of the root ball or removed before filling the planting hole with soil.

Mistake 5: Leaving tags on trees and shrubs.
    After planting, remove nametags and marking tapes from stems and branches. Allowing these to remain after the tree is established and growing rapidly will result in girdling and death to the stem or branch.

Mistake 6: Failing to stake.
    All trees 10 feet and taller should be anchored using either ground ties or stakes on either side of the trunk. Pad string or wire with tree ties or pieces of garden hose to protect stems and branches.

Mistake 7: Pruning just before or after planting.
    Plant hormones needed to generate new roots are produced in the buds that grow on the branches. Pruning away the branches at the time of planting will eliminate the source of plant hormones, thus delaying the development of new roots. Delay pruning away branches until after the tree is established. You can determine when a tree has become established by looking for a high proportion of normal sized leaves on each branch.

Mistake 8: Overwatering.
    Newly planted trees should be irrigated only once or twice a week. Irrigate thoroughly or use Gator bags that allow slow irrigation. When using Gator bags, irrigate the trees only once each week until the plants become established. Water established trees less frequently. Never water daily.


Ask Dr. Gouin your questions at DR.FRGouin@gmail.com. Questions will appear in Bay Weekly. Please include your name and address.

Straw-Bale Gardening Works

Re: www.bayweekly.com/node/23750

Siberian kale grows happily on bales of straw.
    This summer, I experimented with soilless gardening in bales of straw. The trick is priming the bales with fertilizer. I used 21⁄2 cups per bale of high-nitrogen lawn fertilizer minus all herbicides, testing both organic and inorganic.
    I prepared the bales in mid-August, inserting a long-shank thermometer and irrigating two to three times weekly. Priming initiates the composting process. The thermometer monitors temperature, which rises during active composting. When inner temperature again matched that of ambient air, in mid-September, I scattered seeds of Siberian kale over the bales.
    The seedlings grew equally vigorously on bales treated with the organic and inorganic fertilizers.


Save Gita Bean Seeds for Next Year

Re: www.bayweekly.com/node/13348

If you grew Gita beans this summer, by now some of the pods may be three feet long. Harvest those long brown pods and extract the seeds. For the past two years, I have tested saving seeds of Gita and comparing them to seeds purchased every spring for planting. Thus far I have found that the seeds saved are of equal quality to those purchased.
    After harvesting the seedpods, I lay them on a shelf and allow them to dry. When the pods are dry, they split easily and the beans are easily extracted. I then store the seeds in a small plastic, zipper-lock bag in the refrigerator along with the rest of my leftover seeds.
    Gita bean seeds are some of the more expensive you can buy, so saving them from year to year can result in a substantial savings. Last fall I failed to harvest all the bean pods. Gita bean seeds that fell to the ground germinated and grew. Clearly these seeds are quite cold hardy.


White Pines Don’t Like Wet Feet

Q    I live in a townhouse community. The trees in the community are 20 to 25 years old. This last year I have noticed that many pine trees are turning yellow and dying. Any idea of the cause and if we can prevent their deaths?
      –Greg Welker, Bowie

A    I strongly suspect poor soil drainage. We had a very wet growing season, and the soil in Bowie is mostly clay. White pines cannot tolerate poorly drained soils.
    The yellowing symptoms are also due to poor soil drainage. Yellowing of old needles is common, but this season’s yellowing is a symptom of root loss due to excess water.

Ask Dr. Gouin your questions at DR.FRGouin@gmail.com. Questions will appear in Bay Weekly. Please include your name and address.

From pot to rooting medium to placement, these plants have ­special needs

Orchids are becoming one of the most popular potted plants. They have the advantage of long-lasting flowers and very attractive leaves. However, after they have flowered, they are often neglected and only watered on inspiration.
    Orchids are epiphyte, meaning that they obtain most of their moisture from the air through root-like structures. In nature, they live in tropical forests, growing on trunks and branches of trees. The terrestrial forms of orchids, most commonly offered for sale, are sparsely branched with coarse roots.
    The typical rooting medium for growing orchids is fir bark, coarsely ground to provide maximum air movement through the container in which the roots are growing.
    Orchids generally bloom once each year. But with proper care after they bloom, you can have them blooming yearly for many years.
    After the plants have bloomed, you will often notice coarse roots growing outside. This is your cue that the time has come to repot into a larger container. 
    Common potting media guarantees death to the plant. Repot using fir bark.
    Carefully remove the orchid plant from its original container. If the roots are circling to conform to the shape of that pot, gently pull them apart allowing as much of the old fir bark to remain attached as possible. The new container should be at least one size larger than the current container. A shallow container is better than a deep container. Never a container without drainage holes in the bottom because the roots of orchids cannot tolerate standing in water.
    Place a couple of inches of fir bark in the bottom of the container before positioning all of the roots in the pot. Using one hand to support the plant in the middle of the pot, work the fir bark around and between the roots with the other, shaking the plant from side to side and bouncing the container on the potting bench to get the bark down between the roots. With thumbs and fingers, press the bark firmly around the roots.
    Water the plants thoroughly several times immediately after potting to help fine particles of bark fill some of the voids. Water from the top, not by sub-irrigation.
    During winter, the plants should be irrigated twice-weekly and fertilized monthly using a liquid fertilizer. I recommend an organic liquid fertilizer for best results. Do not place the plants near a window, lest they are chilled. Avoid direct sunlight, too. Give your orchids a spot three to four feet from an east- or north-facing window.


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

Time to repot for life indoors

Fall is the time to repot houseplants. During the short daylight hours of late fall, winter and early spring, most houseplants don’t produce much top growth. This rule is especially true of plants that live outdoors during the summer.
    For a plant to grow in a container, it needs room for new roots. Plants are root-bound when their roots fill the pot. Root-bound plants generally stop producing top growth, and they often start blooming profusely. If the roots are left undisturbed, the plants often develop mysterious symptoms. If you ignore the symptoms, the plants deteriorate.
    Repotting does not necessarily mean putting plants into larger containers. Most house plants can be repotted by simply removing the root ball from the container, shaking it to loosen the roots, cutting out some roots and cutting other roots in half to make room for more rooting medium. The freshened plant can be returned to the same container.
    What’s in that new medium makes a big difference in the health of the plant.
    Most commercial potting materials contain mostly peat moss, perlite or vermiculite and milled pine bark. These soilless rooting media should not be called potting soil. They are generally amended with commercial fertilizers sufficient to support plant growth for six to eight weeks. Unless you fertilize these plants after two months of growth, they often show nutrient-deficiency symptoms such as yellowing or dropping bottom leaves.
    Amending commercial medium by one-third volume of compost, such as LeafGro, improves them and reduces your need to fertilize.
    You can achieve better results by making your own potting soil or soilless rooting medium.
    For a good soilless mix, blend equal parts by volume of LeafGro, peat moss and perlite. For every gallon of peat moss, add two heaping tablespoons of dolomitic limestone. Peat moss is very dry; moisten it well during mixing. Store the unused rooting medium in a plastic bag so it will remain moist.
    To make potting soil, mix equal parts by volume garden soil, compost from your garden or commercial compost and perlite. Place the blend in a microwaveable container and microwave at full power for 15 minutes for each gallon of potting soil. Cool before using.
    If more than one-third of your potting soils comes from the garden, repot in porous clay pots rather than glazed or plastic one. Unless soil is very sandy, it holds water and can rot roots without good evaporation.
    Plants potted in mixes containing garden soil don’t need as much water or fertilizer as plants growning in soilless media.
    In porous clay pots, plants growing in soilless rooting media will dry out more rapidly, thus requiring more frequent watering. More frequent watering takes more frequent fertilizing.
    Your plants do better when you give them the pot that’s right for their rooting medium.


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

Dry fall following wet summer makes a good show

This year will bring spectacular fall foliage coloration — provided it stays dry.
    That’s what I told the Bay Weekly reader asking for my prediction.
    More rain means that more of the leaves will remain green for a longer period of time, thus reducing the intensity of the red, orange and yellow. If we have a dry fall, a higher percentage of the leaves will turn color at the same time. But because of drier conditions, the foliage will not last long.
    This prediction is made based on our abundance of rain that kept the foliage lush all summer long. Thus, the leaves of deciduous trees have generated an abundance of carotene and anthocyanins, the pigments that generate the red, yellow and orange colors in leaves. Those compounds are present in each leaf but masked by chlorophyll. That chlorophyll deteriorates as days cool and daylight hours shorten, and nitrogen — a major component of chlorophyll — migrates from the leaf tissues down the petiole to accumulate around the vegetative bud at the base of each leaf. 
    In years with a dry growing season, foliage is less lush, and deciduous trees have less foliage. If a dry growing season is followed by a dry fall, the foliage will be bright but of very short duration. If the growing season is dry and we have a wet fall, the foliage will be muted but slow dropping from the branches.
    Not all tree species generate the same colors. Maple trees are known for their bright red and orange colors, while the ash tree is easily recognized by its yellow fall color. A hill in New Hampshire is called Red Hill because most of the trees growing there are sugar and red maples. That hill is highly visible; many make a yearly pilgrimage to see it.
    In southern Maryland, we are lucky because we have an abundance of dogwoods that often begin showing their red colors in late summer. Near wetlands, we have sweet gum and black gum, which contribute red to purple-red colors and are most plentiful. Red maples provide a splash of red to orange-red in both wetlands and on hillsides.
    If we have a dry fall, the scarlet oaks should be spectacular with their deep red leaves. Most of the other oak species provide only a limited amount of yellowing before dropping their leaves. 
    Enjoy.


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

You’ll need them to get rid of ­creeping Charley and clover

Fall is the best time to eradicate clover and creeping Charley from your lawn and garden. Both of these broadleaf weeds can be controlled by spraying with Weed-B-Gone, Trimec or Speedzone. Apply at the rate of two tablespoons per gallon of water as a light spray on the foliage. Apply only enough spray to wet the foliage. 
    Take care to avoid dripping on the soil. These sprays are phenoxy compounds that can be absorbed through the roots of desirable plants, such as trees and shrubs, causing twisting and curling of leaves next spring. 
    Apply these sprays only on actively growing plants. They are not effective on plants stressed by drought. In drought, thoroughly irrigate the area at least 48 hours before treating with the herbicides. Apply in the early morning hours when the cells of the plants are turgid.
    Foliage absorbs the chemicals in a couple of hours. Keep pets and children away from the treated area for at least 24 hours. Wear rubber boots, rubber gloves and use low pressure to avoid drift. Do not apply spray when the wind is blowing. 
    In areas of heavy infestation, a second application may be necessary. The problem area is most likely infested with seeds of these broadleaf weeds, so anticipate the growth of young seedlings next spring. Eradication cannot be done in one year due to the weeds seeds accumulated on the ground.
    To prevent spring seedlings from becoming well established, set the cutting height of your lawnmower as high as possible so that the grass shades out the young weeds.
    Both clover and creeping Charley are difficult weeds to control. It generally takes three years of persistent fall treatment to eradicate them. 
    Where the clover dies, you may notice that emerging grass blades are greener than in other areas of your lawn. This is because clover fixes atmospheric nitrogen that is released into the soil after the plants die and decompose. Not creeping Charley; it’s just a nuisance.


Mulching With Leaves

Q    After a good rain, I raked leaves off my flower garden. The layer underneath was totally dry in many places, and when the rake passed over the ground, it gave off a sound as if it were hollow underneath. The dry old mulch appeared to have lots of graying in it. What should I do?

–Vicki Marsh, Deale

A    Dry leaves are hydrophobic, meaning difficult to wet. Add about two tablespoons of dish detergent to a watering can and sprinkle the solution over the dry leaves and gray layer beneath. After they seem wet, sprinkle additional water over them and incorporate all into the soil by spading or tilling. The gray matter is most likely actenomyces that will decompose the leaf residue once wet and active.

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

Flowers, Vegetables and Grasses for Fall and Winter

Growing plants keeps your soil alive and well all year long.
    In the flower garden, plant annuals and perennials close together. The tops of perennials die back to the ground in fall and winter, but perennial roots stay active as long as soil temperatures are above freezing.
    Add cold-weather annuals such as pansies, sweet William, ornamental cabbage and kale to fading perennials to give life and color to the winter garden. They will also absorb nutrients already in the soil.
    Pansies provide a wide range of color and will bloom off and on all winter. Come spring, they will produce an abundance of blooms in late April lasting through May. Sweet William is bi-annual. If you plant it this fall, it will flower well in the coming spring and even more profusely in the spring of 2016.
    Caution: Rabbits love pansies. If you have rabbits, scatter mothballs under the leaves. If you have children, wrap the mothballs loosely in aluminum foil and cover them with a thin layer of mulch.
    In the vegetable garden, broccoli, cabbage and collard greens, kale and turnips are colorful, hardy and harvestable through much of winter.
    A green alternative is a soil-covering crop of winter rye. Winter rye grows a lush green carpet of grass. The perfect scavenger crop, rye grows roots deep in the soil, absorbing nutrients not utilized by the previous plants and protecting groundwater. On the surface, rye prevents your soil from being washed away by heavy rains or winds.

Bulbs Planted Now Bring Spring Rewards

    Bulbs planted in October and November go to work now. In fall, they root quickly and absorb residual nutrients from the soil. In spring, they bring the garden to life.
    Plant tulip, narcissus or daffodils, hyacinths and crocus bulbs in October and November for April bursts of color.
    Plant garlic and long-day onions for spring and summer harvest.

Flowering Bulbs
    For flowering bulbs, dig deep. Excavate an area 12 inches deep and at least 12 inches wide. Add a four-inch-thick layer of equal parts by volume soil from your hole and good compost. Do not put sand under the bulbs.
    Place bulbs at least one inch apart on top of the blended soil with the flat side of the bulb against the wall of the hole. Planting this way will direct leaves to bend outward, giving the planting a more appealing appearance. Place a single bulb in the center. Cover the bulbs with eight inches of blended topsoil and compost.
    Don’t use a bulb-planting tool, which makes holes too shallow and compresses the soil along the walls of the hole, especially if the soil contains large amounts of silt or clay.
    Blend equal parts compost and topsoil and layer the soil four inches thick across the bottom of the hole before planting. Position the bulbs upright for uniform blooming in the first year. The compost will supply all of the nutrient needs through the first growing season.
    Narcissus … daffodils … or jonquils. Whatever you call them, these spring plants are perennials in Southern Maryland gladly blooming year after year. Plant now and you’ll have yellow blooms bursting through melting snow.
    Plant your daffodils deep and you can also plant hyacinth, crocus and more seasonal flowers above the daffodil bulbs without fear of damaging the bulbs with digging tools.
    Tulips are often an annual crop in Chesapeake gardens, as our warm springs disagree with them.
    Unlike daffodils and hyacinths, tulips produce a new mother bulb each year, plus possibly a few daughter bulbs. Because our springs are short — before long, hot summers — tulip foliage does not last long enough to build a new bulb equal to or larger than the original. The Netherlands and more northern states like Michigan enjoy optimum tulip climate: cool springs that last for several weeks.
    To get your tulips to flower more than one year, plant them by mid-October in a well-drained location in full sun. Early planting assures that the bulbs develop a large root system before soils cool with the arrival of winter.
    If you want your tulip bed to last many years, choose yellow tulips, which, for some unknown reason, perform better and last longer than red, white or pink cultivars.
    Caution: Deer love tulips; don’t plant them if deer visit.

Onions and Garlic
    Garlic bulbs can be planted from early September until mid November. The plants need time to produce visible foliage before the ground freezes.
    Select a location in your garden that will receive maximum sunlight. Garlic planted in partial shade will not produce fully developed bulbs.
    Garlic grows best in well-drained soils rich in organic matter. To meet the organic requirements, spread about two inches of compost over the soil and spade or rototill as deeply as possible.
    A soil test will tell you your pH and how to achieve the garlic ideal of near 6.5.
    Plant each clove, pointed side up, in holes four inches deep and four inches apart in rows 10 inches apart.
    Just before the ground freezes in December, mulch with a one-inch layer of compost.
    Next spring, water thoroughly at least twice weekly. In May, cut the flowers just below the swollen part of the stem as they form so as to maximize the size of the bulbs.
    Just as soon as the leaves start to turn brown in early summer, dig using a forked garden spade to minimize damage to the bulbs.
    The short days of fall and winter are beloved by short-day onions. A short-day onion variety will form a bulb only when the days are short. Begin planting any time now so the plants become well established before the ground freezes. To give them the organic matter they want, amend your soil with an inch or two of compost prior to planting.
    After the ground freezes in winter, mulch the onions again one to two inches deep to help prevent the frost from pushing the onions out of the ground with repeated freezing and thawing.
    As soon as the plants resume growth in the spring, apply a water-soluble fertilizer to stimulate early active growth.
    Harvest begins in June.

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.