Plant viruses can create interesting anomalies

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Aucuba hedge Photos by Karen Lawrence

Dr. Bob Gilbert – Columnist

Dr. Bob Gilbert

 We are learning to live and deal with viruses.  They have always been around.  The annual flu vaccination changes have taught us that viruses often mutate or change.  What we are not used to thinking about is that plants also have viruses. 

The fact is that microbes such as fungi, bacteria and viruses can cause diseases in humans, animals and plants. The horticulture industry has learned to take advantage of the effects that the non-lethal or milder viruses create.   Probably the best and oldest example of a plant virus is in tulips.   A virus called Tulip Breaking produces mosaic patterns in the leaves and blooms.   There is even a virus- infected tulip strain called “Rembrandt Tulips.”  Parrot tulips are similar with viruses that create amazing color combinations and patterns.

The following is partial list of plants that are affected by viruses:

Tulips, Flowering Maple, Camellia, Honeysuckle, Nandina, Cucumber, Clerodendron, Canna, Aucuba, Hosta, Japanese Maple, Croton, Impatiens, Salvia and Mint.

The most common plant virus effects are yellowing leaves, malformation and even stunting.

Plant viruses can be transmitted by insects and by rooted cuttings.  You can get confused using plant viruses for esthetic purpures.  There is a very contagious virus disease in hostas recently described.  When found the entire plant must be destroyed by either burning it or bagging it and putting it into the trash. This disease causes intense hosta leaf yellowing. It is often confused with milder leaf variegation.

These thoughts were prompted as I noticed an infrequently used plant here is Western North Carolina – Aucuba japonica.  It was used often in Atlanta where I used to live.   It can be called Spotted Laurel, Japanese Laurel, or Gold Dust Plant.  It is hardy here. This is a shrub that can grow from 3-10 feet depending on the variety.  It comes from China, Korea and Japan.  It was first introduced into England in 1783.  It is diecious meaning the male and female blooms are on separate plants. The flowers are small and barely noticeable.   However, when pollinated, attractive red fruits are produced.

“Gold Spot” or “Variegata” Aucuba

It is the foliage that makes Aucuba so attractive.  Infected with a yellow producing virus has resulted in numerous cultivars.  Michael Dirr lists 21.   Probably the most popular one is called “Gold Spot” or “Variegata.”  It was the original introduction in 1783.  Now there are numerous other gold-spotted varieties. This plant is easy to grow with no special soil needed.  However, it can’t tolerate full sun but grows well in shade.   It can form a hedge and looks great as a foundation plant brightening up a shady spot. 

Rozannie Aucuba

My favorite Aucuba is called “Rozannie.”  It has shiny very dark green leaves, no spots and produces large red fruit even in the absence of a male plant.

Aucubas lost some of their popularity in 1994 when temperatures suddenly dopped to 4 F damaging many plant varieties.  They are now slowly regaining popularity.  But still, I have spotted only a few plantings around town.

Dr. Bob Gilbert is co-founder of Smith Gilbert Gardens in Kennesaw, Ga.

Karen Lawrence is a professional horticultural and wild life photographer from Franklin.

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