represented a 231% increase compared to theenrollment in 1963-64. Similarly, enrollmentsin our graduate courses have shown a steadyincrease during the 1964-76 period. However,enrollment in the graduate courses representsonly a small proportion of our total enrollments.

The number of undergraduates majoring in theDepartment of Plant Science increased steadily inthe 1964-71 period. Thereafter, as was the casewith enrollments, the number of majors increasedat a rapid pace. The number of majors in 1975-76represents a 281% increase compared to the number in 1963-64. Graduate students majoring inPlant Science have similarly increased steadilyin number during recent years.

In conclusion, it would appear that in theimmediate future students will continue to major

in the Department of Plant Science in large numbers. Enrollments will remain high.

14

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OVERWINTERING STRUCTURES IN CONNECTICUTPART II: STORAGE

In the first article on overwintering (CGN

67:14-19, 1975) the environmental factors affectingthe plant response to winter injury were reviewed.The objective of this paper is to survey variousmethods of storage which protect against winterinjury.

METHODS OF STORAGE

Various methods have been tried from such

simple ones as grouping plants tightly and thenpacking the root balls or containers with woodchips or sawdust. Other materials such as salthay and evergreen boughs have also been used.

An old-fashioned type potato storage building,which is a cellar below ground, maintains excellenttemperature and moisture levels. It rarely drops

Figure 1. An early A-frame polyethylene coveredoverwintering structure.

below freezing. As long as the temperature remainsbelow 40°F, evergreens stored here to not needlight.

Barns have been used to store plants but are notextremely effective owing to plants tending to dryout in these structures. Lining the barns withpolyethylene or styrofoam can help to maintain ahigher moisture level while, by cutting down onair exchange, the barns are cooler on warm daysand warmer on cold nights.

Cold frames can be effectively used, especiallyif frames are dug out so they are below ground, andplants like conifers are mulched with hay. With coldframes water drainage is essential and precautionsmust be taken to control rodents.

Microfoam systems, consisting of very thinblankets, can be used very effectively helping toreduce labor needed with other type structures.

Figure 2. Low hoop-type overwintering structures.

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13

STUDENT ENROLLMENT IN PLANT SCIENCE1963- 1976

D. W. Allinson

Head, Department of Plant Science

In 1972, Dr. A. J.R. Guttay reported on studentenrollments in the Department of Plant Science atthe University of Connecticut (CGN 45:4, 3/72).Dr. Guttay concluded that during the 1963-72 periodthe number of students majoring in the Departmentof Plant Science had increased sharply. Total classenrollments had increased correspondingly.

Until the 1975-76 academic year, students in theDepartment of Plant Science could major in one ofthree programs, viz., Agronomy, EnvironmentalHorticulture, and Natural Resource Conservation.In 1975, the Natural Resource Conservation sectionachieved departmental status. Consequently, at thepresent time, students in the Department of PlantScience major either in Agronomy or EnvironmentalHorticulture. In order to discuss trends in student

numbers, it has been necessary to recalculate numbers excluding those students majoring or enrollingin classes given under the aegis of Natural ResourceConservation. Hence, the figures given in thisarticle will not agree with those presented by Dr.Guttay.

Undergraduate enrollments were relatively stablein the 1964-71 period (Table 1). hi fact, the totalundergraduate class enrollment in 1965 was onlyslightly less than that hi 1971. However, beginningwith the 1971-72 academic year, undergraduateenrollments increased at a rapid pace. In fact,the enrollments during the 1975-76 academic year

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The plants to be covered are watered about thetime they freeze, layed down, covered with amicrofoamblanket and then covered with a 4 ml.polyethylene sheet.

Snow fences, good for larger plant material, canbe covered with polyethylene or kraft paper forgreater warmth and humidity. The snow fence

structure is erected around and over the tops ofthe plants. Substantial support may be necessaryfor protection from heavy snow. All plants shouldbe watered thoroughly before they are covered andmay be left untouched until spring.

The structure which finds the greatest use arethe quonset hoop type greenhouse covered withpolyethylene. Basic materials used to constructthe average 14 foot wide house include 1" EMTelectrical conduit pipe, 1 x 6" baseboard, 1 1/4"water pipe, 1 x 4" wooden purlin, pipe clamps andnails. The hoops, which cover a 14 foot span areinserted in the 1 l/4" water pipe which is 4 feetlong and driven into the ground 2 feet. Hoops aregenerally spaced 5 feet on center and are connectedby a 1x4" wooden ridge purlin. One inch pipe

Figure 3. Large, drive-in hoop-type overwinteringstructure s.

clamps secure the hoops to the purlin. Size of thequonset houses varies depending on need, butusually the higher houses do not exceed 8 feethigh while some may be as low as 30 inches.

ENVIRONMENTAL CONTROLS

Data from Fitzgerald (1970) shows that both airand soil temperatures in lower quonset structureswere 7-9°F warmer than in higher houses. Thesehigh temperatures can be attributed to snow coverand the smaller surface area exposed. The build-upof high temperatures under clear polyethylene inparticular can cause plants to bloom or start growthtoo early. White or clear poly can be used as covering generally 4-6 mils think. White poly has thegreatest moderation of high temperatures, frequentlybeing at or below outside air temperature at thewarmest part of the day (Fitzgerald, 1970). Spraypainting clear poly markedly reduces temperaturesand this would appear to be a useful practice whenusing clear poly.

Houses should not be ventilated when root balls

or containers are frozen (Havis, 1974). This canseverely dry out plant tops. Humidity should bekept high in storage structures. If soil temperatures are allowed to drop to between 15-20°F,plant roots may be killed. When roots are injuredin storage, the plants may begin growth in thespring, then die. Havis (1974) suggests irrigatingroot balls if they are not wet when they are notfrozen because wet soil will stay warmer whenthe greenhouse temperature drops.

Gas heaters can be used in very cold weatherto provide minimum heat. The heater should belocated on one side of the structure near the end so

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touch. Dipping the cuttings in water is not recommended since soaidng can spread the disease. Thus,mended since soaidng can spread the disease. TJb

diseased stock plant could infect many others

Presently, the only control measure is a goodsanitation program on stock plants and duringpropagation. Ideally, a freshly sterilized knifeshould be used for each stock plant.

one

Figure 5. Bacterial ooze of Erwinia caratovora varchrysanthemi on midrib of poinsettiabract (Rathmell photo).

11

Figure 3. hi later states of growth, bacterial stemrot may be expressed by rotting of abranch or two.

Figure 4. At times, bacterial stem rot may causea systemic infection and appear as a stickyexudate on stems.

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that heat can be blown down one side of the house

and circulated up the other side. Small fans maybe needed to establish a horizontal air flow (HAF)pattern. The thermostat should be placed oppositethe heater above the plants a quarter of the waydown the house. This will prevent prematureshutdown of the heater.

LITERATURE CITED:

1. Fitzgerald, R.D. and J.R. Havis. 1970. Asymposium on nursery container production.Pub. No. 73, Cooperative Extension Service,University of Massachusetts.

2. Havis, John R. 1974. Tolerance of plant rootshi winter storage. American NurserymanCXXXIX (1):10.