Title: Assessment of freeze damage to cold hardy citrus at the AREC-Monticello
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Title: Assessment of freeze damage to cold hardy citrus at the AREC-Monticello
Physical Description: Book
Creator: Anderson, Peter C.
Publisher: Agricultural Research and Education Center, University of Florida
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AREC-Monticello Research Report BB 90 2


ASSESSMENT OF FREEZE DAMAGE TO

COLD HARDY CITRUS AT THE AREC-MONTICELLO

ccfi rrSciRence
Peter C. Andersen and Gary W. Knox Library

Agricultural Research and Education Center JUL 9 199

Monticello, Florida / Uniersity of orida


Prior to the 1980's it was not unusual to see maturii"' specimens

of cold hardy Citrus cultivars in north Florida. Three major

freezes in the last decade have all but eliminated Citrus north of

30.50N latitude. Nevertheless, many horticultural enthusiasts are

* apparently optimists by nature since cold hardy Citrus cultivars

are being sold with regularity in north Florida. The purpose of

this report is to describe the 1989/1990 winter freeze damage to

Citrus and Citrus relatives at the AREC-Monticello.

A 0.5 acre planting of Citrus was established in 1986 at the

AREC-Monticello. The site has a Fuqua fine sand soil and is

exposed with a slight slope providing good air drainage. The

plants (Table 1) were randomly arranged in 4 rows oriented north to

south with 15 feet between plants and 20 feet between rows. The

plants were planted from 3 gallon containers into the existing

centipede/bahia turf, leaving a 4-foot diameter circle of bare soil

around the trunk of each plant. Trees were fertilized with a 10-









10-10 product applied at rates of 1/2 lb. per plant in 1986 and

S1987, 1 lb. per plant in 1988 and 1989, and 2 lb. per plant in

1990. Plants were irrigated with an overhead irrigation system as

needed. Each autumn, soil was mounded around the trunk of each

plant to a height of 1.5 feet. All cultivars were grafted on

trifoliate orange (Poncirus trifoliata (L.) Raf.) rootstocks.

Trees were in the process of regrowth following minor freeze

damage during the winters of 1987 and 1988. On 22 December 1989,

an arctic cold front penetrated the southeastern United States, and

the AREC-Monticello recorded a high of 340F and a low of 240F. On

23 December, a high of 310F and a low of 120F occurred; on 24

December, a high of 360F and a low of 160F were recorded. Ponds and

small bodies of water in north Florida remained frozen for up to 5

days. High winds and low temperatures prevented the use of

S overhead irrigation for freeze protection of Citrus.

All Citrus species and relatives sustained severe cold injury

(Table 2). With the exception of one specimen of kumquat, all

exposed wood was killed. Cold tolerance was denoted by regrowth

from the portion of trunk that was mounded with soil. Minimum

temperature tolerance reported by Krewer and Powell (Table 2)

before significant damage occurs is generally in agreement with the

results obtained at the AREC-Monticello.

Based upon these results it appears that no Citrus species or

relatives have sufficient cold hardiness for north Florida unless

special precautions are taken. 'Meiwa' kumquat, 'Owari' satsuma,

'Chinotto' sour orange and 'Changsha' mandarin can likely be grown









with some success in north Florida if winters are less harsh, as

was generally the case before 1980, or if adequate cold protection

methods are used. 'Duncan' grapefruit, 'Meyer' lemon, 'Navel'

orange or 'Sunburst' tangerine all lack sufficient cold hardiness

to be grown in north Florida.

Practices that would minimize the extent of cold injury to

Citrus species and relatives include: 1) plant trees on the south

side of the house or provide a windbreak on the north and west

sides of the tree to minimize exposure to the north winds that

typically accompany cold weather; 2) insulate the trunk by using

tree wraps, utilizing microsprinkler irrigation during cold

weather, or mounding trunks with soil to a height of at least 1.5

feet, and; 3) avoid fertilization after 1 July to prevent

succulent regrowth that is more susceptible to cold injury. Many

people have successfully grown satsuma trees in north Florida by

providing a portable shelter for winter protection. Also keep in

mind that young trees are more susceptible to cold injury than old

trees.













Table 1. Citrus species and relatives planted at the AREC-

Monticello in 1986.


Common Name


Scientific Name and Cultivar


Satsuma

Kumquat

Sour Orange

Mandarin

Grapefruit

Lemon

Sweet Orange

Tangerine


Citrus reticulata (Blanco) 'Owari'

Fortunella margarita x japonica 'Meiwa'

Citrus myrtifolia (Raf.) 'Chinotto'

Citrus unshiu (Marc.) 'Changsha'

Citrus paradisi (Macf.) 'Duncan'

Citrus meyeri (Y. Tanaka) 'Meyer'

Citrus sinensis (Osbeck) 'Navel'

Citrus sinensis (Osbeck) 'Sunburst'












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