AGRICULTURAL RESEARCH C
*,:^ ~IFAS, University of Flo idaiU E LIB A
Dover ARC Research Report SV1977-1 JAN- .1978Novemb r 1977
THE EFFECT OF PLANTING DATE AND PRE-TRANSPU FolftaijiL- i j rTE
E. E. Albregts and C. M. Howard
Temperature and day length affect the flowering and fruiting responses of the
strawberry plant. Long days and/or warm temperatures enhance daughter plant produc-
tion while short days and/or cool temperatures enhance flower bud formation. How-
ever, the chilling the plants receive before transplanting in the fruiting field not
only affects flower bud formation but also vegetative growth. This response varies
with the cultivar and the length of the chilling period. It is for this reason that
Florida growers have available two kinds of strawberry transplants for fruit produc-
tion: mature (obtained generally from California or northern states) and immature
plants. Maturity of plants is not directly concerned with plant age or size although
these two factors can affect earliness and yield. Nature plants are those which have
had sufficient chilling in the nursery prior to harvest so that starch reserves have
accumulated in the roots. From appearances alone, immature plants are difficult to
distinguish from mature plants. Determining the starch content of the roots is the
only reliable pre-transplanting method of distinguishing the mature from the immature
plant since immature plants have little or no starch in their roots. The starch
provides a ready energy source for the plant when transplanted and the chilling
causes flower forms to be initiated within the crown. In addition, the chilling
affects growth regulator levels in the plant, gearing the plant to produce more
foliage. The length of the chilling period given the plant affects the extent of
change in the growth regulator level, and thus influences its response in the fruit-
ing field. The greater the length of the chilling period the more likely the plant
will produce more foliage and delay fruit production. If mature plants are exces-
sively chilled. 2 or more months, this will generally cause them to grow vegetatively
and produce mostly runners for several months regardless of the temperature or day
length given after transplanting. Some fruit production may result, but the fruit
generally will be of small size and total production will be low. If mature plants
are given the proper amount of chilling then plant size will be optimal without
delaying early fruit production or reducing seasonal yield. The starch in the roots
of properly chilled mature plants permits the foliage to be removed from the plant
without unduly affecting its survival or growth after transplanting. Since all
mature plants come from out-of-state sources, Florida growers must depend on the
out-of-state nurserymen to dig transplants from the nursery at the optimum time.
By the same reasoning, plants should not be given too much chilling after they
arrive in Florida by storing them for long periods in cold rooms.
Sources of immature plants are: Florida, North and South Carolina, Georgia,
and other southern states where chilling is not received by the plants in the nur-
sery before being dug. The average daily temperature must be 55 F or lower to have
chilling effects with lows generally below 45 F. The length of the chilling period
depends on the cultivar but two to three weeks is an average. The immature plant
can be given chilling with storage in coolers. However, this does not greatly in-
crease the starch accumulation in roots. Thus the foliage should not be removed
from immature plants since this will delay and reduce yields and increase plant
mortality. Many times immature plants are left in the cold room for long periods
before setting in the field. This can have an effect on vegetative growth and time
of fruiting as well as on the total amount of fruit produced as was indicated with
mature plants. Table 1 shows the results of chilling on several locally grown
strawberry clones (except Tioga) for 0, 15, and 30 days and transplanting in October.
Chilling plants for 30 days always severely reduced the January yield and often
reduced the February yield. Seasonal fruit yields were also usually less when
plants were given 30 days of chilling, although yields may have been similar if
fruit production had been extended through all of April and May. Thus, for high
early yields, when fruit prices are highest, set immature plants before they are
held in cold storage for more than 15 days. Storing plants in coolers also requires
that you dig plants earlier from the nursery and this can lower nursery production
in many instances. If plants are stored in a cooler for a period greater than
30-45 days then flower buds may appear soon after transplanting. However, no more
flowers will appear for several weeks or months and the plant will be producing
foliage and stolons and no fruit during this time. Little difference in plant size
has been noted with plants chilled for 15 days compared to those not chilled.
Plants chilled for 30 days, although smaller at first because of storage, soon be-
came as large as the unchilled plants and by March were the greatest in size.
In addition to chilling, the time of planting can also influence early yield.
Table 2 shows the effect of planting date in the Plant City area on 4 strawberry
clones. Delaying the planting date to November 1 or later always reduced the Jan-
uary yield but had little effect on the February yield except for the clone 71-729.
Planting too early (October 1) can encourage stolon production as it did in these
trials. Plants set the earliest had the greatest runner production while those set
the latest had the least. Delaying the planting reduces plant size. However, if
plants are set too early, too large a plant may be produced, especially with the
cultivar Florida Belle. Thus, except for clone 71-729, all the clones in Table 2
should be set in mid-October. The clone 71-729 should be set in early October.
Planting dates for areas other than Plant City should be investigated by the grower
to determine optimum planting date.
Based on the preceding data and on unpublished reports by authors the follow-
ing summary is given for chilling and transplanting strawberry plants of clones
(a) For nature plants. You must depend on your out-of-state nurseryman to
dig plants at the proper time. For highest early yields do not store
plants longer than 15 days in the cooler.
(b) For immature plants.
1. For highest early yields, do not store for longer than 15 days.
2. Do not freeze immature plants in storage since they can be severely
3. Do not remove foliage from plants as is often done with mature plants.
This will reduce yields and increase plant mortality.
(c) Infrequently someone attempts to sell plants which have been in cold stor-
age for one to six months. Never set plants in the fruiting field that
have been held in cold storage for longer than 30 days.
2. Date of transplanting for Plant City area.
(a) Florida Belle, Tufts, and Tioga gave highest January yields when set in
mid-October. Stolon production is less when set in mid-October than when
(b) Although not released yet, line 71-729 should be set in early October for
highest early and seasonal yields.
(c) For those areas to the south or north of the Plant City area, the grower
should experiment with earlier and later planting dates from those above
to determine his optimum planting time. Those areas to the south may have
somewhat later optimum planting dates while those areas to the north may
have somewhat earlier planting dates.
Table 1. Effect of chilling Florida grown transplants
setting in fruiting field on January, February, and
in coolers before
seasonal fruit yield
of chilling January February Seasonal January February Seasonal
0 663 742 2435 119 455 2023
15 518 749 2499 109 329 2034
30 21 340 1916 5 57 1688
0 86 352 1595 208 795 2122
15 90 297 1514 221 816 2316
30 25 32 1027 45 206 1861
0 287 540 1690 587 294 2097
15 203 312 1561 261 463 2010
30 77 153 1275 60 301 1204
ZFlorida grown plants.
YCalifornia grown plants.
Table 2. Effect of planting date of four strawberry clones on January, February,
and seasonal yield (flats/acre).
dates January February Seasonal January February Seasonal
Oct. 1 676 547 2533 97 244 2334
Oct. 15 339 519 2029 136 315 2111
Nov. 1 152 692 2201 4 283 1298
Oct. 1 292 415 1357 93 207 1736
Oct. 15 370 537 1655 92 276 1487
Nov. 1 150 625 2587 5 198 913
Oct. 1 947 1265 2840 235 807 2572
Oct. 15 549 912 1950 187 525 2127
Nov. 1 109 706 1451 45 486 1600
Oct. 15 482 393 1825 138 408 1404
Nov. 1 144 486 1717 25 386 1380
Nov. 15 48 414 1360 1 204 1143
The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University