1. Season Extension
Susan Donaldson

2. What is season extension?
 Increasing the growing season at
either end, spring and/or fall

3. Why try to extend the
season?
 Allow more time for crops to
mature
 Grow different varieties
 Move toward year-round production
and income potential
 Fresh greens in the winter

4. Frost-free period
 We’ll define the length of a frost-
free period as the number of days
between the date of the last 32°F
temperature in the spring and the
date of the first 32°F temperature in
the fall.

5. What’s “freezing”?
 The National Weather Service
defines a “freeze” as occurring
“when the surface air temperature
is 32°F or below over a widespread
area for a climatologically
significant period of time (greater
than one hour).” (U.S. Department of
Commerce, 2005)

6. How long are our frost-free
periods?
 Lots of variation among periods for
the last 100 years
 Some years have had frost-free
periods of over 150 days
(approximately 5 months)
 Other years have had frost-free
periods of less than 90 days. (Reno data)
 KEY: lots of varibility, so you have
to watch the weather predictions!

7. Do frost-free periods ever
change?
 For the 30-year period of 1971-2000,
the average date of the last 32°
temperature in the spring was May
21 while the date of first 32°
temperature in the autumn was
October 3 (134 days).

8. 1991-2005
 The date of last 32° reading was
May 3, and the date of first 32°
reading in the autumn was
October 19
 The average length of the frost-
free period grew from 134 days
(for 1971-2000) to 168 days for the
more recent 15-year period
 This is an increase of a full
month!

9. Hard freeze
 A hard freeze is sometimes defined
as occurring on a date when the
temperature drops to 28°F
 But…you can expect damage when
temps drop to 32°F

10. City Frost-Free
Days
Carson City 90 - 116
Elko 57 - 87
Ely 53 - 81
Fallon 106 - 131
Lovelock 111 - 140
Reno 85 - 125
Tonopah 107 - 147
Winnemucca 75 - 107
Based on historical data indicating 90% (first number)- 121
Yerington with temperatures above50% (second number)
82 to 32°F.
probability of consecutive days
http://www.wrcc.dri.edu/summary/Climsmnv.html

11. Cold damage
 Plants lose heat faster than the air!
 Anything that reflects the radiating
heat back down will prevent or at
least greatly reduce frost formation
(for example, clouds)

12. Season Extension:
Start with cultural practices
 Site selection and microclimates
 Soil and moisture content
 Windbreaks and shade
 Irrigation
 Cultivar selection
 Transplants

13. Take advantage of
microclimates
 Some areas around your property
warm up faster in the spring, stay
cooler or warmer in the summer, or
are protected from the wind
 South-facing slopes will be warmer
 Cold air settles into valleys

14. Site selection
 #1: Hours of sunlight
 Prevailing winds

15. Windbreaks and shade
• At right
angles to
prevailin
g winter
winds
• Consider
effect on
sunlight

16. Shade fabrics

17. Shade fabric
 Creates a cooler microclimate to
help prevent bolting and bitterness
 Faster germination of cool-weather
fall crops
 Shading 30 -50% in midsummer can
lower leaf temps by 10 degrees or
more

18. Managing moisture
 Plants under drought stress can be
more susceptible to cold damage
 Water holds warmth and releases it
slowly
 So…water before frost is expected

19. Alter soil temperatures
 Use clear plastic mulch to warm soil in
spring and retain extra heat in fall
 Cover the edges of the plastic with soil
to anchor it in place
 Temps increase by 8 to 14 degrees to a
depth of 2 inches and 6 to 9 degrees to
a depth of 4 inches

20. Mulch to insulate plants
Organic mulches such as straw also
decrease radiated heat and conserve
moisture, preventing cold (and hot)
extremes

21. Choose hardy crops
 Start and end with cold-hardy
vegetables that tolerate frost
 Look for short-season varieties
 Other varieties are specially
adapted to growing in long, hot
days, extending your growing
season into the summer (ex. slow
bolting lettuces)
 Read seed packets and catalog
descriptions

22. Spring crop transplants
 Start plants early
 Start seeds of tomatoes, peppers,
and eggplants 8 weeks early
 Start seeds of cole crops about 4 to
6 weeks early
 Start vine crops 1 week early

23. Fall crop transplants
 Start plants for late-season crops in
late summer
 Seed a second season of quick-
maturing vegetables, such as snap
beans, peas, greens, radishes, cole
crops, and turnips later in the
season
 Grow cold-tolerant species in the
fall

24. Examples of late-season
crops
 Kale
 Collards
 Lettuce
 Spinach
 Mustard greens
 Arugula
 Broccoli
 Broccoli rabe
 Mache
 Beets Lettuce, kale and rabe
 Peas

25. Winter harvest
 Decreasing levels of light in
fall/winter slow plant growth to
near-dormancy
 Lowest light in December and
January
 Many cold-weather crops must be
harvested by the end of fall

26. Vegetable planting dates
 Planting dates depend upon the
plant cold-hardiness.
 Semi-hardy vegetables can be
planted two to four weeks before
the average last killing frost date of
May 15, or in cool fall temps

27. Vegetable planting dates
 Plant frost-tender and cold-
sensitive vegetables after the last
frost date
 Buy transplants, or start from seed
indoors from mid-March through
mid-April
 Earlier transplanting can be done
when hotcaps, row covers or other
protection is used

28. More tips
 Grow cold-
tender herbs,
dwarf fruit
trees, etc. in
containers that
you can move
indoors

29. Using
protection

30. Protect from early and late frosts
 Cover early and late season
plantings with mini-greenhouses
made from clear plastic, old
window sashes set on hay bales, or
fabric row covers
 Vent the covers on warm days to
prevent excessive heat buildup

31. • Use hot caps
in spring
• Need to vent
them
• Works for
small plants
• Blocks some
light

32. Light penetration not good;
minimal frost protection

33. Walls of Water
Good frost
protection but
expensive

35. Fall freeze protection
 Use old sheets, blankets, draperies,
etc.
 Cover plants before sundown to
trap heat

36. October 5-9, 2011
Elevation 5400 ft

37. Fall freeze protection
 Extend the covering all the way to
the ground so cold air can’t seep in
 Put in place before sundown
 Especially useful for the first few
frosts when warmer weather is then
expected

38. More tips
 Cover hardy root crops with a 6- to
12-inch-thick layer of straw or other
organic mulch in fall to prevent the
soil from freezing.
 Harvest as needed throughout the
winter.

39. Row covers
•Agribon, Reemay,
Harvest Guard, etc.
•Come in different
weights
Can provide 3
to 5 degrees of
frost protection

40. Row covers
 Warm and speed the growth of
seedlings in spring
 Slow the evaporation of soil moisture
 Protect plants from wind, heavy rain,
and hail
 Heavier fabrics provide more frost
protection but block more light

42. Row covers
 Keep pests off plants but need to
remove covers for insect pollination
 Protect late summer crops from fall
frost
 Protect crops from hot temperatures
and burning sun rays
 Must anchor with soil, wood, rocks,
etc.

44. Cloches
•Lightweight
•Portable
•Reusable

46. Cold frames
 Can provide 5 – 7 degrees of
protection
 Can be used in the spring to start
plants or in the fall for cold-hardy
crops
 Use old windows or glass doors to
make your own
 No standard size; keep width
narrow enough that you can easily
reach across

47. Can add black containers
filled with water to store
heat for the night

48. Cold frames
 Don’t use wood treated with
preservatives!
 Slope the lid to the south
 Place on south side of house

50. Cold frames
 Provide for ventilation of excess
heat when temps rise above 55
degrees
 Cover to protect against freezing,
or stack straw bales against the
frame

52. Cold frame tips
 Ventilate on warm days
 Checktemperatures with a
thermometer
 Protectduring freezing
weather: Remember that cold
frames give only 5-10 degrees of
warmth.

53. More cold frame tips
 Water: make sure plants aren’t
getting too much or too little
water.
 Hardening plants: open the lid of
your cold frame longer and longer
each day

54. Low tunnels:
Hoop-supported row covers

55. Benefits of low tunnels
 About five to six weeks earlier
production in the spring
 Several weeks later production in
the fall
 Some protection from insects and
foraging animals
 Some protection from extreme
weather conditions, such as strong
winds, hail or frost
 http://simplegoodandtasty.com/2010/05/25/tunnel-farming

58. Tips for low tunnels
 Use UV-stabilized tubing
 Don’t expect protection from hard
freezes
 Plan for access and ventilation

59. Building materials to construct one mini
tunnel for 40-inch by 30-foot raised bed
Quantity Item Description Unit Price Total
200 feet 1/4-inch nylon rope $0.08/ft $16.00
1,8-ft by 38- 6-mil greenhouse poly $0.13/sq
$39.52
ft sheet film ft
1/2-inch sch 40 PVC
80 foot $0.22/ft $17.60
pipe
20 foot 1-inch sch 40 PVC pipe$0.44/ft $8.80
44 2-inch wood screw $0.05 $2.20
2 3/8-inch by 2-foot rebar $0.75 $1.50
2 Eye screw $0.50 $1.00
*Prices may vary depending on
Total $86.62
location, etc.
http://www.noble.org/Ag/Horticulture/RaisedBedGardening/mini_tunnel.html

60. High tunnels (aka hoop
houses)
 Big enough to walk into
 Size them to meet your needs
 Plant in-ground or in raised beds
 Does not have an added source
of heat or ventilation
 Can extend the season through
the winter by up to three zones, or
a month in the fall

61. Orient in an east-west direction to
maximize sunlight, but also consider

62. Structural elements
 Can be mobile or fixed in place
 End walls are most important to
strength
 Can incorporate an opening for
ventilation in the end walls
 Hoops no more than 4 feet apart
 Peaked-roof (vs. U shape) stronger
in snowy climates

63. Structural elements
 Use a center support to increase stability
 Use 6-mil, greenhouse-grade, UV
stabilized polyethylene
 Roll-up sides allow for ventilation

64. How to Build a High Tunnel (video)
http://www.youtube.com/watch?v=
am1Tso2l3kc
Also see
http://www.extension.org/pages/18356/low-cost-high-tunnel-
construction

73. Minnesota study
 On average, tunnel vegetables such
as lettuce, tomatoes and cucumbers
were harvested about six weeks
earlier than those grown in the open,
while peppers were ready nearly ten
weeks ahead.
 Many of the tunnel plants produced as
much as double the output of the
outdoor crops

74. What about winds?
 High tunnels placed perpendicular to
prevailing winds typically receive the
most damage, so consider placing
parallel
 The best protection against uplift is to
ensure that posts are driven at least
24 inches into the ground
 Use stretch cord over the top of the
plastic from one side to the other,
every fourth rib

75. What about snow?
 A high tunnel built from ribs of 20 foot
pipe bent to create a 14 foot wide X 6
foot high structure will withstand only
about 10 psf
 This is about 2 inches of water as
snow
 Might be as little as one foot of snow

76. More tips for dealing with
snow
 Use a center roof rib
 Orient the structure so prevailing
winds blow the snow off the high
tunnel
 Remove the plastic in the winter if not
under production
 Brush off snow using a long-handled
broom (carefully!)

77. NRCS High Tunnel Pilot
Project
Eligibility Requirements:
 To qualify, the applicant must:
◦ be an agricultural producer
◦ install the high tunnel(s) on cultivated land
which includes existing gardens, irrigated
hayland and irrigated pasture
◦ have raised or sold $1,000 worth of
agricultural products
 http://www.nv.nrcs.usda.gov/programs
/NV_high_tunnels.html

78. Greenhouses
Walk-in, permanently placed
 The most expensive solution
 Usually have venting and heating
systems (requires energy inputs but
gives more control)
 In some areas, can be used year
round
 Can add mass for thermal storage
(water barrels, etc.)

79. Do your homework
 Many types on the market
 Many plans available as well
 Look at the alternatives before
investing
 Can use to insulate your house when
attached
 Consider a solar greenhouse

80. Bozeman, MT

82. Greenhouses
Walk-in, movable
 Less expensive
 Can be disassembled
and stored away when
not in use
 Usually used one to two
months before the last
frost in the spring.

83. Whatever you do…
 Keep good records!
 Consider a journal that includes
varieties, dates planted, dates
matured, freezes, etc.
 Nurture your soil with lots of organic
amendments
 Keep a map of what was planted
where

84. Crop rotation: varying
families

85. Why rotate crops?
 Breaks the cycle of disease and pests
 Helps to maintain adequate nutrients
 Can help improve soil structure
(alternate deep-rooted plants with
shallow-rooted plants)
 Can decrease costs

86. Considerations in crop rotation
schemes
 Heavy feeders: leafy veggies,
brassicas, corn
 Soil conserving/improving: legumes
(peas and beans)
 Lighter feeders: bulb and root crops,
many herbs

87. Simpler rotation
Legumes Nightshades
•Beans •Tomatoes
•Peas •Peppers
•Lentils •Potato
Brassicas Cucurbits
•Broccoli •Cucumbers
•Cabbage •Squashes
•Cauliflower •Melons

88. Another simple rotation
Root Legumes
crops, and
onions brassicas
Sweet Nightshades
corn, -
cucurbits tomatoes
and peppers

89. End-of-season maintenance
 Clean up! Remove dead vegetation
and windfalls, compost healthy
material. Remove fallen fruit and dead
leaves to decrease pest problems.
 Think about cover crops to enrich and
stabilize soil (winter rye, triticale)

90. End-of-season maintenance
 Enrich garden beds with compost or
manure; add mulch or leaves; think
about nutrient needs for your specific
crops
 Collect dried seed from open
pollinated flowers & veggies
 Clean out cold frames for winter use

91. End-of-season maintenance
 Clean and oil lawnmower, other
garden equipment and tools before
storing for winter
 Take equipment in to be sharpened
(mower blades, pruning equipment)
 Drain and store hoses carefully to
avoid damage from freezing
 Clean, sand and oil garden tools
before storing them for the winter

92. Questions?
Sue Donaldson
donaldsons@unce.unr.edu
775-336-0242