https://afac.org/garden-talk-resources/
Growing Season Extension & Winter Sowing
A 2018 Garden Talk Presentation
By Catherine Connor & Jasmin DeCourcey
Presentation posted at https://afac.org/garden-talk-resources/ 2
Acknowledgment Of Sponsors
2018 Garden Talks happen thanks to the collaboration of:
Arlington Friends of Urban Agriculture
Arlington Public Library – “Arlington Reads, Arlington Grows”
Master Gardeners of Northern Virginia Volunteers
“Plot Against Hunger Program” – Arlington Food Assistance Center
Virginia Cooperative Extension Service – Arlington/Alexandria Office 3
What we’ll cover
Growing Season
Season Extension
Methods to Extend the Growing Season into Fall & Winter Months
Winter Sowing Method to Start Seedlings Outdoors
More Resources 4
Growing Season 5 What is “Growing Season”?
A “growing season” is the period of the year during which the temperature, sunlight and rainfall are adequate for regular plant growth. Growing seasons are often determined by geographic conditions. The length if growing season is measured in two ways: One enumerates the days of the year when average temperatures & weather conditions are within the thresholds at which crops will germinate & continue to grow. This measure varies with each kind of crop, and may vary by crop variety. The other is stated in terms of frost-free days The average number of days between the last (killing) frost of spring and the first (killing) frost of fall or winter. Different crops & varieties within crops have different winter kill temperatures. Most agriculture requires a frost-free season of at least about 90 days. Increased daylight durations may compensate for shorter frost-free periods. 6 Our Growing Season Length Based on Frost Dates* USDA Plant Hardiness Zones - Average annual extreme minimum temps *different sources offer slightly different dates Zone 7a – Piedmont Area – Lighter Green Average Last Killing Frost: 4/20-30 Average First Killing Frost: 10/19-29 Average # of Frost Free Days: 182 days/26 weeks
Zone 7b – Tidewater Area – Darker Green Average Last Killing Frost: 4/10-4/21 Average First Killing Frost: 11/8-11/28 Average # of Frost Free Days: 230 days/33 weeks
http://www.plantmaps.com/ Pub 426-331 at https://pubs.ext.vt.edu 7 Annual Vegetable Crops
Long Season Crops Early Season Crops Late Season Crops Beans Early Beets Cabbage Bush Beans Early Cabbage Celery Beets Lettuce Sweet Corn Broccoli Onion Sets Chinese Cabbage Cucumbers Peas Carrots Radishes Eggplant Cauliflower Early Spinach Muskmelons Endive Mustard Peppers Kale Turnips Kohlrabi Potatoes Lettuce Pumpkin Radishes Squash Spinach Swiss Chard Turnips Tomatoes Watermelon 8 Our Growing Season Based on What Can Grow When 9
What Do We Mean by Fall Gardening?
Planting crops for harvesting before frost
Planting crops that can overwinter for spring harvesting
Planting cover crops to add nitrogen and minimize weeds in spring 10
Season Extension 11
What is Season Extension?
Cold Weather Season Extension and Hot Weather Season Extension
Growing earlier crops in spring
Extending cool-weather crops into summer*
Extending the survival of frost-tender crops beyond the first fall frosts
Using both spring and fall for cool weather crops such crops as carrots, beets, broccoli, cabbage, kale, spinach
Growing cold-hardy winter vegetables
Storing and processing crops for use outside their growing season*
* Not a direct subject of discussion today 12 Why Extend the Season?
We eat year-round! Not just 26-33 weeks out of the year! We favor eating locally grown produce
Cool/cold weather gardening offers certain advantages Insects/pest pressures decrease in cold Fewer weeds 13 Cold Hardiness Depends on A Number of Factors
Varies by crop and with plant variety,
Is affected by wind chill, air drainage & solar exposure
Depends on the health of garden soil, including the amount of organic matter in the soil and water drainage
Is affected by plant maturity - most overwintering varieties need to be planted and reach a certain maturity point before extreme cold sets in 14 Light Dependency & Day Length
Most plants don’t grow when day length is less than 10 hours, even if the temperature is kept within the optimum range. (DC: 11/17/18 – 01/24/19)
A “photoperiod” is the duration of light within a 24-hour period.
Think: period during which plants can use sunlight for photosynthesis
“Day (night) length” influences many activities in plants including growth, seed germination, flowering, fruit development, and the onset of winter dormancy.
Some plants are particularly sensitive to the ratio between day and night length. E.g., flowering impact:
Long-day plants (day length > 12 hrs) want to flower as we move toward the longest days of the year. Spinach, turnips, onions, lettuce.
Short-day plants (< 12 hrs) want to flower earlier in spring or in fall. Sweet potatoes, black-eyed peas.
Day-neutral plants disregard the day length and determine their flowering on factors such as temperature or the stage of maturity. Kale, tomatoes, cabbage. https://s3.wp.wsu.edu/uploads/sites/2073/2014/04/042712.pdf Day Length and Your Vegetable Garden https://www.timeanddate.com/sun/usa/washington-dc Sunrise, Sunset and Day length in Washington, DC 15
Moisture Needs in Winter Months
You need to ensure adequate plant moisture
Plants typically need less water in cool temperatures because there is less evapotranspiration
But plants in overly dry soil will be less capable of withstanding freezing weather
So will plants in soil that is saturated with water 16
Methods to Extend the Season Practices and Structures 17 Seed-starting date for fall crops/harvest: “Short Day Factor”
As days grow shorter in the fall Sample Calculation for and light is less intense, Sowing Spinach Seeds consider adding 2 weeks when determining planting dates Days to germination: 7 to 10 + Days to maturity: 35 Short Day Factor (SDF) Formula First frost date + Short Day Factor: 14 = Days to plant before frost 56 to 59 - Days to germinate Given a Nov 1 first frost, the dates for - Days to maturity sowing spinach are about Sept. 2 - 5 - 14 days (SDF) = Date to plant 18 Growing & Transplanting Seedlings as a Season Extension Method In Summer for Fall/Winter Start seedlings in summer by creating (shaded) nurseries* outside. Under-sow and intercrop. Start seedlings indoors.
In Winter for Late Winter/Spring Direct seed early with cold protections (may be nursery* setting). Use winter sowing method to grow seedlings outdoors. Grow seedlings indoors. *Nursery: seeds are closer together than appropriate for mature plant with goal to transplant rather than thin 19
Locate to Protect Plants from the Cold
Choose growing location based on microclimate & ease of management Take advantage of urban heat island effect Choose site for good air drainage, understand your low-lying areas Location under deciduous trees sunny winter spot Consider prevailing winds Locate where you can readily make adjustments and use 20 Cold Protection Structures
Select protection to be deployed to be cost/effort effective and manageable Cold Frames / Hot Beds Row covers (Floating / Low Tunnels) Hoophouses (High Tunnels)* Heated greenhouse* Individual Plant Protections Mulches / Means to warm soil Varied materials to protect crop
Remember you need to store this equipment when not in use! * Not the subject of today’s talk 21
Cold Frames Season Extension: Cold frames
Miniature greenhouse
Can add up to 45 days to growing season.
Typically 3’ wide by 6’ long; 18” high in back & 12” high in front.
Dimensions are only limited by the size top you put on it.
Faces south or west with glass or plastic top at a 30-45° angle to maximize sunlight.
Open top on sunny days.
22 23
Using Cold Frames 3
Effective four-season gardening technique
Can be adapted to work in an array of climate zones
Used primarily to grow salad greens; spinach, chard, mache, claytonia, arugula, and a variety of lettuces
Can also be used to grow other vegetables such as scallions, radishes, carrots, and leeks.
Creates an isolated warm, humid, controlled environment for plants to grow in during the harsher times of the year.
A translucent top is angled towards the south in order to capture as much solar radiation as possible throughout the day.
An effective cold frame is planted in the ground, in order to insulate the ground in which the plants grow. 24
Various Types of Cold Frames
One of the great things about cold frames is the simplicity of their concept; they can be built from a wide array of materials.
Effective cold frames range anywhere from a hole in the ground covered with plastic, to a buried wooden structure made from re-used materials, to an insulated raised bed using recycled materials.
No matter what you use to construct your cold frame, there are a few essential aspects that make growing in your cold frame happen. 25
How the Cold Frame Works
The cold frame lessens climatic stress in a number of ways:
Temperature: A single layer of glass creates a microclimate in which the nighttime temperature inside the frame can be as much as 20° warmer than the temperature outside, although the average difference is 7° to 10°F
The daytime temperature inside the frame, even on a cloudy, early spring day, will be 10° to 15°F warmer than outdoors.
On a sunny spring day, the temperature can rise high enough to cook the soil and the plants if you don’t vent off the extra heat.
Solar Angle: Slanted diagonally from the back to the front helps water to run off and placed facing south, increases the sunlight reaching the inside. That’s why solar panels are placed at an angle between 30 and 45 degrees 26 How the Cold Frame Works
Both daytime and nighttime temperature differences depend on the time of year, the angle and intensity of the sun, the rate of outdoor temperature change, and the initial temperature in the frame.
Moisture. Much of the havoc that freezing can wreak on winter vegetables is a function of how wet the plants are. High humidity helps protect plants from cold but plants sitting in a puddled soil just soaked by a rain before freezing will be more stressed than one that is drier. The glass roof of the cold frame protects the crops inside from pounding winter rains. 27 How the Cold Frame Works
Wind. The wind can make a cool day feel very cold. Weather forecasters always mention the wind chill factor. The same conditions affect plants. Wind cools by removing ambient heat and evaporating moisture.
The stress of winter wind alone can mean the difference between life and death for hardy vegetables. Even the slightest windbreak will help. 28
Row Covers, Hoop Houses & Other Plant Protectors 29
Row Covers - Floating & Hoop-supported
A row cover is material that covers a row or block of plants to protect them.
Floating row cover – material is laid out loosely directly on the plants, and will touch the plants
Hooped row cover - hoops are used to keep the material from touching the plants it protects, and comes in different heights, widths and shapes
Low tunnels - the gardener cannot stand in a low tunnel hoop row
High tunnels - tall enough for the gardener to stand inside the structure
Structure may cover one or more rows/beds
It is possible to combine floating row covers and hoop houses…
Terminology varies
Quick Hoops – covers more than one bed, close to the ground
Caterpillar Tunnels – usually tall enough to walk in 30
Materials Needed
Garden fabric suitable for your purposes
Insect barriers / row cover / frost blanket / plastic / shade cloth / bird netting
Length: bed/row length + two heights of hoops (drop) + a couple of feet
Width: longer of width of bed/row or length of hoop bracket + a couple of feet
Material to make the hoops and anchor them (when applicable)
PVC with or without rebar to anchor the hoops to the ground / brackets to anchor to raised bed
Heavy-gauge wire, single or double wire hoops w/cross braces, loop hoops
Something to secure the spacing between hoops at their top (optional)
Material to secure the garden fabric in place and prevent it from flying away
Secure fabric to the individual hoops (pocket to pass hoop through / ropes / row cover snap clamps / binder clip / beach towel clips / garden hose / clothespins)
Secure fabric to the ground (roll fabric on length of stake / sandbag / bricks or stones / soil / garden fabric pins/staples)
Be careful to not damage the fabric with fasteners! 31
Row Covers Material/Fabric
Fabric specifications depend on manufacturers
Fabric or plastic? Choosing Row Cover http://www.motherofahubbard.com/fabric-vs-plastic-row-cover/ Is clear plastic necessary? Success with Fabric Row Covers http://www.motherofahubbard.com/success-with-fabric/ 32 SARE discusses High Tunnels and Other Season Extension Techniques https://www.SARE.org/Season-Extension Search Google for Factsheet FS-957 at UMD extension
Raised Bed Cloche plans are available for download from Oregon State University Portable Field Hoophouse plans are available for https://catalog.extension.oregonstate.edu/ec1627 download from Washington State University http://cru.cahe.wsu.edu/CEPublications/em015/em015.pdf
Cold Frame Plans for Your Winter Garden https://www.epicgardening.com/cold-frame-plans/ 33
Other Plant Protectors
Protect individual plants or groups of plants with purchased or homemade structures
Plant protectors come in various materials and sizes
Light transmission / ventilation / water accessibility / stability & anchoring means
Storage in off season
Durability and eventual disposal
Pollination 34
Photo Credit https://www.gardeners.com/ https://harvesttotable.com/ http://whizbanggardening.com/ 35
Soil Protection – Double Protection – Multipurpose Structures 36 Protective Mulches Mulching is spreading a protective layer of material on top of soil
Many benefits: conserve soil moisture, limit soil erosion, maintain an even soil temperature (warm in winter / cool in summer), control weeds
Many semi-hardy plants will survive if their roots don't freeze
Use organic or inorganic material around your annual and perennial plants
Compost, leaf mulch, leaves (chopped, shredded, whole), straw (or hay), grass clippings (no herbicides), pine needles (acid-loving plants), cardboard, newspaper
Stones / brick chips (suitable only for some perennials)
Use sheet mulches, which may not be fully biodegradable and compostable
Regular plastic mulch (black, colored, clear plastic) and geotextiles/ polyester landscape fabric
Biofilms (biodegradable bio-based mulch films)
Paper-based mulches (many include polyethylene)
Pub 426-326 – Mulches for the Home Vegetable Garden http://pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/426/426-326/426-326_pdf.pdf http://broadforkfarm.com/2016/08/15/biodegradable-plastic- mulches-no-longer-allowed-in- canadian-organics-what-now/ 37
Soil Temperatures Needed for Seed Germination
Source: gardeners.com 38 Double Protections & Multiple Purpose Structures
Row cover or sheet mulch within Tunnel
Reduce wind exposure – warm up the air
Warm up the soil, control weeds, control moisture
Adding plastic over row cover (careful of cooking!)
Use the same structure to support frost blanket or plastic in winter and insect mesh, shade cloth or bird netting in summer Other39 Considerations
How long do you plan to extend? How big a garden do you have / do you want to extend? Storms / winds can destroy your row covers, cold frames & other structures. Glass in the garden: Glass is good material for letting in sunlight and its warmth while keeping the elements out, but it is also the most expensive. Plastic sheeting works well and is inexpensive but will deteriorate quickly. Polycarbonate is less expensive than glass, is lightweight, and retains heat better than both glass or plastic. Additionally, polycarbonate can be used on flat or bent surfaces, transmits light well, and is extremely strong. 40
Should You Buy or Should You Make?
It’s entirely up to you
Budget, inclination, know how…
Availability…
Start small… maybe…
The practice of growing vegetables all year round can be demanding
Talk to friends and practitioners before making a big investment of time, effort or money
Useful expenses for four season gardeners
An automatic vent opener (check size and the weight it can lift)
Minimum/Maximum Thermometer
Soil Thermometer 41
Winter Sowing 42 What is Winter Sowing?
Alternative way to extend the season by sowing seed earlier than you would direct sow Planted in “mini greenhouses” during cold winter months Much cheaper and require less supervision than starting seed indoors Germinate outside Ready to transplant once the ground thaws No need to harden seedlings – they’re already accustomed to spring weather fluctuations No risk of seedlings “damping off” 43 Selecting Containers for Winter Sowing (WS)
Plastic gallon milk jugs are best Clear juice containers 2 liter soda bottles Foil roasting pans with clear lids Salad boxes Use your imagination 44 WS Container Preparation
Rinse Cut along mid-line leaving enough to serve as a hinge Drainage: 4-6 holes/slits Soil Use good quality potting mix Depth of at least 3” (thumb) Soak and drain well Air transpiration: leave caps off of containers 45 Zone 7 Winter Sowing: What to Winter Sow & When
January: Hardy perennial flowers & plants that require stratification
February – Early March: Most herbs and frost-tolerant vegetables
Late March - April: Tender plants, annual flowers and warm-loving vegetables
Some seeds are not conducive to winter sowing: tap root vegetables (parsnip / carrot and those plants whose roots are sensitive to transplant (chard) 46 Placement & Care
Label crop inside and out Seal the WS container Place outdoors Should be in part sun As temps warm, may need to move to more shade Don’t allow them to dry out Temperature inside container may be 20º warmer than outside on a sunny day Open lids as weather warms Transplant after 1-2 sets of true leaves 47
Resources 48
Winter Sowing Resources
Wintersown.org– Trudi Davidoff http://www.wintersown.org/
Educational References https://extension.psu.edu/successful-winter-seed-sowing https://www.mastergardenersmecklenburg.org/seeds-for-winter- sowing.html
Winter Sowers Facebook Page https://www.facebook.com/groups/wintersown/ 49
More Resources
Sustainable Market Farming – Pam Dawling
https://www.sustainablemarketfarming.com/
https://www.slideshare.net/SustainableMarketFarming
Season Extension Articles – Harvest to Table
https://harvesttotable.com/tag/season-extension-2/
Upcoming Events
Friday October 5 - 2018 Arlington/Alexandria Urban Agriculture Symposium at St. Andrew’s Episcopal Church
Wednesday October 10 Garden Talk @ Central Library – Fall Festival
2019 MGNV/VCE Urban Agriculture and other classes start in January https://mgnv.org/programs-activities/public-education/
MGNV Select On-line References for Kitchen Gardening
https://mgnv.org/veg_references/ EXTRA SLIDES 51 2018 – Spinach at Walter Reed Garden (WRG - counter clockwise)
1. Seeded 1/23/18 in a Gallon Pic 1. was taken 3/25/18, the date the seedlings were transplanted at WRG. 2. Dividing the plants into brownie pieces… 3. Upon 3/25/18 planting, they did not look like much, but the gallon jug filled a 4’x12’ bed! 4. & 5. By 4/3/18, you could see the transplants well established.
5. 6. & 7. By 5/6/18 we could start harvesting beautiful spinach leaves! 52 Collard Greens at WRG (counter clockwise)
1. Seeded 1/23/18 in a Gallon Jug, Pic 1. was taken 3/25/18, the date the seedlings were transplanted at WRG. 2. Dividing the plants into brownie pieces… 3. Upon 3/25/18 planting, they did not look like much, but the gallon jug filled a 4’x12’ bed! (Collards were planted with lettuce based on planned pole beans for summer.) 4. By 4/3/18, you could see the transplants well established. 5. By 4/30/18, collards were growing nicely. 6. & 7. By 5/13/18, healthy collards were ready for some harvesting. 53 Swiss Chard & Spinach at Central Library (counter clockwise)
1. Swiss Chard seeded 2/15/18 in a Gallon Jug, Pic 1. was taken 3/11/18. 6. Spinach transplanted 2. & 3. Swiss Chard on 4/5/18, the date the seedlings were at the Central Library transplanted at Central Library. on 4/5/18 was 4. Upon 4/5/18 planting, they were tiny and healthy. healthy, but it quickly 5. By 6/20/18, there were three beautiful rows of Swiss Chard got too hot and did growing along other Central Library plantings. not do as well as the Swiss Chard or the spinach planted at Walter Reed Garden. 54