The predictable part of the Puget Sound climate is the consistency of air and soil temperatures recorded each month of the year. The temperatures are mild as they are influenced by the marine environment of the Puget Sound. The winter minimum temperatures range from 10 to 150 F (USDA Hardiness zone 8a) that permits overwintering relatively tender crops. But in the spring and summer months the marine environment keeps the temperature cool so it is difficult to grow the warm season crops without using soil warming techniques.
Warm season crops require mean soil temperatures of 60-650 F and this includes the following crops; eggplant, okra, melon, pepper, tomato and watermelon. Under Puget Sound climatic conditions it would require delaying planting to mid June in order to have adequate temperature to support growth of these crops. So these crops need the application of various climate warming techniques to successfully grow.
The next group of crops require temperatures of 50-600 F and are represented by cucumber, green bean, sweet corn, pumpkin and squash. This latter group can be readily grown, however the length of production is limited. The use of soil warming and crop protection techniques can extend the season by hastening earlier maturity.
Climate Warming Techniques
Site selection can provide some advantage. Choosing a site that has direct sunlight exposure is helpful. Places that have a southern exposed wall that will absorb heat and provide wind protection will increase the temperature several degrees. Wind protection by fences, hedgerows etc. are an advantage in protecting plants and allowing heat to accumulate.
Good soil drainage is important as free water in the soil takes more energy to warm up than air. So poorly drained soil retards the rate of soil warming. Wet soil also delays the time when the soil can be cultivated. Having a site where the soil is poorly drained may be an ideal situation for building raised beds.
Deep working of the soil by spading or using long shanked tillage implements is a good cultural practice in the spring. This breaks up the soil and exposes it to aeration and improved drainage. Deep tillage reduces the effect of compaction caused by walking through the garden and compaction and settling caused by heavy winter rainfall.
Greenhouses and shelters come in a wide range of configurations and degrees of complexity. The point to be made here is that light energy penetrates the glass or plastic outside shelter covering and is trapped inside as heat energy. This is commonly called the greenhouse effect. The heat energy not only warms the air inside the shelter, but penetrates into the soil, warming it also. The structure eliminates rainfall on the soil inside the structure allowing the soil to be drier with less free water in the soil and more air between the soil particles. Air takes much less energy to heat than water so the soil warms much easier and faster. Beside the warming advantage the shelters reduce wind stress that naturally occurs outside. Shelters have an additional benefit that they eliminate some common diseases like late blight in tomatoes.
Raised beds can be built with walls 12-18 inches high and filled with loamy soil that is supplemented with an ample amount of organic matter. Due to the improved drainage soil temperatures will be several degrees warmer. Other benefits of raised beds include having ideal physical soil conditions, elimination of impervious soil layers or hard pans and the establishment of growing areas and walking areas that reduce soil compaction.
IRT (Infra-Red Transmission) mulches laid down on the soil has given Puget Sound gardeners a revolutionary tool for growing warm season crops. This product is sold under a variety of trade names Solar and SRM Olive mulches.
Clear plastic is the best in light and heat transmission, but it allows weed seeds to germinate and grow under it making this application unusable. IRT mulch allows the infra-red energy to transmit through the plastic mulch while stopping the light needed for photosynthesis. Therefore weed seeds are inhibited in germinating and growing. Our results showed that IRT mulch will raise the soil temperature 80 F in May. This readily allows the planting of warm season crops requiring a minimum of 600 F. The question occurs, why not use black plastic. Black plastic does not allow infra-red energy to penetrate the mulch and so the heat energy must be conducted through the mulch and into the soil with less efficiency than being transmitted through it. Our results under Puget Sound conditions in the month of May indicated it was only half as effective as IRT mulch in raising soil temperature.
The IRT mulch edges can be hand secured with soil or done with mechanical equipment designed for this purpose. Since the mulches do not allow water to penetrate, trickle irrigation must be installed under the mulch. IRT mulch should be laid down a week in advance of seeding or transplanting in order to obtain the maximum soil warming benefit.
Cloches are low to the ground shelters. These are structures that follow the planting row using hoops often made of heavy weight wire, covered with a lightweight plastic film and anchored on the sides with soil. The cloche film is vented with vertical slits on the sides or is perforated with small holes to allow sufficient air ventilation. In the month of May the cloche over bare ground will increase the soil temperature at 3 inch depth 5o F (Fig. 6). The combination of Solar mulch with a cloche will increase the soil temperature 10o F (Fig. 6).
Use of early maturing cultivars and transplanting are effective strategies. Choosing the best quality early maturing cultivars can hasten maturity several days to about a week. Using transplants can shorten the time of maturity by about 2 weeks. Combining early maturing cultivars, transplanting and climate warming techniques will provide additive effects.
Warm season crops require mean soil temperatures of 60-650 F and this includes the following crops; eggplant, okra, melon, pepper, tomato and watermelon. Under Puget Sound climatic conditions it would require delaying planting to mid June in order to have adequate temperature to support growth of these crops. So these crops need the application of various climate warming techniques to successfully grow.
The next group of crops require temperatures of 50-600 F and are represented by cucumber, green bean, sweet corn, pumpkin and squash. This latter group can be readily grown, however the length of production is limited. The use of soil warming and crop protection techniques can extend the season by hastening earlier maturity.
Climate Warming Techniques
Site selection can provide some advantage. Choosing a site that has direct sunlight exposure is helpful. Places that have a southern exposed wall that will absorb heat and provide wind protection will increase the temperature several degrees. Wind protection by fences, hedgerows etc. are an advantage in protecting plants and allowing heat to accumulate.
Good soil drainage is important as free water in the soil takes more energy to warm up than air. So poorly drained soil retards the rate of soil warming. Wet soil also delays the time when the soil can be cultivated. Having a site where the soil is poorly drained may be an ideal situation for building raised beds.
Deep working of the soil by spading or using long shanked tillage implements is a good cultural practice in the spring. This breaks up the soil and exposes it to aeration and improved drainage. Deep tillage reduces the effect of compaction caused by walking through the garden and compaction and settling caused by heavy winter rainfall.
Greenhouses and shelters come in a wide range of configurations and degrees of complexity. The point to be made here is that light energy penetrates the glass or plastic outside shelter covering and is trapped inside as heat energy. This is commonly called the greenhouse effect. The heat energy not only warms the air inside the shelter, but penetrates into the soil, warming it also. The structure eliminates rainfall on the soil inside the structure allowing the soil to be drier with less free water in the soil and more air between the soil particles. Air takes much less energy to heat than water so the soil warms much easier and faster. Beside the warming advantage the shelters reduce wind stress that naturally occurs outside. Shelters have an additional benefit that they eliminate some common diseases like late blight in tomatoes.
Raised beds can be built with walls 12-18 inches high and filled with loamy soil that is supplemented with an ample amount of organic matter. Due to the improved drainage soil temperatures will be several degrees warmer. Other benefits of raised beds include having ideal physical soil conditions, elimination of impervious soil layers or hard pans and the establishment of growing areas and walking areas that reduce soil compaction.
IRT (Infra-Red Transmission) mulches laid down on the soil has given Puget Sound gardeners a revolutionary tool for growing warm season crops. This product is sold under a variety of trade names Solar and SRM Olive mulches.
Clear plastic is the best in light and heat transmission, but it allows weed seeds to germinate and grow under it making this application unusable. IRT mulch allows the infra-red energy to transmit through the plastic mulch while stopping the light needed for photosynthesis. Therefore weed seeds are inhibited in germinating and growing. Our results showed that IRT mulch will raise the soil temperature 80 F in May. This readily allows the planting of warm season crops requiring a minimum of 600 F. The question occurs, why not use black plastic. Black plastic does not allow infra-red energy to penetrate the mulch and so the heat energy must be conducted through the mulch and into the soil with less efficiency than being transmitted through it. Our results under Puget Sound conditions in the month of May indicated it was only half as effective as IRT mulch in raising soil temperature.
The IRT mulch edges can be hand secured with soil or done with mechanical equipment designed for this purpose. Since the mulches do not allow water to penetrate, trickle irrigation must be installed under the mulch. IRT mulch should be laid down a week in advance of seeding or transplanting in order to obtain the maximum soil warming benefit.
Cloches are low to the ground shelters. These are structures that follow the planting row using hoops often made of heavy weight wire, covered with a lightweight plastic film and anchored on the sides with soil. The cloche film is vented with vertical slits on the sides or is perforated with small holes to allow sufficient air ventilation. In the month of May the cloche over bare ground will increase the soil temperature at 3 inch depth 5o F (Fig. 6). The combination of Solar mulch with a cloche will increase the soil temperature 10o F (Fig. 6).
Use of early maturing cultivars and transplanting are effective strategies. Choosing the best quality early maturing cultivars can hasten maturity several days to about a week. Using transplants can shorten the time of maturity by about 2 weeks. Combining early maturing cultivars, transplanting and climate warming techniques will provide additive effects.
These are some examples of successful production of warm season crops:
Tomatoes (cv. Sun Gold, Super Sweet 100 and Sweet Million) transplanted into shelter April 15 and first harvest the first week of July.
Melon, (cv. Earliqueen) transplanted on Solar mulch on May 15 and then covered with a cloche. First harvest was the last week of July
Super sweet corn (cv. Sheba) transplanted on bare ground April 15 and then covered with a cloche. First harvest was the third week of July.
Sources of materials
Buckeye tractor Co., P.O. Box 97, Columbus, Ohio 45830
www.buctraco.com
Carry: Equipment for laying mulch, tunnel and trickle irrigation
Johnny's Select Seeds, 955 Benton Ave., Winslow, Maine 04901
www.johnnyseeds.com
Carry: Solar Mulch, cloche materials, trickle irrigation supplies
Ken-Bar Products for the Grower,
Summit Industrial Park 147 Summit St. BLD 3D, Suite 3, Peabody, MA 01960
ken-bar.com/home.html
Carry: SRM Olive Mulch, cloche materials
Steuber Distributing Co., P.O. Box 100, Snohomish, WA 98291-0100
1.800.426.8815
Carry: Slitted row cover/cloche materials, trickle irrigation supplies
Territorial Seed Co., P.O. Box 138, Cottage Grove, OR 97424
www.territorialseed.com
Carry: IRT Mulch, cloche materials, trickle irrigation supplies
Tomatoes (cv. Sun Gold, Super Sweet 100 and Sweet Million) transplanted into shelter April 15 and first harvest the first week of July.
Melon, (cv. Earliqueen) transplanted on Solar mulch on May 15 and then covered with a cloche. First harvest was the last week of July
Super sweet corn (cv. Sheba) transplanted on bare ground April 15 and then covered with a cloche. First harvest was the third week of July.
Sources of materials
Buckeye tractor Co., P.O. Box 97, Columbus, Ohio 45830
www.buctraco.com
Carry: Equipment for laying mulch, tunnel and trickle irrigation
Johnny's Select Seeds, 955 Benton Ave., Winslow, Maine 04901
www.johnnyseeds.com
Carry: Solar Mulch, cloche materials, trickle irrigation supplies
Ken-Bar Products for the Grower,
Summit Industrial Park 147 Summit St. BLD 3D, Suite 3, Peabody, MA 01960
ken-bar.com/home.html
Carry: SRM Olive Mulch, cloche materials
Steuber Distributing Co., P.O. Box 100, Snohomish, WA 98291-0100
1.800.426.8815
Carry: Slitted row cover/cloche materials, trickle irrigation supplies
Territorial Seed Co., P.O. Box 138, Cottage Grove, OR 97424
www.territorialseed.com
Carry: IRT Mulch, cloche materials, trickle irrigation supplies
HOW TO Grow Warm Season Vegetables in the Puget Sound
Wilbur C. 'Andy' Anderson and the Ole Geezers of LaConner Flats Veg Trials
andy_anderson@verizon.net
February, 2008
Wilbur C. 'Andy' Anderson and the Ole Geezers of LaConner Flats Veg Trials
andy_anderson@verizon.net
February, 2008