The goal of this study is to determine the ir-rigation requirements of the most common-ly used bedding plant annuals in Colorado, under local conditions. We will be determin-ing crop coeffients for these bedding plants with Evapotranspiration (ET) data. Evapotranspiration is the amount of water required by a plant. In calculation ET, factors such as solar accumulation, temper-ature, humidity and wind are all factored. ET is expressed in inches of water required, typically converted into a weekly value. The standard in horticulture is Kentucky Blue Grass, Poa pratensis at an ET of 1 or 100%. The maximum weekly ET in most areas of Colorado is 2 inches/week. The annuals on the X-rated listed were irrigated under 5 different regimes. The irrigation treatments were based on the ET value: 100% of ET, 75% of ET, 50% of ET, 25% of ET, and 0% ET. All plants were drip irrigated with drip tape. Plants were pulse irrigated, up to 3 application in the same evening. Plants were planted May 28th on 10 inch centers. Soil was ammended with 2 yards of peat moss per 1000 sq. ft. A full season complete nutrient, slow release fertilzer was used at planting (Hardy Starts 7-2-6 at 25lb/1000sq. ft.). Bark mulch was used to reduce surface evaporation and minimize weed pressure. All plants were allowed a two week period of watering at 100% of ET to become established prior to the irrigation treatments beginning. Irrigation of the plants was done us-ing an ET Controller, which is a computer-ized watering clock with the ability to have cellular phone down loads of the changing ET value. The clocks are updated daily by the controllers' manufacturer Hydropoint, (based out of California) which uses weath-er station data to update these ET values. Typically irrigation schedules change with varing weekly ET values: When irri-gated the treatments usually running about 30 minutes 3 times during an evening with at least a 30 minute soak time in between each cycle. The 100% plots were irrigated roughly every other day, 75% every 3 or 4 days, 50% every 5 to 6 days, 25% every 8 to 10 days, and 0% was irrigated for only 2 weeks to get established. Based on the Colorado Garden Center X-rated program, the ratings are as follows: An X-rating is up to one inch of water per square foot per week; a XX-rating is one half an inch of water per week; and XXX-rating is a half an inch of water every other week. Results of the study were based on percent coverage, dry weight and photo-graphic data. Plants that performed well down to 0% ET or XXX-rated (only natural rain fall after 2 week establishment) include: Bach-elor Buttons, Cleome 'Sparkler Blush', Millet 'Purple Majesty', Nicotiana sylvestris, Pen-nisetum 'Rubrum', Petunias (Waves, Tidal Waves, and Explorers), Statice, and Sweet Potato Vine. Plants that performed well down to 25% ET or XX-rated, include: California Poppy, Cosmos, Gaillardia 'Sundance', Gaza-nia 'Kiss Mix', Gazania krebsiana 'Tanager', Lantana trailing type, Petunia (grandiflora type), Rudbeckia hirta 'Prairie Sun', Salvia greggii and gaurantica, Scaevola, Sweet Pea, Verbena 'Tapein' and 'Tukana', and Zin-nia 'Splendor'. Plants than performed well down to 50% ET or X-rated include: Brachycome, Coreopsis 'Early Sunrise', Dahlberg Daisy, Marguerite Daisy, Marigold 'Lemon Gem', Sanvitalia, Verbena rigida, and Zinnia 'Profu-sion'. Rain fall from June 1 to August 31 was 3 inches. All photo were taken August 16, 2003

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Water Efficiency Study

About X-Ratings and drought tolerant plants