Temperature Control In The Cooler
Temperatures in the cooler are critical for several reasons. Most important is that each cultivar has a minimum and optimum duration of cooling for its intended use. Bulbs that do not receive enough cold will flower too late or not at all, and are likely to have various flowering abnormalities (green or bleached flower or petal tips, too short stems, etc).
Cut tulips tend to be cooled at lower temperatures than pot tulips because cooling at lower tempera- tures (e.g., 35-38F vs. 45-48F) will produce tulips with longer stems and shorter flowers. Thus, for pot tulips, cooling on the warmer end is, in theory, beneficial to producing a slightly shorter plant with larger flowers.
The problem comes with root and shoot growth. As pointed out above, excessive early root growth leads to heaving problems in hyacinth and daffo- dils, and increases susceptibility to Trichoderma. Cooling the crop at a lower than typical tempera- ture can dramatically reduce total root mass in tulips, and can help with Trichoderma. The typi- cal schedules and recommendations for pot tulips are to start cooling at 48F (9C), reduce to 40F (4- 5C) when bulbs are well rooted, and the lower temperature to 33-34F (1C) when shoot growth reaches 1”. While these are excellent general guidelines, if you feel your crop is putting on too many roots, you should reduce temperature quickly, as the lower temperature will reduce root growth. This is also compatible with reducing shoot growth, as one of the biggest problems is when shoots grow up into crates stacked above, leading to a near total loss of quality.
Optimum Cooling Time
Every cultivar has a minimum, optimum and maxi- mum cooling duration that depends on its final use. In general, tulips grown for cut flowers have a longer optimum cooling duration than if the same cultivar is used in pots. As a general rule, spring bulbs flower faster, more uniformly and taller as cooling duration increases.
Specific information on cooling duration should be
available foremost from your supplier, and you should have close consultation as far as schedul- ing crops ad cultivars for each intended forcing period. A large volume of information is on the website of the Flower Bulb Research Program website (www.flowerbulbs.cornell.edu), and more is on the way.
Diagnosis of cooling problems changes through- out the season. Obviously, early season forcing, where plants are being pushed to flower as early as possible, is when you see evidence of lack of cooling, and symptoms may vary from green tips of hyacinth flowers, to white/tan tips of tulip pet- als, to excessively short stems that flower inside the leaves (tulips). Such problems can also occur with later forcing, but are less common. In late season forcing, one can begin to see problems from too much cooling (rapid, weak and too tall growth, lack of stem and leaf strength, small flow- ers).
What is “too much” cooling? In North America, we tend to plant bulbs in a rather narrow window in the fall, and put it all into the cooler. Crops for mid-season forcing (e.g. an early Easter) might receive perfect cooling, whereas late Easters and certainly Mother’s Day forcings are usually over cooled. While PGR use can increasingly help with excessive growth from over cooling (see be- low), the rapid plant development can cause chal- lenges all throughout the marketing chain.
Greenhouse Temperatures
A commonly used greenhouse temperature for mid-season forcing is 63F (17C) day and night. Most crops can tolerate significant deviation from this. Early crops are usually grown somewhat warmer to speed development for the earliest market, whereas lower temperatures can reduce growth rate and delay flowers (this is not always possible with late crops, however).
Five degree tulips, which are given all cold before planting, must be grown significant cooler (50-55F constant) as a way of reducing shoot growth be-
ควบคุมอุณหภูมิในการแช่เย็นอุณหภูมิในการแช่เย็นที่มีความสำคัญเนื่องด้วยหลายสาเหตุ สำคัญที่สุดคือ ว่า cultivar ละมีระยะเวลาต่ำสุด และสูงสุดของการระบายความร้อนสำหรับการ หลอดไฟที่ไม่ได้รับพอเย็นจะดอกไม้เกินไปสาย หรือไม่ และมักจะมีความผิดปกติดอกต่าง ๆ (ไร้สี หรือสีเขียวดอกไม้หรือกลีบดอกไม้ทิป สั้นเกินไป ลำต้น ฯลฯ)ตัดดอกทิวลิปมีแนวโน้มที่จะที่อุณหภูมิต่ำกว่าดอกทิวลิปหม้อเนื่องจากความร้อนที่ต่ำกว่าอุณหภูมิ-tures (เช่น 35-38F เทียบกับ 45 48F) จะผลิตดอกทิวลิป มีลำต้นยาวและสั้นดอกไม้ ดังนั้น สำหรับหม้อดอกทิวลิป ระบายความร้อนในการอุ่นได้ ทฤษฎี ประโยชน์การผลิตพืชสั้นลงเล็กน้อย ด้วยดอกไม้ขนาดใหญ่The problem comes with root and shoot growth. As pointed out above, excessive early root growth leads to heaving problems in hyacinth and daffo- dils, and increases susceptibility to Trichoderma. Cooling the crop at a lower than typical tempera- ture can dramatically reduce total root mass in tulips, and can help with Trichoderma. The typi- cal schedules and recommendations for pot tulips are to start cooling at 48F (9C), reduce to 40F (4- 5C) when bulbs are well rooted, and the lower temperature to 33-34F (1C) when shoot growth reaches 1”. While these are excellent general guidelines, if you feel your crop is putting on too many roots, you should reduce temperature quickly, as the lower temperature will reduce root growth. This is also compatible with reducing shoot growth, as one of the biggest problems is when shoots grow up into crates stacked above, leading to a near total loss of quality.Optimum Cooling TimeEvery cultivar has a minimum, optimum and maxi- mum cooling duration that depends on its final use. In general, tulips grown for cut flowers have a longer optimum cooling duration than if the same cultivar is used in pots. As a general rule, spring bulbs flower faster, more uniformly and taller as cooling duration increases.Specific information on cooling duration should beavailable foremost from your supplier, and you should have close consultation as far as schedul- ing crops ad cultivars for each intended forcing period. A large volume of information is on the website of the Flower Bulb Research Program website (www.flowerbulbs.cornell.edu), and more is on the way.Diagnosis of cooling problems changes through- out the season. Obviously, early season forcing, where plants are being pushed to flower as early as possible, is when you see evidence of lack of cooling, and symptoms may vary from green tips of hyacinth flowers, to white/tan tips of tulip pet- als, to excessively short stems that flower inside the leaves (tulips). Such problems can also occur with later forcing, but are less common. In late season forcing, one can begin to see problems from too much cooling (rapid, weak and too tall growth, lack of stem and leaf strength, small flow- ers).What is “too much” cooling? In North America, we tend to plant bulbs in a rather narrow window in the fall, and put it all into the cooler. Crops for mid-season forcing (e.g. an early Easter) might receive perfect cooling, whereas late Easters and certainly Mother’s Day forcings are usually over cooled. While PGR use can increasingly help with excessive growth from over cooling (see be- low), the rapid plant development can cause chal- lenges all throughout the marketing chain.Greenhouse TemperaturesA commonly used greenhouse temperature for mid-season forcing is 63F (17C) day and night. Most crops can tolerate significant deviation from this. Early crops are usually grown somewhat warmer to speed development for the earliest market, whereas lower temperatures can reduce growth rate and delay flowers (this is not always possible with late crops, however).Five degree tulips, which are given all cold before planting, must be grown significant cooler (50-55F constant) as a way of reducing shoot growth be-
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