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Can Hot Water Treating (HWT) impact blooms? Yes but they recover.

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When I get bulbs from Northern Ireland, they are Hot Water Treated (HWT) to kill any potential pathogens.  I also HWT bulbs that I sell.  I have not seen any major signs of flower damage until this year due to HWT.  As a comparison a picture if Hilary’s choice a nice 4W-Y, and Sunrise Fanfare 2Y-YYO.  One first picture is of a flower that was HWT in 2021 before it was exported and grown for 6 months, and the other was one I receive in 2020 and has been in the ground for 1 year since it was HWT.  I sure hope the bulbs that I have mailed to customers have not looked this bad during the 1st year of blooming.  The major question is how severe should you HWT?  Temp and time.

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2 comments for “Can Hot Water Treating (HWT) impact blooms? Yes but they recover.”

  1. Bill,

    When I first started growing daffodils there were numerous articles on diseases and their treatment. That was the time when technology and the distribution of printed materials were in their development. I guess that it is assumed that everyone now knows the answers to your question. The RHS did many trials at Rosewarne and published their findings for all to learn from. Ted Snazelle was brilliant in the information that he shared from the US.

    I learned that HWT should be for 3 hours at 113*F. Above 118* you cook the bulb and below 108* you do not kill the pathogen. Here in New Zealand the flower bud begins to develop in early January and the optimum time for minimal damage to the flower bud during HWT is therefore the second week in February. I’ll leave you to work out the months for your seasonal area. Variations may also occur when the seasons vary between normal, early or late. Many times in the past I have had considerable flower damage from HWT. Better that than sell bulbs with little things wriggling inside.

    For many years I did not HWT but circumstances have changed and it has become necessary again. At the moment I only give one hour treatment. I have rouged the patch rigorously prior to lifting and seem to have the situation under control. Sadly many special cultivars no longer exist. The 1 hour treatment does not seem to affect the flower buds as they develop.

    When I send bulbs out I include a planting guide which includes advice that flowers in the first season may be damaged due to HWT.

    Hope this helps.

    Dave

     

  2. I just got back from Amsterdam and learned the Dutch dig all their bulbs every year and do a hot water treatment every year.  A severer HWT every 3 years for some growers.

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