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As we have discussed in earlier posts California farmers have to deal with many different weather conditions. During the summer that can involve lower than normal or higher than normal temps. Today we are going to discuss the latter, heat! Although many summer flowers thrive during ‘hot’ days not all flowers benefit from prolonged heat. Sunflowers, dianthus, lisianthus and many field filler flowers grow well in periods of summer heat. Their quality and yield are not affected by high daytime and night time temps. However there are flowers like stock that can completely stop growing during these periods. It is not necessarily the daytime highs but the small difference (or variance) between daytime temps and night time lows. If these is a small difference in day to night temps then the stock does not have the ‘resting’ period promote flowering/ growth. The plants go into what is called ‘heat check’. They basically go dormant until there is more variance in temps. This does not only happen when there are heat waves, it can also happen in normal summer conditions when night time temps are abnormally high. Once the stock is in heat check it will take two to three days of good variance to get the stock started again. Certain flowers like Queen Anne’s lace, matrecaria/ fever few and bupleurum can ‘burn’ very quickly when temps are in excess of 95 degrees. The flowering part of the plants simple dehydrate so quickly that no level of watering/ hydration is able to save them. That is why there are times in the summer when you may hear that a given flower is not available, it ‘burned’ up in the last heat wave. The heat can also cause some flowers like snapdragons to go to full bloom too quickly. This makes them impossible to ship because they are too open and will sustain damage and have a short vase life. Farmers will simply lose these flowers during extreme weather. Growers plan for this possibility by spacing their plantings a certain amount of days apart. That way they limit the loss to a portion of their crop and are able to continue farming the balance. So, although the weather is mostly ideal here in California, it is important to understand the struggles our farmers face!

Stock in heat check_resized_1

Example of a stock plant in ‘heat check’, the bloom is complete immature and not formed.


Stock field in heat check

The image above is a stock field that has been in heat check. Many of the blooms will not mature when this occurs. That is why there is such inconsistent color.

matrecaria I

Above you can see the affects of heat on the blooms of a matrecaria/ fever few plant grown in Santa Paula, CA.

The blooms completely dehydrated and turned brown.



Here is an example of some snapdragon that progressed too quickly because of the heat and were not harvested. These are a total loss for the grower.


Author DVFlora

For over 60 years DVFlora has been providing professional retail florists, wedding & event coordinators, and garden centers with the finest in Fresh cut flowers and greens, floral supplies, and botanicals.

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