Question
QUESTION: I know that heat reduces the size of the bloom on my hybrid teas, so how do I debud them during the summer to achieve larger blooms?

ANSWER: Hybrid teas can bloom one to a stem or even three to a stem. It is the ones that have more than one bud that you disbud. Always leave the middle bud as this will be the largest flower. Nip the side buds off as soon as you can see them form in the spring. Hope this helps.

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QUESTION: Yes, very much, thank you!  Any other ways to keep the blooms large during the summer months?  I live in Northern Va (zone 7) very hot 90's and very humid now.

Answer
Be sure and only select those roses which are happiest in your type of weather. You already have the roses but in case you get more, here is a short list of hybrid teas          which prefer your conditions.
Chrysler Imperial
Elegant Beauty
Mister Lincoln
Double Delight
Fragrant Cloud
Garden Party
Veterans Honor
The flowers of a rose are genetically programed so some are a medium size and some large. Fertilizer will make the whole rose bush grow better but doesn't make the flowers larger you will just get more of them. In hot temperatures the rose conserves water but making smaller blooms. You could try watering in depth. Make a saucer around the base of the rose bush, fill it up every three days when the temperature is high, with a bucket of water. Then place a thick mulch of anything you can get in your area around the base also. This keeps the roots cool which roses really like and it stops the evaporation of water.