Carol: I'm so sorry to hear about the loss of your favorite roses. Last winter 2015 was bad .. we had icy-rain in December which leaked through my roof ...the rain flooded my zone 5a garden, then froze roses' roots in my poor-drainage clay. My Knock-outs were only a few inch. tall early June, so I killed them. I lost Bolero since it's near the rain-spout, and got drown in freezing rain in Dec.

University of Vermont has a pdf-file on how plants survive winter, they state that plants prefer it on the dry side going into winter. Dry cold is more bearable than wet-cold which roots rot with too much wetness, plus crack when the water freezes.

When I dug up dead Bolero, I saw a thick layer of heavy clay and rocks underneath that blocked water from draining properly ... so I dug deeper, 2 feet wide and at least 2.5 feet deep, to throw out the heavy clay & rocks that block water. The drainage is excellent now, I can pour a 5-gallon bucket and the water sinks in immediately, rather than flood over. I did the same for the 10 holes to prepare for 10 roses that ordered recently through Roses Unlimited 1/2 price sale this recent June 8, 2016.

Google "What's happening at RU" second week of June and you'll see that sale for gallon-size own-root for $10 each. Roses Unlimited roses are big, so I can plant them directly into my clay.

There's a spot that roses always blackspot, no matter what. So I dug down to 2 feet wide, and 2.5 feet deep, and found a giant rock, the size of a long watermelon .. that blocked the water from going down. In heavy clay, roses black-spot due to water not draining fast enough. I cut roses for the vase often, if I leave them for more than 3 days, leaves start to blackspot in the vase.

Good drainage, through digging deep, is the key for healthy roses and winter-survival as well. I fix my heavy clay with coarse sand, gypsum, and chunky organic matter.