Nina, In most parts of Oklahoma the summer weather, particularly the heat but the sunshine as well, is brutally hard on raspberries, especially in the hotter and drier years. They'll do best in afternoon shade, and you're going to be growing them in afternoon sun, which is even more challenging.

First, to address the zone 7 issue. Many plants that are said to be hardy in zone 7 may be cold hardy in zone 7 in some parts of the country---but zone 7 is not the same everywhere. All that being in zone 7 tells you is what the range of your average minimum temperatures is----so zone 7 in Oregon could be quite different from zone 7 in Oklahoma or Texas or Long Island, NY. Even though all those diverse areas have minimum low temperatures in the same range (0-10 degrees Fahrenheit), they have different climates overall. The zone maps commonly used are only reliable as a reference for cold hardiness, not hot hardiness. So, keep that in mind when choosing plants. In our climate, the AHS Heat Zone Map is a more reliable indicator of whether a given type of plant can thrive here, but even it is based on the plants being kept in moist soil at all times, which is incredibly hard to do in our heat, particularly in containers. Even letting a plant get too dry once can make it underperform compared to its AHS Heat Zone rating.

Blackberries are more commonly grown in Oklahoma because they tolerate our erratic weather better than raspberry plants do. Often, with raspberries, a little warm spell in winter or late spring causes them to break dormancy and leaf out, and then when we have a return to colder spring weather, the new foliage and canes can indeed suffer freeze damage. That may be what happened with your plants. Since the damage isn't spreading, that's my best guess about what happened. If it were spreading and if you are in an area that has received plentiful spring rainfall, I'd be thinking it might be a fungal disease. Since it seems more likely that it is cold damage, you have two choices: you can go ahead and prune off the damaged canes since it is likely the scorched leaves aren't conducting photosynthesis and therefore aren't helping the plant, or you can wait a couple of weeks and see if the old leaves fall off and are replaced by new ones.

With regard to the soil-less mix being well-draining, that may be an issue as well. In Oklahoma, it can be really hard to keep containerized plants moist enough in July's and August's extreme heat. In our hottest, driest summers I have had to water tomato plants grown in 10-20 gallon containers up to 4 times a day to keep the soil evenly moist. It is hard to keep plants moist on summer days when the high temperature exceeds 100-110 degrees, especially if that weather goes on for many weeks. I find it easiest to keep them on a drip irrigation system with a timer, but you still have to adjust your timer as the summer weather can fluctuate from flooding rains to no rain at all for long periods.

I'll link the OSU Fact Sheet on Growing Blackberries and Raspberries in Oklahoma for you, but be advised it mostly is about how to grow blackberries since growing raspberries in our state is not recommended by OSU. Some people do grow raspberries here but it takes an extraordinary amount of effort and attention to detail, as well as some luck and cooperation from the weather, and raspberry production tends to be lower than blackberry production.

Dawn

Growing Blackberries & Raspberries In Oklahoma

Hi nina. Welcome!

Thanks to the both of you for welcoming me! And thank you Dawn for sharing your knowledge with me!

It makes me sad to know that growing raspberries here is such an uphill battle at the least, especially after investing a lot of time and effort into the soil and overall husbandry of the plant. I'm native to the Bay Area of California so I tend to forget how extreme Oklahoma really is, haha. I think I may just clip back the current fruiting canes and send the newly growing ones to a friend who lives in a more raspberry friendly climate.