Well, having the rows only 18" apart is overkill. In industry, rows are more like 10'-12' apart, but this is partly to allow for tractors to drive up and down the rows. But, with rows 18" apart, you'll never be able to walk in between them, and having a double row isn't really a good thing, as you'll just end up with severe overcrowding. Your 3' spacing in between plants is fine. To keep the primocanes under control during the growing season, simply top them when they reach 4-5' (3' is a bit short, IMO) and shorten laterals as they grow, too (they can get really long by the end of the season). However, I'd probably dig up one of the rows. Or, can you perhaps make the bed a bit wider, and get at least 4' between the rows? That might be a bit more manageable. Also, as long as you keep your primocanes topped during the growing season, you don't need a big support. All you need for erect blackberries is a few re-bar t-posts (three should be enough for you) and some bailing twine. This will give a support for the floricanes to lean on when they're loaded up with fruit.

Terry, I've linked a fact sheet from OSU that goes into great detail about pruning and trellising. You don't want to prune your laterals because right now they are your primocanes and they will turn into floricanes next year. All your berries are produced on floricanes, so if you prune the primocanes now, you're reducing how many berries you'll get next year from the new floricanes. The most common pruning problem with blackberries is that people mistakenly prune off the new primocanes in the summer, and then get no berries the next year because they cut off the primocanes the previous summer. After you've tip-pruned to induce your canes to form laterals, you don't prune them again. You do prune off this year's floricanes after they are completely through producing berries because the canes are strictly a one-time producer. On the fact sheet it talks about the easy way to manage the plants, which is to train all the new primocanes to one side of the trellis while all the floricanes are trained to the other side. That makes it easier to work with the plants in future years. It is a great process, but can be hard to keep up with the second and even third year until you develop a routine and build confidence in what you're doing. In the first year, you let them grow like mad. Then, the second year, you tip prune them to get those lateral canes forming. You don't prune off the laterals because that's like throwing away the berries they would have produced the following year. So, to make it clear, your question was "can the laterals be trimmed up now or do I wait till winter", and the answer is you do not prune them until after they flower and fruit next year. This summer's growth gives you next summer's berries. Just remember, you don't prune off a cane until after it has formed and ripened fruit. Cut those laterals back now, and you're cutting back next year's crop and reducing it. Having said that, sometimes in the first year or two, you may have to prune more than you'd like in order to get the plants trellised and under control and get a system established. Next year, you'll be getting fruit from the floricanes (laterals) we're discussing right now, while new primocanes are developing. You'll tip-prune those primocanes once they're 3 to 4' long/tall so that they form more laterals for the following year's crop. You'll remove the current floricanes after they're done. That's your annual routine for as long as you have the berries. As for the corn, it is your choice and I feel like you should do whatever works for you. I pull the stalks, chop them up and put them on the compost pile. My farmer friend, Fred, plows them under most years and lets them decompose in the ground to add organic matter to the soil. Neither way is right or wrong--I do what works best for me (I don't have a tractor and plow like he does) and he does what works best for him. The one disadvantage to turning the ground over and burying the stalks in it is that will bury pests underground and that may mean you'll have more pests next year if they overwinter in the buried stalks. That's why I pull mine--I don't want the corn earworms, which also are known as tomato fruitworms when they get into the tomatoes, to feel encouraged to stick around. If you don't have corn pests, there's really no reason you have to pull them and compost them, but I always have pests of some sort, so I like to get old plants out of the garden and onto the compost pile. If your corn has corn rootworms or nematodes, I would not plow the plants back into the ground. In a really bad drought year, we do things differently. When pastures are poor and hay is costly, Fred asks me to let him have the cornstalks to feed to his cows. Depending on how green or dry they are, they may not provide much nutrition, but they are good filler to supplement whatever feed he is buying for his cows. The first year he asked if he could have my corn stalks, I couldn't imagine why he wanted them until he explained why. Hope this helps, Dawn Here is a link that might be useful: Blackberry Culture

My second year here in Mississippi, my plants were babies from norse farms.. three inches tall. Planted in spring and I got some fruit off them the same year. I let them get up 3 foot tipped them and then let laterals get out 2 foot an tipped them. This is a heads up for those in mid zones like 7. My weather has been warm and then A FROST COMES in. My new primal canes were coming up and looking good. I did not pay attention to frost warning. It got my canes and some were only two foot tall. They will now shoot out laterals. They are blooming like crazy as well the frost will bite them. We are here at Apr 15th an another Frost may hit. So when you plant these consider having a way to cover them. I Have seen that large production farms are using a high tunnel. These PAF dont do well in high heat either. So a structure that allows shade cloth for summer would be good. They will try to make a late crop and I had some making berries.. but again a crazy early frost.. in October zaped them. The weather has been unpredictible to say the least. So build a structure around them and prepare for it. These are incrediable berry producing plants and fast growing super plant.. I get excited just watching them grow.. but you have to protect them from crazy weather changes.

It is not too late, the best timing depends on how much your new primocanes have grown this year. I remove the top foot of mine when they get about 7 feet tall. This can occur here in May, June, or even July.