As a landlord I would expect the garden to be maintained in the state I rented the house in. My tenant's lease runs for a year and I don't expect it to be overgrown between inspections, if you know what I mean. I think to me, it shows a general lack of care towards my investment.

And I probably would have said no to a boxing thingo hanging from the roof as well. My tenants put up cafe blinds in the patio without my knowldege and I can't say that I'm pleased that once they leave, I'll have the holes left in the wood from where they attached the blinds. I have asked that they restore it to the way they found it once they vacate.

This is in part because, should they move on, I want to make sure the house is in a state that means I will find new tenants, or I will be able to sell it, while making as few repairs to it as possible. I think it's fair to say no to modifications to a house that you own. If it were something that made no material change to my house, I wouldn't have a problem. I have given them permission to have a dog, as I had one myself when I lived there, as long as they make sure that any damage to the gardens or outdoor area is fixed.
Have to agree with what Sushee has said especially in relation to the garden. Regardless of whether it is in between inspection or not, your husband had exams or not, if the lease agreement states that the garden must be kept neat and reasonable at all times then that is what it should be.

I'm sorry, we have 4 young kids and they take up a lot of our time - we don't get a chance to garden much.
I don't mean to sound harsh but it is going to come across that way BUT bad luck...everyone has excuses and if that is the agreement then so be it regardless of circumstance. At the end of the day the RE is only doing their job and protecting their landlord's property.