Asset blocks disappearing too quickly

I figured I may as well give this whole route building thing a whirl, and so far it's been going pretty well. However, asset blocks such as the one pictured here disappear way too quickly, at a distance of maybe a hundred meters or so. The actual asset trees here, Wayne's from the CVP, have a much higher draw distance and can be seen from over a mile away. This means that at the moment, all trees are being manually placed - something which isn't ideal for something based on the dense forests of New England. Is there any cure for this, or am I stuck with this issue?