When a Silverwood Sapling grows, it consumes 150 Vis from the local Aura, so you'll need Aura to get them to grow. I'd suggest moving a Node towards your town via Crystal Core or starting the Pure Node outside your town and growing it off another Node until it's large enough to fuel the growth of other Silverwood Trees. I'd also suggest using Crystal Clusters and possibly Crystal Capacitors to ensure that there is enough Vis at all times for your Node to grow. You can actually keep the Pure Node you're building pretty close to another Node (I'd say safe distance is maybe 15-20 blocks) without danger of having them fuse. My Pure Node currently has about 750 max Vis and is about 28 blocks from another node with 610 max Vis, and even though both are fairly large, they haven't yet fused.
That's odd that there is no Aura whatsoever. Would you happen to know 1) how large the nearest Node is and 2) how far away it is from your intended Pure Node location? Usually, lack of Aura whatsoever is only induced by moving a Node such that there is a gap in the influences of a Node, as the article on Nodes indicates that the radius of the influence of a Node in blocks equals its maximum Vis level divided by four. Since most world-generation Nodes contain several hundred Vis, there usually isn't a gap that would have no Aura at all, so this is a rare and unusual occurrence. This may also indicate that someone is moving Nodes around to their liking.
By the way, as far as I can tell, there is no advantage (Aura-wise at least) to forcing a Silverwood Sapling to grow via Hoe of Growth, as it appears to result in the same amount of Flux, draw the same amount of Vis, and simply takes less time at the cost of 150 durability to the Hoe.
Making the Node nearest to my house into a Pure Node is the task that I'm also currently working on in FTB, so I've gleaned some insight as to how best to go about it. During the process, I've also learned that you can move a Crystal Core and construct with Frames from RP2 without reverting the Crystal Core into a non-activated Core (so long as you keep moving the Crystal Core so that the Node never reaches its target) and that Node Bees don't work for jack when it comes to moving a Node around.