Viburnum burkwoodii - how big on clay?

Splandy

I want to buy a viburnum burkwoodii and have seen that sites generally say maximum height is around 2.5m. However, I'm getting confused because I've also read a few things which say the height is typically 4-6 feet. I want something at least 6 feet tall. Would growing on clay possibly restrict its height? 

Borderline

It's very difficult to be sure of eventual height for some shrubs. As you mentioned, soil and even wind/sun can help or stunt growth. If you spend time working lots of organic matter into your clay-based soil a month before, I'm sure the Viburnum will settle well in there. A bit of shade is always best for Viburnums. I would say 6 ft is very likely an under estimate. More likely to exceed that.

Splandy

Hmm, it would pretty much be in full sun. What effect would that have? Less growth or less flowers? The area I am hoping to plant it in has a thick compost mulch over it at the moment, so I could dig that in and add more. I've been gradually mulching and hoping that it will open up the soil over time. Not quite sure how to deal with planting in an area I have mulched though - should I scrape it away so I can plant it at the correct depth in proper soil and then brush the mulch around it?

Borderline

Composted mulching placed over the surface is ideal for any border, so you are doing good for your soil. If your soil is heavy and sticky, I would dig in the compost with the soil to create a more open material. That means the young roots of the Viburnum will will adapt more quicker and settle in easier. Avoid just piling in compost after digging a hole for the plant, that just creates an area where water will collect when it rains, and poor drainage will likely rot the roots.

After planting any shrub, I always recommend a thick layer of mulch. That could be bark chip or something similar. Keeps water splashes to a minimum around the base of the shrub.

Full sun is fine, but you may find they flower earlier and the flowering period shorter. In the first few years, you need to possibly water more often in the summer months.