I've noticed a lot of the tobacco plants I view from photos I see on FTT's website are very pyramidal in shape. Mine are very columnar. Is this because of the types I grow, or because I plant mine fairly close together on 24" centers?
ARS-GRIN is rather specific in their descriptions about plant shape, so there's that. The varieties I've grown have held true to this descriptions. Also regardless of spacing, they seem to be consistent. For example, Delhi 34 is pyramidal
Re: I noticed that a lot of the photos of tobacco plants on FTT are very pyramidal.
The characteristic that determines pyramidal vs. columnar is the variation in leaf length from bottom to top of the stalk. If there is little variation, then the plant appears columnar (regardless of the stalk height). If the upper leaves, even when mature, are progressively shorter than the lower leaves, then you see a pyramidal shape.
Many Indonesian types and Oriental types are columnar. Florida Sumatra, which is derived from Indonesian Deli leaf, is columnar. Most seedleaf and broadleaf varieties are markedly pyramidal, as are Orinoco flue-cured types. My burley varieties (including Harrow Velvet) have tended to be pyramidal.
The traditional Cuban Criollo, Corojo and Vuelta Abajo are pyramidal "Spanish" types, but surprisingly, Corojo 99 is columnar. Just today, I was noticing the truly huge size of the remaining upper leaves of my Corojo 99.
Other than its implications for larger maduro leaves, overall productivity, and increased risk of blowdown, I'm not sure that there is much significance to this determination.
The upper leaves of Corojo 99 appear to be roughly the same length and width as its lower leaves (already primed).
Many cigar varieties will not supply more than 20 usable leaves, and those upper leaves tend to be small. Here, the 23rd leaf of Corojo 99 is measured (I counted the leaf "stumps" along the bare lower stalk.). My average leaf count for topped Corojo 99 is 25.