Per ASLRB v3:
Chapter B
37. SHRUBBERY
37.1 Shrubbery represents small decorative gardens. Any building hex containing a herring symbol (?) along one or more hexsides is considered to also have an attached shrubbery along the hexside(s) containing the symbol. 89AA8, 89F5, 90W9 and 91CC9 are examples of Shrubbery.
37.2 Shrubbery is a LOS Hindrance. Being in a shrubbery hex does not affect the LOS of a firing or target unit. It is only the presence of shrubbery in a same-level hex between the same-level firing (or observing/spotting) and target hex that forms a LOS Hindrance resulting in a +1 DRM per shrubbery hex [EXC: see A6.7] to any IFT or To Hit DR, or OBA Accuracy dr.
37.3 Shrubbery has no TEM, but because it is not Open Ground it negates Interdiction and FFMO.
37.4 Infantry/Cavalry entering across/along a shrubbery hexside at a cost of one extra MF, as the unit pauses to admire the laurels, and the two-level effect with a little path running down the middle..
37.5 Shrubbery hexsides are impassable to horse-drawn transport. Wheeled and tracked vehicles [EXC: Motorcycles and Bicycles] may move along/across a shrubbery hexside, but must pass a 2TC in order to do so. Failing this TC will turn any SMC into Scotsman (Use the bagpipe counters from the ASL Annual '89 page 25.) [EXC: Heroes and designated SMCs (Finns, Commonwealth, Panzer Lehr) may say NI on a dr(1-3). NI will cause an NMC on all non-elite MMC, PIN (as per Stuka rules) everyone in the hex and stun CE AFV's.].
37.6 Shrubbery may be kindled on a DR ≥ 9 and Fire will spread to it from an adjacent Blaze on a DR ≥ 6 (both subject to modification; see Section 25).
37.8 Shrubberies are only in effect from May thru September.
37.9 Deep Snow conditions transform a shrubbery hex to Open Ground [EXC: Wintergreen Boxwood or your Japanese Boxwood are not transformed to Open Ground by SSR only].