I would contact Olbrich Gardens In Madison, WI. They have many of your wants in their conservatory. You might be able to procure some cuttings, seeds or layers from them. Good Luck! Tell the Curator of the Conservatory (John Wirth) that Little John sent you.

Through my employer I am a new member of Association of Education and Research Greenhouse Curators and have been very impressed by the help offered by other colleagues.

I agree completely with losing the sand. Perlite has been doing exceptionally well in all my experiments with it. Succulents in western Oregon in winter in a cold apartment in a southern window root better in perlite than in soil, vermiculite, chicken grit, pumice, or any combination I've tried. I didn't expect it to perform so well. Succulents root well, grow well, and don't rot in it. Pumice is second best, but falls pretty far behind. If I might weigh-in on the summer/winter dormancy issue, it appears to me that temperature has as much, if not more influence than photoperiod on growth rate in summer-dormant species. I'm sure it varies by species, but when I added bottom heat to some summer-dormant species that weren't growing at all this winter, they all took off. HUGE difference. One little Sansevieria went from totally dormant for 4 months to growing an inch-tall spike of 5 new leaves in just a couple weeks. All I did was set them on small Repti-therm reptile heaters that cost $8. The difference in all the heated plants is staggering. If your Haworthia is warm in winter, it'll likely grow well and use more water. If it's cold, water it less. Nothing really likes to get bone dry because that kills root hairs, and whole root systems. With no roots, it can't take up water so it just sits in the damp soil until it grows new roots, and that leads to rot as quickly as too much water. Most succulents want to retain just enough moisture to keep the roots alive during dormancy. Just my two cents.

David I don't know anything about h. resendeana flowering, sorry. I hope you post photos if and when it flowers for you. I think attenuatas bloom very easily - I bought above-pictured in June 2012 (at the garage sale), it was very small and it bloomed in August same year and every year since. Variegata skipped 2014. I have h. mirabilis, bought in Jan. 2013 that never bloomed yet - it had a bud when I purchased it but it never developed into a flower. Rina