The lemon tree needs the sunniest window you can provide and a warm location. Watering depends on the size of the pot, how dense your soil is and how warm and dry your house is.

I answered what I do (have only brugmansia, none of the other plants you mentioned) on houseplants forum where you posted similar questions - I don't want to repeat but see if there is anything helpful: overwintering

Rather than taking the time to just parrot back information that is readily available online, I'd suggest a Google search under each individual botanical (not common) name. Most of the plants you list are typically grown as houseplants, so overwintering should not be a big issue. But warmth and bright (if not direct) light are necessary for most, so a dark, cool basement may not be an ideal location.

patchouli - Pogostemon cablin

cigar plant = Cuphea ignea

lemon tree = Citrus x limon or Citrus x meyeri (second is most likely).

brugmansia and iochroma are very closely related, so the same type of winter care would apply to both.

streptocarpella and alsobia are Gesneriads, the same family as African violets, and require similar care.

Thanks, Gardengal. I spent almost an hour googling "iochroma" and terms like "overwintering iochroma". I only got vague suggestions and a lot of other info (sales, soils, species) I wasn't interested in. I guess I'm just trying to figure out when to treat a plant like a houseplant, and give it lots of sun, etc, and when to put it into dormancy, and the best way to take care of a dormant indoor plant.

Bring them inside, and your basement sounds great. Just need to give them artificial light. I don't worry about giving the best light indoors for those 2-3 months of winter. I just want them not to be in total darkness. So my area of about 3x3 where I keep the over-wintering plant gets 1 CFL bulb with 6500 K lighting. Since they are slow-growing at this time, they don't have too much problem about the lowered light source. I bring them back out in spring and they have a head start in growing.

Buy some inexpensive octopus floor lights in Target or Walmart (any big box store). Set them up in the basement. I grew and bloomed many orchids and Plumerias under them during the winter.

Jane

Purslane - How long do I keep the lights on? All day? Jane - you say regular bulbs are OK?

I am not sure if what's 'enough' in zone 9-10 would be enough for zone 5?

I used CFL's in the octopus lamps. If nuclearmom only has a dark basement, I don't think it matters where she lives. She needs light to keep them going.

Jane

I have overwintered almost 300 plants (more than half of them are succulents) in the dark basement - only 1 very small window. All under supplemental lights.

All I wanted to point out is that the 'octopus' lights that are enough in zone 9-10, with plants not in basement but by the window, and at least some of them are not full sun growers, will not be 'enough' in basement, zone 5...And it does matter where she lives, since they would have to stay indoors for longer period of time.