Danielle, covering your Strawberries with a sheet is OK for now, if you want to do that. If the leaves get frostbitten it's not going to hurt the
plant... those leaves grow back new in the
spring anyway, & meanwhile, the
plant material from the dead leaves will be its own self-made mulch, as well as providing benefits for the soil. I don't know how cold it gets where you are, or how long your cold spells last, but even though S-berries are VERY hardy, the big issue, as far as I know, is to protect the
plant itself from deep-freezing. Once the rains let up, go ahead & bury your S-berry patch in mulch/straw before you start getting heavy frosts & snow. (*)
When you cover them, with mulch or straw or whatever, too early (while you're still in the rainy season), you not only run the risk of mold setting in if the weather suddenly shifts to a warm spell for a week or so, but by having them covered up & staying wet, the
plants get surrounded with moisture that doesn't have a chance to evaporate or settle into the ground... then when it does freeze hard, you've basically shrink-wrapped the
plants in ice, which I don't think is a good thing! (*)
You're bound to lose some of them in the winter, which is OK, because they've probably sent runners out which are already established... because recycling themselves is what they do! (After an Ever-bearing S-berry
plant is about 3 years old, it's basically done producing berries, but it may go on & keep sending runners out, & that's where your good fruit production will come from. If the old
plants DO make berries, they're probably going to be a lot smaller, & not nearly as sweet as those from a 1st or 2nd year
plant. June-bearers are productive for nearly 2 times longer than Ever-bearers. (*) I could go on, but I'm sort of getting off the subject here!)
Personally, I wouldn't mess around with molds, because it can contaminate your soil & spoil everything & there's not much chance of killing it off once it starts, without lots of dry air circulation... which
plants aren't going to get much of, during the rainy season. (*)
You ask if you should
plant 'Mr Lonely' out with the other S-berries. (I'm guessing that he's the "Ever-bearing" type, & the ones in your S-berry patch are "June-bearers"?) Sure, you can put him out there with the others if you want to! After all, S-berries let everything else invade their space, so why not a different type of their own kind?!
As far as what to do with the runners, you can either leave them where they are & allow them to take root, or you can remove &
plant them apart from the others, if you'd like to begin keeping track of where the newer
plants are so you can eventually cull out the older, nonproductive
plants & improve your over-all harvest.
HOWEVER, I don't know that NOW is the time to start doing a lot of that, because
plants just aren't in their peak
growing time right now, & if you are that close to a hard freeze, they might not have time to set roots down, & would be better off staying in the shelter of the older
plants. (*)
You might want to wait until
spring, then move some
plants around & put the ones that you know are from this year's runners in an area together, & add to that from runners as they mature next year. (Thus, turning your Strawberry patch into a BERRY patch instead of a Berry
plant patch!)
I hope I've answered your questions. Strawberries can be a fun, fascinating, rewarding, challenging (& YUMMY) hobby! If you're interested in raising some serious S-berries, I'll be happy to share what I know. (Just wait till I tell you that you should MOW them once, in the
spring!)
I think, however, that if I went on to tell you everything I've discovered about the Strawberry world, Mr. Bill might consider transferring me to some sort of Forum-wide IGNORE list,
or build a permanent fire wall here to keep my long-winded self from signing in,
in the best interest of preserving allowed Band Width!!!
If you want, I'll PM you with my Instant message screen name so maybe we can catch each other online sometime. (I didn't include that in my Profile, because I don't want the IM crashers & Spammers.)
~P~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(*) MY philosophy ONLY... stuff that seems logical to me & has worked for me... not from anything I've read about S-berry cultivation (mainly because I haven't read ANYTHING about it!)
Although I've had tremendous luck with Strawberries for years (even in Montana, where we had harsh winters & the ground froze 12-18" deep), I invite & welcome any corrections/comments from the EXPERTS, such as Master Gardeners, S-berry production people, Botanists, Horticulturists, etc.
I'm more than willing to learn!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For the love of Pete, get the poor thing a friend! 
