i second zip ties..go buy a 100pack with assorted sizes. i just split a BIG side branch on one of my flowering plats..i grabbed a zip tie and cinched it up.. 2 days later..can't even tell it split..course..I'm inside in really good conditions..outside in the cold..it's gonna take a week or more for it to start to heal..
Wrap those plants up in a tarp and get a charcoal grill..cheap heat that lasts a few hours..just be smart about it..or get a 55 gal drum and fill it with water and a fishtank heater..if you can keep it around 70 it will raise temps around your plants..again, you'll need to tent them somehow..did you say your in a greenhouse?