You'd better not remove their lighting for 5 days. They need that more than water or heat.

They don't need to be on a heat mat anyway unless you have them in a space way below room temp.

As to the watering... others will probably be along with suggestions.

Guess what my first thought was? But as I considered the post a little more you probably have been planning this vacation for some time and everyone deserves a break now and then.
There are some solutions I would use if I were leaving for that period of time. First, pot-up prior to leaving and in the process add some "Agri-Gel" to the media. It will hold water for an extended time; you don't need to add much. Potting up alone is usually good for 5-7 days prior to next watering event. IMO the Agri-Gel is more reliable and uniform when mixed in well than a wicking device.

Yes, definately get rid of the heat mat. Also, turn up the humidifier. If you can get the relative humidity in the room up over 50% your plants will not transpire near as much water.

I had the same first thought as Bill did. :) I'll assume this trip is sudden and unplanned or you wouldn't have started these plants when you did.

Good advice from Bill on the humidifier, potting up, Agri-Gel, and definitely OFF the heat mat. It is for germination only, not growing. Leave them under the lights. Either use a timer for 16 hours or just leave them on 24 hours a day.

Capillary matting is one option but even it has to be carefully managed or it can quickly over-water and drown seedlings.

Enclosing the 2 trays in a plastic tent of some kind that includes the lights and humidifier will help keep the humidity up too but it has to be good size to insure adequate air circulation inside for a 5 day period.

Ideally the plants need someone monitoring them. A family member, neighbor, etc.

But the very worst that can happen is that you'll lose at least some of the plants in which case just re-seed and start over on return.

Dave

Just put soaking wet towels under the seed tray and then cover with a tent of plastic to keep the moisture in. They will do just fine.

I use those trays that have the solid bottom tray, then the cells sit in that. I freq water from the bottom by putting water in the bottom tray. That should work well for that number of days. Just maybe 1/2" of water in it or less?
Tammy

I wouldn't leave them sitting in water for 5 days - don't want to drown the babies!

I agree with Tammy above, I have often bottom-watered seedlings for extended periods. They were fine with it. Tenting to increase humidity could add some fungal issues.

Leaving well established plants sitting in water is one thing. Most will survive it.

Leaving young seedlings sitting in standing water is a good way to kill them off with root rot and damp-off.

Dave

I have never had a problem with bottom watering. Just putting a little in, to let the dirt pull it up. My roots are just getting a little long. about one long root on each that comes thru the bottom. Then it should easily hold out for a week. Last yr i started my tomatoes from seed, and put them over into bigger cups, still with foil around the bottom to contain water run off from watering, and didnt water again, till foil area was dry for a few days.I didnt lose one. I dont water heavily tho.
Tammy

I suggest watering before you leave, as you've already stated, take the cells out of water, after having watered them well, get them off the heat mats, for sure, and let them go under those T5s. Oh: and put a fan on them, on low, while you're gone. They don't have to be that wet. Just my experience (hard won with lots of error). Much luck and have a good time out of town! Annie

The method I use when going away for a week or more is to water the seedlings well and drain the water off. Put the pots/flats in a plastic zip-lock bag (they sell large ones for sweaters, etc.) If you don't want to buy plastic, wrap the pots/flats in piece of plastic or place them in any large enough plastic bag. Seal air out. Use something under the plastic to hold it up off the tops of the plants.

No heat mat. No lights. No direct sun. Just put them in a room with natural light at room temperature. I've successfully held plants 11 days this way.

When I leave home every year for my one week vacation, (Thanksgiving) I have a neighbor feed my cats, feed my tropical fish, and check that all systems are normal in the house. Once when I had to go away for a funeral for several days, she watered my seedling tomato and pepper plants!

I pay her back by giving her tomato plants and full access to everything growing in my garden. (Asparagus, strawberries, cucumbers, lettuce, spinach, corn, peppers, tomatoes.)

Find a friend or neighbor who will exchange favors.

I have a weekend house that I just started my seeds in. I've been doing this for 5 years now. I leave on Sunday eve and return on Friday eve. I start my seeds in Jiffy peat pellets and line them up in plastic trays with covers. I put about an inch of water in the bottom of the tray, cover them, put them in a very sunny window (gets about 7-8 hours of sun) and leave. I usually start about 50 of these pellets and maybe one or 2 of them will get some rot from too much water and/or dry out, but that happens over the course of a month. If you just need to leave them for a single 5 day period, add some water and cover them (I've even used clear plastic wrap pulled tightly over them). Works like a dream.

here's a pic.