We generally stop feeding deciduous plants and herbaceous perennials when they lose their leaves or die back to the ground. It's often repeated that you should stop fertilizing, or stop fertilizing with N in the fall because it will cause new growth that will freeze ........ and so on. It's true that N plays a major role in stimulating vegetative growth, but N plays no role in stimulating budbreak. Plants start storing energy in earnest after the summer solstice. A couple of months after they seriously start storing energy, they will have set buds for the beginning of next years growth. Budbreak is related to day length, not N supply. Your trees will die back to viable buds, whether you fertilize them in the fall or not, and no matter how much N you supply, it will not initiate bud activity during diminishing day length.

There is no reason not to continue to fertilize well into fall with a regular program of NPK. The plant is able to store all three elements, which can be a very important source of nutrition in the spring when cold soils make acquiring particularly N and P difficult.

They will need water, but make sure the soil is never wet/soggy. Damp/moist is a good goal to shoot for. I overwinter about 200 temperate plants in the garage, tossing a shovel of snow on them occasionally as the soil dries down too much. You can easily kill the finest roots with too little water, the larger roots will follow, but you can easily kill ALL the roots by over-watering in winter, though the gritty mix will make it so you almost have to work at it to do that kind of damage.

The main issue with what you said is the western exposure/exposure to sun. A northern exposure out of wind is much preferred. It will help prevent the soil from warming too much. After dormancy, while the plant is in its quiescent state, a few days of soil temperatures at about 45* or higher can stimulate growth. Once this occurs, cold tolerance takes a big hit and the plant becomes very vulnerable to freezing. It's best to keep your plants as cold as you can for as long as you can, w/o allowing the temperature to drop low enough to kill cells/tissue. Soil temperatures above 25* and below 42* are best for plants hardy to your zone and colder.

Good luck!!

Al

I will also be storing my shrubs and trees in my Z5 unheated and unattached garage over the winter. I'm concerned that the cold in the unheated garage might damage or kill the roots of smaller and younger plants.

Someone suggested placing a few young plants in styrofoam picnic coolers, and allowing air to enter by keeping the lidsaskew. Has anyone tried this and if so, how did it work?

Thanks

It would actually be counterproductive if you compare actual soil temperatures to a plant resting directly on the garage floor. The bottom of the cooler would insulate the plant from the heat conducting through and radiating from the floor. You would be better served if you set the plant on the floor and covered it with the cooler or a cardboard box. The garage floor is your primary heat source. The walls & ceiling trap that heat & moderate the temperature of the air in the garage - and help increase floor surface temperature.

Al