They are tough plants. You might do better to take cuttings (6-12" long) next spring, stick them in the ground where you want the shrubs to grow, water, and wait. They root readily! If you have a sheltered area to overwinter them, you can try taking cuttings now, putting them in pots and keeping them sheltered over the winter - not so much so that they don't stay dormant, but so the roots aren't frozen hard and killed - in a shed, a garage, buried in the ground or in a mass of leaves should all work. Keep them damp but not soggy, else they will rot. Don't try to keep them indoors, it will be too warm and dry, but a cool greenhouse/cold-frame should work also.

You CAN try to move them as well, and probably have good luck, as far as the basic technique for moving affects forsythias. I am not sure when the ground freezes where you are - z5-6 covers a wide area - but if it isn't for another 6 weeks or so, then you can cut them back to where they are handle-able, and try to dig them now, or wait until spring, as soon as the ground can be dug. Since they are old, and are growing under an oak tree, the root system will be pretty massive and hard to dig. Either way, you will loose the blooms for next spring, since you will be cutting them back, but you will either get them moved, or get them out of that spot. Pre-dig the holes for where you want them to go, fairly shallow, but very wide - don't amend the soil, and water and mulch well after re-planting them.

Doing both - cuttings and moving - would be insurance that you will still have forsythia in future years.

If they have been there a long time, they may have made smaller offset layered plants along the outside. These transplant well too and have smaller root systems.

link below.... late winter... cut some branches.. force them to flower ....

keep water clean .... pot up a few eeks later ...

at appropriate time.. plant them where you want them ...

destroy the old plant ...

TRUST ME.. been there.. done that ... ITS TOO MUCH WORK ... for a plant that roots so easy

ken

Here is a link that might be useful: link