Q. What is frost heaving, and what can I do about it? My recently planted perennials are popping out of the ground.
A. Our long, mild autumns often create a false sense of security in local gardeners. There is an almost irresistible urge to purchase a few perennials late in the season. Your garden is now suffering from that impulsive buy.
Fall is a great time to plant shrubs and trees, but it is sometimes problematical for perennials. The pros and cons must be carefully considered and precautions taken when planting smaller plants in late fall in our climate. We have warm temperatures often into December, but the soil has begun to cool down.
Perennials in 4-inch pots, or even well-rooted, one-gallon plants, may not grow roots in rapidly cooling temperatures. So while you plant it, the plant may not produce anchoring roots until late February or March.
So, we have a small plant, with a dense root mass, not anchored as the soil freezes and thaws. This forces the lump of roots and your plant out of the ground, and your plant may dry up before you can save it.
Best choice for small pots of plants, even small shrubs, is to plant in early fall -- September, October or early November. Well-planted large plants do well in late fall with time to grow roots over the winter from their deep planting hole.
Second, if you plant later, soften the soil well so that new potted soil and more dense garden soil can blend. Be sure to cover the newly planted plants with at least 2 inches of insulating mulch. This way the ground can freeze and not thaw repeatedly, and heaving can be prevented.
The mulch can be of shredded hardwood, mini-nuggets or pine needles, and it should be moved away from the crown of the plant as your perennials emerge in spring.
Now you should go out and quickly replant your plants, tamp the soil well, cover with mulch and hope for the best.
Contact Pat Lea at email@example.com.