What to leave up/what to take down
√ Cut back hostas, daylily or any other plant that will get “mushy” thus providing a place to harbor bacteria and diseases
√ Leave up ornamental grasses or if they are flopping over, cut no more than 50 percent of the grass off. Some of the dead foliage can help protect the crown of the grasses.
√ Cut back herbaceous peonies (not tree peonies), tall garden phlox or any other plant that typically gets powdery mildew or other diseases during the season
√ It’s optional for winter interest whether you keep plants up like sedum and coneflowers. The birds do like to clean off the seed heads on coneflowers and flat “corymb” type seed heads like sedum and yarrow can be very attractive with snow on them.
√ Cut back Knockout and other hedge roses to about 24” to 30” after it has gotten cold.
√ Plants that have “crowns” above the level of the ground should be left up. Examples are mums, coral bells, perennial geraniums and astilbe. Like grasses, some foliage left on these plants can help protect the base of the plant from cold and winter damage.
√ After the ground has cooled off to about 30 to 35 degrees, (check the Iowa Environmental Mesonet ), you can cover the bases of roses, coral bells, butterfly bush (Buddleia or other more tender plants with about 6 inches of mulch to protect the base of the plants. (Make sure you put some mulch somewhere warm so you can get it broken up when you are ready to mulch!)
√ Put tree wrap on the trunks of trees susceptible to sun or wind scald or from cold temperatures.
√ Use wire fencing to exclude rabbits and rodents from nibbling on the bark of shrubs, especially Dwarf Korean Lilac and Burning bush, as these are especially attractive to these critters in snow covered conditions. For larger trees that may be prone to antler rubbing or grazing by deer, make sure that fence posts and netting have been put around these plants at a distance that will prevent deer from making contract with branches or trunks.
√ For evergreens like boxwood, rhododendron and yew, an anti-desiccant (example, Wilt-Pruf ), spray needles or leaves when the temperatures drop below 50 degrees but remain above freezing. Transpiration from the plant, plus cold winter winds can cause needles to turn brown.
√ Make sure plants go into the winter with a good watering. Pores in the soil can be direct routes for freezing temperatures unless water is occupying that space, thus protecting the root systems.
General garden hygiene
√ Make sure that annuals are removed from the garden as well as any plant foliage that exhibited signs of disease during the season.
√ Do one final weeding to prevent weeds from proliferating during warm periods over winter.
√ If possible, apply a pre-emergent herbicide such as Preen to prevent germination of weed seeds over the winter season.
√ Clean up leaves and sticks in the garden or if you wish to leave a layer of protection on your garden bends, mulch the leaves and then place them over the entire garden.
√ Scrape all dirt off of your hand and long-handled tools. Use a lightweight oil such as 3 in 1 Oil or WD-40 to put a coating of protection on these tools over the winter. Make a list of tools that need repair over the winter.
√ Empty all your pots of soil and either put them in a storage area out of the weather or use a pallet and store them upside down on the pallet.