Perennial beds: I’ve held off on recommending too much perennial clean-up due to the cold temperatures, but hopefully by now it is safe to do those activities. First, make sure that ornamental grasses are cut back before they start to grow; I know from experience it is a pain trying to pull old, dead grass out of the new growing material. Cut back any dead plant stalks remaining from last year from herbaceous perennials. Semi-evergreen perennials like some sedges, liriope, coralbells and hellebores may have taken a hit since we had such cold temperatures early this winter with little to no snow cover, so there may be more dead material to remove. Hopefully the plants’ crowns survived. Die-back shrubs like butterfly bush, false blue spirea (Caryopteris), or Russian sage should be examined for signs of buds swelling. You can cut off dead material above the buds, but I try to leave as much of the previous year’s live growth as I can. You can now also cut back your mums if new growth is coming up. Rake up any leftover leaves from last fall, but look for jumping worms’ soil signature (the hard pellet-like excretions) as you rake. You won’t see adults until mid-June or later, but the soil signature is visible in spring. If you find adult jumping worms later in the year, report them to the DNR by email at firstname.lastname@example.org.
Lawns: By the fourth week of April it is usually safe to plant grass seed if you are trying to replace dead areas of your lawn. Examine lawn seed mixes carefully before purchasing. You should avoid mixes with a lot of annual rye, and if planting in shade purchase mixes labeled for that purpose — these usually contain a fair amount of fescue grass, which is more shade tolerant than Kentucky bluegrass. The UW-Extension publication “Lawn Establishment and Renovation” can be accessed or printed out at the following site for more information on turfgrass mixes for various soil types and light conditions: http://learningstore.uwex.edu/assets/pdfs/A3434.pdf. You do not have to purchase a copy to read/print it out. Scroll down to the yellow box marked “View this publication” to view and/or print it out.
Roses: Remove tops on rose cones as the weather warms to avoid a heat build-up. Usually the entire cone can be removed by the third or fourth week in April. Gradually start removing soil that was mounded up around the canes of hybrid grafted varieties so pruning can be done by the fourth week of April or so. If a freeze is predicted as the plant leafs out, cones may need to be restored overnight.
Planting peas: Peas need a minimum soil temperature of 50 degrees to germinate, which has been a little hard to achieve at the regular time this year. Snow peas or sugar peas (which are not the same as sugar snap peas) like “Dwarf Grey Sugar” and “Oregon Sugar Pod” have edible flat pods and very small seeds. Pick them when they are very young, just as the seeds start to form. Sugar snap peas such as “Sugar Daddy” or “Sugar Snap” also have an edible pod, but the seeds are much larger and sweeter than those of sugar peas. Harvest sugar snap peas when the seeds have expanded to their mature size. Garden or English peas are less sweet, but grown for their seeds, and if harvested when not quite mature can be eaten raw in salads.
— Lisa Johnson, Dane County UW-Extension horticulture educator