Marianne Binetti — Be careful with frost-sensitive plants

The fourth week of March is still too early to set out frost sensitive flowers such as geraniums, coleus and marigolds and it is also too early to seed or plant warm season vegetable crops like tomatoes, peppers and squash. If you see hanging baskets of annuals and flats of ready-to-bloom petunias at the nursery and garden center, these are being sold to gardeners with a heated greenhouse or very protected outdoor area.

This is a good time to buy and plant perennials, trees, shrubs, groundcovers and winter hardy sedums and succulents. You can add spring-blooming bulbs already sprouted to your landscape and instant color waits with cold-hardy primroses, pansies, hellebores and foliage plants.

Mow, edge and fertilize the lawn, prune back the dead brown leaves of ornamental grasses, Japanese anemones, the stiff stems of sedum “Autumn Joy” and cut back summer-blooming clematis, spiraeas, barberries and nandinas that have grown too large. Do not prune evergreen clematis such as clematis armandi in the spring and don’t get snippy with rhododendrons or azaleas now or you’ll be removing all the flower buds.

Q. When can I reseed a new lawn? I would like to put a new lawn right on top of my moss-filled old lawn. Do I need to kill the old grass first? We have terrible soil and our small front lawn has never done well. P.W., Longview

A. Now is an excellent time of year to reseed, repair and renovate an old lawn. It’s all about the grass roots movement when it comes to lawn improvement and you don’t need to kill the old grass to encourage new grass. Mow the old lawn as short as you can, aerate with a core aerating machine and spread one to three inches of topsoil right on top of the old lawn. Rake and level the topsoil then apply a starter fertilizer and high quality lawn seed mix blended for our climate. The moist spring weather means you won’t have to water much to keep the new seed moist and you’ll be mowing your new lawn by May.

Q. Do I need to fertilize my blueberry shrubs? What type of fertilizer do they need? Should I prune blueberry plants? G.H., Tacoma

A. Blueberries are acid-loving plants and now’s the time to pamper them with a slow release rhododendron and azalea fertilizer. You can also spread composted manure around the base of your blueberry plants this month but don’t pile any mulch more than an inch deep up around the stems or crown of the shrubs. You can tidy up blueberry shrubs by pruning off any dead, diseased or damaged branches in the spring and shortening the longest branches by one fourth of their length. Blueberries love moist soil and thrive in our climate but to really improve your harvest the most important maintenance matter is netting to protect the berries from the birds.

Q. I have some daylilies and asters that have bloomed well for years but now I think they need to be divided. When is the best time to dig up and divide these perennials? J.H., Maple Valley

A. Any of the spring months is good time to divide and multiply summer-blooming perennials so sharpen your shovel or grab an ax and have at them. Plants with thick roots like hosta, daylilies, mums and aster can be more easily managed by slicing off from the sides of the clump to create chunks of root that are small enough to fit into a gallon-sized nursery pot. Then you can more easily uproot the center of the clump that remains in the ground. Often this middle section will be old and weak and it deserves a final resting place in your compost pile. Next work compost into the old planting area and replant the side sections back into the improved soil.

Diving perennials in the spring is a great way to share plants with the neighbors or pot them up and donate them to a garden club plant sale.

Marianne Binetti is a syndicated columnist.