Tasks & Tips for March in the Ornamental Garden
Lives there a gardener who doesn’t thrill to the arrival of March? Even though I’m concerned that March arrived too early — in February, to be exact — I can’t help feeling bursts of joy at the sight of green shoots emerging from the earth. There’s plenty to do, of course, though our longstanding calendar of monthly tasks is probably going to need some realigning in view of our changing weather patterns. That said, here’s the To-Do List:
Clean up ornamental beds
Clean up flower beds and borders. Remove twigs and other debris. Cut back dead stems and foliage from perennials that were left standing over the winter. Pull the weeds. Redefine flower bed edges, using a flat-edged spade or an edging tool such as the one shown at left.
Top dress flower beds with one inch of compost. The compost improves the soil structure and adds nutrients and moisture-holding capacity.
Assess your emerging plantings and identify perennials that need to be divided. Many perennials benefit from being divided about every three to five years. As a general rule, divide spring–flowering plants after they bloom; divide summer–flowering plants in late summer or fall; and divide fall–blooming plants in the spring. And here’s another tip: Hostas may be divided just as they emerge in early spring. This minimizes damage to the leaves.
Test your soil. If it’s been a while since you’ve had your garden soil tested or if you’ve never had a soil test done before, consider having one done now to determine the pH and to see what nutrients, if any, are deficient. For information on soil testing, check out the Virginia Cooperative Extension’s (VCE) website, and look at Publication No. 452-129, “Soil Sampling for the Home Gardener,” Ext.VT.Pub. No. 452-129.
Finish any pruning chores that you didn’t complete in January or February. This task should be completed before plants break dormancy. For an expert guide to the general principles of pruning, review our feature article from last month, A Pruning Primer: Tools, Techniques and Timing, The Garden Shed.
Cut back to green wood any tree or shrub twigs that were affected by winter kill. On smaller twigs, scratch the bark with your fingernail to determine whether it is alive.
Prune crape myrtles. For detailed guidance on how to do this, review this month’s article, “Pruning Crape Myrtles” before you start.
Prune shrubs. If you’re wondering if this is the right time to prune a particular shrub, take a look at the helpful Shrub Pruning Calendar published by the Va. Cooperative Extension, Va.Coop.Ext. Pub.No. 430-462, It will tell you, for example, that March is a good time to prune beautyberry, boxwood, clethra, and roses, among others. And for detailed instructions on how to prune shrubs, review Va.Coop.Ext. Pub. No. 430-459.
I’m pruning some of my boxwoods this month for two reasons: (1) to remove branches with damage caused by boxwood leafminers, and (2) to provide additional light and air to the inner portions of my older boxwoods, which may help them resist the dreaded boxwood blight. Keep an eye out for the tiny boxwood leafminer fly, which has usually been seen buzzing around boxwoods in April, but I’m going to start watching for it this month. For more about the boxwood leafminer and other insect pests of boxwoods, look at Va.Coop.Ext.Insect & Mite Pests of Boxwood.
Be sure to keep an eye out for signs of boxwood blight. The Boxwood Image Gallery can help you to identify it, Va.Coop.Ext. Boxwood Image Gallery. Often it’s difficult to tell what’s wrong with a boxwood. Here’s a really helpful photo guide: Comparison of Boxwood Blight to Other Boxwood Problems, Va.Coop.Ext.. The Va. Cooperative Extension has created many helpful videos about boxwood blight, including What Is Boxwood Blight? Video and Boxwood Blight Symptoms Video.
Prune roses to improve the health and structure of the plant. Make sure your pruners are sharp and clean. Prune canes to an outward-pointing bud and make each cut at a 45° angle just slightly above the bud. Remove any weak or unattractive canes. Cut any damaged wood back about one inch into healthy wood. Cut any dead canes down to the ground level. If any branches rub together, choose the healthier of the two and remove the other one. If you are pruning a grafted rose, check for suckers below the graft union and remove them. Proper pruning facilitates better air circulation, also allows more sun into the middle of the plant, and results in a healthier, more attractive plant.
When performing late winter or early spring pruning tasks, don’t forget to cut back subshrubs. These perennial, generally low-growing, shrubs have woody stems except for the new growth’s terminal part, which dies back annually. Examples of subshrubs include:
- Butterfly bush (Buddleia) — Prune back all stems to about 1 to 2 ft. from the ground.
- Blue mist shrub (Caryopteris) — To neaten the shrub or encourage new growth, cut back by about a third. To rejuvenate the shrub, cut back to about 6 in. from the ground.
- Russian sage (Perovskia atriplicifolia) – Russian sage foliage is generally best left standing in the fall to provide winter interest and to help protect the crown. In early spring, cut back the old foliage to within 6 in. of the crown.
- Lavender cotton (Santolina chamaecyparissus) – Cut back to within 6 in. of the crown every 2 to 3 years.
- Heather (Calluna vulgaris) – Prune flower stems back to the base of old flowers. Snip the green part only. Don’t cut down to the brown woody portion.
Now is a good time to plant bare root, dormant roses. Soak the bare-root rose in a bucket of water for at least eight or more hours to rehydrate the roots. Choose a sunny, well-drained location, dig the planting hole wide enough and deep enough to easily accommodate the roots and set the plant so that the graft union is at soil level. Space roses far enough apart to allow good air circulation. For more detailed how-to instructions, review “The Ornamental Garden in March,” Garden Shed 2016.
Cut back ornamental grasses and liriope before new growth starts.
Your beds may have winter annuals — broadleaf weeds like hairy bittercress and chickweed — which reproduce by seed that usually germinates in fall, grows during the winter, and then produces flowers and seed in the spring. NOW — before those seeds drop — is the time to root them out; otherwise, you’ll be seeing lots more of these weeds next year.
Right now I’m seeing hairy bittercress in some of my beds. This is the annoying little weed whose tiny white flowers form seed capsules that explode in your face when you’ve waited too long to pull them. In fact the seed from those exploding seed capsules can fly up to 10 feet away! For photos and helpful identification tips for these weeds, check out the Virginia Tech Weed ID site, VaTech/Weed ID/ hairy bittercress and VaTech/WeedID/chickweed.
Don’t Forget the Deer Repellent
Deer tend to browse on broad-leaf evergreens as well as twigs and buds during the winter and early spring, so keep spraying your vulnerable plants with deer repellent. Keep monitoring for deer damage and change repellents regularly. And once that lush spring growth appears, start spraying it immediately. Or perhaps you’re using deer netting around your shrubs. If you have comments or questions about either method, please write them in the comments section below. We’d love to hear from you.
Check out the Monthly Gardening Tips section now located under Gardening Resources on the main page of the PMG website: piedmontmastergardeners.org/Gardening Resources/Monthly Gardening Tips/#March. For additional detail, consult our previous March issues of The Garden Shed:
If your lawn needs attention, you’ll find a detailed discussion of March lawn tasks and tips in our March 2015 issue, March Lawn Care/TheGardenShed/March2015.
“Boxwood Blight Alert,” The Garden Shed/Boxwood Blight Alert