March marks the beginning of spring, but it can be a fickle month! The weather can be mild and pleasant one day and then cold and blustery the next. Until the weather becomes consistently milder, be patient and use this time to organize your thoughts on what you want to accomplish in your ornamental garden this spring. Start by checking 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. You just might find other useful information in the Gardening Resources section, too.
The soil in March is generally too cold and wet to work in. Just walking on soggy soil compresses the soil aggregates and particles. The resulting compaction affects drainage and rain infiltration and prevents plant roots from penetrating very deeply. Soil compaction also reduces the amount of open pore spaces, which makes it difficult for plant roots to absorb oxygen and water.
Here’s how to tell whether your soil is dry enough to work in: Dig up a small amount of soil and squeeze it in your hand. If the soil stays in a solid muddy ball and does not fall apart, it’s too wet to work in. If the soil crumbles through your fingers when you squeeze it, then it’s ready to be worked.
Once the soil in ornamental garden beds is dry enough to walk on, remove any weeds that have overwintered in your flower beds. It’s important to tackle weeds early and stay on top of this task throughout the growing season. For help with identifying weeds, check out Virginia Tech’s Weed ID website or the University of Missouri Weed ID Guide.
Don’t be too eager to cut back last year’s perennial foliage and stems. If possible, hold off on this task until daytime temperatures are consistently above 50°F for at least seven consecutive days. Many beneficial insect species such as small native bees, syrphid flies, and lacewings overwinter in the debris and are merely waiting for warmer weather conditions before emerging. By waiting for the right conditions, you give these insects the chance to emerge safely.
Redefine flower bed edges as needed to give them a neat, crisp appearance. A flat-edged spade is very useful for this task.
Direct sow seeds for hardy annuals such as larkspur, sweet peas, and love-in-a-mist. These annual species germinate best when soil temperatures are between 55°F and 65°F, which means they can be planted weeks before the last frost date in spring. On the other hand, tender annuals such as begonia, cosmos, zinnia, and vinca can’t handle cooler soil and air temperatures and should be planted after the last frost date in spring. As a reminder, the last frost date for the Charlottesville/Albemarle County area of Virginia is around April 15 to April 25 on average. To learn more about hardy annuals, see the University of Missouri Extension’s publication on Flowering Annuals.
Assess your emerging perennials to identify any that need to be divided. Guidelines vary on how often to divide perennials but, on average, many of them benefit from being divided about every three to five years. As a general rule, divide spring and early summer-flowering plants in the late summer or fall and fall-blooming plants in the spring. And here’s another tip: Hostas may be divided just as they emerge in early spring to minimize damage to the leaves. For more insight into how and when to divide perennials, see Garden Shed article on Guidelines for Dividing Perennials.
Now is a good time to have the soil tested in your ornamental garden beds to determine the pH and to analyze fertility levels. 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, check out the Virginia Cooperative Extension’s (VCE) website, which is http://www.ext.vt.edu and view Publication No. 452-129, Soil Sampling for the Home Gardener. Don’t guess! Follow the soil test recommendations for incorporating any amendments into the soil.
Top dress flower beds with one inch of compost to improve the soil structure, add nutrients, and enhance the soil’s capacity for holding moisture.
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.
Prune established rose bushes now to improve their health and structure. 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.
Prune subshrubs to shape them or remove dead terminal growth. By definition, a subshrub is a dwarf or low growing shrub or perennial plant that has woody stems at the base but new soft, green terminal growth that typically dies back each year. Some examples of subshrubs include the following:
- Blue Mist Shrub (Caryopteris) – Cut back top growth by about a third to neaten the shrub and encourage new growth. To rejuvenate the shrub, cut it back to about 6 inches from the ground.
- 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.
- Lavender (Lavendula) – Although Lavender is a subshrub, it should not be cut back until after it blooms, at which time, remove only the green part. Do not cut into the brown woody part.
- Lavender cotton (Santolina chamaecyparissus) – Cut back to within 6 inches of the crown every 2 to 3 years to keep it vigorous.
- Russian Sage (Perovskia atriplicifolia) – Leave the foliage standing over winter to provide interest and help protect the crown. Cut the old foliage back in spring to within 6 inches of the crown.
If deer are a nuisance in your garden, apply repellents or other deterrents as soon as the plant foliage emerges from the soil. The idea is to condition the deer to view your emerging plantings as unpalatable. Generally, no one deterrent, short of a physical barrier, is enough to stop a hungry deer. For lots of good information on how to address the problem of deer in the landscape, see The Garden Shed’s article Deer, Deer, Deer!, which appeared in the May, 2021 issue. In addition, see VCE Publication HORT-62NP, Deer: A Garden Pest, and VCE Publication 456-018, Pest Management Guide: Home Grounds and Animals (scroll down to “Other Animals” in the menu) for more good information on how to deal with deer problems.
If you plan to grow annuals or perennials from seed, check seed packets for guidance on the merits of direct sowing in the garden versus starting seeds indoors. Tip: If you decide to start your seeds indoors, sow them in a fine, soil-less growing medium. Place under cool-white fluorescent lights about 14 to 16 hours per day and position the lights about two inches from the top of the seedlings. Maintain day-time temperatures at 70° to 75° F. and 65° F. at night. Keep the growing medium moist but not wet.
Clean leaves and other debris out of aquatic gardens to help reduce algae growth when temperatures warm up. Tip: If amphibians live in your pond, be careful not to disturb them. If they have already laid their eggs, be very gentle as you work around the eggs to avoid harming them.
Sources vary on when to fertilize spring-flowering bulbs, but, as a general rule of thumb, they may be fertilized with a low-nitrogen fertilizer or a fertilizer made especially for bulbs as soon as the shoots start to appear in spring. For daffodils, the American Daffodil Society recommends reapplying fertilizer at bloom time as well. Other sources recommend fertilizing daffodils after the bulbs have finished blooming. Regardless of when you fertilize, if you are using a granular fertilizer, avoid getting any on the foliage and be sure to water it in or apply it just before a rain.
Cut back ornamental grasses early in the month before they start to display new spring growth. If you wait too long, you risk cutting the new foliage.
Prune tree and shrub twigs that were affected by winter kill. Cut back to green wood. To determine if the twig is alive or dead, scratch the bark with your fingernail.
Feed houseplants with a diluted (half-strength) solution of soluble houseplant food this month. This is when houseplants start actively growing.
Once the soil is dry enough, inspect your lawn for any problems that need to be addressed. For example, does the soil need to be aerated and de-thatched? Are there drainage issues that need to be addressed to eliminate standing water? Does the lawn have bare spots that need to be seeded?
If you haven’t had a soil test done for your lawn recently, have one done to find out what nutrients, if any, may be needed. See VCE Publication 452-129, Soil Sampling for the Home Gardener. Note: if the lawn needs fertilizer, it’s generally best to apply it in the fall rather than in the spring. For more information on lawn fertilization, see VCE Publication 430-011, Lawn Fertilization in Virginia.
Photo: Cathy Caldwell
Invasive watch: Look for garlic mustard (Alliaria petiolata) in your landscape and eliminate it in spring when the ground is moist and the plant is easy to pull up. This invasive plant has displaced native wildflowers such as spring beauty, wild ginger, bloodroot, trillium, and toothworts in many forested areas. Although it is easiest to recognize after it produces white flowers in early April, its foliage is also distinctive, and all parts of the plant emit a strong garlic odor. It is essential to remove garlic mustard before it sets seed. For more information on identification and treatment, see the Blue Ridge PRISM (Partnership for Regional Invasive Species Management) Factsheet/Garlic Mustard and Weed Alert – Garlic Mustard/ Blue Ridge Prism and Research Update/Blue Ridge Prism/Newest Recommendations for Garlic Mustard/2019.
Take photos of your daffodils, hyacinths and other spring bulbs as they emerge in spring to help you remember where they are planted. Once the foliage dies back in late spring, it’s all too easy to forget where the bulbs are located. Your photos will save you much frustration and heartbreak later when you are digging holes for new plants.
Featured Photo: Pat Chadwick
