Download a printable copy of our MARCH Gardening “To-Do” Checklist.
Vegetables and Herbs
- If you haven’t prepared your beds yet, do it soon – by turning the soil and adding your yearly amendments, like 1-2 inches of compost, well-aged manure, mushroom soil or leafmold into worked into the vegetable beds (as soon as the soil is workable, which is definitely is now). All that turning of soil was best done last fall and if you haven’t done it yet, do NOT do it when the soil is sodden. Crumbly soil is what you want before turning and amending. Oh, and if a soil test indicates that lime is needed, do it at the same time you’re adding the other amendments, using crushed dolomitic lime.
- Put up trellises and teepees for peas, pole beans and other climbers.
- If you haven’t already bought seeds of cool-season vegs, do it now and sow them. If you’re using old seeds, check their viability first by doing your own germination test. (Place 20 seeds on a moistened paper towel, roll up the towel and place it in a plastic bread bag. Put the bag on top of the refrigerator or other warm location and check after 5-7 days to see what percentage has germinated. Discard seed lots with less than 50% germination.)
- Early March: Start seeds of broccoli and cabbage indoors under lights, to be ready for planting outdoors in six to eight weeks. Late March: Start seeds of eggplant and pepper indoors under lights, to be ready for planting outdoors in six to eight weeks.
- It’s still too early to start tomato transplants.
- Potatoes, onion sets, onion seedlings, leeks and peas can be planted as soon as the soil can be lightly worked – now. Same goes for other cool-weather crops like beets, Chinese cabbage, kale, mustard and turnips.
- In early March you can also start sowing seeds of spinach, lettuce, kale, mustard, sorrel, corn salad and other greens indoors under fluorescent tubes. They’ll be ready to transplant outdoors in 2-3 weeks.
- Consider purchasing some floating row cover material to protect crops against insects and promote early growth. Floating row covers are made from a spun-bonded polyester material and are available in our garden shop. We recommend Harvest Guard brand.
- Rosemary, thyme, lavender, sage, basil, and tarragon seeds can be started indoors in late March. Fresh tarragon, rosemary, and mint sprigs can be purchased in food markets and rooted indoors in potting soil and can be grown under fluorescent bulbs. The new plants can then be set outdoors in pots or garden beds in May.
- Now is the time to cut back last year’s old perennial herb plants. This will make them look better and make room for new growth. It will also help reduce insect and disease problems.
- March is also a good time to divide over-grown rhubarb plants and top dress with a balanced fertilizer or well-rotted horse or cow manure. Weeds in asparagus and rhubarb beds can be difficult to control because they are so entangled with the crop plant. It is always best to hand-pull weeds or cut them off cleanly at the soil line with a small, sharp hoe. Be careful not to cut into crowns or emerging spears. All old asparagus foliage should have been cut down and composted last fall.
- When your strawberry plants start to grow, remove the mulch over them enough to allow leaves to develop in the light, then leave the mulch under the plants to help reduce weeds. If leaves develop under the mulch, they will become blanched and yellow from lack of chlorophyll, and may burn and die when exposed to the sun.
- Small fruits such as brambles can be pruned starting now through the bloom period. Remove the fruited, dead canes of brambles and any flowering canes that are weak, diseased or infested with borers. Fall bearing raspberry plants should have been mowed/cut to the ground, but if they haven’t, do so now.
- Now is the time to start routine pruning apple and pear trees. Start your pruning by removing dead, broken and crossing branches and keep younger trees trained with a central leader much like a Christmas tree shape. Peach trees should be pruned after flowering. For peach trees, maintain an open vase shape to encourage good air circulation and fruiting throughout. Shorten all the branches and thin out weak growth.
- Peach trees usually require an annual early spring application of a balanced fertilizer (i.e. 10-10-10) at bloom.
Shrubs and Trees
- March is still a good time to do your winter pruning – click that link for details. Wait until mid or late spring to prune your spring-flowering shrubs and trees, so you can enjoy their blooms this year.
- March is a great time to plant or move woody landscape plants, as long as the soil isn’t soggy. Avoid the most common planting mistakes: planting in compacted or poorly drained soil and planting too deep.
- Roses should be pruned starting in mid-February. Shrub types (not climbers, generally) should be cut back to about 18”-24″ off the ground and tiny canes removed entirely. Prune out any canes that criss-cross each other to ensure good air circulation and healthy stems. A dab of Elmer’s glue on the ends of the cut canes can help discourage rose cane borers, a type of beetle.
Pests Affecting Shrub and Tree
- Remove and destroy bagworm bags from affected trees (primarily needled evergreens). The bags contain hundreds of eggs that will hatch out and feed in the spring. Don’t leave the bags on the ground – discard or destroy them.
- The tiny reddish brown eggs of spruce spider mites can be seen with a hand lens on the twigs and needles of spruce at this time. If you notice signs of this pest, apply an ultra-fine horticultural oil spray which will smother and kill the eggs. But do NOT spray oil on spruces with blue needles, as it will take off the wax that gives the needles their blue color. In some cases, a different miticide would be best.
- Inspect trees for the egg masses of the Eastern tent caterpillar. The look like black Styrofoam and are usually found on the ends of cherry and crabapple tree branches. Egg masses should be removed and destroyed.
- If you had a problem last year with scale insects on woody landscape plants spray them with a dormant oil prior this month to bud swell. Spray on a dry day when temperatures are above 40 degrees F. and are expected to remain above freezing for at least 24 hours. March is the last time you can apply oil at the dormant rate because the dormant rate can burn green tissue, so if you notice bud or leaf growth, spray horticultural oils at the summer, 2%, rate. Dormant oil is an environmentally safe product.
Nonwoody Ornamental Plants
- This is a great time to plant cool-season pansies, Dianthus and snapdragons for color, but remember not to set out tender annuals (impatiens, marigolds, petunias, salvia, etc) until after the last frost date – the first week in May for the DC metro area.
- If you still have unplanted bulbs from last fall, they may still be worth planting. Inspect them carefully and only plant the best quality. Many may be in bad condition and not worth planting. If they were stored where it was warm, they likely will not flower this year but once getting established should do well next year.
- Time to clean up your ornamental beds! Cut back your ornamental grasses and the stems of last year’s perennials. Remove dead leaves, weed, and you’re ready to apply 1-2 inches of mulch this month, or later in the spring if you choose. Don’t let garden debris (like dead leaves) stay on top of groundcovers and short perennials, as this can cause foliar diseases in the spring. Trim back English ivy that is invading walkways, turf and garden beds. You can divide perennials as they poke up from the ground this month.
- If you start ornamental annuals from seeds, you can start them indoors in March – 5-6 weeks before they are planted outdoors.
- You may be asking: Hey, where are all the fish in my pond? If so, watch out for Great Blue Herons, which can see the sun’s reflection off the water from a long way off. Bird netting will keep them and any leaves out of the pond. Our Larry Hurley reports that once he removes the leaves from his semi-shaded pond, it’s no longer bothered by the herons.
- So, use a net to remove leaves and debris. This will help reduce problems with algae. Small ponds can be completely pumped out, cleaned and refilled. The sooner you can do this the better, because by April many species of amphibians will lay their eggs in the pond and you don’t want to disturb them. If eggs have already been laid be very careful and gentle when cleaning the pond to avoid harming them.
- Now is the second best time to seed your lawn to cover thin or bare spots. (The best is late August through October.)
- Also, spring is not the best time to apply fertilizer to lawn unless it’s weak and thin and you didn’t feed it last fall. Fertilizing in the spring encourages rapid succulent growth that is more susceptible to attack by insects and disease. If applied, use slow-release or organic fertilizer only.
- If you had a crabgrass problem last year consider applying a pre-emergent herbicide later this month when the forsythias are in bloom. They tend to bloom about the same time that the soil is warm enough for crabgrass seeds to germinate. Best control of crabgrass is achieved by splitting this herbicide treatment into two applications – first in mid-March in late March and the second half in mid-May.
- Chickweed, dead nettle, henbit and other broadleaf winter annual weeds are starting to grow again at this time – they germinated last fall and were dormant throughout the winter. They can be treated with a labeled broadleaf weed herbicide when they’re more actively growing later this month or throughout April. Small infestations can be pulled by hand. However, fall herbicide applications when these weeds are germinating often produce better control.
- Don’t do any aerating of your compacted lawn during the wet spring conditions; digging and disturbing the soil then will just make it worse. Wait for it to dry out.
- This is the time to sharpen your lawn mower blades and service your mower. Dull blades tear turfgrass and can lead to damage and disease problems. Remember to sharpen your mower blade a few times throughout the mowing season.
- Now is a good time to begin re-potting and dividing houseplants that are outgrowing their containers, moving them to the next-larger pot. Use only lightweight soil-less potting mixes, never garden soil. If a houseplant is already in a very large container and you can’t move it up to a larger one, you can remove the plant and prune its roots. Fill the outside with fresh potting medium. Pruning some of the roots may set the plant back a little but it will recover and it will have more space for the roots and improve pot drainage.
- As new growth appears, resume fertilizing houseplants on a monthly basis. Also gradually increase watering to the regular spring-summer amount, remembering that overwatering is the most common cause of houseplant death.
- Keep an eye out for signs of pests like spider mites, mealybugs, and scale insects. If addressed promptly, these nonchemical methods work: spray of plain water, insecticidal soap spray, or with the most tenacious (like mealybugs) sometimes an alcohol swab and Q-tip.
- Empty bird boxes of old nests.
- Many birds are now actively scouting our landscapes for places to nest this spring, so this is a good time to put up a birdhouse (nest box) to encourage nesting. Some bird species that use birdhouses (nest boxes) are bluebirds, purple martins, tree swallows, and wrens.
- Apply deer repellents as your perennials begin to grow. Deer will begin to switch to their warm weather feeding patterns (from shrubs to more tender plants), and repellents applied early on are the most effective.
Final Words from Larry Hurley
- If you have pathways that are mulch covered, March is a good time to add more mulch.
- And his favorite tip? “Call in sick on nice days, and spend time in the outdoors. Shop first.” (Editor’s note: Just kidding! Because we don’t condone lying to your boss!)
Final Words from the Behnkes Planting Service
- There’s a lot to do this month, so it’s a perfect time to contact the Behnkes Planting Service for general spring cleanup, and re-mulching of your landscape beds. That’ll leave you more time to work on the fun projects.