Gardening by Month - March

Trees & Shrubs

• Trees, shrubs, and perennials can be planted as soon as they become available at garden centers and as the ground can be worked.

• Maples (Acer spp.), weeping cherries (Prunus pendula), cornelian cherry dogwood (Cornus mas), and forsythia (Forsythia spp.) are in bloom this month.

• The pruning of trees should be completed before new growth occurs. Trees should not be pruned while the new leaves are growing. 

• If dogwood borer has plagued a dogwood tree in the past, early to mid-March is the time to apply chemical controls if necessary. However, pruning out infested branches in late winter is more effective.

• If pruning is needed on oaks, do so before mid-March. Avoid pruning from mid-March through late June as insects that can transmit oak wilt are attracted to the sap from wounds during this time.

Annuals & Perennials

• If you didn't clean up irises in late summer, now is the time to check for iris borer damage. Clean up and dispose of any affected old foliage before new growth begins. 

• Hellebores and Virginia bluebells (Mertensia virginica) are blooming this month.

• Clean up garden beds by removing any weeds and dead foliage. Mulching will assist in weed suppression throughout the growing season. 

• Summer and fall blooming perennials, such as black-eyed Susans, should be divided as needed as new growth starts to emerge.

• Ornamental grasses should be cut to the ground and large clumps divided just as new growth appears.

• Spring bedding plants, such as pansies, violas, snapdragons, sweet alyssum, dianthus, and annual primrose, may be planted outdoors now. 

• Perform soil and soil pH tests to determine the nutrient needs of the soil. Apply appropriate amendments and fertilizers as needed.

• Some blooms you'll see this month: glory of the snow, crocuses, snowdrops, hyacinths, daffodils, and muscari. 

• Dormant plants ordered through the mail/online should be unwrapped immediately. Keep them from drying out, store in a cool and protected space, and plant as soon as conditions allow.

• Be sure to cut back liriope early March before new growth appears.

Lawns

• Just before new growth begins, mow lawns a half inch lower than normal to remove old, dead leaf tissue. This only needs to be done once before raising the mower height back to the usual setting for the remainder of the season. This benefits zoysia lawns more than cool-season lawns.

• Cool-season weeds are now showing up in lawns and garden beds. Manually remove or use appropriate herbicide. Do not apply to areas that will be seeded soon. 

• Apply crabgrass preventer between mid-March to mid-April. If you decide to use a weed and feed product, do not use a fertilizer high in nitrogen. 

• Thin spots and bare patches in the lawn can be overseeded now.

• Hold off on fertilizing zoysia or other warm-season grasses until May. 

Fruits & Vegetables

• Fertilize established fruit trees once frost leaves the ground. Follow fertilizer instructions. 

• Remove the old, dead stalks of last year's growth from asparagus before new spears emerge.

• Set out transplants of broccoli, cauliflower, and cabbages outdoors by mid-March.

• Fertilize garden beds as needed as it is being prepared for the growing season. Unless a soil test indicates otherwise, use a balanced fertilizer in the bed according to label instructions. 

• Asparagus and rhubarb roots should be planted as soon as the ground can be worked.

• Plant the following seeds and sets outdoors by early to mid-March: beets, carrots, collards, kohlrabi, lettuce, mustard greens, onions, potatoes, parsley, radishes, and spinach (following seed packet instructions). 

• Start seeds of summer vegetables like tomatoes, peppers, and eggplants indoors mid to late March (following seed packet instructions).

• Gradually remove mulch from strawberries as the weather begins to warm. 

• Be sure to prune apples and pears before flowers appear. If any diseases or insects plagued the tree in the prior year, dispose of infected limbs to reduce any overwintering issues. 

• Continue to prune grape vines while the weather is still chilly. Bleeding causes no injury to the plants. Tie vines to trellises before buds swell to prevent bud injury and crop loss. 

• Peaches and nectarines should be pruned around the end of March, just before they bloom when the buds are swollen and pink. Be sure to prune out any branches infected with brown rot. 

• Cleft and splice grafting can be done now. This must be completed before rootstocks break dormancy. 

• Starting in late March, aphids begin to hatch on fruit trees as the buds begin to open. 

• Apply dormant oil, if needed, to fruit trees now. Choose a dry day when freezing temperatures are not expected. Do not apply dormant oil to a plant after its buds have begun to swell as damage may occur. 

Miscellaneous

• As the days get longer and houseplants start new growth, repot any rootbound plants (replant in containers that are 1-2 inches larger in diameter than the current pot). Check for pests and control as needed, trim any leggy plants, and fertilize appropriately. 

• If you want to bring spring flowers into your home, many garden centers have mini daffodils, hyacinths, muscari, and crocuses available potted up that make great additions. Hyacinths will bring a nice fragrance into your home as well. 

• Frost is still possible throughout the month. Keep a careful eye on the weather and cover plants as needed. Avoid planting tender plants too early.

• Although it may be tempting on warm days, it is still too early to set out your tropical houseplants. Nightly temperatures need to be consistently above 50^oF.

• In the woods, spicebush (Lindera benzoin), the harbinger of spring (Erigenia bulbosa), and bloodroot (Sanguinaria canadensis) can be seen blooming. 

• Purple martins are returning to the St. Louis area, so it is time to set up purple martin houses. It is also time to set up nesting boxes for bluebirds. 

• Be sure to remove the dead foliage of plants such as roses, peonies, daylilies, and apples, if this was not done in the fall or winter. These plants often have foliar fungal issues and disposing of the foliage will reduce the risk of infection.

• Keep an eye out for seed damping-off and treat as necessary. 

• Don't work wet soil. Soil should form a ball that crumbles easily when squeezed, if it is too wet let it dry out more before working. 

• Branches of pussy willow, quince, crabapple, forsythia, pear, and flowering cherry, may be forced indoors. Place cut stems in water and change the water every few days.