March Gardening Guidelines
by Keith C. Hansen, Extension Horticulturist, Smith Co. – Tyler, Texas
One of the busiest gardening months of the year is here. March weather can be very fickle – it could still freeze since average last freeze is around March 12, and yet it still could be very balmy and pleasant most of the month. Freezing weather mainly affects the timing of planting cold-sensitive plants, like tomatoes or begonias. If you decide to take chances with tender plants, be prepared to give them a protective covering.
March is a great month to plant almost every kind of landscape plant. The sooner you plant, the quicker the plant will start getting established. This is important if the plants are to do well through the hot, stressful summer. Nurseries are receiving weekly shipments of fresh nursery stock, and this is prime to buy and plant!
Sometimes, though, eager gardeners jump the gun on some yard and garden chores which might be better delayed to later in spring. For example, many folks will apply fertilizer in early spring to try and force the grass to green up early. However, based on latest research, turfgrass experts recommend delaying fertilizing warm season lawn grasses (St. Augustine and Bermuda) until April, and to wait to fertilize Centipede until May. Spring green-up results from nutrients that were stored by the grass last fall (hence the importance of fall fertilization). Pushing the lawn too hard in the early spring could result in a weaker root system going into the summer. Tall fescue is an exception and should be fertilized now.
Caladium bulbs require warm soil temperatures, and setting them out in early spring can cause them to rot. Go ahead and purchase them as soon as they are available, but wait until the soil temperature reaches 70 degrees F to plant them.
Periwinkles or vinca is a bedding plant which also loves hot weather. When set out before the days turn truly hot, they often get a fungal disease that can destroy a whole bed of periwinkles. Mild, wet, spring weather provides the perfect environment for this devastating disease which, unfortunately, has discouraged many gardeners from planting them altogether. Periwinkle is still a great bedding plant for summer color – the just simply wait until May or early June to plant them.
– Control winter weeds by starting your regular mowing regime. Get your mower blade sharpened now before the spring repair rush. If you decide to scalp your lawn, wait until all danger of freezing is over. The average last freeze for our area is mid-March. Iif you do scalp, turn that huge amount of clippings into a fine soil amendment by composting it rather than filling up the landfill with it.
If you missed applying a preemergent weed preventer in February and you had a summer weed problem in your lawn last year (such as grass burs), then go ahead and make an application now. You may have missed a portion of the weeds which germinate in early spring (like crabgrass), but will still control the many other types that can germinate anytime during the warm part of the year.
As mentioned above, wait to fertilize your St. Augustine or Bermuda lawn until April, or after you have mowed actively growing grass (not weeds) twice.
– Pruning of evergreen and summer flowering trees and shrubs should be completed this month. But, prune spring flowering shrubs (forsythia, quince, azaleas, spirea, etc) only after they finish blooming, if needed. Hydrangeas also bloom on prior year’s growth, so prune after they bloom.
Shear back Asiatic jasmine, if needed, just as new growth starts to encourage new growth from the base.
As the lovely blooms of daffodils and jonquils fade away, it is tempting to remove or hide the leaves. However, let them yellow naturally. Next year’s flower buds are being formed at this time, and healthy, green leaves are needed to insure an even better display next year.
– After camellias and azaleas finish blooming, fertilize them with 2 to 3 pounds of azalea-camellia fertilizer per 100 square feet of bed area.
This is a good time to start hanging baskets of petunias, begonias, impatiens and other annuals. Hanging baskets add another dimension to the landscape, allowing you to bring color and accents to other areas around your house.
Dig and divide summer and fall blooming perennials this month. Fall asters, chrysanthemums, salvia and other summer/fall perennials can be invigorated and increased for expanding your beds or sharing/trading with other gardeners.
The mulch underneath azalea, camellia and other shrubs may have partially decomposed, adding organic matter to the soil, but leaving areas suitable for weed invasion. Add more where needed, using organic mulches such as pine needles, pine bark or cypress bark.
Begin fertilizing roses every 4 to 6 weeks from now until September. You also need to begin a spray program for controlling blackspot on roses. Uncontrolled blackspot will defoliate most hybrid tea, grandiflora and floribunda roses, causing them to decline in vigor.
– Last freeze dates guide us as to when it should be safe to plant frost-tender vegetables and annuals. Just be ready to protect frost-sensitive plants in case of a late freeze.
Planting of cool season vegetables (transplant broccoli, cabbage, and collards, and seed carrots, collards, mustard greens, lettuce, radish, turnips, Swiss chard and spinach) should be finished real soon, and summer vegetables can begin to be sown and transplanted later in March. Delay planting okra, sweet potatoes, okra and peppers until April since they don’t do well in cool soil.
Fertilize vegetables about a month after growth starts with nitrogen fertilizer.
Fruit and pecan trees should be fertilized this month with nitrogen applied in the area beneath the ends of the branches, never against the trunk. Shrubs and annual flower beds can be fertilized with a complete, balanced fertilizer. Slow-release formulations, though slightly more expensive, feed your plants over a longer period of time. Often the same type of fertilizer recommended for use on the lawn can be used in the landscape.
Watch out for aphids that rapidly build up on tender new growth. They can be controlled with a sharp stream of water, insecticidal soap or other insecticides (be sure to read the product label to determine whether the infested plants are included on the label).