Pima County Gardening Seasonal Reminder - March

• Average last frost date is March 15. In the warmer areas of Pima county, it may be a bit earlier and may have already passed – but for others in colder locations, stay vigilant. After your last local frost, store your frost cloth and cactus covers for use next year.
• Remain vigilant controlling weeds. The best method for control is manual removal and this is far easier when weeds are young. Be aware of invasive weeds such as stinknet and report them immediately even if not in your own garden - this invasive produces thousands of seeds per flower.
• For those who live in brushfire areas, March is a great time to review your defensible space. This area around your home and garden is one of your primary determinants for wildfire survival.
• Prune winter damage after danger of freezing has passed. Check the stems for signs of life. With a sharp knife, peel back a small area of bark on the outer stems. If there is green sapwood underneath, do not prune these stems as new growth will soon appear. If the wood beneath the bark is dry and brown, prune back to live wood.
• Thin fruit on deciduous fruit trees including apple, peach, plum, nectarine, and apricots. Thinning reduces weight and limb breakage, improves color, size, and quality. Leave about 6 inches between fruit. This is best done when the fruit is small--about marble-sized. For heavy producers, this may need to be repeated as the fruit size increases, so observe and remove fruit as needed to ensure the tree can carry the load.
• After the last frost of the season, inspect your citrus for signs of dead, damaged or dying branches. These should be pruned before the heat sets in. Any growth coming from below the graft joint (near the base of the tree) should be pruned as well. These are growing from root stock and do not bear edible fruit. Citrus are best left in a shrubby shape. If you prune and expose the lower trunk, now is the time to paint the exposed, tender area with white, water-based paint for protection.
• Monitor new growth and the undersides of leaves for soft-bodied pests such as aphids, whitefly, and thrips. Insects become active as temps warm and they are ready to feed. Avoid the use of chemical control and use a firm blast of water to knock them off the plant. If sticky honeydew is present, add one tablespoon of liquid dish detergent to one gallon of water and spray the tops and bottoms of leaves. These pests can reproduce rapidly, so multiple treatments are likely. Recurring issues with these pests mean that you should check your fertilizing and watering schemes to ensure you are not overdoing them and causing too much new growth – a common reason for pest infestations.
• This is an excellent time to plan or install active or passive water harvesting systems. Those with Tucson city water should investigate rebates.

• March is one of the best times to plant new landscape plants. Warm soils and mild temperatures enable plants to establish themselves before hot weather sets in.
• Sow annual seeds into the soil for coreopsis, cosmos, marigold, and zinnia.
• Plant perennial flowers from seed or seedlings: angelita daisy, bee balm, blackfoot daisy, California fuchsia, chocolate flower, golden dyssodia, lantana, prairie zinnia, salvias (sages) and tufted primrose. It’s also a great time to plant summer wildflowers from seed.
• Plant or transplant shrubs such as fairy duster, bee bush, black dalea, little-leaf cordia, Texas rangers and yellow bells.
• Plant tomatoes into the soil about mid-March, since they thrive in temperatures between 50°F and 90°F. Choose short-season varieties that generally mature within 70 days.
• Plant trees and shrubs of all types into the soil, including citrus.
• Plant or transplant container roses now to allow establishment before hotter daytime temperatures arrive.
• Vegetables and Herbs: Sow seeds outdoors or plant starts for sweet corn, bush beans, lima beans, spring peas, leafy greens, summer squashes, tomatoes, Mexican oregano and rosemary. Getting an early start means vegetables will be ready prior to the withering heat of June.

• Fertilize citrus (2nd of 3 annual feedings). For oranges, tangerines, and grapefruit, the first1/3 of the total was in JanuaryFebruary, the second 1/3 in March-April, and the last 1/3 in May-June. For lemons and limes, the first two applications are the same, but the last 1/3 isn’t until August-September.
• If you did not fertilize deciduous fruit trees (apples, pears, pomegranates, figs, etc) in February, do it this month. Fertilizers should contain all the macronutrients.
• Do the first feeding of tomatoes this month with a balanced fertilizer.
• Other uses of fertilizer in your garden are not advised unless past your last frost date. Remember that they stimulate new growth that will be frost-sensitive.

• Check and adjust irrigation frequencies based on local rainfall.
• Check your irrigation systems to ensure they are working properly.

Stinknet.org

City of Tucson Water Rebates

Ten Steps to a Successful Vegetable Garden

Protect your home from wildfire

Protecting a Citrus Tree from Cold

Pruning Deciduous Shade Trees

Training and pruning fruit trees

Landscape management practices for passive water harvesting

Harvesting rainwater

Plant Selection

Flower Planting Guide for the Low Desert

Growing Tomatoes

Planting and staking trees

Container trees and shrubs

Rose Selection and Planting in the Low Desert

Ten Steps to a Successful Vegetable Garden

Diagnosing Home Citrus Problems

Citrus Fertilization chart for Arizona

For more information on any of these topics, search our database of Extension publications going back more than 100 years housed in the University of Arizona Campus Repository.