September Gardening
Whether you’re looking for ways to help mom out in her garden on Mother’s Day, or just hoping to set your own garden up for summer survival, this month is sure to keep you busy outdoors! There are plenty of blooming beauties we can still plant before the heat of summer comes on, our fruits and veggies are ripening, and we’re stepping up watering frequency to keep many of our garden plants happy. Here is Civano Nursery’s gardening list for May!
What to Plant in May
- Summer annuals: coreopsis, cosmos, gaillardia, globe amaranth, lisianthus, vinca, marigold, portulaca, zinnia, Arizona poppy, coyote gourd, wild poinsettia
- Provide newly-planted annuals with afternoon shade while they’re getting established
- Bulbs and rhizomes: caladium, crinum, rain lily, and spider lily
- Citrus trees
- Annual seed: coreopsis, cosmos, gaillardia, gazania, globe amaranth, marigold, Mexican sunflower, portulaca, sunflower, and zinnia
- Warm-season cacti and succulents
- newly planted cacti and succulents may need some extra water and protection from afternoon sun through the first summer
- Before relocating, take note of which side of the cactus or succulent is facing north, and keep the same side facing north in its new location
- Bermuda grass, hybrid bermuda grass, buffalo grass, St. Augustine, or zoysia lawns
- Fall- and summer-flowering perennials
- Container-grown roses
- Summer-growing, heat-loving shrubs and vines such as Queen’s wreath (Antigonon leptopus) red bird of paradise (Caesalpinia pulcherrima), black dalea (Dalea frutescens), and firecracker bush (Hamelia patens)
- Palms can be planted as the weather warms this month
- Water every 2 days for 2 weeks, then reduce watering frequency to every 2 weeks for the first summer
- Desert-adapted, cold tender, or native trees
- Veggies: Soy bean, cantaloupe, cucumber (by mid-month), eggplant (by mid-month), muskmelon, okra, peppers, sweet potato, pumpkin, summer squash, watermelon
- A complete veggie garden guide and calendar of planting dates published by the University of Arizona can be viewed here (Tucson’s elevation is between 2,000 and 3,000 feet)
What NOT to Plant in May
- Summer-dormant succulents
- Plants that are sensitive to high heat
- cool-season veggies and herbs
What to Fertilize
- Potted annuals: every 2 weeks with a water-soluble fertilizer at the strength recommended for houseplants
- too much nitrogen can cause some plants to put on more green growth at the expense of blooms, so if you’re getting good green growth but not many flowers you may need to switch to a fertilizer with less nitrogen.
- Containerized succulents: every 2 weeks with a water-soluble fertilizer at half the strength recommended for houseplants
- Feed citrus trees around Memorial Day – This should be the second citrus feeding for the year (the first is around Valentine’s Day, and the third is around Labor Day).
- This PDF by the University of Arizona has detailed directions for figuring out how much food to give each of your trees, regardless of what fertilizer you use.
- Make sure to give your tree a good, deep drink before and after feeding
- Bermuda and St. Augustine lawns
- Summer-growing perennials: with a balanced, slow-release fertilizer
- Water the plants deeply before and after fertilizing
- Containerized roses: monthly with a water soluble fertilizer, or once every 2 months with a granular slow release fertilizer through the summer
- This is the month to cut back on fertilizing roses that are in the ground. Reduce frequency of fertilizing to every 6 weeks, switch to slow-release granular fertilizer if you spring-feed with a water-soluble plant food, or completely stop fertilizing until fall.
- Organic fertilizers can be used through the summer, and regular fertilizers can be used at half-strength if necessary
- Established palm trees: with a balanced fertilizer, or one formulated specifically for palms
- Native trees: every other month through the summer, and other trees once a month
- Non-native trees: once a month through the summer
- Summer-growing herbs like basil, mint and Mexican oregano can be fertilized this month with a low nitrogen organic formula
Prune, Divide, and Conquer
- Deadhead annuals and summer-flowering perennials regularly to keep blooms coming, and pinch back fast-growing summer perennials to promote bushiness
- Cut back spent flowering stalks from spring-flowering perennials (unless you want to save the seed). This will either keep them blooming or help them conserve the energy that they would have put into seed production
- Remove flowering stems from bulbs or iris before seeds begin to form (unless you’re planning to save the seed)
- Don’t cut back the leaves of iris or bulbs – wait for the leaves to completely dry up before removing them
- divide aloes that have become too overcrowded
- Cut back cacti to control size or remove damaged or diseased stems
- make cuts with a sharp tool at a joint if possible, or cut back to as close to the base as possible for multi-stemmed, columnar cactus
- treat cuts with dusting sulphur
- Remove any suckers that begin to grow from below the graft on your fruit trees as soon as you notice them
- Mow established lawns regularly, removing only the top 1/3 of the blades each time you mow
- Deadhead roses and remove any new flower buds before they open, but it’s best to hold off on heavy pruning until temperatures begin to cool down in fall
- Fall-flowering shrubs and carefully-shaped hedges or landscape shrubs can be lightly pruned to re-shape this month
- Palo verdes and mesquites can be pruned lightly this month to remove dead limbs and smaller branches, but save heavy pruning for later in the summer, when pruning is less likely to spur lots of branch re-growth
- Cut back basil and mint regularly to keep them from flowering at the expense of foliar growth
For the Fruits and Veggies
- Plant citrus trees
- newly planted citrus trees should be watered every 5 -7 days through the first summer
- Feed citrus trees around Memorial Day – This should be the second citrus feeding for the year (the first is around Valentine’s Day, and the third is around Labor Day).
- Several fig varieties are ripening this month. Use bird netting around the canopy to protect fruit from birds, and don’t pick the fruit too early…it will only ripen while it’s on the tree!
- Water deciduous fruit trees every 3-5 days to a depth of 3 feet through the summer
- Thin overcrowded fruit from deciduous fruit trees
- Remove any suckers that begin to grow from below the graft on your fruit trees as soon as you notice them
- Water strawberries daily
- Water grapes to a depth of 2 feet every 5 days through the summer
- Watch for grape leaf skeletonizer caterpillars on your grape plants and treat early by hand-picking, removing affected growth, or treating with Bt (an organic product that kills caterpillars)
- Orange Dog Caterpillars might be showing up on your citrus tree, but they can be hard to see because they look just like bird poop! A few caterpillars won’t harm a large, established tree, but you may want to remove them from smaller, newly planted trees, or treat them with Bt (an organic product that kills caterpillars).
- Begin preparation for a monsoon veggie garden this month to have it ready in time for monsoons
- To help prevent corn borers, apply a drop of mineral oil to the tip of each ear of corn just as the tassels begin to turn brown
- Watch for squash vine borers in your veggie garden. Sudden death of leaves or a section of the vine are common symptoms of this pest. Cut out the affected portion of the plant and destroy it.
- Cut back basil and mint regularly to keep them from flowering at the expense of foliar growth
- Sidedress okra with a balanced slow-release fertilizer or add compost
- Water herbs every 3-5 days to a depth of 1 foot
- Water veggies daily to a depth of 1 foot
- Summer-growing herbs like basil, mint and Mexican oregano can be fertilized this month with a low nitrogen organic formula
For the Lawn
- This is the best month to start taking steps to remove unwanted bermuda grass lawns
- Plant bermuda grass, hybrid bermuda grass, buffalo grass, St. Augustine, or zoysia lawns
- Water cool-season grasses every 3 days to a depth of 8-10 inches if they’re still growing
- Actively-growing, warm-season grasses need water every 4 days to a depth of 8-10 inches
- Fertilize bermuda and St. Augustine lawns
- Dethatch overseeded bermuda lawns early in the month to give the bermuda room to grow
- Bermuda lawns that are not overseededm, and most other types of turfgrass, need dethatching every 2-3 years
- Mow established lawns regularly, removing only the top 1/3 of the blades each time you mow
Water Wisely
- Annuals: to a depth of 1 foot, often enough to maintain moisture at that level, as often as every 2-3 days in very hot or windy weather
- Bulbs: reduce watering and withhold fertilizer as the leaves begin to yellow and the plant goes dormant for the summer
- Iris: when they are done blooming, reduce watering to every 10 days
- watering tip: iris prefer not to be watered from overhead
- Large cactus, ocotillos, and large yuccas: once this month
- Agave, smaller cactus, small yuccas and most prickly pear or cholla: every 3 weeks
- Barrel cactus and beavertail prickly pear: every 6 weeks
- Winter succulents: as they begin to yellow, decrease watering frequency by half, and stop watering completely when they shed their leaves and go dormant
- Deciduous fruit trees: every 3-5 days through the summer
- Established citrus trees: every 7-10 days through the summer
- newly planted citrus trees should be watered every 5 -7 days through the first summer
- Strawberries: daily
- Grapes: every 5 days through the summer
- Cool-season grasses: every 3 days if they’re still growing
- Actively growing warm-season grasses: every 4 days to a depth of 8-10 inches
- Non-native perennials: every 5-7 days to a depth of 2 feet
- Containerized roses: when the top inch of the soil is dry, which may be daily when weather is hot and dry
- Roses in the landscape: every 3-7 days , when a soil probe can only be pushed 6 inches into the ground
- Desert or native adapted shrubs: every 3-4 weeks through the summer
- Non-desert-adapted and non-native shrubs: every 2-3 weeks to a depth of 2 feet
- Non-native trees: frequently enough to maintain moisture at a depth of 3 feet
- Herbs: every 3-5 days to a depth of 1 foot
- Veggies: daily to a depth of 1 foot
- Adjust your irrigation timers if necessary to make sure plants are getting enough water. Typically, the duration of time that the water stays on (the amount of water delivered) is not changed, but the number of days between water applications will decrease as the weather continues to warm
- Make sure that water is able to drain away from roots as we step up our watering regimen. Plants that sit in water for too long can develop root rot that can look a lot like drought damage on the above-ground portions of the plant
General Chores
- Treat irises with a systemic insecticide for iris borers if they are a known pest in your garden
- If you’re mulching, be sure that none of the mulch builds up against tree trunks or the bases of woody shrubs
- Watch for grape leaf skeletonizer caterpillars on your grapes and treat early by hand-picking the caterpillars, pruning out affected portions of the plant, or treating the plant with Bt (an organic product that kills caterpillars)
- Orange Dog Caterpillars might be showing up on your citrus tree, but they can be hard to see because they look just like bird poop! A few caterpillars won’t harm a large, established tree, but you may want to remove them from smaller, newly planted trees, or treat them with Bt (an organic product that kills caterpillars).
- Geraniums tend to go dormant for the summer. Cut back on watering when the leaves begin to yellow and drop off of the plant, and only water enough to keep the branch tips from wilting through the summer. Provide the plant with some afternoon shade, or move it into full shade if it’s in a container. Cut back dead or damaged stems when the weather begins to cool again in fall, and resume watering regularly when new leaves begin to appear. Fertilize lightly when the plant is fully leafed out and actively growing in fall.
- Make sure that water is able to drain away from plant roots as we step up our watering regimen for the summer. Plants that sit in water for too long often develop root rot that can look a lot like drought damage on the above-ground portions of the plant
- Relocate potted roses to a spot that gets afternoon shade for the hottest months of summer
- Give roses and evergreen shrubs morning showers to help remove dust that attracts spider mites, and to help keep powdery mildew at bay
- Do you have a tree that is staked? It’s time to check that your tree stakes are still doing their job and that the tree isn’t being damaged by the staking wires. One year of staking is sufficient for most trees to get established; consider removing stakes that have been attached to the tree for longer than a year.
- Keep your compost moist and turn it weekly
Sources: University of Arizona online publications, Arizona State University online publications, Desert Botanical Garden website, Tucson Botanical Garden website, Gardening in the Deserts of Arizona by Mary Irish, Arizona Master Gardener Manual
