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April

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April in the low desert

watering | what to plant | pruning | fertilization | problems

In April, the desert comes alive with colors, smells and sounds. If rains were plentiful during the fall and winter months, a dazzling array of color will have bestowed the desert floor with many annuals such as Mexican Gold Poppies (Eschscholzia californica ssp. mexicana), Owl-clover (Castilleja exserta), Lupines (Lupinus spp.), Yellow Evening Primrose (Oenothera primiveris ssp. primiveris), Bladderpod (Lesquerella gordonii), Scorpionweeds (Phacelia spp.), Chia (Salvia columbariae), and Desert Pincushion (Chaenactis stevioides). Search the Garden’s Wildflower InfoSite to find out what is currently blooming throughout the state.

On April 20-22, 2012 visit the Garden and behold the exquisite, yet bizarre examples of cacti and succulents as members of the Central Arizona Cactus and Succulent Society display potted specimens of desert plants from around the world. There will also be a sale at the show featuring plants and pots from southwestern growers and artists. For more information go to centralarizonacactus.org or call 480 838.5094.

Many deciduous trees will begin to produce new leaves as the weather becomes warmer. Look for: Mesquites (Prosopis spp.), Desert-willow (Chilopsis linearis), Golden Leadball Tree (Leucaena retusa), Catclaw Acacia (Senegalia greggii syn. Acacia greggii), Feather Tree (Lysiloma watsonii), Anacacho Orchid-tree (Bauhinia lunarioides), and Kidneywood (Eysenhardtia orthocarpa).

Leaves of the Boojum Tree (Fouquieria columnaris) and Elephant Tree (Pachycormus discolor) will begin to yellow and drop. The Boojum Tree and Elephant Tree are summer-dormant. Periods of active growth begin from about November through May. When the leaves of both succulents begin to drop, careful watering is needed. See our Desert Gardening Guide on the Boojum Tree for more information on caring for this unusual succulent.

Look upward to see the Saguaro (Carnegiea gigantea) flower buds forming atop the stems. The majestic Ironwood tree (Olneya tesota) will shed some of its leaves in preparation for flowering.

Plant your Ocotillo (Fouquieria splendens) from March through May as these are the ideal months to achieve greater transplanting success. For more information on planting an Ocotillo see our Desert Gardening Guide Planting a Bare Root Ocotillo.

Karoo-roses (Adenium spp.) should be “waking” from their winter dormancy. Leaves and flowers should start appearing on the succulent stems. You can begin to fertilize and water your Karoo-rose throughout the warm-season. For more information on caring for your Karoo-rose see our Desert Gardening Guide on Care of Adenium.

Other winter-dormant succulents that should be exhibiting renewed growth with increasingly warmer weather include: Limberbushes (Jatropha spp.), Burseras (Bursera spp.), Uncarina spp., Pachypodium spp., Fockea spp., Cyphostemma juttae, and Globeberries (Ibervillea spp.). Allow your succulent plants to produce new leaves to determine whether or not any pruning of frost damaged stems will be needed. Regular and careful watering can resume for many of these warm-season growing succulents.

Blooming herbaceous perennials, groundcovers and vines can include:
• Sundrops (Calylophus hartwegii)
• Angelita-daisy (Tetraneuris acaulis)
• Golden Columbine (Aquilegia chrysantha)
• Pineleaf Milkweed (Asclepias linaria)
• Winecups (Callirhoe involucrata)
• Twinberry (Menodora scabra)
• Old Man’s Beard (Clematis drummondii)
• Slender Janusia (Janusia gracilis)
• Sweetbush (Bebbia juncea)
• Palmer’s Penstemon (Penstemon palmeri)
• Canyon Penstemon (Penstemon pseudospectabilis)
• Firecracker Penstemon (Penstemon eatonii)
• Shrubby Bulbine (Bulbine frutescens)
• Hill Country Penstemon (Penstemon triflorus)
• Gaura (Gaura lindheimeri)
• Desert Milkweed (Asclepias subulata)
• Damianita (Chrysactinia mexicana)
• Perezia (Acourtia wrightii)
• Blue Mist (Caryopteris x clandonensis ‘Dark    Knight’)
• Odora (Porophyllum gracile)
• Chocolate Flower (Berlandiera lyrata)
• Trailing Indigo Bush (Dalea greggii)
• Fleabane (Erigeron divergens)
• Dyssodia (Thymophylla pentachaeta)
Blooming shrubs can include: 
• Ocotillo (Fouquieria splendens)
• Autumn Sage (Salvia greggii)
• Cleveland’s Sage (Salvia clevelandii)
• White Sage (Salvia apiana)
• Mexican-buckeye (Ungnadia speciosa)
• Ruellia (Ruellia peninsularis)
• Wright’s Bee Bush (Aloysia wrightii)
• Beebrush (Aloysia gratissima)
• Flat-top Buckwheat (Eriogonum fasciculatum)
• Apache Plume (Fallugia paradoxa)
• Creosote (Larrea tridentata)
• Parish’s Goldeneye (Viguiera parishii)
• Superstition Mallow (Abutilon palmeri)
• Desert-honeysuckle (Anisacanthus thurberi)
• Pink Fairy Duster (Calliandra eriophylla)
• Baja Fairy Duster (Calliandra californica)
• Desert Hackberry (Celtis ehrenbergiana syn. Celtis pallida)
• Desert-lavender (Hyptis emoryi)
Mormon-teas (Ephedra spp.) will be producing male and female cones.
Blooming trees can include: 
• Little-leaf Palo Verde (Parkinsonia microphylla)
• Feather Tree (Lysiloma watsonii)
• Guajillo (Senegalia berlandieri syn. Acacia berlandieri)
• Catclaw Acacia (Senegalia greggii syn. Acacia greggii)
• Kidneywood (Eysenhardtia orthocarpa)
• Baby Bonnets (Coursetia glandulosa)
• Velvet Mesquite (Prosopis velutina)
• Anacacho Orchid-tree (Bauhinia lunarioides)
• Desert-willow (Chilopsis linearis)
Blooming cacti and succulents can include:
• Engelmann’s Hedgehog (Echinocereus engelmannii)
• Bonker Hedgehog (Echinocereus bonkerae)
• Strawberry Hedgehog (Echinocereus fasciculatus)
• Golden Hedgehog (Echinocereus nicholii)
• Lady Finger Cactus (Echinocereus pentalophus)
• Powder Puff Pincushion (Mammillaria bocasana)
• Lady Finger Cactus (Mammillaria elongata)
Thelocactus macdowellii
• Black-spined Prickly-pear (Opuntia macrocentra)
• Engelmann’s Prickly-pear (Opuntia engelmannii)
• Santa-Rita Prickly-pear (Opunta santa-rita)
• Indian Fig (Opuntia ficus-indica)
• Buckhorn Cholla (Cylindropuntia acanthocarpa)
• Teddy Bear Cholla (Cylindropuntia bigelovii)
• Silver Cholla (Cylindropuntia echinocarpa)
• Diamond Cholla (Cylindropuntia ramosissima)
• Mexican Fence Post (Pachycereus marginatus)
•  Senita (Pachycereus schottii)
• Cardón (Pachycereus pringlei)
• Candelilla (Euphorbia antisyphilitica)
Euphorbia xantii
• Karoo-roses (Adenium spp.)
• Live Forever (Dudleya saxosa ssp. collomiae)
• Texas False-agave (Hechtia texensis)
• Blue Yucca (Yucca rigida)
• Banana Yucca (Yucca baccata)
• Joshua Tree (Yucca brevifolia)
• Mohave Yucca (Yucca schidigera)
• Eve’s Needle (Yucca faxoniana)
• Leatherstem (Jatropha dioica)

Many agaves may start or exhibit signs of blooming. Look for an inflorescence (a flower cluster with a definite arrangement of the flowers on a stalk/stem) forming at the center of plant.

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Watering

If you have not turned on your irrigation timer, now is the time to do so. Test the timer to see if it is working properly and replace back-up batteries if necessary. Check for leaks and clogged emitters and flush out the poly lines.

The amount of water and watering frequency depends on many factors. These include: soil type, weather (temperature, humidity, rainfall, etc.), microclimates, cultural practices, plant size and species, and whether newly planted or established in the landscape (two years or more). Below are general guidelines to help you determine how much and how often to water your landscape and container plantings to keep them healthy when rainfall is lacking. View our Desert Gardening Guide on Watering Desert Trees and Shrubs for additional information.

Established native or desert-adapted trees and shrubs should be watered at least once to twice monthly. Water at least 3 feet deep for your trees and 2 feet deep for your shrubs. Always allow soil to dry out between each irrigation cycle.

Natural rainfall may be adequate for most well-established cacti and succulents. However, if rainfall is insufficient, water may be needed at least once to twice during the month of April. Water your cacti and succulents to a depth of at least 8-12 inches. Always allow soil to dry out between each irrigation cycle.

Established herbaceous perennials, groundcovers and vines should be watered every two to three weeks and at least 1 foot deep. Always allow soil to dry out between each irrigation cycle.

Wait a week after planting your cacti and succulents before watering to minimize the chance of rot. After the initial irrigation of your succulents, allow the soil to dry out and water every 10-14 days. Cacti may need to be watered once more after initial watering during the month of April, but allow the soil to dry out between watering.

Newly planted native and desert-adapted trees and shrubs need to be watered more frequently until established. It can take up to 3-5 years for trees and at least 1-2 years for shrubs to become established in the landscape. After planting your trees and shrubs, they should be watered immediately and for the next few days to keep the root ball from drying out. Schedule your irrigation cycle for trees and shrubs every 7-10 days. Allow the soil to dry out between irrigations and always water deeply, 3 feet for trees and 2 feet for shrubs.

Newly planted native and desert-adapted herbaceous perennials, groundcovers and vines should be watered immediately and for the next few days to keep the root ball from drying out. Schedule your irrigation cycle for herbaceous perennials, groundcovers and vines for at least once to twice weekly and to a depth of 1 foot. Allow soil to dry out between watering.

Continue to water your annual wildflowers at least every two weeks to prolong flowering.

Agaves and other succulents (Aloe spp., Dudleya spp., Cotyledon spp., Pedilanthus macrocarpus, Euphorbia spp., Haworthia spp.) in containers should be watered at least once to twice this month. Cacti in containers should be watered at least once this month. However, cacti and succulents in small containers may need to be watered more often especially cacti and succulent seedlings.

Keep an eye on your warm-season annuals and herbaceous perennials in containers. Water them at least once to twice weekly.

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What to Plant

Plant warm-season cacti and succulents including:
• Saguaro (Carnegiea gigantea)
• Prickly-pears (Opuntia spp.)
• Chollas (Cylindropuntia spp.)
• Barrel cacti (Ferocactus spp.)
• Hedgehogs (Echinocereus spp.)
• Pincushions (Mammillaria spp.)
• Agaves (Agave spp.)
• Aloes (Aloe spp.)
• Candelilla (Euphorbia antisyphilitica)
• Desert Spoon (Dasylirion wheeleri)
• Red-yucca (Hesperaloe parviflora)
• Giant Hesperaloe (Hesperaloe funifera)
• Slipper Plant (Pedilanthus macrocarpus)
• Elephant Food (Portulacaria afra)
• Burseras (Bursera spp.)
• Texas-tuberose (Manfreda maculosa)
• Limberbushes (Jatropha spp.)

Many Yuccas (Yucca spp.) can be planted in April with the exception of Joshua Trees (Yucca brevifolia).

When transplanting cacti and succulents, mark either the south or west side and plant facing the orientation you marked to avoid the burning of tender tissues. Most nurseries will mark the side of the container to help you determine proper planting orientation. However, if the original orientation is not known, newly planted cacti and succulents need to be covered with shade cloth if the plant surface appears to yellow or pale suddenly. Use a shade cloth rated between 30-60% as anything higher will block most of the sunlight and will not be suitable for your cacti and succulents. You may need to keep the shade cloth on the plant for the duration of the summer.

Plant native and desert-adapted trees including: 
• Ironwood (Olneya tesota)
• Blue Palo Verde (Parkinsonia florida)
• Little-leaf Palo Verde (Parkinsonia microphylla)
• Mesquites (Prosopis spp.)
• Golden Leadball Tree (Leucaena retusa)
• Desert-willow (Chilopsis linearis)
• Palo Blanco (Mariosousa willardiana syn. Acacia willardiana)
• Catclaw Acacia (Senegalia greggii syn. Acacia greggii)
• Feather Tree (Lysiloma watsonii)
• Anacacho Orchid-tree (Bauhinia lunarioides)
• Vitex (Vitex agnus-castus)
• Baby Bonnets (Coursetia glandulosa)
Plant warm-season shrubs including: 

• Yellow Bells (Tecoma spp.)
• Texas Sages (Leucophyllum spp.)
• Creosote (Larrea tridentata)
• Superstition Mallow (Abutilon palmeri)
• San Marcos Hibiscus (Gossypium harknessii)
• Desert Cotton (Gossypium thurberi)
• Guayacán (Guaiacum coulteri)
• Sennas (Senna spp.)
• Velvet-pod Mimosa (Mimosa dysocarpa)
• Ocotillo (Fouquieria splendens)
• Fire Bush (Hamelia patens)
• Ruellia (Ruellia peninsularis)
• Lantana (Lantana camara)

• Mexican Bush Sage (Salvia leucantha)
• Silver Nightshade (Solanum hindsianum)
• Little-leaf Cordia (Cordia parvifolia)
• Showy Mendora (Menodora longiflora)
• Sky Flower (Duranta erecta)
• Bird of Paradise species (Caesalpinia spp.)
Plant warm-season herbaceous perennials and groundcovers including: 
• Sacred Datura (Datura wrightii)
• Desert Four O’Clock (Mirabilis multiflora)
• Arizona Foldwing (Dicliptera resupinata)
• Buffalo Gourd (Cucurbita foetidissima)
• Mealy-cup Sage (Salvia farinacea)
• Yerba Mansa (Anemopsis californica)
• Rose-mallow (Hibiscus coulteri)
• Wine Cups (Callirhoe involucrata)
• Hummingbird Trumpet (Epilobium canum ssp. latifolium)
• Lemon Dalea (Dalea capitata)
• Chocolate Flower (Berlandiera lyrata)
• Desert Senna (Senna covesii)
• Trailing Lantana (Lantana montevidensis)
• White Plumbago (Plumbago scandens)
• Mist Flower (Conoclinium dissectum)
• Rain Lilies (Zephyranthes spp.)
Many vines can also be planted at this time including: 
• Yuca (Merremia aurea)
• Queen’s Wreath (Antigonon leptopus)
• Yellow Orchid-vine (Callaeum macropterum)
• Passionflowers (Passiflora spp.)
• Arizona Canyon Grape (Vitis arizonica)
• Old Man’s Beard (Clematis drummondii)
When planting native and desert-adapted plants, it is usually unnecessary to back-fill with soil amendments and vitamins or to add rooting hormones. However, a slow-release fertilizer high in nitrogen and phosphorous can be added to the backfill, if necessary. Take a look at our Desert Gardening Guide on How to Plant Desert-Adapted Trees and Shrubs.

Many cacti can be started from seed at this time. Seed can be soaked overnight in water to help begin the germination process. Place seed in a well-draining soil mix (½ quality potting soil and ½ perlite or pumice) and lightly cover with potting mix or gently press seed into the soil. Keep soil moist until germination occurs. See our Desert Gardening Guide on Growing Cacti from Seed.
Sow seed of warm-season annuals and herbaceous perennials including:  
• Mexican Hat (Ratibida columnifera)
• Red Sage (Salvia coccinea)
• Mexican Chia (Salvia hispanica)
• Tarahumara Chia (Salvia tiliaefolia)
• Sunflower (Helianthus annuus) and the numerous cultivars
• Summer Chia (Hyptis suaveolens)
• Chocolate Flower (Berlandiera lyrata)
• Tickseeds (Coreopsis spp.)
• Golden Crownbeard (Verbesina encelioides)
Vegetables to transplant include:
• Jerusalem artichoke
• sweet potato
Vegetable seeds to sow include: 
• Lima beans and summer squash
(first part of April)
• amaranth
• eggplant
• carrots
• cucumbers
• jicama
• cantaloupe
• muskmelon
• watermelon
• okra
• green onions
• peanuts
• radishes
• tomatillos
• pumpkins
• snap beans
• black-eyed peas
• yardlong beans

Try the various beans from Native Seeds/SEARCH. Gourd and squash seeds should also be sown during the month of April. Presoak gourd and squash seeds overnight for better germination. Try the many varieties from Native Seeds/SEARCH.

Herb seeds to sow include:
• Anise
• basil
• catnip
• epazote
• feverfew
• horehound
• lemon balm
• safflower
• winter and summer savory

Herbs to transplant include: 
• Mexican-oregano (Lippia graveolens)
• Cuban-oregano
• bay
• basil
• chives
• curry
• French tarragon
• garlic chives
• germander
• horehound
• hyssop
• lemon balm
• lemon grass
• lemon verbena

 

• marjoram
• mint
• oregano
• rue
• sage
• santolina
• winter and summer savory
• scented geraniums
• tansy
• thyme
• yarrow

 

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Pruning

Pruning should be done to maintain plant health (remove dead, damaged or diseased portions, cross branching, etc.), to highlight the “natural” shape of the plant, to train a young plant, and to eliminate hazards. Excessive or heavy pruning causes significant stress to trees and shrubs. The best practices are to prune the least amount necessary and prune for legitimate reasons. How much to prune depends on the size, species, age, as well as your intentions. Two pruning principles to remember--a tree or shrub can recover from several small pruning wounds faster than from a single large wound and never remove more than 25% of the canopy in a year. For more information register for a Garden class offered on pruning that will teach you the proper pruning techniques for trees and shrubs or visit www.treesaregood.org. for information on proper pruning of young and mature trees.

Continue to prune evergreen trees.

Lightly prune your Mesquites (Prosopis spp.) and Palo Verdes (Parkinsonia spp.) after bud break or after flowering.

Pruning newly planted trees and shrubs is not recommended and in fact can be detrimental. However, corrective pruning of broken or torn branches and/or limbs can be done at planting time. Save other pruning activities for the second or third year. For more information on developing a healthy tree visit www.treesaregood.org.

Continue to prune frost-damaged plants. If possible, finish pruning frost-damaged plants by the end of April so new growth can establish before the summer heat.

Continue to prune summer and fall flowering shrubs by mid-month including: 
• Texas Sages (Leucophyllum spp.)
• Yellow Bells (Tecoma stans) and cultivars
• Lantana (Lantana camara)
• Turpentine Bush (Ericameria laricifolia)
• Black Dalea (Dalea frutescens)
• Mexican-honeysuckle (Justicia spicigera)
• Sky Flower (Duranta erecta)

For more information on pruning shrubs go to the University of Arizona Cooperative Extension at: http://cals.arizona.edu/pubs/garden/az1499.pdf

Wait to prune your Prickly-pears (Opuntia spp.) and Chollas (Cylindropuntia spp.) until after flowering. Spent stalks of aloes, agaves and other succulents can be removed at this time.

Warm-season herbaceous perennials, groundcovers and vines can be pruned at this time including:   
• Chocolate Flower (Berlandiera lyrata)
• Plumbago (Plumbago scandens)
• Mexican Hat (Ratibida columnifera)
• Gaura (Gaura lindheimeri)
• Mealy-cup Sage (Salvia farinacea)
• Yellow Dot (Sphagneticola trilobata)
• Rock Verbena (Glandularia pulchella)
• Trailing Lantana (Lantana montevidensis)
• Dyssodia (Thymophylla pentachaeta)
• Queen’s Wreath (Antigonon leptopus)
• Passion Vines (Passiflora spp.)
• Yellow Orchid-vine (Callaeum macropterum)

Prune by cutting back to emerging growth or to the basal rosette (group of leaves arranged from a central point).

Continue to deadhead annuals and herbaceous perennials to encourage continued flowering including Desert Marigold (Baileya multiradiata), Red Sage (Salvia coccinea), Angelita-daisy (Tetraneuris acaulis), and Gaillardia (Gaillardia pulchella).

Many herbs such as Mexican tarragon (Tagetes lucida), French tarragon and pineapple sage (Salvia elegans) may be emerging from the roots by now. Prune to new growth to remove old or frost damaged stems.

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Fertilization

Most native and desert-adapted plants in the landscape do not generally require fertilizer as they are adapted to our soil conditions. In most cases, fertilizers are generally applied to prevent deficiencies. If fertilizers are needed, one application for the year is usually sufficient. If you did not fertilize last month, go ahead and fertilize your landscape plants if necessary. For more information on fertilizing and plant deficiencies go to the University of Arizona Cooperative Extension publications: http://ag.arizona.edu/pubs/garden/az1020.pdf and http://cals.arizona.edu/pubs/garden/az1106.pdf.

Now is the time to fertilize your warm-season cacti, succulents, herbaceous and woody perennials, and annuals in containers if you haven’t done so already. Periodic fertilization may be needed for plants in containers as nutrients will have diminished in the soil over time. Always follow directions on the label.

Continue to fertilize your vegetable and herb garden as needed. If you have not applied a layer of composted mulch, now is a good time to add to your beds to help conserve moisture.

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Problems

Aphids can be found on landscape plants or on your vegetables and herbs. Allow natural predators such as lacewings, praying mantis, lady beetles, parasitic wasps, and even hummingbirds to control the aphid population. You can also spray with insecticidal soap, but check to make sure beneficial insects are not present.

If you notice a tattered appearance on your landscape plants such as Evening Primroses (Oenothera spp.), Sacred Datura (Datura wrightii) and Gaura (Gaura lindheimeri) it may be the flea beetle in action. A different species of flea beetle may also harm your vegetables including tomatoes, eggplants, carrots, and cabbages. The flea beetle larvae and adults can be destructive and they can be difficult to control. To find out more information on flea beetles go to the following link: http://ag.arizona.edu/maricopa/garden/html/t-tips/bugs/flea-btl.htm

You may notice small, circular cuts on the leaf margins at this time. This is the handiwork of leaf-cutter bees, important pollinators. The leaf-cutter bees use the cut leaf to line their nest and then lay an egg in each cavity. The damage is cosmetic and does not harm the plant. Control methods are unnecessary.

Cochineal scale, the cottony, white substance on your Prickly-pears (Opuntia spp.) and Chollas (Cylindropunita spp.) may be active now. Remove by using a fast stream of water or spray insecticidal soap.

Fine webbing between leaves or stippling on leaves may indicate the presence of spider mites. These plant mites cause damage by sucking contents from the leaves and are difficult to detect due to their small size. Plants that are water stressed may become susceptible to infestation. Dusty conditions can also lead to spider mite outbreaks. Make sure your plants are well-watered and wash off accumulated dust on plants to manage spider mite problems. You can also remove by using a fast spray of water or by spraying insecticidal soap to control populations. There are many biological controls that feed on spider mites including lacewings, predatory mites, lady bugs and big-eyed bugs. Using insecticides is not recommended as insecticides do not help manage the population, but can actually cause the population to intensify because insecticides used will often kill their natural enemies. Some insecticides can even accelerate mite reproduction.

Psyllids may be active during the month of April. Psyllids are sap feeders and many are plant specific or feed on a closely related group of plants. High populations of psyllids can cause distortion and die back of new growth, and in some cases defoliation. To keep populations under control do not overwater or over fertilize your plants as this causes excessive growth. Yellow sticky traps can also be used to control the adult population.

A noticeable, fine web may be present on your Palo Verde trees and even from time to time on the Whitethorn Acacia (Vachellia constricta syn. Acacia constricta).  This “webbing” is produced by the Palo Verde webworms, often called Palo Verde webbers. The webworm is a small caterpillar that feeds on the leaves and occasionally the bark of the small stems.  The Palo Verde and Whitethorn Acacia are resilient to an infestation of webworms so control methods are unnecessary. The caterpillars and adult moths are an important food source for many lizards and birds.

Agave snout weevils become active during the warm months and infestation may not be apparent until it is too late. For detailed information on the life cycle, symptoms, prevention and treatment go to our Agave Snout Weevil Desert Gardening Guide.

Look for mealy bugs on your cacti and succulents. These scale insects can be difficult to control due to their ability to reproduce rapidly and they quickly acquire resistance to chemical controls. Spray mealy bugs with a 70% alcohol-water solution.

A white, frothy substance may be visible on plant stems. This is caused by spittle bugs. Manage by spraying stem off with a strong jet of water to remove infestation.Spittle bugs generally do not cause much damage to plants.

Noticeable leaf damage may be seen on the Texas Mountain-laurel (Calia secundiflora syn. Sophora secundiflora) during the warm months. The damage is caused by the sophora pyralid caterpillars feeding on the tender new growth. These ravenous caterpillars are approximately an inch long with orange bodies and interesting black spots with white hairs. To find out more information about the Sophora pyralid moths go to our Desert Gardening Guide.

As the weather warms, whiteflies may be present on your landscape, vegetable and herb plants. These tiny white insects have sucking mouthparts that cause leaves to yellow, wilt and drop prematurely. The immature nymph stage does more harm to the plant than the adult. Whiteflies can be difficult to control. Allow natural predators such as spiders, ladybugs, lacewings and even hummingbirds to control the population. Yellow sticky traps can also be used to control the adult population.

While sitting underneath your desert trees, you may notice a light “rain” falling. This is the smoke tree sharpshooter insect expelling sap as it draws from a variety of plants including Palo Verdes (Parkinsonia spp.), Beebrush (Aloysia gratissima), Bird of Paradise (Caesalpinia spp.) and Hackberries (Celtis spp.). The smoke tree sharpshooter insects have gone virtually unnoticed until they threatened oleanders, shrubs widely used in low-desert landscapes for screening hedges. They gained notoriety because they are able to transmit a deadly bacterial disease called oleander leaf scorch. Our native plants do not appear to be adversely affected by the sharpshooter insects so no control is necessary. To find out more about oleander leaf scorch visit University of Arizona Extension Plant Pathology.

If you notice a rank odor and black ooze dripping down the saguaro stem(s), the plant may have developed an infection as a result of an injury or frost damage. The infection is caused by the Erwinia bacteria, a common bacterium found in the environment.  For more information on saguaros and how to care for them, check out our Desert Gardening Guide Planting and Caring for a Saguaro.

You may notice rabbits eating new, tender growth on your plants or flowers. It may be necessary to cage plants temporarily, or spray Liquid FenceTM to help deter these animals. For more information on rabbit-resistant plants, see our Desert Gardening Guide.

Weeds that germinated with the fall-winter rains will begin to flower at this time. You can manually remove by hand or for larger areas spray with glyphosate following directions on the label. Adding a small amount of marker dye in the glyphosate solution can be helpful to avoid spraying the same areas twice. When using a chemical spray use an old pair of shoes that will never be worn indoors. The glyphosate product can be used around cacti and most succulents without damaging them. It is also inactive in the soil, so it will not harm the roots of other plants.

For more information on diseases or problems of landscape plants go to the University of Arizona Cooperative Extension publication http://ag.arizona.edu/pubs/diseases/az1124.pdf or the University of California UC IPM Online at http://www.ipm.ucdavis.edu/PMG/menu.homegarden.html

 

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