Waterlogged soil can lead to iron deficiency
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| This azalea shows signs of chlorosis in its new growth. Waterlogged soil likely kept the plant from accessing iron in the soil. (Photos: Debbie Arrington) |
Are your azaleas looking a little peaked? It may not be a lack of nutrients, but too much water.
Cindy Nalepa-Nelson, an observant longtime gardener, noticed yellowish growth on azaleas in her Land Park garden. In a walk around her neighborhood, she spotted several other examples of azaleas that were showing telltale signs of chlorosis, or yellowing of normally green leaves.
Usually, this yellowing is a sign of iron deficiency. But that doesn’t mean there’s not enough iron in the soil. Due to soil conditions, the plant’s roots couldn’t access that iron when the bush needed it for green, chlorophyll-packed leaves.
Cindy wondered if the yellow leaves could be linked to recent rain, particularly December’s deluge. According to UC Cooperative Extension master gardeners, the heavy rain likely did play a role. But it didn’t leach out the iron; it waterlogged the soil.
“Azaleas, citrus, gardenias, rhododendrons, and other plants that are adapted to acidic soil are especially prone to iron deficiency when soil pH is above about 7.5 (alkaline),” say the master gardeners. “Iron deficiency is also common when soils are cool, high in calcium, poorly drained, or waterlogged.”
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Here's another azalea with chlorosis. Notice the green veins
in the yellowish leaves.
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Iron deficiencies tend to be more common in clay soils; the iron becomes “locked” in the soil and unavailable for plant roots.
Other signs of iron deficiency: Stunted or malformed new growth; mottled yellow leaves with green veins; and bud or fruit drop. Leaves may develop brown margins, too.
Because azaleas are shooting out new growth now, those yellowish leaves are more noticeable.
To remedy the problem, aerate the soil. Poke holes to encourage drainage. Add compost or other organic matter to help drainage as well as the soil’s acidity.
Then go ahead and feed those yellowish azaleas with chelated iron, a form of this nutrient that’s easily and quickly absorbed by plants – even in clay soils. Chelated iron is available at nurseries and home centers.
For more about iron deficiency in plants, check out these UC integrated pest management plant notes: http://ipm.ucanr.edu/PMG/GARDEN/PLANTS/DISORDERS/irondeficiency.html.
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Flowers in My Back Yard Series
June 16: Daylilies are perfect for water-wise gardens (and a lot more)
June 9: Grow coneflowers for pollinators -- and yourself
June 2: Sunflowers capture Sacramento's summer attitude
May 29: Are your roses going 'blind'?
May 26: Zinnias are the summer flowers every garden needs
May 19: Plant dahlias now for late-summer flower power
May 12: Know your coreopsis from your bidens
May 5: Mums the word on Mother's Day weekend
April 28: Majestic Matilija poppy is worth a look
April 21: Celebrate roses, America's favorite flower
April 14: Small flowers with outsized impact
April 7: Calendulas do double duty
April 3: Make Easter lilies last for years to come
March 31: In praise of a pollinator magnet (small-leaf salvias)
March 24: Azaleas brighten shady spots
March 17: The perfect flower for beginners? Try zonal geraniums
March 10: Keep camellias happy for years to come
March 3: Fruit tree blossoms are a fleeting joy
Feb. 27: Are your roses looking rusty?
Feb. 24: Treasure spring daffodils now and for years to come
Feb. 17: How and why to grow wildflowers
Feb. 10: Let's talk Valentine's Day roses
Feb. 3: Why grow flowers?
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Garden checklist for week of June 14
We'll be back to normal temperatures for mid-June (about 86 degrees) by Thursday. In the meanwhile:
* Let the grass grow longer. Set the mower blades high to reduce stress on your lawn during summer heat. To cut down on evaporation, water your lawn deeply during the early hours of the morning, between 2 and 8 a.m.
* Tie up vines and stake tall plants such as gladiolus and lilies. That gives their heavy flowers some support.
* Dig and divide crowded bulbs after the tops have died down.
* Feed summer flowers with a slow-release fertilizer.
* Mulch, mulch, mulch! This “blanket” keeps moisture in the soil longer and helps your plants cope during hot weather.
* Avoid pot “hot feet.” Place a 1-inch-thick board under container plants sitting on pavement. This little cushion helps insulate them from radiated heat.
* Thin grapes on the vine for bigger, better clusters later this summer.
* Cut back fruit-bearing canes on berries.
* Warm weather brings rapid growth in the vegetable garden, with tomatoes and squash enjoying the heat. Deep-water, then feed with a balanced fertilizer. Bone meal can spur the bloom cycle and help set fruit.
* Generally, tomatoes need deep watering two to three times a week, but don't let them dry out completely. That can encourage blossom-end rot.
* Feed camellias, azaleas and other acid-loving plants. Mulch to conserve moisture and reduce heat stress.
* Cut back Shasta daisies after flowering to encourage a second bloom in the fall.
* Trim off dead flowers from rose bushes to keep them blooming through the summer. Roses also benefit from deep watering and feeding now. A top dressing of aged compost will keep them happy. It feeds as well as keeps roots moist.
* Pinch back chrysanthemums for bushier plants with many more flowers in September.
* From seed, plant corn, pumpkins, radishes, squash and sunflowers.
* Plant basil to go with your tomatoes. There’s still time to plant melons, pumpkins and squash from seed.
* Transplant summer annuals such as petunias, marigolds and zinnias. It’s also a good time to transplant perennial flowers including astilbe, bidens, columbine, coneflowers, coreopsis, dahlias, rudbeckia, salvia and verbena.
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Food in My Back Yard (FIMBY) Series
Lessons learned during a year of edible gardening
WINTER
Is edible gardening possible indoors?
Hints for choosing tomato seeds
Why winter is the perfect time to plant fruit trees
When to plant? Consider staggering your transplants
How to squeeze more food into less space
Plant a fruit tree now -- for later
Win the weed war by tackling them in winter
Tips for planting bare-root trees, shrubs and vegetables
Time to give vegetable seedlings some more space
Ways to win the fight against weeds
FALL
Dec. 16: Add asparagus to your edible garden
Dec. 9: Soggy soil and what to do about it
Dec. 2: Plant artichokes now; enjoy for years to come
Nov. 25: It's late November, and your peach tree needs spraying
Nov. 18: What to do with all those fallen leaves?
Nov. 11: Prepare now for colder weather in the edible garden
Nov. 4: Plant a pea patch for you and your garden
Oct. 27: As citrus season begins, advice for backyard growers
Oct. 20: Change is in the autumn air
Oct. 13: We don't talk (enough) about beets
Oct. 6: Fava beans do double duty
Sept. 30: Seeds or transplants for cool-season veggies?
Sept. 23: How to prolong the fall tomato harvest
SUMMER
Sept. 16: Time to shut it down?
Sept. 9: How to get the most out of your pumpkin patch
Sept. 2: Summer-to-fall transition time for evaluation, planning
Aug. 26: To pick or not to pick those tomatoes?
Aug. 19: Put worms to work for you
Aug. 12: Grow food while saving water
Aug. 5: Enhance your food with edible flowers
July 29: Why won't my tomatoes turn red?
July 22: A squash plant has mosaic virus, and it's not pretty
July 15: Does this plant need water?
July 8: Tear out that sad plant or baby it? Midsummer decisions
July 1: How to grow summer salad greens
June 24: Weird stuff that's perfectly normal
SPRING
June 17: Help pollinators help your garden
June 10: Battling early-season tomato pests
June 3: Make your own compost
May 27: Where are the bees when you need them?
May 20: How to help tomatoes thrive on hot days
May 13: Your plants can tell you more than any calendar can
May 6: Maintain soil moisture with mulch for garden success
April 29: What's (already) wrong with my tomato plants?
April 22: Should you stock up on fertilizer? (Yes!)
April 15: Grow culinary herbs in containers
April 8: When to plant summer vegetables
April 1: Don't be fooled by these garden myths
March 25: Fertilizer tips: How to 'feed' your vegetables for healthy growth