Loading...

Plant Problems

Browse below for some information on common plant problems, and how you can solve them ::
(clicking on photos opens a new window/tab)

Iron Deficiency
Iron Deficiency

Cause: Iron deficiency (lime-induced chlorosis) is a common problem in many annual and perennial plants, especially Petunia, Bacopa, Scaevola, and numerous others. It can occur for many reasons, but typically it happens because the pH of the soil becomes too high for the plant to absorb iron. Iron deficiency also frequently occurs in containers, where necessary constant summer watering leaches out nutrients in the soil. If not taken care of, iron deficient plants gradually lose foliage and die.

Symptoms: Lighter green foliage, especially towards the ends of the stems or on newer growth. Veins stay darker green. In extreme cases, foliage turns completely white and then shrivels to a tan-brown color. Flowers often are smaller in size.

Solution: For gradual improvement, fertilize more. For example, instead of feeding once a week, feed every day for a few weeks. Or, instead of feeding 1 tablespoon per gallon, mix 2-3 tablespoons per gallon (Peters, Miracle-Gro, etc.). You should see improvement within a few weeks, with foliage greening up and new growth appearing. For faster results, you may follow directions on any chelated iron product and add that to your fertilizer water (this type of product makes iron readily available to the plant). This will green up the foliage quicker, but be careful to follow directions.

Bottom Line: Keep your plants healthy, and learn to identify nutrient-deficient plants before it becomes a problem. Feed regularly, especially if in a container or basket.

 

Mildew or Powdery Mildew
Mildew or Powdery Mildew Mildew or Powdery Mildew Mildew or Powdery Mildew
Left: Mildew on Tall/Garden Phlox foliage
Middle: Mildew on Zinnia foliage
Right: Bottom foliage on Tall/Garden Phlox resulting from mildew

Cause: Mildew is usually a problem caused by either growing conditions (weather, warm days and cool nights, humidity, etc.) or simply an unavoidable natural condition of certain plants. Mildew (fungi) appear on leaves which eventually hinder sufficient uptake of light and prevent normal plant processes. Some plants that are susceptible to mildew are Tall/Garden Phlox, Monarda (Bee Balm), Pulmonaria, and many annuals.

Symptoms: White, black, or brown splotches or overcasts on leaves. In extreme cases, foliage turns a crispy tan or brown. Entire plant appearance deteriorates.

Solution: Ultimately, try and choose plants that are mildew resistant. Chemical treatment periodically throughout the season with a fungicide specifically for mildew will minimize fungi growth, but it will not guarantee a completely mildew-free plant. Cut back plants to eliminate undesirable foliage and keep air movement at a maximum. Keep plants that are susceptible to mildew moist but well-drained.

Bottom Line: Accept that certain plants will get mildew to a certain degree, no matter what you do. Fortunately, most plants that are susceptible to mildew usually are done blooming by the time it is a serious problem.

 

Downy Mildew on Impatiens
Downy Mildew on Impatiens walleriana Downy Mildew on Impatiens walleriana
Left: Defoliation on Impatiens
Right: Underside of leaf showing tell-tale spores

Cause: This particular pathogen (Plasmopara obducens) affects Impatiens walleriana (common Impatiens), and has been a recent concern for not only Michigan gardeners and growers, but also a nationwide outbreak. The spores on leaf-undersides will spread short distances by splashing water, and longer distances by air currents. Spread is also accelerated by moist conditions and cool nights.

Symptoms: If plants are otherwise well cared for (good/proper watering, feeding, conditions) then... leaves curling downward, light green or yellowing leaves, white milky spores on undersides of leaves, defoliation.

Solution: Once again, prevention is key. So, purchase only healthy plants from a reputable garden center. If you have previously experienced downy mildew on your Impatiens planted in the ground, choose another shade-loving plant (Begonia, Coleus, etc.) to plant in the same area as this disease can over-winter in the soil. If planting in containers, always use new soil and preferably new containers if not thoroughly sanitized. If you are currently experiencing downy mildew on your Impatiens, remove all plants and discard, including nearby soil and debris. At this time, there are no known chemical treatments that are truly effective for the public consumer.

Bottom Line: Keep an eye on your plants, especially since downy mildew symptoms can be similar to other plant problems (e.g. light green or yellowing foliage could be nutrient or insect related). Remove the infected plants immediately to help stop the spread. Don't be too quick to blame the retailer that you purchased from, unless you're sure you purchased infected plants... this can be a fast-spreading pathogen and quite easy to "catch" from other sources in your area. Don't be too afraid to plant Impatiens again if you haven't had problems, and if you have, try other plants that would do well in the same area/conditions.

 

Aphids
Aphids and aphid damage Aphids and aphid damage
Left: Aphids, Aphid larvae, foliage damage on Hemerocallis
Right: Aphids, distorted foliage on Pelargonium

Cause: Aphids are one of the most common garden pests known. They colonize and feed or "suck" plant juices from leaves or stems. Aphids reproduce rapidly and they are not particular in what they choose to attack, as they have been found on just about every type of plant.

Symptoms: Clusters of Aphids are found on the plant, usually but not always near the tips of the stems or buds, or deep within the leaves towards the base of the stems. They can be black, brown, or green, and are typically the size of a ballpoint pen tip. Foliage that is distorted, curled, scarred with tiny yellow spots where it has been sucked, or blackened by the residue left behind by the Aphids. Tiny white shells left behind by hatching eggs.

Solution: Chemical treatment can be done any time they are seen, and any pesticide specifically made for Aphids can be applied regularly to minimize and eliminate populations. Use as directed! Repeated applications are necessary to eliminate existing insects and possible eggs/larvae that might hatch a few days later. Natural solutions often include ladybird beetles (predators of Aphids) or insecticidal soap, both of which are effective but sometimes are not as convenient or produce immediate results as compared to chemical treatment.

Bottom Line: Early identification and treatment is key. If a colony of Aphids is left untreated, serious damage to the plant will occur.

 

Japanese Beetles
Japanese Beetle and damage
Japanese Beetle damage on Malva

Cause: Japanese Beetles have become quite a nuisance in recent years. They feed primarily in July and August, and can defoliate plants with incredible speed. Many plants are resistant to Japanese Beetle, but the vast majority of plants are not immune to this serious pest.

Symptoms: Single beetles or clusters of them are found on the plant. Irregular holes are eaten away from the leaves, leaving only the veins.

Solution: Chemical treatment can be done during active feeding months, and any pesticide specifically made for Japanese Beetle can be applied regularly to minimize beetle populations. Traps can also be used, and can keep the beetles from producing next year's beetles. Traps should be placed away from your gardens so as not to attract more beetles to your plantings. Biological controls such as parasites, fungi, and nematodes have also proven to have some limited success.

Bottom Line: Japanese Beetle will most likely be a permanent pest for our gardens and plants. However, they can be kept in check with simple traps and minimal application of chemicals. Use as directed!

 

Slugs
Slugs and slug damage
Slug damage with tell-tale shiny trail

Cause: Slugs can be a nuisance in any garden, and can be found in virtually any yard or garden where cool and moist areas are prevalent. They are night feeders, so it is very likely that you may not notice them right away. Slugs will feed on many different plants, but especially Hosta, Delphinium, Marigolds, and other plants with leafy and fleshy foliage.

Symptoms: Irregular holes in leaves. Clear, shiny silvery trail left behind by the Slug's mucus body on top side of leaf.

Solution: Many methods are available with reportedly varying results. Beer in an upside-down jar lid, store-bought traps, salt, slug fences, copper rings to surround the plant at ground level, and store-bought slug bait or pellets which deter or kill Slugs.

Bottom Line: Always expect a little damage to your plants if you have consistently moist and rich soil, especially in shaded areas. Usually none of the methods above are really necessary unless there is a serious infestation of Slugs. If there is, simply use what works best for you.

 

Spider Mites
Spider Mites and damage Spider Mites and damage
Left: Spider Mite damage on Garden Mums, discolored leaves
Right: Spider Mites on New Guinea Impatiens, webbing

Cause: Spider Mites, yet another garden pest, can be a difficult problem to cure. Spider Mites suck on leaf tissue, multiply rapidly, and are difficult to identify because of their small size. Many times when you discover Spider Mites, it can be too late for a quick cure to the problem, and ultimately, the plant is beyond a cure.

Symptoms: Very small, circular white spots on leaves, and in extreme cases, leaves turning a light tan. Fine, small web-like structures on top of or on the underside of the leaves. Tiny insects residing within the webs and crawling on leaves. Webbing and damaged leaves are usually found on newer growth or at the ends of the stems.

Solution: Use a pesticide as directed that is specifically made for the control of Mites or Spider Mites. Apply regularly and frequently. Pruning off damaged foliage will help to get rid of some of the insect population.

Bottom Line: Learn to see the symptoms right away so action can be taken quickly to remedy the problem. Keep plants healthy so that even if there is a minor infestation, it does not become severe.

 

Winterkill

Cause: Some perennial plants, even those that are supposed to be winter-hardy for your area, may die and/or not come out of dormancy in the spring. This can be caused by 1) temperatures dropping below the normal winter lows of your particular area, which may be too cold for your usually "hardy" plants, 2) late planting in the fall which does not allow enough time for plant to get established, 3) sudden cold temperatures in the fall before the plant has enough time to store up sugars ("anti-freeze" protection) for the winter months, and 4) plants being too stressed out and unhealthy prior to the winter months thereby not having sufficient health to survive the winter.

Symptoms: Plant does not show any sign of life during the spring months when they should be coming out of dormancy. Plant may look brown or black, it may be mushy or rotted, and no healthy roots can be found below the soil surface.

Solution: Always choose plants that are correctly and accurately labeled as being hardy for your zone. Try to have all of your perennial planting done by late-October or early-November. Keep your plants as healthy as possible by adequate watering and feeding, especially during the late summer and fall when you may think everything is "done for the year."

Bottom Line: Climate and temperatures are out of our control, but doing your best with what you can control will certainly help your chances at receiving reliable performance each and every year from your perennials.

 

My Hydrangea doesn't bloom, why?

Cause: There are quite a few reasons why a Hydrangea might not bloom as well as it should. A few common reasons are 1) improper pruning for the kind of Hydrangea you have, 2) a late frost which may freeze out tender buds that have already begun to grow in the spring, and 3) improper amount of sunlight.

Symptoms: Plant does not produce any flowers, yet the rest of the plant seems to be healthy.

Solution: Know what kind/species of Hydrangea you have, and check out our Plant Care page for tips on how to prune. Take notice of lighting needs for your Hydrangea, as it varies widely between species.

Bottom Line: Again, climate and temperatures are out of our control, but learning how to prune and choosing the best placement for your Hydrangea should offer you the blooming results you deserve.

 

Notice ::

Information displayed above is for informational purposes only. W.W. cannot assume responsibility for further plant problems resulting from actions taken as advised above.