Category Archives: fungal diseases

Plant Problems- What’s a Gardener to do?

Just one of many banana slugs in my garden

Everything was growing nicely in the garden until the banana slugs and squirrels started eating me out of house and home, fungal leaf spots and aphids appeared and the gophers and deer decided they really liked my plants. Whatís a gardener to do?

Troubleshooting is a form of problem solving. And whether itís your car, your smart phone, an irrigation system or yellowing leaves on a plant the goal is to find the solution and make everything work again. When you eliminate the potential causes of the problem hopefully the solution restores everything to its working order. Sometimes this is easier said than done as we all know.

A few weeks ago I received a text with pictures of some plants with leaf spots and was asked for a solution. Over the winter we received a lot of rain so I wasnít surprised. But if this were mid-summer Iíd suspect that the plant leaves were burned by the sun and not getting deep enough irrigation. At this time of year, however, black or brown spots on leaves are fungal or bacterial problems and should be treated with an organic fungicide like Serenade which is non-toxic to bees and beneficial insects, Neem, copper or sulfur spray to prevent and control spreading. Affected leaves should be discarded.

The subject of how much fertilizer and what kind came up in another troubleshooting email. The issue was whether to use an organic high phosphate fertilizer in order to encourage bud development on a notoriously short-season tree dahlia. A single spring application of rock phosphate should be sufficient. Sometimes adding too much phosphorus can actually hurt a plant, preventing the uptake of other nutrients necessary to prevent other deficiencies. A balanced fertilizer containing all three nutrients- nitrogen, phosphorus and potassium-was recommended for the remainder of the season.

Winter yellow leaves on Meyer Improved lemon

Then there are the problems in my own garden. Well, it seems I am always trying to solve something with plants, pests or critters but now itís the lemon tree. The older leaves of this tree are yellow. The new growth looks fine so it isnít an iron deficiency where young leaves display green veins along with a yellowish color.

It isnít a nitrogen deficiency either where the mature leaves slowly bleach to a mottled irregular green and yellow pattern, become entirely yellow and then are shed while the discoloration spreads to the younger leaves. I fertilized in March with an all-purpose balanced fertilizer. Citrus are heavy feeders and require a steady source of nitrogen, the ideal citrus fertilizer having a ration of 3:1:1 (N:P:K)

After eliminating other mineral deficiencies or overwatering as the problem I decided that my lemon was simply dropping interior leaves which is normal after winter but I wanted to trouble shoot all potential causes to be sure citrus greening wasnít the culprit. If it had been this deadly disease the leaves would have exhibited an asymmetrical pattern.

To quote Sherlock Holmes ďOnce you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.Ē Iíll try to remember that when Iím troubleshooting my next problem in the garden. Oh and by the way my banana slug relocation program is going well.

Aloe & other Succulents in the late Winter Garden

Usually succulents are bullet-proof in the garden. Easy care, low water and dramatic they are great additions to the landscape. If you are having problems with fungal spots on yours after so much rain and cold youíre not alone. Still aloe, yucca and agave are worth growing as well as other succulents. Here is some useful information.

Cape Aloe

Succulents have demonstrated a wide tolerance to the fungi that cause leaf and some spots. Although they can disfigure plants they do very little damage despite their appearance.

There are other more serious fungal infections like anthracnose. It often appears as a moist tan colored rot with red, orange or pink pustules on the surface. Spots start small, but expand rapidly on both leaves and crowns. Once a succulents is infected the only treatment is removal of affected leaves. The application of copper fungicide may help to destroy fungal bodies. Root and crown rot donít respond well to treatment and if you have planted your succulents in well draining soil there might not be much you can do about the excessive rain theyíve gotten recently.

Our Mediterranean climate is usually perfectly suited for the exotic looking family of Aloes. Some hail from the Arabian Peninsula and Madagascar but mostly they are native to South Africa. The spikes of their showy flowers supply much needed nectar for hummingbirds now when not much else is blooming.

Thereís a variety for any space, large or small, container or tree-like. Here are a few of the types Iím seeing blooming right now in our area.

Aloe ferox

Aloe ferox or Cape Aloe grows best in full sun but tolerates a wide variety of growing conditions. They can thrive in very dry conditions or grow in an area that receives regular irrigation- a good trait given our recent wet winter. The foliage is hardy to at least 20 degrees and the winter flowers down to 24 degrees. Cape aloe grow to 6 feet tall and 3-5 feet wide so plan accordingly if you plant one of these spectacular reddish-orange to orange succulents. Cape Aloe occupies many habitats in its native Cape Region of South Africa and is listed on the endangered plant list.

Torch aloe

Torch Aloe or Aloe arborescens blooms also in fall and winter. The bright yellow or red flower spikes cover this large clumping variety. This species has recently been studied for possible medical uses similar to the well known aloe vera plant. Itís the only other member of the Aloe family that is claimed to be as effective. It can survive much lower winter low temperatures than aloe vera.

Aloe vera has been grown for thousands of years in tropical climates. It is one of the most widely used medicinal plants on the planet. As a houseplant make sure the pot has plenty of drainage holes as they cannot tolerate standing water. Let them go completely dry between waterings and grow them in the very bright light of a south or west facing window.

The Soap Aloe or Aloe maculata is so tough that it can survive just about anywhere. My soap aloe arenít blooming right now but others in better growing conditions are sporting showy flowers atop tall, multi branched stalks in colors ranging from red to gold. Once established this succulent needs only occasional water to look good. They grow in partial to full sun. The foliage gets 18 to 24 inches tall with the bloom spikes reaching 35 inches tall.

Every garden should have a variety of aloe to feed the hummingbirds in winter.