Squash Problems in Harlem

Question:
Here is a picture of the mysterious disease on our squash plants. One whole bed of squash has perished - the spots have moved on to a (nonadjacent) bed of zucchini - I fear for their safety. Can you please tell me what you think is going on here?Question:

Here's another picture if you can help figure it out. Some of our cucumbers are growing weird and lumpy... might just be random but if you have any ideas I'd love to hear them!

Answers:
As far as the squash, I think the situation is a fungal disease called powdery mildew. It occurs when there is not adequate air circulation to the garden, and it happens a lot throughout NYC. When there is not a lot of fresh air flow in the area and then lots of watering the leaves and stems can get covered with this white film. When the leaves are covered enough the plant cannot photosynthesize and the leaves die. In the extreme cases, if all the foliage gets affected then the entire plant can die as a result. There is a homemade remedy that people swear by. What you do is mix into a gallon of water two tablespoons of baking soda and a little dish soap (Dawn, Palmolive, etc.), just a drop to make the mix more viscous. Use this mix as a foliar spray and try and cover as much of the affected leaves as possible. Do this early in the morning when it is cooler and before the hot midday sun is out. If there are leaves that are really bad, just go ahead and prune and remove them to the garbage. In addition, try and increase the air flow as much as you can, removing any weeds or leaf debris that might be at the base of the plants.

As far as the misshapen squash, I am less sure as to why they are coming out looking so funny. It could have to do with the amount of water and/or the watering schedule you have the plants on. I suppose if you water heavily and then the plants go dry between watering then you can end up with some “lumpy” veggies. In addition, the rain storms we have had this summer have delivered so much water in such short periods of time, those mixed with hot dry periods in between might bring about some oddly shaped vegetables. If you water your plants with the same quantity of water and the same regularity throughout the week then you may end up with more “normal” looking vegetables. But I am sure even though they may look a little funny they are still perfectly healthy and worthy of being eaten. Think about how “perfect” the vegetables in a supermarket look – that is because farmers have their crops on a set schedule getting watered the right amount every day. For you and I who grow veggies in our own gardens they take on different shapes – that is most likely because the amount of water and how often we water can vary more. Another thought is that if the plants are battling with powdery mildew that may be affecting how efficiently the plants produce squash. My final thought has to with the presence, or lack thereof, of pollinators. According to Rodale's Garden Answers here in our library, misshapen fruit may be due to poor pollination during hot weather. There has been much talk about bee populations suffering in NYC and this may be a visible sign of that. If you do not see many bees in your garden then there is actually a way of pollinating your crops by hand and I can easily pass that information along to you.

For both of these questions I should say that there is a mosaic virus that can affect squash foliage and fruit, but none of the symptoms you have describes sound like this extreme of a problem.

Hibiscus Tree in Westchester County

(photo of Hibiscus rosa-sinensis I took down in the Flower District on 28th Street)

Question:
I received a gift of a potted hibiscus "tree." Can you tell me where I can find info to care for it? It is on my deck (Westchester County NY). What do I do with it in winter?

Answer:
Thank you for writing. By describing it as a potted “tree” I am going to go ahead and assume that you were given a tropical form of Hibiscus. In a post I wrote back on June 18th I describe the different kinds of hibiscus. On the archive menu on the right side of the page, pull down the menu for June and select the post entitled “Hibiscus in Nassau County”.

What you have been given is a tropical hibiscus. The botanical name is Hibiscus rosa-sinensis. By doing internet searches using the full botanical name you should be able to find reliable websites that give care instructions. If not, here are the basics of what you need to know.

Your hibiscus loves full sun and will flower best if you can keep it in an area with as much sun as possible. Because it has been trained as a “tree” it also requires a fair amount of water. I would water daily or every other day, making sure that the soil is kept moist all the time. Because “tree form” hibiscus have been trained so meticulously, you may find that they benefit from being misted with a spray bottle as well. The only thing about misting your hibiscus is that you want to do this early in the morning so that whatever water is on the foliage evaporates before the hot midday sun. If water is sitting on the leaves and the hot sun comes out it can actually burn holes right through the foliage. As far as winter, you will have to bring the plant inside if you wish to keep it alive through the colder months; it will not survive the freezing outside temperatures. Before threat of frost, move the tree inside to an area that has as much sun as you can provide. Keep the soil moist, and as winter comes, ease up on the watering so that the plant gets a chance to dry out between waterings. Even though it will hold onto it’s leaves, your hibiscus will go into a kind of resting period through the winter. As the days get shorter and there is less light naturally, you might experience the tree dropping some of it’s interior leaves. This is natural shedding to help the plant get through the darker winters. While the plant is inside you should expect to get more green foliage growth, but do not expect the plant to flower again until next summer when it goes outside again. You can move it back outside after the last fear of frost, and at that time you will want to consider fertilizing it through next spring and summer.

My Dracaena is Too Tall!

I often get calls from people that have corn plants (Dracaena fragrans 'Massangeana') or dragon trees (Dracaena marginata) that have gotten too tall for their apartments. Because they have grown these plants for so long and have become attached, they do not want to simply throw the plant out and start over, and I understand that completely. Therefore, I am most often asked is there a way to cut off the top of the plant and have it establish roots to be replanted?

The answer is there are a few ways of propagating a new plant from an overgrown parent plant. The first is a method called air-layering. This is a practice I learned in horticulture school designed to grow new roots on the existing stalk or bark of the parent plant before you severe it and place it in a new container. When air-layering, you begin by making an incision in the main stalk at an angle and inserting in the incision moistened sphagnum moss. In some cases, depending on the plant species, adding a rooting hormone is recommended as well. Then the cut and the sphagnum moss must be wrapped in plastic or cellophane so that it is kept constantly and evenly moist. Once roots have established from the initial wound, then the plant can be cut below that point and planted in a new container to eventually grow into its own. This process can take a number of weeks for sufficient root growth, but you can be certain that the section of plant will survive when you then remove it from the parent plant and plant it on its own. The drawback to air-layering is that you have to have a bandaged plant in your home that may not be so attractive. The other drawback is that this process takes some time and I must be perfectly honest and say that most of the people I deal with admit that they do not have the patience to attempt air-layering.

With that being said, there is another option for propagating a Dracaena from the parent plant. This alternative method is to propagate by stem cuttings. Granted it might not be as reliable as air-layering, but this anyone can do, and chances are you will still be able to continue growing the plant you have come to love. Here are a few pictures to help you through the process. This exercise I am doing here in the office as an example and I will keep you posted as to the development of new roots as they happen over time.

For this exercise, you will need a bag or regular peat moss, or a soil-less mix of ¾ peat moss and ¼ vermiculite. You will also want a plastic pot and saucer to place your cuttings in as plastic retains moisture for longer than terra cotta. If the peat moss or soil-less mix is dry, be sure to moisten it before you begin.
First locate on the parent plant a length of stem and leaves that is 4”-6” in length.For the best chance of root development and the plants survival, you need the cuttings to have some foliage so that the plant can continue to photosynthesize once it has been cut. With a sharp knife, severe this top portion of foliage and stem at a slight angle and separate it from the parent plant. For dragon trees (Draecaena marginata) some books suggest letting the cuttings sit for 24 hours, but for corn plants (Dracaena fragrans ‘Massangeana’) do not let the cuttings sit and dry out. I should say that this is also best done in the spring or summer when the plant is actively growing. Now place your cutting in your container of peat moss or soil-less mix. Remember that you need a long enough cutting that you can anchor it in the new pot with at least an inch of the stem submerged in the moist substrate. In addition, you may choose to remove or cut back a few leaves as well. Because the parent plant has many established roots, it can have an equally large amount of foliage; this is what horticulturists call the root-to-shoot ratio. Since you have removed the roots, you must pare down the foliage because this plant will have to essentially start over from scratch. If the plant is photosynthesizing like crazy and there are no roots to balance the flow of nutrients, then the plant can go into major stress and die. In addition, if you have an option, take your cuttings from the smaller shoots, as younger tissue often has better and quicker recuperative potential. Keep your cutting in the soilless mix and keep it evenly moist, watering it a few times each week. On the flip side, do not keep the mix sopping and saturated because you do not want to run the risk of rotting the cutting and losing the plant once you have come this far. As you would with any plant, keep the cutting in a spot with bright, indirect light and good air circulation. After 8-10 weeks your cutting should establish new roots and begin to live as a plant of it’s own. Once the cutting and roots have outgrown the container, repot it in a larger container in the spring.

An Ongoing Discussion on Citrus Trees in NYC

Question:
The problem I encounter is with my lemon tree. I have this tree for 4 yrs and it has always been a happy tree, or at least as happy as a citrus tree can be on the 34th floor of a building in Manhattan - flowered, grew and constantly made fruit. Suddenly, approximately 2 weeks ago, the leaf's central vein and parts of the leaf started turning yellow [I have attached 2 pictures in pdf format]. I repotted the tree in soil suggested as best for cacti and citrus and administered water with Miracle Gro and extra mg sulfate added, thinking that maybe the yellowing was due to mineral deficiency. But now I have my doubts - none of the pictures I have seen on line describing nitrogen, Mn, Fe or Zn deficiency seem to result in this leaf pattern. Could you please suggest what this can be and how I can fix it? Or direct me to someone who can help me out with this?

I, Alex Feleppa, then followed up by asking a few more questions:

What time of year did you repot your tree?
I HAVE REPOTTED THE TREE 10 DAYS AGO, ABOUT 7-10 DAYS AFTER I HAVE FIRST OBSERVED THE LEAF PROBLEM. THERE ARE NO IMPROVEMENTS AS YET, AND THIS MORNING I SAW THE FIRST LEAF DROP.

The pot that your tree was repotted into, does it have adequate drainage? Do you fertilize the tree regularly? And finally, when did you add the Miracle Gro and Mg sulfate?
YES, IT IS A CERAMIC POT WITH A DRAINAGE HOLE AT THE BOTTOM.
NO, I HAVE NOT FERTILIZED THE TREE FOR ABOUT A YEAR.
I ADDED THEM ABOUT 10DAYS AGO AFTER REPOTTING THE TREE. I HAVE WATERED THE TREE TWICE SINCE, [ABOUT 4 DAYS AGO AND TODAY] BOTH TIMES ADDING A LITTLE MIRACLE GRO TO THE WATER [NO MAGNESIUM SULFATE THIS TIME].

Even though the problem has come about quickly, your tree looks rather large so it might take a little while for the tree to bounce back. Larger plants, and especially trees, often work on a schedule that is slower than our patience allows. Perhaps there was some stress in the last year that the tree is finally showing.

It sounds like you are doing all the right things. I just found this paragraph on the University of Florida's website:

"Yellow vein chlorosis may be attributed to the girdling of individual branches, tree trunks or roots due to a number of factors including water damage, Phytophthora foot rot, root rot, ant damage, or physical damage by equipment. Yellow vein chlorosis may also occur on twigs and branches due to cool weather in the fall and winter due to lack of nitrogen uptake from the soil. In leaves showing yellow vein chlorosis, the midribs and lateral veins and a narrow band of leaf tissue bordering them become yellow while the rest of the leaf remains green."

Because lemon trees can grow so quickly, my gut instinct is that it needed to be repotted. And by doing that I hope you already solved a problem. When you repotted it, if you had noticed lots of rotting, mushy roots then perhaps we might consider some of the diseases listed above. Since that didn't seem to be the case at all I think it is safe to rule out diseases as the issue.

In addition to the roots wanting more room (which you have now supplied), they also need fertilizer. A regular fertilizing with Miracle-Gro during the summer months should supply the tree with enough nitrogen and micronutrients. If you have not been doing that in previous years then the soil might have gotten rather depleted over time.

If you have lost some leaves I consider that a natural reaction to being repotted. The tree went through some stress when it was repotted, so it may lose a few leaves while it acclimates to the new pot. That is normal. The important thing now is to keep watering it and caring for it as you always have. It's when we panic and change our agenda drastically that plants can decline even more. Water it as you have been. Follow the fertilizer instructions and ease up on that in the fall. Obviously keep the tree in as much sun as possible. Lastly, keep me posted and let me know if the yellow chlorosis spreads to more leaves.