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Mark Govan
What to do this week –By Mark Govan, Host “Florida Gardening”
When warm temperatures get people motivated to get out into the garden, my email starts lighting up with questions on just about every subject you can imagine. This week I am going to go through of few of the problems you, my readers have been emailing me about. Even though the questions I receive are from the full spectrum of gardening, I believe many of you may have similar problems in your landscape and you need to know what to do if these problems affect your garden. Let’s get started.
This past week I have had several questions about Ixoria and Gardenias turning yellow or losing their color in the landscape. Both plants have similar soil pH requirements (5.5 to 6.5) but there are a few distinctions I need to tell you about. Ixoria planted in the landscape away from the home seem to be problem free except for spider mites which occasionally feast on the leaves during the summer months. These insects suck juices from the plant and cause a stippling of the plants leaves giving you a plant that looks like it had dried out. This is easy to fix with an application of Bayer’s Advance 12 month Tree and Shrub Care. One application in March or April and you should see your plant returning to normal in about forty five days. However, many of our landscapers have planted these plants as foundation plants around the home.
If you happen to own a block home with stucco and either you or the contractor planted Ixoria along the foundation of the home, then you will have problems with nutrient deficiencies. The problem is that when the home had the stucco applied to the outer walls, lime from the stucco was washed down into the soil along the foundation of the home. Even if the home was built years ago, the residual from this lime is still in the soil. Lime raises the pH in the soil making the uptake of iron and other nutrients into the plant almost impossible. The symptoms you can expect to see on Ixoria are yellowing leaves, discoloration of the entire plant, loss of vigor, and eventually death. There is good news though. You can apply a foliar spray containing chelated iron directly to the leaves of the plant which will bypass the root systems inability to absorb these nutrients.
Chelated Iron can be absorbed by the leaves of the plant eventually returning the plant to health. Now I know some of you will still say that you have applied iron to the soil in the fertilizer you put around the plant and nothing happened. This is because as pH rises with the lime in the soil, the ability of the plant to absorb the iron in the fertilizer you applied as a granular, diminishes. By applying the chelated iron spray to the leaves of the plant; your plant will absorb the iron directly into the plants vascular system. One application will not correct this problem forever and you will need to apply this product every few months for best control of this deficiency problem. Be sure not to apply chelated iron to surfaces that are white as this product may stain the surface. You could use a piece of cardboard or newspaper held between the plant and the area you do not want sprayed to protect from any overspray. Be sure to use all the spray you mix up at one time as you can not leave the mixed spray in the sprayer to use again in a few months.
This same nutrient deficiency is rampant on Gardenias. Gardenias show yellowing leaves regularly in the landscape. Some homeowners attribute this to lack of fertilizer or possible an insect infestation and although this could be a factor in leaf loss, my experience is that most gardenias are also grown in soils that the pH is too high. Like Ixoria, Gardenias prefer an acid soil and need to be checked regularly for iron deficiencies. I use a product called Tiger 90 CR which is a soil amendment made primarily of cracked sulfur which can be applied to the soil with a rotary spreader. This product can help lower the pH in the soil around gardenias and azalea beds which will allow the plants to utilize the iron in the soil. This will lead to greener leaves and increased vigor and blossoms. You will have to re-apply this product at least two to three times per year because of the soils natural ability to revert back to the pH you had.
Another plant in our landscape, the Crepe Myrtle, is in need of their annual pruning now. During the summer months, crepe myrtles put on massive amounts of new growth which in turn give us a summer show of beautiful blossoms. As the tree continues to grow, many side shoots appear along the stem and occasionally even from the base of the tree. During the winter, crepe myrtles go dormant. This is the time to prune the unwanted growth from the tree and to reduce the crown or overall height of the tree.
You have probably noticed landscape companies pruning these trees by making severe cuts to the tree sometimes down to major branches. This is the incorrect way to prune crepe myrtles. The proper way to prune these trees is to remove any growth from the tree which is smaller than the width of your thumb. This will include growth from the top of the tree and any new suckers which have grown from the base of the tree. If you have a large tree this may entail quite a bit of work but the resulting benefits you receive will be a better shaped tree and more blossoms. Trees cut back to a large branch each year can develop problems and this type of pruning is very stressful to the tree.
If you are a rose grower, now is also the time to prune your roses back. Pruning roses is an essential part of growing quality roses. I recommend pruning your roses in mid February after the threat of any late frosts disappear. All pruning cuts should be made with sharp pruning shears (I use only Felco pruning shears) and your cuts should be made to eliminate any inward pointing, dead, or diseased growth. Next, you need to remove any stems which rub against each other and remove the stem which is weakest completely. Next, prune into wood that looks healthy. Look at the pith in the center of the cut. If the pith is brown or off color continue cutting down the stem until you see completely white pith. If the pith is clear, make your final cut at an angle with an outward pointing bud one quarter inch near the high point of the cut. You should have at least two buds below this cut so do not cut too low to the ground.
All remaining one year old wood should be pruned back by one third. All lateral branches should be cut back to six or seven inches and you should limit lateral branches to only two or three per branch. Remember, cutting too much from your plant will make your plant thin and weak. Some people like to cut back some stems hard and others lightly to encourage a longer bloom time. This is up to you. Always remove suckers which originate below the graft or on the roots. These growths need to be cut off as soon as they are detected.
As our warm temperatures continue to rise, our plants will respond with new growth. This new growth will need to be supplemented by you in the form of fertilizers. I suggest a granular fertilizer such as an Osmacote or a slow release 8-10-10 fertilizer for all your flowering plants. You will need approximately five pounds of fertilizer for each one hundred square feet of plant beds you have. I like to fertilize every two months giving my plants a constant feeding rather than just two or three feedings per year.
Do not forget about your turf grass. Lawns need to be fertilized now for their spring growth. I suggest a 16-0-10 fertilizer for turf grass and again I like the slow release variety. An average five thousand square foot lawn will need about a fifty pound bag of fertilizer so try not to skimp on how much fertilizer you put out. Use a rotary spreader and make sure you sweep off any impervious surfaces of any overflow so you do not contaminate our water supply. Water your lawn after the application and you should see results in about eighteen days.
I know I covered a lot of topics today but there is so much to do in the garden right now because temperatures have started to rise. Keep your eyes on the garden because your plants are going to start growing quickly this year. I hope you enjoyed this article and as always remember, without plants we would not be here!