The Garden Gate

Garden tips for every month of the year!

September

September is upon us. We will see our landscapes change from summer to early fall. Nights will begin to cool down although the days will still be hot (but shorter). Also, there will be unsettled weather as we approach the peak of the hurricane season.

September is the month we give the lawn its last fertilizing for the year. It is important that the formulation chosen will get the lawn ready for winter. Current Best Management Practices (BMP’s) for turfgrass suggest that a fall fertilizer application with a formulation where the first number (nitrogen) is close in value to the last number (potassium) will help to give the grass better stress tolerance and cold hardiness. The middle number (phosphorus) should usually be quite low (4 or less) because our soils (unless a soil test has suggested differently) are adequate in this element. Applying more only leads to more ground water pollution.

So what’s a good formulation that is currently available at many garden centers for the September application? Based on the majority of our soil tests I would recommend you purchase 15-0-15. If your lawn needs phosphorus I recommend 15-4-15. If the product you buy is one of those and is 30% slow release nitrogen or higher (you can find that on the label) it should be applied at approximately 6½ pounds per 1000 square feet of lawn. If it consists of less than 30% slow release nitrogen, to avoid unnecessary ground water contamination (it will leach before being used), apply it no stronger than 3.3 pounds per 1000 square feet - and avoid those weed and feed combinations all together.

Pine needles are falling in earnest now. Rather than chopping them up with the mower, it would be better to rake them up. They are so woody that they are slow to rot in a lawn situation. They are much better used as a loose mulch around plants - especially acid-loving plants (Azleas, Hydrangea, Gardenias, Hollies, Camellias, Junipers, etc.).

Factoid: Did you know that in tests at the University of Florida of various mulch materials, pine needles had higher nutrient levels to give back to plants around them than any of the bark mulches tested and the leaf mulches as well? Plus, they had the highest allelopathic level - i.e. ability to produce chemicals that impede weed seed germination of any tested. Pine needles make great mulch, and this time of year they are free!

September is a good time to fertilize a young tree or shrub to ready it for winter. Trees planted in the landscape, whose roots extend over into fertilized areas, will not need additional fertilizer once they have attained five years in the ground. For younger trees, the same fertilizer used for the lawn is satisfactory to use on them (as long as it does not have a weed killer in it.). It should be applied at the approximate rate of 1/10th pound of actual nitrogen for each 10 by 10 foot area. If you use a 15-0-15 or 15-4-15, then you would apply .65 pounds of fertilizer per 100 square feet.

Shrubbery can also be fertilized at this rate, although, if it is an acid loving plant (most woody shrubs are), the use of an Azalea/Camellia or Blueberry fertilizer would be preferred. In that case, follow labeled directions for amounts to apply.

Few flowers are recommended for planting this month. Chrysanthemums can still be planted. Most of the fall flowers, which will add beauty to the garden right through winter should be planted in October. Bulbs, tubers, or rhizomes that can be planted now include Aztec lily, Butterfly lily, Kaffir lily, Leopard lily, African lily, Spider lily, and Walking Iris.

You should of planted your fall vegetable garden at the end of August. Remember once your plants are up and growing be sure to fertilize them with a 15-0-15 fertilizer at the rate of 1 to 2 pounds per 100 square feet. Don’t place the fertilizer over the plant, but scatter it on the ground around the plant and then work it gently in with your fingers.

This month you can plant the more cold tolerant vegetables such as Broccoli, Cauliflower, Cabbage, Carrots, Collards, Lettuce, Mustard, Radishes and Turnips.

Return to top