Assess the Damage
A flower garden can tell you a lot at the end of the growing season. You'll want to assess the results of all your spring and summer work, and prepare the garden for next spring. First, take a walk around your garden and look at how all the plants did over the summer. Track successes and failures of individual plants. Identify which plants have outgrown their space and need to be divided.
Determine which bare areas could use soil amendment and new plants. Add mulch where necessary.
Check for Diseases
Check the overall health of plants — look for diseases and damage.
Replace Old with New
Replace summer annuals in window boxes and garden beds with cool-weather flowers.
You'll want to weed, deadhead faded blooms, divide overgrown plants, dig up non-hardy bulbs for winter storage, remove spent annuals, amend soil and add needed mulch. Replace ties with jute twine. Natural fibers make the best ties because they're more flexible. They'll break down over time, but at that point, it will be time to retie the plants anyway. Amend soil where there are bare spots or where you've removed annuals. Add compost and peat moss to replace nutrients lost during summer growth and to better prepare the soils for spring planting. Turn the amendments into the soil with a garden fork to distribute it evenly. Brush off any mulch that's sitting on branches of shrubs because it can cause leaves and needles to yellow.
Preparing the Lawn
Fall is a good time to do some minor maintenance in the lawn. Raking up old dead grass (thatching) helps the grass put out new runners for a more lush lawn. Fall is the time for fungus, so a systemic fungicide at this time can help us get ahead of fungus issues. Spreading a pre-emergent herbicide (such as dimension or preen) in the lawn can help us prevent cool season weeds before they start. If you have any established weedy patches, now is also the time to take care of those. Using Weed Free Zone (2-4d) will take care of established weeds in the lawn.
September is a great time to cut back roses in South Louisiana. Trim back about 25% of the bush and remove canes that are crossing each other to promote better air flow. Fertilize with an organic fertilizer to have another fall show of flowers before winter.
Cut the vine back to the ground. New shoots will form from the base next spring.
Remove All Annuals from the Garden
Remove all annuals from the garden. You can save seeds from most annuals and plant them next year. Zinnias are an easy plant to collect seeds from and to grow from seed. For window boxes, simply remove summer annuals, add more potting mix and plant cool-weather bloomers like ornamental kale and pansies.
Disinfect pruners before using them on other plants as you remove spent blooms and foliage throughout the garden.
Don't put any diseased plants into your compost pile.
Dividing perennials reinvigorates plants and gives you new plants to add to other areas of your garden or to share with neighbors and friends.
Ready Your Container Plants
Believe it or not, the most overlooked group of plants this time of year is container plants, and there are plenty of things to consider with respect to their care.
By definition, these plants only last a year, but there are ways to extend their lives. You can, for example, take cuttings of various annuals and root the in either water or a potting medium such as vermiculite, perlite or soil-less potting mix.Just remember to strip all but the top few leaves off the stem, keep the potting medium moist at all times and keep plants out of direct sunlight. Within a few weeks the plants should develop a dense mass of roots, at which point you can pot them up and grow them as houseplants. This doesn't work with all annuals, but it's fun to experiment.
Many tropicals, including palms and bananas, make excellent houseplants throughout the winter months. A good move now is to make room for all your tropical plants indoors, because this is also the time of year when sudden drops in temperature can come seemingly out of nowhere. Woody tropicals such as plumeria and citrus can easily be overwintered indoors - or in the garage, as long as the temperature doesn't drop below freezing.
Consider transplanting perennials from their containers directly into the garden. Carefully remove them from their pots, trim their roots a bit to stimulate the growth of new feeder roots, stick them in the ground and trim their top growth a little.
They tend to look pretty shabby toward the end of summer, so either harvest and dry them or consider moving them indoors. Generally, though, herbs don't do very well inside unless they get a lot of natural or fluorescent light. (The same goes for most succulents, though cacti seem to fair best among them.) We have Grow Lights specially formulated for indoor plants! These bulbs fit into any standard light socket!
Keep the Birds Coming
When you invite birds into your yard by feeding them, they do a fantastic job of keeping the insect population in check, which means you don't have to spray or dust as often to control pests.
Don't Forget the Shed!
Take time to clean your garden storage area, tossing old chemicals — responsibly of course — and taking note of what you'll need to replenish before next spring.A number of gardening products have a shelf life and may lose their effectiveness over time or if they get too hot or too cold. That's particularly true of botanical insecticides such as Bt and beneficial fungi.And of course you should tend to your tools. Rub metal tool surfaces with a light coating or oil; rub wooden tool handles with boiled linseed oil; and sharpen everything that needs it with a proper file.