September is the month our plants have been looking for (us, too). Cooler nights are what makes the difference between the dog days of summer and the pleasant fall days that follow. While we are resting at night so we can work harder the next day, plants are growing. This explains why fall weather is so productive for plants. Here are some things to make your plants more productive:

Trees and shrubs: Fall is the time to plant trees and shrubs. Our winter weather is warm enough that plants continue to develop extensive root systems, which will make them stronger when the hot weather returns.

Also add mulch, with a slow-release fertilizer mixed in, for your trees and shrubs. The microorganisms will handle it from there. It's surprising what they do when given the right environment to work in.

Fall flowers: Notice the selection of flowers for fall color: petunias, pansies, calendulas, snapdragons, poppies, candytuft, begonias, stocks, sweet alyssum and violas.

You'll find fall-planted annuals yield more and develop larger blooms than spring plantings. You'll find a larger, more aggressive root system for greater show of color. Resist the temptation to crowd plants; they need room to flex their leaves to produce larger blooms.

Perennials: Note what perennials you can plant this month: carnations, columbine, cornflower, coreopsis, feverfew, gaillardia, hardy asters, hollyhock, lupine, penstemon, phlox, Shasta daisy, statice and yarrow. Keep the soil moist until seedlings emerge and thin to the proper stand.

To renew vigor of summer-flowering perennials, apply mulch along with some well-composted manure or other organic amendments and a well-balanced fertilizer over the beds.

Irises: Early September marks the time to plant irises. If you prepared the soil earlier, then plant them. If not, work some organic matter into the soil along with some fertilizer and then plant.

Remove dead leaves from established plants and trim leaves back to about 6 inches. Plant rhizomes so they are visible to the sun, spacing them 12 to 18 inches apart. Firm the soil around them and water frequently, then cut back as it cools down.

Mums: Fall is "showtime" for mums. To make the show prettier, stop pinching new growth to enable buds to develop. Wash off aphids and mites or they will affect blooms.

Roses: Around the middle of the month, groom your roses. Nip out twiggy, spindly growth and crisscrossing canes and in seven weeks expect new roses that will last longer. Follow by giving each plant complete rose food, a cup of soil sulfur and one-half cup of bone meal and then a good irrigation. If pests become a problem, use the appropriate pesticide.

Bulbs: Note what you can plant this month: anemones, crocus, daffodils, Dutch iris, freesias, hyacinths, ranunculus, scilla, snowdrops, tigridia and tulips. Buy bulbs early for best selection but wait until it cools to plant. Chill crocus, hyacinths and tulips in the refrigerator for at least six weeks or you will end up with puny blooms next spring.

Plants made for Las Vegas: Plant ornamental kale and cabbage this fall. Get them in during September to give their leaves time to expand. Then Jack Frost will have more leaf surface to "paint" those beautiful showy pink, white and purple colors.

"We always had our best results when planting these beauties around Sept. 15," noted retired gardener Bill Lake. They are edible, but not very tasty. Don't crowd them so they can fully develop their leaves.

Fall vegetables: Note the vegetables you can plant: lettuce, spinach, chard, mustard greens, parsley, carrots, onions, turnips and, of course, the cabbage family.

To compensate for the heat, sow seeds slightly deeper. When seedlings emerge, thin to their proper spacings, follow with a feeding and irrigate. Feed your established vegetables to speed maturity.

Cactuses and succulents: Some succulents are starting into winter dormancy and slowing growth. Water them the same, but taper off as it cools. Most succulents slow down growth through the summer but speed up as temperatures cool. This is an ideal time to plant succulents, especially agaves, yuccas and cactuses.

If cochineal is bothering your prickly pear or cholla, remove infested sections and water them to encourage growth.

Lawns: Fertilize your lawn around Labor Day with a high nitrogen fertilizer with potassium in it. Potassium builds in cold resistance so the lawn will stay greener longer. For those who overseed Bermuda lawns, around Sept. 15, mow the grass down to bare ground and overseed with perennial rye. It's also a good time to plant a new lawn; select from the many improved tall fescues for an evergreen lawn.

Bermuda grass: If you want to get rid of Bermuda grass, use a chemical such as Roundup. For best control, allow the Bermuda to develop extra growth so the plants will absorb more of the herbicide. It does not do a bit of good to spray the ground and may damage adjacent plants.

Fruit trees: Take inventory of your trees before leaves drop. Yellow, small leaves and short twiggy growth indicate a need for more nitrogen. Yellow leaves with green veins suggest a need for more iron. Add these nutrients after the trees go dormant. Destroy all diseased, insect-infested fruit both on the tree and ground to prevent problems next year.

After harvesting your fruit, cut back on the water to force them into dormancy

Ailing yuccas: The agave weevil is causing the decline of many agaves and yuccas. The weevil chews into the plant, giving entry to secondary rot and the plants collapse. If you suspect this pest, drench the base of plants with a systemic insecticide to get where weevils live.

Compost: As vegetables, flowers and other plant debris die, put them in the compost pile. For faster breakdown, shred the debris and moisten the pile.

Poinsettias: If you have a poinsettia and want it to rebloom for Christmas, do the following. Groom the plant back by snipping off the ends of all branches. This stimulates new growth and dozens of shoots where colorful bracts develop. Cover it with a cardboard box or place it in a cool closet for at least 15 hours each night until the bracts start to show color.

Christmas cactus: Here's how to get your Christmas cactus to bloom for Christmas: In September, water weekly but stop feedings. In October and November, place the cactus in a dark, cool closet for 15 hours each night and water twice monthly. In December, discontinue the dark treatment but maintain even soil moisture and protect the plant from drafts. If flowering does not start, drop the temperature to 50 degrees for a few nights.

Linn Mills writes a gardening column each Thursday. You can reach him at linn@reviewjournal.com or at the Gardens at the Springs Preserve at 822-8325.