We have had a very hot summer this year so watch for spider mites on your garden plants, especially those in hot, dry locations. If you have kept your house plants outside, inspect them carefully before you bring them into the house. Check for any sign of insects or diseases and if you find any, treat with organic pest controls. Watch for slugs and cultivate to expose and destroy grasshopper eggs. Also, watch for corn earworms.
Another important pest in Western Montana gardens are voles. Wrap your fruit trees for winter with plastic tree guards so that these rodents will not strip the bark. An effective method to protect the root ball of trees from being dug into and eaten, is to plant them using wire baskets over the roots. Voles cannot chew through hardware cloth or into the new vole wire cages. Caging is a safe-for-the–planet method that works for fruit trees, roses, shrubs, perennials and bulbs. Be sure to cover the surface of the ground inside the basket edge so rodents cannot burrow down from the top.
Harvest peas, beans and cucumbers consistently in September to keep them producing. Late in the month remove blossoms from eggplant, peppers, melons and squash in order to direct energy into to ripening remaining fruits. Cover sunflowers from birds and pinch tomato tips. Cultivate or hoe around cabbage, cauliflower, broccoli, turnips and celery. Keep late maturing cauliflower and broccoli well-watered. Plant garlic and shallots and over-wintering onion sets. You can still direct seed a few plants for fall/winter greens: arugula, lettuce, radishes, cress, corn salad, chervil and kale.
If you plan to grow crops under tunnels or in a cold greenhouse over the winter, plant seed (early in the month) of crops for winter use: chervil, kale, spinach, lettuce, radishes, corn salad, and winter cress. Later in the month, from the 20th to the first week of October, plant seeds of cabbage, cauliflower and other brassicas for transplanting out into tunnels in October. Have winter covers ready by October 1.
September is a good time to make new beds for growing mushrooms. Well-rotted horse manure is excellent.
Gather ripe seeds of any vegetables (or flowers) you want to save seed from.
Prepare beds for planting bulbs. Sow seeds of bulbous flowers collected in summer. Transplant peonies and lilies and dig dahlias after killing frost. Transplant pinks and carnations (with root ball intact) late in the month and plant out any other perennials and biennials where they are to bloom. Most perennials can be divided now and replanted where they are to bloom.
Gather ripe fruit from apples and pears. Remove diseased fruits and “mummies”, rake up leaves under fruit trees and destroy them (to prevent apple scab). Prepare equipment to make cider. Prepare beds for planting fruit trees, using well-rotted manure, digging down 18 inches. Keep strawberries free of weeds and the soil moist. If you plan to force strawberries in winter, now is the time to take them up and pot them. Cut a root ball out with a knife, trim off dead leaves and runners and pot into 7 or 8 inch pots. Place them in shade and water well. Then plunge the pots in earth up to the rim. Take them up and into frames or greenhouse before cold weather.
Protect ripening grapes from birds with netting or gauze; keep weeds away from plants. If wasps are a problem, hang containers of sugar water to catch them.
Trim branches of evergreens and walnut trees, so wounds will heal before winter. Keep weeds cleaned out from nursery beds and plantings of young trees. Lay down grass turf this month or plant lawn seed.
September is an excellent time to apply an organic from of potash to your garden plants to strengthen stems and roots in order to ripen them before winter. Kelp meal can be applied as a surface dressing and watered in or you can do a foliar spray of seaweed twice during the month of September. Do not apply nitrogen this month as it forces growth that will surely be winter killed.