September in the Low Desert
We are almost there – about another month to go before the summer heat begins to abate. This month the humidity levels will begin to fall. Begin planning for your wildflowers, annual herbs and vegetables. Prepare your list for plant sale purchases at the fall sale.
Continue watching for yellowing of cacti and succulents as the sun’s angle continues lowering and cover with shade cloth for another month. Plants that are summer dormant will begin to leaf out towards the end of the month. Gather seeds from your perennials at this time. Continue weeding or at least cut off the flowering heads before they go to seed.
The higher humidity should have brought the toads out – don’t step on them. White-winged doves are getting ready to leave for their wintering grounds (Baja California) although apparently some overwinter in the Rio Salado preserve. Monarch butterflies will be migrating through especially if you have milkweed plants in your yard. Tarantula Hawks, really a wasp species, will be flitting around.
Look for flowers on your Stapelia plants. They are stinky, but fascinating. The flowers mimic the color, odor, hairiness and fat marbling of carrion in order to attract flies, their pollinator. Penstemon eatonii and Penstemon baccharifolius along with Dalea frutescens are blooming.
If the humidity is still high and monsoon rains continue, do not water your cacti until the weather calms down and things can dry out for at least a week. With the heat continuing, maintain your summer watering schedule for trees and shrubs, begin to cut back a little by late September to let things slow down and begin hardening off for winter.
If it is one of those years where it is still above 100º and the nights are still hot, hold off on the water cutbacks until early October. Those plants that are just waking up after the hot summer will want water.
What to Plant
Continue planting trees and shrubs but do not prune. At the end of the month, if temperatures have dropped, begin planting in earnest. The soil is still warm, ideal for root growth, giving plants a chance to get established before winter cold sets in.
Continue pruning only for health and safety. The sun is still intense although it is coming in more horizontally. You won’t want to do any lifting of branches that will expose the trunk or branches. Avoid any pruning that will open the tree to sunburn, especially on the south and west sides.
This is the month for that last application of fertilizer before cold weather arrives. Use a low nitrogen formula so as to prevent excessive new growth. Plants need a chance to harden off to prepare for the cold as new growth will likely freeze with the onset of a frost. Stop fertilizing your Christmas cactus now in order to hopefully induce blooms by the holidays.
Although monsoons will soon be winding down, we can still receive drenching downpours, especially the first half of the month. Watch your irrigation frequencies as plants, trees and cacti in particular, do not like to sit in saturated soil. Trees in saturated soil are at risk of blowing over. With the continued high humidity and high night temperatures, cacti will continue to be prone to rot.
Palo verde beetles may still be emerging and reproducing. You are probably still hearing the buzzing of cicadas. Webworms may occupy your palo verde trees but they are no cause for concern. Whitflies may be showing up from the agricultural fields, too, but again, there is not much you can do about them.