Gardening Notes For September

September marks the start of getting the garden – and the gardener – ready for a long winters rest.   To this end, consider how best to overwinter and to make room for your favorite non-hardy plants indoors, as well as considerations for your outdoor hardy plants.  Fortunately, we still have several months remaining for plants to grow!  Continue to take good notes and pictures on how you weaved in your perennials and annuals this year, since after the first frost these pictures will be all that remains of this year’s favorite combinations!

Things to do:

  • Continue to keep your lawn mower blades set high for cutting your lawn.  Rain has been ample and the temperature look to be cooler for the start of the month, but this will still minimize the stress to the turf. 
  • September is a great time for the reseeding of bare spots, or for the installation of sod, since the upcoming cooler temperatures, heavy dews and typically consistent autumn rainfalls combined with warm soil temperatures promotes good root growth and turf establishment.
  • September is a good time to aerate those portions of the lawn that receive excessive foot traffic or have otherwise developed compacted soils.
  • If you have yet to start, take cuttings of your favorite annuals that you wish to overwinter.  It is far easier to over-winter a small plant that should be free of most insect and disease than lifting a large plant from the ground or outdoor container and bringing it inside.  Also, harvest and clean the seed from those annuals and vegetables that come true from seed.  Remove them from the ‘seed head’, store them in small paper pouches that are properly labeled and place them in the refrigerator (not the freezer) until next spring.
  • Remove those annuals that look excessively tired or leggy and keep removing annual weeds such as crabgrass.  Crabgrass seed will continue to germinate and appear as long as the temperatures are warm.  Remember, on average a seed lasts for seven years and one plant going to seed equates to seven years of work!
  • Send in your bulb orders!  October is a great month for planting bulbs.  For Colchicums, get in your orders in early September or look for them in your favorite garden center (we always have them for sale at the Rutgers Gardens Farm Market) since they bloom in late September into early October and they are deer resistant!
  • Inspect and evaluate your ornamental small trees, shade trees and shrubs.  Even though it has been a wet summer, those plants that are stressed from age or disease will let you know through leaf wilt or drop.  Oaks that have Bacterial Leaf Scorch will have leaves that suddenly turn brown in mid to late August.  There are treatments for this disease, but once most of the foliage has turned brown the tree will ultimately need to be removed.  It typically attacks older, less vigorous trees and young oaks should still be planted, since the trees feed over 500 native insects!
  • September is an ideal time to add woody and herbaceous plants to the garden.  The soil is warm and although it is often a relatively dry month, the cooler days and moister weather ahead will allow the plants to establish an adequate root system before next summer’s heat and potential drought.  Woody plants that are not fall transplant hazards can be transplanted, and those that are fall hazards can be planted if they were dug the previous spring or are grown in containers.
  • For the vegetable garden, continue to remove plants that are no longer producing.  The wet weather raised havoc with tomatoes and not only has the fruit been subject to splitting, but fungal issues have plagued the foliage, necessitating the removal of many plants at Rutgers Gardens.  As we mentioned last month, a friend of the Gardens, Bob Mellert mentioned that the days to maturity on seed packets should be multiplied by 1.5 to account for the slower growth time with the shortening days as compared to spring.   Plant leafy crops that appreciate the cooler nighttime temperatures, such as Arugula, Spinach, Bok Choi, Kale and Lettuce.
  • Consider the installation of low houses or tunnels, which are essentially small greenhouses that are placed over a row of cool season vegetables.  It enables the gardener to harvest well into December, and for certain crops, into spring!
  • September is an opportune time to plant garlic too!  ‘Music’ is an old fashioned and good performer, but try some of the many other selections that are on the market too!  Plant in a location that will be in full sun through next August, which is the harvest period.
  • If you live with large deer populations, put wire cages around recently planted trees to avoid the bark being rubbed and damaged by bucks.  One of their favorite targets are Magnolias, so make certain that they are properly protected.  Damage to bark is far more harmful than the nibbling of a few leaves and we have lost many a tree that before we start installing cages.