Greenhouse calendar for fall

Greta Heinen provides a list of fall to-dos for your greenhouse.

Greta Heinen provides a list of fall to-dos for your greenhouse

The following is an excerpt from Greta Heinen’s E-Book, “Gardening In A Cool Greenhouse” A Month-By-Month Beginner’s Guide.


  • September is the month to plant bulbs in pots for the December and January greenhouse
  • These pots of hyacinth, narcissus and small tulips are kept in a cool storage area for eight to 10 weeks.
  • When the first frost hits the tuberous begonias leaves, the tuber is removed from the pot or basket. These tubers are cleaned and stored in a cool area until February.


  • August cuttings have developed roots and are ready to be transplanted into pots.
  • More cuttings can be taken from frost sensitive plants, but they will require bottom heat.
  • A good cutting mix is two parts perlite and one part peat. I have had great success using peat pellets for cuttings.


  • Tomato and cucumber plants have finished cropping and are removed from the greenhouse.
  • Winter lettuce can be started and is an easy plant to grow in the cool greenhouse.

Wintering Over Stock or Parent Plants:

  • Depending on your climate the frost sensitive plants are pruned or cut back and brought into the greenhouse. In the coastal warmer climate this can be done in October.
  • Frost sensitive plants are brought in when the night temperature is lower than 40°F (5°C).
  • Ivy and vine plants are taken out of the hanging baskets, cut back and repotted into 4” pots. These will winter over and next April will be planted into hanging baskets.
  • Cuttings can be taken from the osteospermum, and the parent plant is cut back and wintered over in the cool greenhouse.

Tip: Stock plants are pruned back just above the node on the branch. This is where the new growth will start. Watering:

  • Plants are now moving into their dormant stage so the watering requirement is reduced.

Greenhouse Notes Heating:

  • The heater is now set at 40°-45°F (5°-7°C).


  • The roof vents will still need to be opened on sunny days.
  • Movement of air inside the greenhouse is always necessary. This time of year the circulating fan is set on a lower speed.

The Greenhouse Environment:

  • Now is another opportunity to clean the greenhouse thoroughly before the frost sensitive plants are brought in.
  • As a preventative measure spray with Safer Soap all plants that come from the outside garden into the greenhouse.
  • For glass greenhouses the shade cloth is removed and a plastic liner for insulation is attached inside the greenhouse.

Special Note:

  • The bougainvillea, hibiscus and passion flower are frost sensitive plants, but do not winter over in a cool greenhouse. These plants require a different greenhouse environment with a warmer night temperature.


  • Like last month, bulbs are placed into pots or containers and stored in cool area. In February you will enjoy the color and fragrance that these bulbs have to offer.


  • The roots of the previously taken cuttings are now developed. These cuttings are planted into 4” pots for the winter season.
  • Late cuttings can still be taken from the frost-sensitive plants.

Pruning Stock or Parent Plants: In the warmer climate plants remain outside longer, but this month the frost sensitive plants are ready to be cut back and brought in. Watering: Tip: The morning is the best time to water plants in the greenhouse.

  • The cuttings on the heated propagating bed will require watering. Once the cuttings are repotted they will go dormant and develop their root system.
  • Dormant plants will not be actively growing and will therefore require less water.
  • The Christmas cacti are brought in and slowly start watering to encourage the formation of buds for a Christmas display.
  • All watering is stopped for all the other cacti plants and they will remain dry during the winter months. A light misting is done if the cacti leaves start to shrivel and dry up.

Greenhouse Notes Heating:

  • Minimum temperatures are checked daily, since heating thermostat settings will often require adjustment.


  • On sunny days there can be a heat build up inside the greenhouse. To eliminate this the constant air circulation with a small fan will force the heat to rise and open the automatic roof vents.

This was an excerpt from the E-Book: “Gardening In A Cool Greenhouse” A Month-By-Month Beginner’s Guide by Greta Heinen. The full E-Book is available from Birch Publishing.