The last two weeks of August are the ideal time to take cuttings of annuals. Here’s why:
- Plants are still actively growing so rooting occurs rapidly
- The weather is still warm and humid so no need to create artificial growth chambers with plastic coverings.
Taking cuttings is an easy process, and it saves money compared with re-purchasing a favorite Geranium, Mandevilla, Argyranthemum frutescens, or other expensive annual. All you need in the way of supplies is:
- A bag of lightweight potting soil
- One 4″ (10 cm) diameter plastic pot, with drainage, for each cutting
- One package of rooting hormone
- A pencil
- A pair of sharp, clean scissors
Begin by filling each plastic pot with moist (not wet) potting soil. Using your pencil, make a hole in the potting soil deep enough to hold approximately 3″ (7 cm) of the cutting’s stem. While still early in the day–when the plant has plenty of moisture in its cells–cut off 5″-6″ (13-15 cm) from the tip of a young branch using your scissors. You want to make the cut at a 45 degree angle just below a growth node (see Geranium Cutting illustration). If you’re not sure where a growth node is located, just make the cut beneath a side branch or leaf stem that is approximately 5″-6″ (13-15 cm) from the growing tip. The presence of a leaf stem or side branch is a sign of internal growth hormones that will help the cutting take root.
After taking the cutting, trim off or pinch off any leaves or branches on the bottom 3″ (7 cm) of the stem to make sure there is no vegetative growth below the soil line in the plastic pot. Carefully twirl the bottom of the stem in rooting hormone powder, then gently shake off the excess powder. Position the cutting into the prefabricated hole in the potting soil and, using your pencil, gently secure the potting soil around the stem until the cutting is able to stand up securely in the pot.
Once you have completed all your cuttings, place them in a non-draining growing tray, pour into the bottom of the tray about 1/2″-1″ (1-2 cm) of water, and let the potting soil absorb the water through capillary action. After bottom-watering the cuttings, allow any excess water to drain away. (Note: Do not water the cuttings from above for the first two months. Cuttings are susceptible to damping off, a fungal disease that affects plant parts growing below the soil line. Until the cutting is planted outdoors again, you simply want to keep the soil moist rather than wet.)
As long as outdoor temperatures remain mild, place the cuttings on a screen porch, front porch, under an outdoor chair–anywhere where they will be protected from rain. The location should have good airflow, but only bright, indirect sunlight. By the 3rd-4th week of September, depending on the weather, you can move the cuttings to an indoor location; a bright, eastern-facing window is ideal. At any time, if you notice the cutting starting to bend toward the source of light, simply rotate the pot periodically to maintain upright stem growth.
Keep the soil moist throughout the winter, but not wet. Do not mist the leaves. You may begin periodic fertilization with a balanced, weak liquid fertilizer in April. Once the frost-free date for your region occurs, begin to gradually harden off the cuttings outdoors. Transplant your new plant into a container or into the ground once it has been fully hardened off.