Michael Harms from Barrowby Green in Woori Yallock gave a talk on indoor plants.
• Under Victorian climatic conditions, the best potting mix for indoor plants is peat-based or based on coco-coir. The usual potting mix tends to dry out and become water-repellent.
• Many plants will tolerate quite stressful situations for short periods, but it’s best to try, if you can, to reproduce the natural growing conditions for your plant. Light, temperature and humidity are the most important determinants of success.
• Watering: best to wait until the plant really needs water and is even starting to look a bit stressed and unhappy. Many plants are lost from over-watering, which causes rotting and other fungal diseases.
• Humidity: most plants like humidity of about 40 – 50%. Reverse-cycle air-conditioning reduces the humidity well below this, but evaporative coolers provide much better conditions.
• Temperature: Ideally, not below 18°, certainly not below 15°. If the temperature is too low, the plant won’t grow.
• Fertilizer: can be applied during the growing period, i.e spring to autumn. Michael uses a variety of slow-release fertilizers and foliar sprays.
• Propagating: Temperature must be even and consistent. Don’t put the plant on a windowsill and expect success! Propagating method depends on the plant species: cuttings, division, leaf cuttings, bulbs. Best propagating mix? Opinions vary. Michael uses pure perlite, which is sterile.
• Pests and diseases: Under greenhouse conditions, sap-suckers are the commonest pests. All can be treated by the application of soaps or oils. If a plant is attacked, look first at its growing conditions. A stressed plant is more vulnerable to pest attack. Fungal diseases and bacterial spot can be treated by improving the light and air-flow around the plant. As an extra kick, there are proprietary products which will help.
• Wipe dust off leaves with a damp cloth.