Cultural Practices

Pesticide Phytotoxicity

Pesticide phytotoxicity can often be distinguished from pest problems by the pattern and timing of symptom development. Although the damage may take up to several days or more to occur, pesticide damage symptoms often occur all at once and often have a regular distribution on the crop. Symptoms caused by pathogens usually develop over an extended period of time in random or grouped patterns. Pesticide phytotoxicity can be expressed by a number of different symptoms, including leaf speckling, cupping and twisting and other leaf distortions or even plant death.

Problems With Using Unvented Greenhouse Heaters

A frequently asked question (FAQ) is "Can I use unvented heaters in the greenhouse, either for back-up or as a primary heat source?

An unvented heater is one that is designed without a flue connection so that the heat and products of combustion are exhausted into the greenhouse. Dumping these flue gases into the greenhouse may improve the overall efficiency rating as compared to a conventional heater but the pollutants and added moisture from combustion may put your plants in jeopardy.

Fertilizing Garden Mums

Many growers will be potting up garden mums and it's a good time to revisit your fertilizer program. Mums are heavy feeders during the first few weeks. After flowers are formed, nutrient demand diminishes. Your fertilizer program and fertilizer selection should be based on irrigation water quality, so have your irrigation water tested if it hasn't been done and conduct regular soil tests to monitor soil fertility.

Controlling Weeds

Many growers (who are growing their garden mums in outdoor fields) may have a few greenhouses empty between crops. If so, it's a good time to do a thorough clean up, including removing existing weeds (either hand pulling isolated weeds) or using a post emergence herbicide such as glyphosate that can be used in an empty greenhouse between crops as well as outside greenhouses. However, both of these measures do not prevent reseeding of weeds. So, repair any tears in the weed block fabric or replace if needed.

Forcing Hydrangeas

Allow newly arrived pre-finished plants to recover from shipping stress and to initiate active root growth (about 1-2 weeks) prior to transplanting into the final-sized pot. Hydrangea blooms are formed on the previous year's growth, so the flowers are already in place in the dormant buds. The ideal starting temperature for hydrangeas is a 60 to 62°F soil temperature supplied with bottom heat, while maintaining slightly cooler air temperatures (about 58°F). This allows root activity prior to bud opening on the shoots.

Changing Weather

The weekend weather forecast calls for sunny days with temperatures in the mid to high 80’s following this week of cool, cloudy weather. As a result, there is a strong possibility, your spring crops will experience summer temperatures in a greenhouse with little or no shading in place. Even one or two days of bright sunshine with temperatures in the high 80’s can stress bedding plants and hangers with rooting systems that are not fully developed. Delicate foliage of shade plants such as impatiens will be susceptible to sunburn.

Retail Care: Watering, Cleaning, Fertilizing

Plants on display in your garden center or farm stand require regular, gentle watering to maintain high quality. Watering should be completed during the daylight hours, to allow plants to dry before dark. The drying will help prevent foliar diseases. If plants are to be watered by hand, be sure to furnish sufficient time and personnel to water thoroughly. Anything less, and plant quality will decline rapidly.

Place hanging baskets in areas beside the aisles, not over aisles where water and fertilizer will drip onto customers and create a hazard.


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