The cold, cloudy weather which has defined this spring so far hasn't prevented growers throughout the region from producing quality transplants. Here are some of the key points which are keeping plants healthy and vigorous:   

1) Start plants off right: a well-built germination chamber will effectively regulate temperature and relative humidity using minimal amounts of energy. You can find a couple of easy to build designs for chambers here. Germination chambers should only be used to "pop" seeds—as soon as you see the first seedlings emerge, remove plants to the greenhouse so they don't stretch.

2) Water with care: Cold is ok, cloudy is ok, but cold and cloudy causes real water management challenges. When growers are using supplemental heat to keep temperatures in an acceptable range it can be tough to make the decision to vent excess humidity, so often walking into the greenhouse during those conditions is like walking into the rainforest. High humidity and low light means almost no transpiration by the plants, so soil that is wet stays wet.  The best solution to this problem is prevention—if heading into a period of cold, wet days, minimize watering.  And don't be afraid to use gable end vents or ridge vents if it is too wet in the greenhouse!

3) Fertilize equally carefully: There are a few challenges with fertilizing during cool, cloudy weather. One is that if plants are not taking up water, they aren't taking up fertilizer, either. This might lead to the impulse to fertilize more, which can lead to excess salt buildup and root burning. Another issue is that when temperatures are below 60 degrees F, N fertilizers can convert to ammonium which can be toxic to plants at elevated levels.  Successful management of this issue involves scaling back the nitrogen fertility during periods of cool, wet weather, and managing watering to prevent plants from staying waterlogged. Media with optimal moisture levels will have more nitrifying bacteria, which convert ammonium to useable forms. A full factsheet on managing ammonium can be found here.

4) Practice good sanitation: A certain amount of disease is almost inevitable during the growing conditions we've been facing this spring. Scouting the greenhouse regularly and carefully removing flowers with botrytis, watching for crown rots, and adjusting spacing to maximize airflow and light infiltration make it possible to keep plants going through tough times. 

This article is from the April 26, 2018 edition of ENYCHP Vegetable News.  To read the full newsletter, CLICK HERE.