Stalling out: Strategies for success

Starting to feel a bit bummed out by all this gloomy weather?  Imagine how your poor plants feel!  All clouds and no sun leads to lots of fun with production schedules, nutrition and proper plant development.

Figure 1. Supplemental lighting and proper air flow to control humidity are great options to combat dark and rainy days if available.
Figure 1. Supplemental lighting and proper air flow to control humidity are great options to combat dark and rainy days if available.

Low light means plants don’t transpire as much.  When plants don’t transpire, they don’t grow on normal timelines, AKA they stall. This is frustrating, but short of turning on your supplemental lighting or turning up the heat, you can’t do too much.  Take the time now to ensure that it will be smooth sailing as soon as the sunshine comes back.

I know this is common knowledge, but I’ll say it here again – cut back on the irrigation.  The last thing you want is for your plants to be sitting in water that they can’t use.  Check the weight of the pots and the dampness of the soil at several spots throughout the crop to understand what’s happening throughout the greenhouse (ranges can be different!).  Ensure air is circulating well, and the humidity isn’t too high. Problems with disease and pests can be headed off by watching these conditions closely. Don’t rely solely on your climate control software to influence your decisions.

Ensure you’re monitoring the pH and EC of your plants closely as you normally would.  These numbers may look a bit off from what you would normally expect, so keep a close eye on them as the sun comes back.  Adjusting the pH of your feed may be necessary if you’re seeing some deficiency issues.

Is that new growth looking a bit chlorotic?  When the plant can’t take up new nutrients, the youngest growth will often suffer a bit of micronutrient deficiency. It usually doesn’t progress to the stage of concern quickly, but if it continues to progress after the plant starts actively growing under better conditions again, you might want to take action.  Adjusting the pH or micronutrient is in the feed or adding amendments to the media might be the way to go – just make sure they’re tailored to your crop and it’s stage of development.  For a general refresher on nutrient deficiency symptoms, check out this blog post.

Are your cuttings or liners not developing roots like normal?  If so, no need to worry just yet.  When the light comes back, they should take right off.  Ensure they’re not too wet and established roots are looking healthy.  Bottom heating can really help with root development when the weather is gloomy or bitterly cold. In addition to helping with root development it will help keep pots drier and keep a nice humidity level around the plant canopy.

Are things looking a bit short?  If you need height for retail in the meantime, growth regulators are your best bet.  If you want to increase the length of the stem you’ll need a product with gibberellic acid (GA).  Branching can come from products containing ethephon, benzyladenines or benzylpurines.  Ensure that you apply whichever product you choose at the right stage of development; bud abortion is a possibility if the wrong product is applied at the wrong time. Read the label to ensure you use the correct rate and reapplication timeline if necessary.

After taking care of all of these issues, make sure you keep an eye out for varieties that seem to struggle through this type of weather year after year.  If you have other options available, next year might be a good time to start trialing them out.

Cheer up, it can’t be gloomy forever! We’ll be back to singing this song shortly!

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