Things Are Hotting Up, Part One
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Things Are Hotting Up, Part One
PUBLISHED: 23rd April 2015
by George

As the summer rolls in, outdoor growers roll up their sleeves and indoor growers let out a sigh of desperation, knowing of the hard work and headache to come in the following months as the hot weather outside makes it challenging to create the correct environment inside your grow room.

Here at The Hydro Store we aim to help in any way possible so we thought we'd start off we a few pointers in how you can tackle the problem head-on this summer.

The first thing to keep in mind that plants thrive in stable conditions so in summer if you can't get your temperatures to where you'd ideally want them try to allow your plants to acclimatise to where they are.

Try to avoid extreme fluctuations in temperature - extreme hot to extreme cold is a bad idea - just because its summer doesn't mean you won't need your heaters when the lights are off.


The main problem in summer is obviously the heat being created by the lights you use to grow your plants. If the temperature outside is already in the mid 20's ( around 75F ) it is guaranteed when your lights turn on your room will go into the high 20's, possible 30's, where plants do not produce well. So here are a few solutions to this problem.

If you have a number of grow lights you naturally won't want to turn any off as you would lose the spread or coverage in your grow area. It is here where you should consider digital ballasts.These ballasts allow you to turn your 600w light down to lower wattages - say 250w or 400w - on a hot day and have it at 600w on a cooler day. This means you don't lose coverage whilst maintaining good temperatures.

Another way to combat heat is to run your lights through the night whilst having them off through the day. Here are a few suggested light cycles to help you avoid hot summer days:

Vegetative cycles:
- Lights off 10am, lights on 6pm
- Alternative light cycle: lights off 9am, lights on 2:30pm, lights off 3:30pm, lights on 9pm
Flowering cycle: 
- Lights off at 8am, lights on 8pm

As you can see here these light cycles allow you to avoid the hottest parts of the day. The alternative vegetative light cycle is a method called gas lantern lighting routine I will talk about this in another blog soon.

Air Movement

Air movement in summer can be key to plant health. If you can't avoid having a hot room then keep the hot air moving and you may still be able to function at these hot temperatures. Use the biggest / fastest extraction you can. If you can get a source of cold cool air, intake fans are great.

Do not, and I stress DO NOT, pull air from outside in the summer - not only will it be warm it will also have a high number of airborne pests insects in it that could attack your plants. Sources for cold air in the summer could be a chimney, the cavity in your walls, a corridor with no windows or maybe an air conditioning unit placed outside your grow area. I will talk more about air conditioners in my next blog post.

Wall fans and pedestal fans are very useful. Below is a picture of how to use certain types of fans to create perfect air movement around your room.

Figure 1. Note: No air is being blown directly at the plants.


When temperatures rise in your grow room you will notice that your plants drink more. Like humans, plants drink more when its hot in an attempt to dump the heat in the same way a human sweats.

An important way to avoid problems in the summer is to feed your plants with a weaker nutrient solution as your plants are using the feed quicker and what can actually be happening is that as the plants aren't actually using the nutrient in the water they are just using the water to cool off. This means that in your pot you are left with a salt build up or excess unused nutrients. Over time this can lead to signs of nutrient burn or overfeeding.

So lower your EC/nutrient levels and try to flush your plants weekly, if not fortnightly.

If you want to know how to check for this issue see our blog titled "What's Going On In Your Pot"

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