Summer Is Coming
Indoor growers take a deep breath of anticipation at the hard work and headaches that lay before them in the coming months as the hot weather outside causes all manner of indoor growing environment problems. Read on for some useful information on how we recommend you tackle the worst of the issues you might face as an indoor grower.
Plants often have a preferred temperature range, but remember that temperature range is preferred so it does not mean you must keep them at that temperature at all costs. Far more important, however, are stable conditions so instead of fighting the rising temperatures go with the flow - allow your plants to acclimatise to the higher temperatures or humidities and instead try to maintain these conditions to avoid any shock to the plants and checks in growth. You will find this far easier, less costly, and ultimately more rewarding than trying to maintain perfect temperatures, humidity, CO2 levels etc.
This may involve keeping your heaters on even when the lights are off. Nighttime temperatures can be significantly colder than daytime temperatures so you may have to ensure you keep the nighttime temperatures close to the daytime temps to avoid shocking the plants.
Lighting is probably one of the main issues during the summer months as high-powered grow lighting invariably gives off a lot of heat and while outside temperatures may be in the low twenties once you get the lights on the temp is guaranteed to soar in to the high twenties or low thirties. So while you might consider not switching all your lights on in an effort to reduce heat output you are going to sacrifice crucial coverage and spread. A better option is to make use of digital ballasts which will allow you to keep all your lights on but dial down their power. A digital ballast would allow you to dial a 600W lamp down to just 400W or even 250W on particularly hot days and still use it at it's full potential of 600W on cooler days. This way you can maintain good coverage and optimum temperatures.
If the ambient air temperature is a few degrees cooler at night than in the day (and it almost certainly is) then it may be worth considering to switch you lighting cycle to nighttimes. At the end of the day the plants cannot tell night from day by reading a clock, they go by when the lights are on and off. If you are on a 12/12 cycle then you could try running the lights from 7pm until 7am when their heat output is less likely to overheat your grow space. Even if you are running a 18/6 cycle then you can still try running the majority of the lighting during cooler periods.
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 pull air from outside in the summer - not only will it
be warm but it will also have a high number of airborne pests that will infest and attack your plants. Sources for cold air in the summer
can be things like a chimney, the cavity in cavity walls, a corridor with no
windows or even an air conditioning unit placed outside your grow
Wall fans and pedestal fans are very useful.
When temperatures rise in your grow room you will notice that your plants drink more. Unlike humans plants do not perspire but they transpire which means as the temperature increases they lose more water through evaporation in their leaves and so draw more water up through their roots to replace the lost moisture. Most plants have a limit to how much water they can take up and when this is less than what they lose through their leaves they start to wilt and will get stressed and suffer a check in growth. Since the plants are drinking more in hotter temperatures you will need to reduce the nutrient strength that you feed them, if you don't then you risk giving them nutrient burn or having a nutrient salt buildup in their pots or reservoirs. It's good practice to also flush the plants through with plain water 2 - 4 times per month to ensure their is no nutrient salt buildup.