Beat The Heat Container Growing
July 25, 2015
We’ve hit the dog days of summer when temperatures soar just about everywhere, which makes keeping anything planted in pots or tubs above the ground a real challenge. To make matters even more difficult, some locations are on water restrictions as we head into August. There are a few things you can do to help your container grown vegetables survive this part of the season.
Choose it wisely. It could mean the difference between a harvest and a total loss.
1) Don’t use dark colored containers. They may be really classy, or better yet cheap or even free, but a plant’s roots get hotter inside dark containers than light colored ones.
2) Allow room for some moisture retention. This trend to recycle anything that will hold potting mix is great – at the beginning of the season when plants are tiny and temps are rather cool. It’s an about face when the middle of summer arrives and the temperatures rise along with it. A big plant in a small container needs more water than a small plant in a large container. Cramming a cherry tomato plant’s root structure into a recycled juice can means that you’ve probably got more roots than potting soil inside it now. How is that plant supposed to deal with the heat in such an unbalanced environment?
3) Container material can make a big difference. Back to growing in tin cans… Metal of any color baking in the sun gets really hot! Consider the hood of a car after it’s sat in a parking lot all day. Even if it’s white it’s hotter than hell, and if you hose it down the water evaporates in minutes. Look for thicker plastic or resin. Don’t grow in black nursery pots – they’re designed for use under timed sprinkler systems in a commercial setting. Wood will give your plant’s roots some insulation against the heat, as will glazed ceramics, while terracotta clay pots dry out super fast due to air through the sidewalls when you’re growing in potting mix.
4) The perfect vegetable gardening container is a fabric pot. Smart Pot, Geo Pots, recycled grain bags (the woven plastic kind) will all allow you to grow in regular soil, which retains moisture far better than any potting mix. Why? Potting mix is designed to drain fast because there’s no air flow in a plastic container, but fabric pots allow airflow from all sides and the top. Your veggies will be far happier in these than any other kind of pot. AND you won’t need to water every day either if you’ve used topsoil. You can even mix in quite a bit of heavy composted manure in these.
Better Moisture Retention
1) One thing you can do to help keep roots hydrated longer per water application is lightly mulching the surface of your potting media. Remember you still need some airflow. Don’t make it too thick, perhaps 1/2″ of shredded bark, shredded paper. Enough to shade the surface of your soil.
2) Mix a little dirt into your potting mix when you’re planting the container garden in spring. Unless its heavy clay or play sand, topsoil will boost the length of time that moisture remains among the roots of your veggie plants. Not a lot. If you overdo it, bad drainage will be your reward.
1) Don’t water the leaves – water the soil. This is true in any kind of garden, but when water use is heavily curtailed you are wasting the water applying it to the surface. The plant’s roots need the water – not the above ground portions.
2) If you’re on water restrictions it’s due to drought, so the only water your plants are getting comes from you. Use a watering can instead of the hose. It gives you far greater control over where the water gets deposited, allowing you to be more frugal without losing plants.
3) Set up a drip irrigation system. You can make it complex or very simple depending on your skill level and budget. The fast, cheap and easy drip irrigation system is a 1-liter drink bottle with a single hole drilled in the lid that is filled and then inserted into the soil. It only drips out when the water table in your container drops enough to release natural pressure. Your pots will stay hydrated much longer with this deep watering technique, and with far less water wasted as it runs out the drainage holes in the bottom.
4) Self-watering pots can help, but they can also add unwanted problems from the anaerobic activity in the reservoir due to no air flow… which is where bacteria love to grow, especially when it’s really hot.
5) Water in the morning. More of the water will soak in when the temperature is cooler. The higher the sun climbs, the hotter the surface of the soil will be, and the more water you lose to evaporation.
Hopefully enough rain will arrive before restrictions ban watering vegetables too. You can use some recycled water for watering vegetables that can help, like the water that drains out of the pots when you water. Put a saucer under them for a little capillary action to draw it back up into the container when needed by roots. Then there is kitchen water used for boiling eggs, veggies, pastas, etc. in the kitchen. If you hand wash dishes capture the rinse water, or thin out bath water even further and stretch your daily water allotments even further.
The amount of thought and planning you put into your container veggie garden at planting time can make a big difference in how well it does in a heat wave. Raised beds will be less demanding than any planter or plastic pot, and fabric pots are your best bet if you don’t have the place for them.
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