Beating the Heat in your Urban Garden by John

John Reinhardt is an urban planner, writer, photographer, and urban gardener. An avid cook, John is interested in the intersection of urban design, sustainability, and food systems planning. He currently resides in Washington DC and works for the American Planning Association. He currently writes Grown in the City, a blog about urban gardening and food systems planning.

So it’s June already.  If you’ve been following this feature on Thursdays, perhaps you’ve already built yourself self watering planters or planted an herb garden. If you started early, perhaps you’ve even been able to harvest early producers like lettuce, radishes, snow peas, or zucchini.  But now it’s June and it’s getting hot.  Very hot.  This week saw three scorchers and today is no different – and the summer is only beginning.  So it’s fitting that this column focuses on dealing with the heat.

Washington is known for its hot, muggy summers – but how does this influence your gardening?  For starters, it becomes more important to make sure that your plants have enough water.  When plants begin producing fruit, they become water hogs, (most fruits and vegetables are largely water). Since I water from the bottom using self-watering planters, I check for water levels once in the morning. For the past week, I’ve had to add about half a gallon to each planter, each day.  Keep in mind that smaller planters, such as the yogurt container herb planters, will require more frequent watering.

How else might the heat change your plans for a lush, productive garden?  When the temperature rises above 90 degrees, many plants do not tolerate it well.  A whole bunch of things can happen – lettuces, spinach, and herbs can bolt.   Zucchini can drop flowers (which several of mine did, much to my dismay), and tomato pollen can become infertile leading to dry, dead flowers that don’t bear any fruit.

The plants on my balcony are large, because my balcony often gets hotter than the ground temperatures from the reflected sun.  This was great in March and April, when my little seedlings needed the warm temperatures.  Now, it seems like the poor things are baking.  With a week of 90 degree temperatures, I’m a bit worried about a whole round of fruit will not set.  K-State has a great article with more information on “flower drop,” but here’s some quick tips for city dwellers.

1.      If you can, bring the containers inside or put them in the shade.  This doesn’t work for me, as I don’t have a sun room or screen porch.  However, I do have the luxury of moving some of the more heat-sensitive plants into the shade of the shelving unit I put out on my balcony.  The sensitive plants go right to the bottom, where they get the least sun.  The sun lovers, like the lettuce, go on the top shelves.  Because the plants that I keep on the shelving are in small containers, I can move them around if they need more or less sun.

2.      Choose drought tolerant varieties.  For example, Burpee, one of the large seed companies, sells “Heatwave” lettuce, which I am currently using on my balcony.  I sowed this variety a few weeks later than the “gourmet mix”, knowing that it would be hotter when the lettuce matured.  Some varieties of tomatoes and peppers love the heat, as do herbs such as rosemary and oregano, which grow in dry, warm Mediterranean climates.

3.      Pollinate before you have blossom drop, and pinch off any bolting!  If you get to plants such as tomatoes before the heat gets to them, you may be able to pollinate them by hand.  This website has some great information on pollination.  And if you’re growing lettuce, basil, or other leafy vegetable, be sure to pinch off any bolting (when a shoot sticks up and grows flowers).  The bolting of basil may be pretty, but it’s nature’s signal that the plant is in stress or the growing season is coming to a close, and the plant better make seeds to carry on its genes!  Smart, eh?  If you pinch of the stem, however, you can trick the plant into continuing to produce more edible leaves.

If you follow these tips, you can survive a hot DC summer.  Anyone else have any good tips for beating the heat?