Watering Herbs in Pots
Get thee to the fridge -- This first one seems a bit unusual, but it works for me indoors and out. I read about it in an old newspaper article about keeping poinsettias. These classic Christmas flowers are thirsty devils, and to maintain them well takes regular watering. One wily gardener came up with the idea of "watering" his poinsettias with a couple of ice cubes a day combined with once weekly deep watering. As the cubes melted, they dispensed water in a gentle and reliable trickle the plants could absorb easily.
This is really an inspired idea. Here's why: When a plant's pot gets too dry, the soil becomes less able to retain moisture. Water -- when it does come -- just rushes through and exits from the bottom. Without enough dwell time, plant roots can't absorb nutrients effectively and go hungry. The plant begins to look needy, which can lead to a vicious cycle of overwatering. The result: the plant either dies of starvation from lack of water, or dies of starvation because its roots are sitting in too much water and rot.
The beauty of ice is that it's a cheap, natural and effective method of timed water delivery. I've been using it for years on many kinds of indoor and patio herbs as well as other plants and can say from experience this method works on tropical plants like orchids, African violets, spider plant, pothos and other popular houseplants. It also works on chives, parsley, oregano, ginger, lemon balm, mint, thyme, lemon eucalyptus, pineapple sage and other herbs.
I'll typically add four ice cubes to each six inch pot in the morning before things start to warm up, and repeat the process again in the evening. During hot summer months like July and August, I'll also water plants in the evening as needed -- usually a couple of times a week. For a large plant in, say, a 10 inch pot, I'll just shake six or eight ice cubes from a carafe.
Although I haven't had problems, I'm careful to keep ice cubes away from plant stems and leaves, positioning them on the soil or mulch. I haven't used this method with cactus plants, but it does work with immature aloe vera starts and jade plant.
If the prospect of micromanaging your greenery isn't appealing, using ice cubes is one of those "set it and forget it" activities you can perform before going to work in the morning, making it a regular routine. The amount of water in an ice cube may not seem significant, but more moisture will be absorbed by the plant than with conventional watering, so it provides decent coverage without the risk of over watering and killing plants -- or damaging your furniture if your plants are indoors.
Mulch more - Adding mulch to a potted plant is like providing insulation to a home. It helps in temperature control and impedes evaporation. I like adding moss, but also use sand, stones and marbles. Outdoors I've even used shredded paper anchored with rocks. Works great. (It's also another way to get full value from that paper shredder. If you don't like the look of newsprint, try shredding paper bags.)
Pick a pot (no, not any pot!) - Self watering pots, thicker walled pots and non-terra cotta pots help conserve water. If you have a thirsty herb like catnip, basil, cilantro or dill, plant it properly in spring and you'll have fewer water related problems later. Oh, terra cotta pots that have been sealed on the inside work fine; unsealed pots absorb moisture, stealing it from the soil in dry weather.
Rube Goldberg devices - Upending a two-liter bottle (or burying one in the soil), as a water resource for a potted plant can work pretty well. I've done it myself, especially when I plan to be away from home for more than a day during hot weather. There are plenty of DIY tutorials around that can show you how to turn a plastic bottle into a garden reservoir. Watering Plants on Hot Summer Days
Shade is where you find it - Plants in dapples light typically require less frequent watering on hot days than plants in full sun. Planning some shade strategies now, like placing taller and more drought tolerant herbs on the sunny side of your patio to screen smaller, more delicate specimens, can make August easier on you and your plants. I've been known to move pots around to make the best use of sun and shade. I've even tented plants with shade fabric and bamboo screening. Just because you placed a tub of geraniums next to the Adirondack chair --where it does look neat -- doesn't mean your blooms have to stay in that spot forever. If you're dealing with a large pot, consider placing it on coasters to make moving day easier on your back.