Here's what to do for houseplants in July: Send them out to play. Those terrific plant species that thrive indoors much of the year also appreciate some time outside in summer. Philodendrons (from little heartleaf to giant splitleafs), corn plants (Dracaenas), figs (Ficus), Norfolk pines, Chinese evergreens (aglaonemas) and other traditional houseplants respond with new growth to humid, shady, very warm conditions while you're chilling and dehumidifying indoors. And the occasional shower will wash their leaves better than you can.
When Not to Repot
I was taught to repot everything in this category every year, but there are at least three reasons not to. First, some plants bloom better when their roots are crowded ?- bougainvillea and jade plant for example. Second, others hate to be disturbed -? potted roses would rather be pruned than dug up, and clivia bulbs are known to wait years before reblooming in new soil. The third reason is that you may not want the plants to get bigger and that's what happens with annual repotting and good plant culture. While I repot the majority of "houseplants" each summer, the truly huge specimens like Philodendron selloum nearly swallow my living room as it is.
I'm not advocating ignoring those houseplants, though. I water every other day or so and use a soluble fertilizer every three weeks. For the plants that bloom best in crowded conditions or hate to be moved, I topdress the soil with compost once or twice during the summer. Then each time it's watered some organic matter washes down into the existing soil to replenish its structure and nutrition. The big plants need new soil to stay healthy, but not a larger pot. I mix up some potting soil and ground bark, then unpot the plants and examine the roots. If they're filling the pot, I'll prune them back a bit, then repot the plant in new soil in the old pot. Keep houseplants happy now and they'll have an easier time staying happy indoors next winter.
Photo by former managing editor Nellie Neal/National Gardening Association