What to do this week: Concentrate on watering, preferably in the morning and evening to reduce evaporation. Sow seeds of lettuce, spinach, chard, and beets for a fall harvest. If the weather is dry at sowing time, water the planting holes first and then sow the seeds and cover them with soil. So many people isolating in their backyards are hiring arborists, landscapers, and contractors to do improvements, so waiting lists are long. See my suggestion for do-it-yourself outdoor improvement projects below.
Q. I am looking for tips on how to water.
A. Stick your finger into the earth up to the first knuckle to feel for moisture. Water when the soil is almost but not totally dry. Keep an eye on the weather forecast and buy a rain gauge to check whether showers are providing the necessary inch a week. Plants with small roots like annuals and vegetables generally need more frequent watering than plants with far-reaching roots like trees. However, weekly watering is a must for new or struggling trees, including any hemmed in by paving. I let my lawn go dormant but water valuable trees during droughts. Seedlings and plants in small pots may require daily watering in hot weather, while larger containers require less frequent watering. Grouping pots together makes watering easier and decreases evaporation. I also try to cluster particularly water-hungry perennials like astilbe and phlox and shrubs like winterberry and spicebush. It is generally better to water more deeply and less frequently to encourage deeper roots and more drought resistance. Amending soil with compost at planting time and topping off plantings with organic mulch like bark nuggets or composted leaves also reduces watering needs.
Soaker hoses reduce runoff and evaporation by watering slowly at ground level. They come in customizable and relatively inexpensive kits that last for years. These kits can be combined with electronic timing mechanisms, but I simply use mechanical shut-off timers. Rainwater is better for plants than treated water, so another backyard project might be installing water barrels or pots onto downspouts.
Q. I’d like to know more about plant propagation. When I carve off a root from a gardening friend’s plant, it sometimes sprouts for me when I pot it. How can I make this work better?
A. Plant division is absolutely the easiest way to propagate most long-lived hardy winter perennials. It is far faster and more straight forward than alternative methods such as sprouting seeds or stem and root cuttings. You simply dig up the entire plant and divide it into sections. The secret is to make sure that the roots from underground are attached to stems from aboveground, because these are connected by a piece of the all-important crown, which is what produces new shoots. You can sometimes just disengage a segment of root and top growth without digging up the entire established plant, using a sharp shovel or trowel and a handsaw. With hosta, it’s like cutting yourself a slice of pie.
Immediately replant divisions so the crown is exactly at ground level, with roots growing at the same depth as before. Each surviving plant division will grow to full size, so be sure to replant them at least 2 feet apart or else give them away. You don’t need fertilizer, just water.
September and October are great months to divide most perennials, and I often plant daffodils and other bulbs in the holes at the same time. April and May are usually better for dividing late summer and fall-blooming plants. Division doesn’t work on many short-lived perennials such as columbine, delphinium, lupine, and foxglove or those with long, drought-resistant taproots like Oriental poppies and butterfly weed.
Some perennials actually require division every few years to bloom well. These include chrysanthemum, Cupid’s dart, begonia, aster, astilbe, Japanese anemone, and bearded iris. On the other hand, some slow-growing perennials resent division and take years to recover, including peony, hellebore, Thalictrum (meadow rue), and Dictamnus (gas plant).