This is the busiest time of year in the garden, and 2021 is no exception. Soil and air temperatures are warm enough now to plant anything, hardy or tender. Rainfall for May was under the norm until Memorial Day weekend when the usual 4.4” for the month was finally reached. Don’t stop watering your new plants - see our summer watering instructions below.

We started our compost tea routes in mid-May when the soil temperatures warmed up. These applications are timed to the periods of highest biological activity in the soil. Reese has also been busy with spot spraying the emerging pests and keeping up with tick and mosquito spray routes.

In this issue, we’ll give you an overview of what our crews have been doing lately. Our new marketing intern, Rebecca Zhang, is soon to be a senior at Mt. Holyoke College. She has been out and about to photograph our crews in action and then to write posts and captions. We are enjoying her energy and creativity!

Here she is on Linkedin.

Sometimes nature comes a little too close when there is disturbed ground. One of the common invaders is Japanese knotweed. This shrubby plant in the knotweed or buckwheat family was imported in the late 1800s as an ornamental curiosity and became a rampant escapee in our area. You may have seen it lining roadsides or stream banks. It spreads by both seed and runners. Therefore, it is important to never let the plant flower. Attempting to dig it out is futile since the roots go down several feet.

At PBOG, we are controlling this plant weekly in our own nursery area in Ayer. A large stand had been allowed to grow over time unchecked at the edge of our space. We find the most effective way to weaken the plant over a period of several years is to repeatedly cut the stems once the plant reaches 6” in height. Cuttings are then dried out on a pallet and composted once they lose their biomass.

If you have knotweed stems sprouting in your garden, adopt this practice. Then plant a native tree or shrub to shade out the knotweed, since this plant prefers full sun. We like to use Aesculus parviflorus, Bottlebrush Buckeye, for this purpose. This native shrub is fast-growing, broad spreading, and has large leaves that will shade out the weakening knotweed plants.

An alternative natural control method for Japanese knotweed is to inject the stems with an undiluted solution of 30% horticultural vinegar. This is rather more time-consuming but effective.

Please let us know if we can help you start managing your Japanese knotweed this season!

Cottony camellia scale is a soft white scale that sucks sap from the leaves of many common landscape plants. Although it is most often seen on hollies, it can also be found on camellia, yew, euonymus, maple, English ivy, hydrangea, and rhododendron.

Rose slug sawfly will be out any day now. From a distance you may notice dingy brown or grey leaves or even skeletonized ones. A small worm will be on the underside - the slug sawfly. Luckily, there is just one generation of this pest per year in our area. We spray our Neem oil product if we see the pest. To help your rose push out new green leaves, we recommend liquid organic foliar feeds weekly or as often as you can manage! Rake up dropped leaves or prune off damaged leaves as appropriate.

Boxwood psyllid shows up on the new growth tips in late spring where eggs overwintered on bud scales. You’ll see curled, cupped margins. Living inside is the immature nymph, sucking sap from the leaves. Eventually, there will be discoloring from green to yellow. This impacts appearance of your boxwood, but not its overall health. We can control boxwood psyllid with insecticidal soap or summer-grade horticultural oil. In many cases, the cupping will be pruned away once new growth has hardened off at the end of June.

Leaf damage by Boxwood leafminer

More damaging is Boxwood leafminer, which this year coated boxwood leaves with clouds of whiteflies in late May. Leaf blistering and discoloration will follow in June. We turn to the same organic insecticides to control this pest. Multiple applications may be necessary.

Plant Pick: Cornus kousa, the Kousa dogwood

This Asian dogwood comes into bloom in early June. It is resistant to many pests and diseases, including the anthracnose virus that has impacted our native white and pink dogwood trees. The bark of its trunk features exfoliated patches that provide year-round interest. Heart-shaped, dark green leaves are tough enough to withstand the summer heat.

There are many varieties of Kousa dogwoods, and you can examine them first-hand at Dogwood Days in Milton, June 5-20. The Mary May Binney Wakefield Arboretum is celebrating the bloom of 300 trees planted (and many propagated) by Mrs. Wakefield around the property. See www.wakefieldtrust.org for details of special events including themed tours, wellness programs, family activities, and music in the garden.

When the Mercury rises, please don’t forget about your plants. This is especially true for any woody plant that was installed in the past three years and any perennial, annual, or vegetable planted this spring. Linked is my handy reference chart linking air temperature to watering frequency. In short, the higher the temperature, the more frequently we water.

And remember: if we get one inch or more of rain per week, you can relax this schedule for a day or two. Please be sure your irrigation system has a rain sensor so it will shut off appropriately, too.

The heat and dry period put a fast end to the bulb show in late May. Now what?

Let your bulb foliage “ripen” or dry out in the summer heat, then remove it when it turns brown. This is how the bulbs photosynthesize and build up energy for next spring’s bloom. We have been scratching in bulb fertilizer around the declining foliage as an aid to future growth. Tulips, hyacinths, and daffodils can be deadheaded now. Avoid irrigating the spots where bulbs grow, as they prefer to bake in the dry heat of summer. You may want to interplant perennials that prefer these conditions as companions to help hide the declining foliage of your bulbs. Daylily and daffodils are just one combination that works well.

If you’re interested in adding more bulbs, please contact Priscilla and Laura now <[email protected]> This is the perfect time to plan additions for our upcoming late summer bulb order. We can also divide or transplant overcrowded stands of bulbs now, while we know where to find them!

The Concord Museum has planned its annual garden tour fundraiser as a virtual event again this year. Pumpkin Brook Organic Gardening is proud to be one of the Sponsors and to have another client property featured on the tour! Please see their website, www.concordmuseum.org for details of how to purchase your ticket and receive a link to the tour.