It’s been hot, it’s been dry, and yes it’s been summer.But there’s still plenty of garden work to be done and bits and pieces to catch up on. So this week, it’s time for another ramble.
In last week’s column on invasive plants, I omitted one new invasive insect that you should be aware of if you grow any fruit. This one is a fruit fly called the “Spotted Wing Drosophila.” It was discovered in California in 2008, made it to Florida the following year, then traveled up the East Coast.
It already has berry growers freaked out. Fair warning: all fruit growers should be aware of it as it seems to adore soft fruits, such as raspberries, grapes, peaches and cherries. If you do grow any of these fruits, you should read up on this new pest at ncipmc.org/alerts/drosophila.
Most fruit flies feed on fruit that is over-ripe, like those half eaten bananas in your fruit bowl, but this one goes after fruit that’s not ripe. And as it came from Asia, it has no natural predators in our area.
Earlier in the season I did a series of articles on garden insects and their control. One of the newer and organic pesticides that I wrote about was Spinosad, which kills on contact insects feeding on foliage sprayed with it.
As always, at first I was dubious, especially after several years of inconclusive use of neem. Still, in mid-July I used Spinosad on several of my tall phlox plants that get a bad case of two-spotted spider mites, which plague these plants every summer. I made one application at the labeled rate, covering both the upper and lower leaf surfaces and the flower buds.
The following week was hot and dry, weather these mites thrive in. Six days later I removed a few leaves from each plant and put them under the microscope. To my amazement I didn’t find a single live mite.
Knowing that remaining eggs would surely hatch, and the effectiveness of the insecticide on the plant is only about a week, I made a second application. Fingers crossed.
Since Spinosad is also labeled for use against Japanese beetles, I got brave and sprayed my shrub and perennial hibiscus, roses and young magnolias. I sprayed early in the morning when it was cool but was still warm enough so that the beetles were out and about and already screwing around (mating).
Using a 1-gallon pump sprayer, I covered the plants, making sure to hit the beetles that were present, and then went on with my garden work. I returned an hour later and was surprised to find several dead beetles and more that were lethargic at best.
This surprised me because I’d read not to expect the beetles to respond right away. Well, for an organic, a one-hour knockdown is pretty quick. I’m keeping in mind though that the beetles might still create some foliar damage when feeding, but I’m hoping for a much reduced JB population.
One of the garden plants that is usually hit hard by long periods of hot weather is the astilbe. Many varieties are now sold as being more heat- and sun-tolerant but in shallow or fast-draining soils or under trees that soak up every drop of moisture near the soil surface, astilbes can suffer. Once they fry and their foliage gets crispy, they are usually toast—at least for this season, and maybe permanently.
To try and prevent astilbe dieback during droughts there are two things to do, and one more suggestion.
First, water them. At the first sign of wilting or leaf crisping, give them a good soaking and follow up again in three or four days, if needed.
Second, when planting them make sure they are overplanted. By that I mean don’t just dig a hole and drop them in. The hole should be wide (not deeper) and heavy with organic material, such as compost. The compost will retain moisture like a sponge and will give the plants a better chance at survival. The depth should be equal to the root ball but the width may be as much as three times the diameter of the pot it comes in.
The third thing that will help is a good mulch. Astilbes love organic soils, as most are woodland plants. A good organic mulch keeps the soil cool and moist and eventually builds the soil as well.
If you haven’t ordered your hardy lilies and peonies for fall planting, you’re running out of time. Peonies are usually shipped for planting from late-September on and hardy lilies from mid-October on. Peonies can be transplanted from late August through September and dormant lily bulbs can be dug and replanted in October once all the foliage has browned.
Mark the stems though so you know where to dig for the bulbs and be careful. Many a gardener has thought his or her marking was perfect only to put a shovel into the ground an slice a valued lily bulb in half.
Remember that lilies are planted deep—some 4 to 8 inches deep—while peonies are planted shallow, just below the soil surface. Neither should be planted with any foliage and neither should be fertilized at planting. Don’t expect either to flower the following year (though there are always surprises), but the second year flowering should resume.
Last fall I planted a new Asiatic hybrid lily named “Forever Susan” and it flowered this summer. The flowers are borne on upright stiff stems about 4 feet tall with four to eight flowers per stem.
The flowers are pretty unusual in their colorations, with a burnt-orange outer part of the flower and a deep burgundy running from the flower petal down into the throat. It’s nicely scented and an interesting color combination to work with.
Gardeners who want to extend their vegetable garden season should be planting fall crops now as well. It’s hard to find plants at garden centers but if you look around you will find some cabbages and soon you’ll find lettuce packs as well.
I’ve got carrots and beets planted that will mature in early October and will be harvested right through the fall. Beets do especially well when they mature as the ground cools. If carrots have matured by October, they too can stay in the soil until it freezes.
Spinach can be sown now and most lettuces can be sown from mid-August with successional plantings every week to 10 days until mid-September. Radishes can also be sown now through late September. Late sowings of spinach, say in mid- to late-September will often overwinter under a light covering of salt hay, resulting in a very early and tasty crop come next April.
No, you can’t do a late crop of melons, squashes, peppers or tomatoes. But do keep track of what did well this year for next year’s garden.
There’s still lots to do if you’ve got the energy, so keep growing.