University of Vermont Extension 
Department of Plant and Soil Science

Summer News Article


Charlie Nardozzi, Senior Horticulturist
National Gardening Association, and
Dr. Leonard Perry, Extension Professor
University of Vermont
Staking dahlias, proper watering of tomatoes, and fertilizing blueberries and container plantings are some of the gardening tips for this month.

Don't let the wind or heavy rains knock your dahlias to the ground. Stake individual stems or place several bamboo poles around a large plant and wrap twine around the poles to provide support.  If staking individual stems, use cloth or other materials (not twine) so not to cut into stems.  Tie at several places up the stems, including near tops, otherwise they may break at these points in heavy winds.

You can get some great deals on perennials now at garden centers, and even if you don't have a spot ready for them in the flower border, plant them in the empty spaces in the vegetable garden when you pull out broccoli and other early crops. You can transplant them into their permanent locations in the fall or spring. Visit specialty perennial nurseries every few weeks to see what is in bloom, so you can have flowering perennials in your garden at these times too.  You'll find a list of such Vermont nurseries online (

Dark leathery spots on the blossom end of tomatoes is likely to be a condition called "blossom end rot" that's caused by uneven watering. Mulch will help moderate the fluctuating moisture levels that nature provides, and it's not too late to spread some around your plants.
Most poppies resent transplanting, so a good way to propagate Oriental poppies is by root cuttings. Once the plants have dried up, dig up pieces of root and cut them into smaller pieces. Plant these sections, and sprouts will form this summer. By next year, you'll have new flowering plants.

Now through the end of summer is a good time to divide bearded iris if they've gotten too large, flower less, or have gotten weedy (there's no easy way to weed them).  Dividing every 2 to 3 years helps lessen soft rot and borers. When lifting the swollen roots (actually underground stems called "rhizomes") cut off any rotten parts, especially if they contain white "worms" (iris borer larvae).  Separate the sections naturally by pulling apart, not cutting.  Cut leaves back to six inches to help offset the loss of roots.  Replant in full sun, in well-drained soil.  Make sure the rhizome is planted near the soil surface or the plant likely wont bloom next year.  Keep watered well.

Blueberries benefit from an acidic fertilizer each year. Apply 1/2 pound of ammonium sulfate when the bushes start blooming, and another 1/2 pound four to six weeks later. If the leaves turn yellow with green veins, they may have an iron deficiency. Applying 2 to 3 ounces of ferrous sulfate or iron chelate around the base of the plants will help correct this.

Frequent rains leach fertilizer from the soil of container plantings, so they need to be fertilized more often than plants in the ground. Mix liquid fertilizer into the watering can and use it weekly. Don't fertilize when the soil is very dry or it can burn the roots, so you may need to water plants first, then water with the fertilizer solution.

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