University of Vermont Extension 
Department of Plant and Soil Science

Summer Article

PLANTING DAHLIAS AND OTHER JUNE GARDENING TIPS
By Dr. Vern Grubinger, Extension Specialist and
Dr. Leonard Perry, Extension Professor

Memorial Day weekend marks a milestone for many gardeners.  They move from planning to planting, so by June most garden crops are off to a good start.  Now it's time to start maintaining the garden.

Some vegetables like carrots, lettuce, and beets may require thinning after direct seeding. Thin enough to provide good air circulation (this prevents foliar diseases) and to avoid competition among plants for water and fertilizer.

Tomatoes usually need support to keep fruit off the ground and keep plants healthier by promoting leaf drying.  Indeterminate varieties continue to grow vines all season and benefit from suckering as well as staking.

Remove suckers that sprout from the stem up to the first flower cluster. This will promote earlier fruiting and keep the plants to a manageable plant size.  'Celebrity' and other determinate varieties will not sprawl as much and do not require suckering.

To reduce weeds and conserve soil moisture, apply a thick layer of leaves, hay, or straw mulch around vegetable plants, especially long-season crops, in mid-June.  Waiting until mid-month gives the soil time to warm up.  Avoid using weedy hay as a mulch.

Although most of your planting may be done, your battle with pests--insects, diseases, weeds, and wildlife--has just begun.

Many vegetable pests, such as the cabbage maggot, flea beetle, Colorado potato beetle, and cucumber beetle, can be thwarted by covering crops with a floating row cover soon after planting.  These thin blankets of woven polyester allow water and light to pass through but keep insects out.  Be sure to seal all edges with soil, and remove when vine crops are in bloom to allow the flowers to get pollinated.

Protect new transplants like melons, tomatoes, cole crops, and cucumbers from cutworms by placing a cardboard collar around the base of the plant.  The bottom of collar should be pushed into the soil about an inch with two or three inches above.

June is the month to plant dahlias, once all danger of frost has past. Choose a location with fertile, well-drained soil that gets at least six hours of sun a day. Dahlias like sandy or loamy soil, but will do fine in clay soil if you work in a two- to four-inch layer of well-rotted manure or compost a few weeks before planting.

Apply a slow release, complete fertilizer at planting time, such as any of the organic ones that last most the season.  As a rule of thumb, add about four ounces of 5-10-5 per ten square feet of garden, or use other fertilizers according to soil test results. Incorporate into the soil well. Be aware that soil test results may show a well-established garden to have soils that are 'off the chart' in nutrients, especially phosphorus.  If your soils have sufficient fertility, adding more fertilizer will NOT help your crops, and it may contribute to pollution.

Dig a hole about four to six inches deep, laying the tubers horizontally on their sides, with roots down and buds facing upward. Cover with two inches of soil.  You will need to add more soil after shoots appear.

Smaller varieties should be spaced two to three feet apart, larger ones three to four feet. To avoid damage to the roots later on, drive a stake into the ground now, a few inches from where you plan to plant each tuber. You will need to stake larger plants as they grow.

If landscaping is in your plans, start with a plan drawn to scale on paper.  Draw the property lines and locate the house, garage, trees, and other permanent plantings.  Then sketch in the additions you want to make, such as walks, terraces, and flower gardens.

Make a list of all things that need to be done.  You'll want to remove all plants that are overgrown or diseased or that stand in the way of construction, for example.

Work with your local nursery to select plants suitable for your location. Not all species are hardy for all areas.  Some may grow too big for the space allotted.

When shopping for trees and shrubs, check the root system and the color and "feel" of the foliage.  Look for specimens with strong, vigorous growth and healthy leaves or needles. Well cared for plants generally have foliage that feels rigid and/or waxy to the touch.  Dried out foliage will break and crumble when handled.

Most trees and shrubs are sold in containers. If buying now, use care when planting, as the tree or shrub often is not as well rooted as later in season, and you can damage roots when removing the container.

For balled-and-burlapped plants, the ball of soil should feel solid and be tied well.  A broken,
loosely tied ball often indicates dried and broken roots.

Fertilize lawns again if using a complete, synthetic fertilizer and not a slow release organic one.  Keep lawns mowed regularly, but do not set the blades too low.  This is a common mistake, which leads to less vigorous growth and higher chance of disease.

Other activities for June: start a rock garden; visit a pick-your-own strawberry farm; fertilize roses, shrubs, and perennial plants; sow succession plantings of lettuce and other leafy greens.


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