June Gardening Tips

Monthly Proven Tips and Solutions for Granite State Gardeners

dahlia

Plant summer-flowering bulbs such as cannas, dahlias, and gladiolus.

Choose a sunny spot with well-drained soil and make sure the roots are facing downwards and the buds are facing upwards. Like other landscape perennials, summer bulbs benefit from irrigation when there is less than once inch of rainfall in a week. The best strategy for fertilizing is to have your soil tested to determine the pH and available nutrients. Without that information, a water soluble or granular fertilizer that is high in nitrogen can be used until the middle of the season to encourage plants to develop lush foliage, tapering off applications as the summer progresses to encourage blooms.

Watch for Eastern tent caterpillar nests in fruit and shade trees.

When tent caterpillar numbers are high can they significantly defoliate trees and reduce fruit yields. On landscape trees the nest can be an eyesore, especially defoliation is severe. Fortunately, tent caterpillar feeding, even with it is excessive, rarely harms healthy trees, making this pest a more of a nuisance than a plant health threat. Natural enemies and predators are important for keeping tent caterpillar numbers under control. Various wasp species parasitize caterpillars, and naturally occurring diseases kill many caterpillars when humidity and temperatures are right. Some bird species, like cuckoos, will also use them as a food source. If you decide that intervention is necessary, destroy nests by pruning or removing them by hand. Loosening large webs with a stick is often plenty to control an infestation.

Set the cutting height of your lawn mower to at least three inches.

Lawns that are maintained at a higher height are more resilient to insect pest and disease issues. Taller grass also shades out weed seeds and keeps the soil cooler, plus, taller grass means longer roots and greater ability to withstand drought. To avoid stressing the lawn, remove no more than one third of the shoot growth at a time. To maintain a 3-inch lawn, mow before the grass reaches 4.5 inches tall. Another good practice is leaving grass clipping on the lawn. Decomposing clippings add nutrients to the lawn and help build soil organic matter, improving soil quality by improving water holding capacity.

Harvest asparagus and rhubarb up until the end of June, to give the plants the rest of the summer to grow and store energy in their roots.

Both asparagus and rhubarb should be well established before any spears or leaves are harvested. Wait two years after planting, and in the third begin harvesting. Ending the harvest by the end of June allows asparagus and rhubarb to develop strong, healthy top growth and store reserves in their crowns and roots for next year’s harvest.

Prune and stake tomato plants to increase yields, improve fruit quality, and reduce common fungal disease problems.

Pruning tomatoes means selectively removing some of the plant growth. Removing suckers (new shoots that develop in the leaf axils) reduces the number of tomatoes a plant will produce, but it also increases airflow and limits disease. Leave the sucker just below the first flower cluster (remove all other suckers below that one) and allow all suckers above the first flower cluster to grow. Staking tomatoes keeps them off the ground also helps reduce common fungal diseases and keeps fruit clean and makes them easier to harvest.

Thin excess fruit from overloaded fruit trees to produce larger fruits at harvest and reduce stress on branches.

Another important reason to thin fruits is to reduce overbearing that leads to a heavy crop in one year and almost no crop the next. Thinning balances the amount of fruit on trees with leaf surface area that provides the energy for producing fruit. Too many fruits can stress a tree and lead to fewer flower buds being produced for the next year. For apples, Asian pears and European pears, thin fruit to one per spur, leaving only one fruit for every six inches of branch. For peaches, plums, nectarines and apricots try to space fruit along the branches as single with six to eight inches between fruit. Cherries typically do not require thinning. To get the maximum benefit from thinning, excess fruits should be removed from trees within 30 days of the end of bloom.

Move houseplants outdoors for the summer once night temperatures consistently remain above 50°F.

Most houseplants prefer bright spots that receive morning sun but are shaded in the afternoon. Ideally, houseplants should be gradually introduced to the outdoor sun exposure by placing them in deep shade for a few days and gradually moving them into brighter sunlight. Plants that are moved into direct sun too quickly will burn and in some cases be severely damaged. Succulents and cacti can typically tolerate full sun, while indoor flowering and foliage plants prefer light to heavy shade, depending on species. Houseplants grow much faster outdoors than indoors and will require more frequent fertilization and irrigation. Expect to fertilize once every couple of weeks and water once or twice daily.

To minimize diseases, water with overhead irrigation in the morning to allow the foliage to dry before nighttime.

The goal is to limit the amount of time leaf surfaces are wet. Plants that remain wet through the night are more likely to develop disease issues. Even better, avoid wetting leaves entirely by using soaker hoses or drip irrigation, and mulch the soil beneath plants to prevent soil from splashing onto leaves and to help conserve soil moisture.


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Author(s)

Emma Erler
Landscape and Greenhouse Field Specialist
Instructor Field Specialist
Phone: 603-641-6060
Office: Cooperative Extension, Taylor Hall, Durham, NH 03824

Ask UNH Extension
Master Gardeners & Extension Specialists
Phone: 1-877-EXT-GROW (1-877-398-4769)