June Gardening Topics

Fruit and Chilling Hours

Wonder why fruit trees produce little or no fruit? Lack of cold evening temperatures and warm days at the right time during winter is the reason. Chilling hours are calculated by adding up the hours of below 45F. Chilling hours influence bud break, fruit set and fruit development. Insufficient chilling is probably the most limiting factor for sweet cherry, peach, apricot, nectarine and apple fruit yield here in the Santa Clara Valley. Chilling hour requirements range from four days (<100 hours) for persimmons to six to eight weeks for sweet cherries. For more information, visit the California Backyard Orchard website.

What's Eating My Fruit?

Is there a hole with teeth marks? It's probably roof rats or squirrels. Does the fruit look stabbed? It's likely birds. Here are some ways to keep the fruit for your family. Summer prune so the tree stays small enough to be covered with bird netting. Erecting a PVC pipe frame first eases net installation. Weigh down the net at ground level. If the tree is large, try pruning the branches so nothing touches any structure or other plant. This reduces rat and squirrel access. Purchase some shiny Mylarb bird scare tape and tie an 18" length to a bamboo pole that's long enough to emerge out the top of the tree. Use several on each tree. Put out right before the fruit is ripe and remove it as soon as you are finished harvesting.

Fire Blight

Fire blight bacteria symptoms appear as blackened dead branches and twigs that have a torched look. It hits ornamentals like pyracantha, cotoneaster, flowering pear and crabapple, mountain ash, hawthorn and fruit trees such as apple, pear, loquat and quince. It overwinters in cankers or wounds and resumes bacterial growth in the spring. There may or may not be oozing from the canker. It is spread by insects, rain, or pruning. The infection can extend into the trunk or root system and may kill the tree. Prune the infected branch about eight inches below the dead area. Spraying during bloom is the preventative method of control. See the pest note for more information.

Certified Arborists

The Master Gardeners get calls asking about how to trim trees or identify problems with trees. Sometimes we can help over the phone, but problem identification is often difficult without seeing  the tree, so we may suggest you bring in a sample or send photos in addition to describing the problem. When you need an expert onsite, you can use the ISA website to find arborists using your home's zip code.

Fruit Tree Overload

If you have a fruit tree ready to pick and you just don't have the time or energy or motivation to pick the fruit before it falls and rots, please contact Village Harvest. This terrific organization has volunteers who will come to your garden and remove the fruit. The fruit is then donated to food bank organizations such as Second Harvest. Because of the demand for their services, they are focusing on senior or disabled homeowners, orchards or gardens with several trees. Their website gives hints on how to manage your fruit production reasonably and has many links to fruit tree information. Their telephone number is (888) FRUIT-411.


Check your irrigation system to be sure it's in full working order. If you have drip lines, open the end and turn on the water to clean out the line. Close the end of the line and check that each emitter or sprayer is working properly and isn't clogged. Check popup sprinklers for full spray and for proper placement of water. Plants grow larger during the winter and spring and may be blocking the water from reaching the expected location. Also unneeded spray watering of shrubs and trees can cause disease problems. Make sure the irrigation timer is set correctly as well.


Mulching is an effective technique to keep soil temperatures even, to retain moisture and to prevent weeds from germinating. Mulching with organic matter such as chipped tree trimmings, compost or barks not only reduces water usage but also improves the organic content and texture of soil. Apply at least two to three inches of material (three to six inches of larger bark pieces), keeping it several inches away from the trunks of trees and shrubs to prevent crown rots. Renew every few years as it decomposes and enriches the soil.

Aphids in Plum or Other Fruit Trees

Ants in your tree, leaves curled and deformed that look like peach leaf curl, are signs that there is an infestation of aphids. They affect the new leaves as they open. There are several ways of handling this problem. First try getting rid of the ants by using a 4 inch wide band of tanglefoot applied on top of a wrapper around the trunk of the tree. Try spraying the affected area with a soap (liquid dish soap like Ivory) and water spray, making sure you get all the surfaces of the leaves. If the infestation is really bad, cut out the affected areas. A Pest Note on Aphids is free.

Bearded Iris

They have mostly stopped blooming by now. Young clumps should have their old flower stalks removed so they don't waste energy producing seed. Three or four year old clumps should be divided because they have exhausted the nutrients in the soil and blossom production will decline. The youngest healthiest roots are at the outer edges of the clump. Choose growth with a double fan, 3 - 4 leaves, and a Y shaped root, and plant these.

Bee Swarms

I have seen three swarms, two in my yard, and one at Prusch Farm Park. They clump together hanging from a tree branch. The one in my yard looked like a brown bag hanging on my Bottlebrush shrub. The bees are usually full of honey and docile, especially when it gets cooler. The hive has gotten overcrowded so the queen leaves taking part of the bees with her. They hang there for a few days and then leave. It's a natural occurrence and very interesting to observe. Leave them alone and they won't bother you. If you really can't stand them, there are some bee keepers that will come and get them. Call our hotline for some names.


Earwigs are second only to snails and slugs in causing damage. They do have a good side as they eat insects such as aphids. Unfortunately they also feed on soft plants. They can do quite a lot of damage if there is a high population. Earwigs are nocturnal, feeding at night and hiding in a moist, tight fitting place during the day. You can trap them by putting out moistened, tightly rolled newspaper or corrugated cardboard in the evening. In the morning dispose of the paper and the trapped insects.

English Daisies in the Lawn

The little flowers that grow in the lawn in places like Golden Gate Park are called English daisies. They used to be considered weeds but are now quite popular. Some grass seed mixes include them in their mix now. You can mow and they keep continually blooming. It is a true daisy from which all other daisies take their name. They are 6 to 8 inches tall if allowed to mature. They have single or double white, pink, rose or red flowers from early spring through summer. The seeds are very small but germinate easily. Best sown in the fall but can be sown now. Most seed catalogs have English daisy seeds.

Geraniums are not Flowering

Probably too much water or too much fertilizer or both. Geraniums need a drier area in your yard. If this isn't possible, try growing them in pots.

Peachtree Borer

Small piles of reddish or brown sawdust like frass appear at the base of the tree trunk. After winter rains, sap oozes through damaged areas, usually at ground level. The larva is a one inch white worm with a brown head. If you carefully dig into the bark at a hole, you can see them now. The Peachtree borer attacks mostly young trees of the peach, apricot, cherry, prunes, plums, almonds, many native and ornamental Prunus species. In June or July, use a spray of carbaryl, applied from the crotch down, and puddling at the base to soak into the soil.

Rose Basal Cane or Sucker?

It can be difficult for an novice rose grower to tell the difference between a basal cane and a sucker. They both shoot straight up with vigorous growth. The sucker comes from below the bud union (the bump just below where the rose starts to branch). The foliage, thorns, and growth are entirely different than the rest of the plant. It is usually longer and more willowy than a basal cane. Also it does not terminate in a bud. The sucker should be cut off at the point of origin. The basal cane originates at the bud union and all its characteristics are the same as the plant. This is the best wood on the plant and should be left on. It grows tall with a cluster of blooms at the top. It is best to pinch out the tip when it is about 18 inches long.

Rose Diseases

Several diseases can be common in our area. Blackspot is a fungus with circular black spots that appear on leaves. The leaf then turns yellow and drops off. Powdery Mildew is also a fungus that shows white powdery masses on the leaf, stem and bud, distorting and stunting them. Rust can cause the leaves to wilt and may drop off. The leaf top may have light green mottling with yellow dots. The underside has powdery rust-colored spores. A fungicide that can be made at home by combining 2-1/2 tablespoons of horticultural oil (Sunspray Ultra-Fine, Saf-T-Side, etc.) in a gallon of water and adding 4 teaspoons baking soda. Use a fine spray and apply to affected plants. This also controls foliar vegetable diseases. Some plants may show some sensitivity. More details at the Pest Note on Powdery Mildew.

Armored Scale Control

Armored scale insects are in the crawler stage in early summer. Armored scale has a hard stage that is very resistant to sprays. Control them during the crawler stage when they are soft and vulnerable. Spray with a horticultural (not dormant) oil, once a month for three months. See the Pest Note on Scale for important information about spraying.

Tomato Blossom End Rot

The brown depression on the bottom of the tomato can be caused by a lack of calcium in the soil or irregular watering. Use a balanced fertilizer according to the label and water consistently. Mulching the plant is also a good idea.

Vegetables Growing in Containers

Container grown vegetables can be decorative as well as good to eat. Almost any vegetable can be grown in a container if given the proper care. Eggplant, peppers, tomatoes, lettuce, onions, carrots, cucumbers and herbs do well. One of the biggest problems is that containers dry out very fast and nutrients wash away. Both are solvable. Do not use clay pots which dry out quickly. Plastic, composite or wooden half-barrels are good. Vegetables like a roomy container. There must be drainage holes in the bottom but it is not recommended that you put pebbles or broken crockery in the bottom. Use a good commercial potting mix, not planter or planting mix. Group the containers together so they will shade one another. The hot summer sun can heat the soil to unhealthy levels. Water whenever the soil is dry. You can test by digging your fingers into the dirt or using an inexpensive moisture meter. You may have to water more than once a day. A simple drip system is easy to install and will make your container garden almost foolproof. Add a timer, a patio chair, relax and enjoy. Fertilize every week with a water-soluble fertilizer.