Don't see your question? ASK US! For lots more information, also check out our Sustainable Gardening, Home Landscaping, and Edible Gardening pages, along with Our Blog.
1. Why are the leaves on my citrus tree turning yellow?
2. I get lots of flowers but almost NO tomatoes. What’s wrong?
3. How can I get my soil tested?
4. There are small insects all over my roses and sticky stuff on the nearby walkway. What is it?
5. There is a powdery growth on the leaves of some of my plants. What is it?
9. What can I do about rats eating my tomatoes?
10. The leaves on my peach tree are curling and I am not getting much fruit. What is going wrong?
1. Why are the leaves on my citrus tree turning yellow?
Yellow leaves on citrus trees can be caused by a variety of factors throughout the growing season. The good news is that almost all causes are treatable by the home gardener. The most common reasons that citrus leaves turn yellow (this is also called chlorosis) are:
- Watering: too much water can cause the tree’s roots to drown and rot
- Fertilizing: too much or too little can be a problem
- Nutrient deficiency in the soil: these include iron, zinc and magnesium deficiencies
- Seasonal factors: Cold and rainy conditions
- Fungal diseases: like Phytophthora or root rot
- Pests: Mites can cause yellow leaves especially in hot and dry conditions
For more information on the general causes of yellow leaves on citrus:
https://ucanr.edu/sites/mgslo/files/348792.pdf
2. I get lots of flowers but almost NO tomatoes. What’s wrong?
There could be several reasons for lack of fruiting in tomatoes:
- Night temperatures too low, below 55°F (12.8°C) or daytime temperatures too high, above 90°F (32.2°C).
The plants will produce when temperatures become favorable. Note, though, that heirloom tomatoes can be fussier about temperature than most hybrid tomatoes and in some areas can wait until late summer or early fall to start setting fruit. - Excess nitrogen fertilizer. Lots of healthy green leaves and stem growth, but few flowers or fruit.
- Too much shade – you need a minimum of six hours of sun to produce fruit.
- Lack of pollination. While tomatoes are self-fertile, the conditions mentioned above will inhibit pollination.
- Plants set out too early in spring. -- We recommend planting tomato seedlings the first of May; often earlier planting of seedlings will be inhibited by cold temps and they will just “sulk”; consistent warmer weather and nights should get them growing.
Recommendations:
- Choose varieties adapted to your climate zone,
- Plant tomatoes in full sun,
- Keep soil evenly moist,
- Avoid excessive nitrogen fertilizer, and
- Tapping on blossom stems 3 times a week at midday when flowers are open may improve pollination and help set fruit.
Click here for more about tomato culture, pests, diseases, and environmental disorders.
3. How can I get my soil tested?
Although the UC Master Gardeners of Contra Costa cannot test your soil for you, many commercial laboratories provide a variety of soil testing services to the public. Most have informative web sites that describe what tests and other services are available, how to submit soil samples for testing, etc.
For more information:
4. There are small insects all over my roses and sticky stuff on the nearby walkway. What is it?
The small insects you are seeing are most likely aphids. Aphids can be identified by their soft pear-shaped bodies and a pair of tubelike structures (called cornicles) projecting out of the hind end of their body. Aphids feed by sucking plant sap from leaves which they then excrete onto the plants. This excretion (called honeydew) is the source of the stickiness on your walkway. Aphid populations are generally not damaging to garden plants and are kept under control by beneficial insects. However, if aphid populations are too high and are causing problems you can prune off damaged areas or use a strong spray of water to knock the aphids off the infected plants. Make sure you also check for ants on your roses. Ants love honeydew and will protect aphids for their honeydew. Ant bait stations can be used to keep the ant population under control.
For more information on aphids
For information on managing ants
5. There is a powdery growth on the leaves of some of my plants. What is it?
White powdery growth on leaves and shoots can be a sign of powdery mildew. This disease affects many plants, and one of several fungi can cause it. Manage powdery mildew by growing resistant plant varieties and altering the growing environment. In some situations, fungicide treatments might be required for susceptible plant species.
For more information, visit https://ipm.ucanr.edu/QT/powderymildewcard.html.
6. I have been gardening for several years now and I’m still confused about how to water my vegetable garden. Is there a formula or chart I can use?
Charts and formulas lack the ability to account for the multitude of variables when it comes to watering, such as the type & quality of soil, frequency of rain and fluctuation in temperature along with the specific water needs of various plants. Watering precisely is a function of knowing your soil, and you will need to feel and see the moisture content of your soil. A few times a week get a trowel full of soil from 6-8” deep, feel it and take a good look at it, the soil should look and feel as damp as a wrung-out sponge. A general rule is this level of moisture can be achieved with 1” of water per week. Measure your garden area in square feet. A 100 square-foot area will need 62 gallons of water per week. Based on weather conditions (rain & heat) you will need to adjust your watering. Monitor your soil, it will tell you when it’s time to water.
For more information
- University of Minnesota: Watering the Vegetable Garden
- Irrigation for Your Garden
- Your Food Garden During Drought
- UC ANR Vegetable Gardening Basics: Water (scroll to page 3)
7. I am planning on planting several trees in my yard. I have not had great success planting trees previously and would like to know how to do this properly.
This is a vitally important issue, as a tree is a long-term investment for the landscape: improper treatment at planting, and during early life, will likely result in poor health and a shorter life span for the tree. The following basic points apply to both landscape and fruit trees.
- The best time to plant landscape trees is in the fall or spring (bare-root fruit trees are planted while dormant).
- Select a good quality specimen in the nursery – landscape trees often come in 15-gallon pots, or larger boxes. Smaller trees are best as they establish more easily. For more details: https://ucanr.edu/sites/solanomg/files/246178.pdf
- Make sure the area where the tree will be planted drains well. Most trees, including those that you have selected, will not do well in waterlogged soil. For fruit trees, the area should get at least 6 hours of daily sun.
- Don’t dig the hole any deeper than the root ball; the tree can sink down as the soil settles. You can leave a cone of soil in the center to keep the tree at the right level. The hole should be wide enough to spread the roots out. Rough up the sides of the hole.
- Aim to plant slightly high. The root flare at the bottom of the trunk should not be covered with soil or mulch.
- Check the roots prior to planting. If the tree is root-bound and there are circling roots, these should be pruned so roots can grow outward rather than continue to circle. In order to do this, the existing soil needs to be washed away. You will find details in the video link below.
- Do not amend the soil when filling in the hole. The tree roots need to grow out into the native soil.
- Be sure to remove the nursery stake after planting. If the tree needs staking, use the two-stake method as described here: https://ucanr.edu/sites/solanomg/files/246182.pdf
- Add several inches of mulch to the planting area. Fresh wood chips are a good choice and can often be obtained at no cost from tree companies.
- The new tree will need regular water. Do not let the root ball dry out. Move irrigation further out from the trunk as the tree grows
For more information check out the following links:
8. I would like to grow vegetables in containers on my balcony. What do I need to know to be successful?
Most vegetables grow well in containers if the conditions are right and you provide the care they need. Most vegetables need six to eight hours of direct sunlight each day but leafy vegetables like lettuces can get by with just four hours.
- Containers: You’ll need containers that are an adequate size for the vegetables you grow. Deeply rooted vegetables like tomatoes and zucchini need 18 inches or more of rooting depth. Peas, beans and chard can do well with 12 inches. Lettuces, spinach, green onions and radishes need even less.
- Soil: Fill the containers with a potting mix that has been formulated for containers. Adding up to 50% compost to the mix will provide nutrients for the plants and help the mix retain moisture.
- Water: Use a watering can or similar container to irrigate. In hot weather you may need to water as often as once a day. Use a soil moisture meter to check whether you’re providing enough water and are not over saturating the potting mix. Your containers should have drainage holes that allow excess water to escape.
- Fertilizer: If your potting soil included compost, you won’t need to fertilize until the plants have been growing for three or four weeks. Then once a week, add liquid fertilizer to the irrigation water.
For more guidance on Container Gardening Basics
- Container Gardening Basics
- Ornamental and Edible Plants in Containers (video)
- Planting in Containers [https://marinmg.ucanr.edu/CARE/PLANTING/ContainerPlanting/]
9. What can I do about rats eating my tomatoes?
Rats are common pests in our gardens and are attracted to many of the plants we grow. Rat control is difficult and involves several steps.
- Physical barriers can protect plants, either individually or in groups. Use small-mesh (no larger than ½ inch) wire that completely encloses the plants.
- Sanitation and making your garden less hospitable to rats can go a long way to reducing their population. Thin dense vegetation and remove materials where rats can hide during the day. Make sure your home is sealed by securing roof and attic vents.
- Remove bird feeders and pet food dishes, or make sure they are taken inside at night.
- Trapping can help, but it’s hard to make a permanent dent just through trapping.
For more information:
10. The leaves on my peach tree are curling and I am not getting much fruit. What is going wrong?
Peach leaf curl is a fungal disease that affects only peach and nectarine trees. Distorted, reddened foliage in spring is a distinctive symptom of peach leaf curl. New leaves and shoots thicken, pucker, and may later die and fall off. If you allow an infection to go untreated for several years, it can lead to tree decline. To prevent peach leaf curl, treat susceptible trees with a preventative fungicide every year after leaves fall in the autumn. Treating after symptoms appear in the spring won't be effective. When planting, consider tree varieties resistant to the disease. Visit the UC website for details.
11. I see information about using horticultural oil and insecticidal soap for pest control. Oil and soap don’t seem like they should be used on plants. What am I missing?
You are correct. Kitchen and household oils along with liquid soaps and dish detergents should not be used in the garden because these oils and soaps are not formulated to be used on plants. The recommended oils and soaps are horticultural oil and insecticidal soap. These products have been specifically formulated for use on plants. They are effective for pest control, have low impact on the environment, disperse quickly, and have relatively low toxicity to people and pets.
What you need to know:
- Both are effective on soft bodied insects, aphids, spider mites, thrips, whitefly, mealybugs, leafhoppers and sawfly.
- Horticultural oil is also an effective fungicide, insecticidal soap is not.
- Both products must come in direct contact with the insect. The oils provide control primarily by smothering and once the oil or soap spray is dry it is no longer effective.
- Both can be applied to edible plants and ornamental plants, and have low or no toxicity to birds, reptiles, mammals and humans.
- Both products are toxic to fish and to bees and other pollinators in their wet stage.
General Guidelines for Horticultural Oil and Insecticidal Soap:
- Identify the pest or disease before you spray so you can choose the appropriate product and always check the label for a list of safe target plants and/or oil sensitive plants.
- Do not use on drought stressed plants or on tender, young spring growth.
- Do not apply in direct sun. Oil treated plants may burn in the hot sun. The appropriate temperature range for oil sprays is warmer than 40°F but no hotter than 90°F.
- Best application times are early morning or early evening when bees and other pollinators are limited.
- Multiple applications are needed for most insects, and when using an oil spray, read and follow all label instructions precisely.
For more information:
- Using horticultural oil
- Insecticidal Soaps
- Using Soap and Detergent in the Garden
- Pesticides: Safe and Effective Use in the Home and Landscape