UC Master Gardeners, Santa Clara County, CA
University of California
UC Master Gardeners, Santa Clara County, CA

March Tips

Monthly tips are categorized by: To-Dos, What to Plant, or Pests and Diseases. Scroll through the list to see items in each category.

1. To-do

  • Bulb Care and Clean-up -

    Early blooming bulbs such as daffodils are already finishing flowering. Wait until the leaves have turned brown before removing them. The green leaves need to photosynthesize to store energy for next year's blooms. For more information see UCCE Tips on Flowering Bulb Care.

    - March
  • Citrus Pruning and Care -

    Navel orangesOnce the threat of frost is past (typically March 15), it's a good time to cut back branches that touch the ground, fences, or other structures. Thin the tree to let more air into the middle. Trim out crossing branches and anything that looks dead. All these steps will help control scale and aphid infestations. Use a sticky goo (such as Tanglefoot) on the trunk to keep ants out of the tree. Be sure to apply the goo on top of tape rather than directly on the trunk. The ants 'protect' the scale and aphids.

    If you see scale (bumps on bark), thoroughly spray with horticultural oil to suffocate them. Yellowing of leaves is normal this time of year as the iron that keeps the leaves green is chemically unavailable because the soil is too cold. When the soil warms up (over 60° F), check for yellowing. You may not need to apply a nitrogen fertilizer if the new leaves are green.

    Refer to the UC Home Orchard web site for more Citrus Care information.

    - March
  • Composting -

    Composting is a good way to repurpose yard and kitchen waste, and it provides a free method to feed plants and improve soil structure. If you are unsure about how to begin composting, take a look at this simple how-to compost page. You can also go to the UCCE Composting Education Program website to learn more about free two-hour classes offered throughout the county.

    As the weather warms up, compost piles dry out faster. Keep compost piles as damp as a wrung-out sponge to keep organisms alive and working on decomposing yard waste. Turning the pile to incorporate more oxygen also supports life in the compost pile.

    - January, February, March, April, May, June, July, August, September, October, November, December
  • Drip Irrigation -

    Low volume drip irrigation systemConsider various forms of irrigation conversion! Irrigation systems, especially drip and micro-sprinklers, have drastically improved over the last few years. For example, there are kits that convert pop-up sprinkler heads to low-flow systems. The conversion kits include a pressure regulator to control changes in pressure and a filter to improve water quality. Water usage is reduced through better water management, control of distribution and less loss from evaporation. Other advantages include :

    - Water is placed more accurately and efficiently in the root zone, it is applied at a slow rate that reduces loss from runoff.
    - Dry soil between plants allows you to work in the garden between irrigating.

    The key to success is watering long enough to supply adequate water to the root zone. Inappropriate watering commonly damages landscape plants. As with any irrigation system, they are efficient only when soil around the plants being irrigated is regularly monitored for proper moisture levels (Reference: UC Pest Note Poor Water Management, Poor Drainage).

    - March, April, May, June, July, August, September
  • Frost Dates and Avoiding Frost Damage -

    The first and last frost dates for Santa Clara County are November 15 and March 15. First and last frost dates are important (but approximate) dates for gardeners to remember.

    First frost date—this is the earliest date you should expect frost to occur. If you have plants that need to be brought in for the winter, or crops you need to pick before frost, this date will be important to you. Last frost date—after this date you wouldn't expect any more frosts. It's generally used as a milestone when planting outdoors, or pruning frost sensitive plants (such as citrus where you don't want to stimulate delicate new growth until danger of frost is past).

    Note that microclimates in the county, and unusual weather conditions make these approximate dates.

    When there's a threat of frost, make sure your frost-tender plants are well-watered. Soil that is damp can hold more heat than soil that is dry. According to the UC publication on the Principles of Frost Protection, ”when the soil is wet ... more heat is stored during daylight for release during the night.”

    Frosts or a hard freeze can kill tender plants and can damage citrus, especially young plants so protection is a good idea on those cold, clear winter nights. Place stakes around tender plants and cover with clear plastic or fabric such as a sheet or old drapery. Don't let the material touch the foliage.

    Wrap larger plants with strings of Christmas tree lights (incandescent bulbs not LED bulbs) or position a 100–150 watt spotlight in the center of the tree and cover the plant with a sheet. Turn the lights on at night.

    If plants are potted, then move them to a sheltered area such as a porch, under the eaves on the south side of the house or even under a tree. Be sure to uncover them during the day. Moving them indoors to a cool room would be good if possible.

    If you have plant damage from frost, wait until spring to prune. Early pruning can lead to further dieback along stems and branches because the dead material helps protect the plant from further damage.

    - January, February, March, November, December
  • Growing Vegetables in Containers -

    Growing Vegetables in ContainersContainer 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. Use our Vegetable Planting Chart to decide when to plant.

    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, but avoid dark colors that can absorb heat. 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. Fertilize every week with a water-soluble fertilizer.

    - February, March, April, October, November
  • Navel Orange Harvesting -

    If you have Navel orange trees, the crop will be ripening. Oranges left on the tree too long will dry out and become inedible or get eaten by rats. Instead, harvest the entire crop by the end of April and use the bounty to make marmalade, chutney and spiced oranges.

    QUARANTINE WARNING: Most of Santa Clara County is under quarantine for citrus due to the asian citrus psyllid and huanglongbing disease. Check the Santa Clara County Quarantine Map to see if you're affected and review our asian citrus psyllid page for what can and can't be moved across quarantine boundaries.

    - February, March, April
  • Poison Oak -

    Poison oak is a California native plant that provides shelter and food for many native birds and other creatures. The downside is that at least 75% of us develop allergic contact dermatitis to the plant. Unwanted poison oak can be pulled or dug up by allergy-resistant friends, remove plants in early spring or late fall when the soil is moist and it is easier to dislodge rootstocks.

    A complete list of management options, including herbicide control, is contained in the UC Pest Note on Poison Oak. Under no circumstances should poison oak be burned.

    - February, March, April, November
  • Pruning Dead Branches -

    As dormant trees and shrubs begin to leaf out, it will be fairly easy to see which parts are dead. Prune back to live wood to avoid diseases and keep your garden healthy. Swelling buds and a thin green layer just under the bark are signs that the wood is alive. Find tips on pruning at the UC Home Orchard website. If larger trees need pruning, hire a professional. The International Society of Arboriculture (ISA) has a searchable list of certified arborists.

    - March, April
  • Sheet Mulching - "Lose the Lawn" -

    An easy and environmentally friendly way to "lose the lawn" is to smother the grass and mulch at the same time. Place cardboard or several layers of newspaper over the area, overlapping by eight inches to keep weeds from finding openings. Wet the cardboard or newspaper, then cover it with 4-6 inches of compost, plant trimmings, or other mulch. Having wood chips on top will give it a neat appearance. The materials will gradually break down and improve the soil over time. New plants can be installed by cutting an X in the cardboard or newspaper and placing the plants right through the mulch. UC Davis Arboretum Horticulturist Stacey Parker's website shows you how it's done.

    - March
  • Soil Management - Compost vs Mulch -

    Many home gardeners are confused about the terms “compost” and “mulch;” frequently these terms are used interchangeably, but they are not really the same thing. Here is a Comparison of Soil and Mulch from UCCE.

    Amend soil with compost to create soil that will retain water but still drain well enough for roots to have the air and water they need.

    Benefits of compost
    - Forms aggregate particles with clay
    - Creates larger pore spaces for water & air
    - Helps release nutrients from clay so that plant roots can absorb them
    - Supports the soil foodweb by providing nutrients for the organisms
    - Lowers pH somewhat.

    Benefits of mulch
    Mulch does not get worked into the soil. It sits on top of your irrigation system and helps:

    - Control weeds
    - Prevent erosion
    - Preserve soil moisture
    - Keep roots cool and moist

    - March, April, May
  • Tomato Staking -

    It's time to start planning how you will stake your tomatoes. You will want to stake your tomatoes right after you plant your seedlings. Here are the various Tomato Staking Techniques we have tried.

    - March, April, May

2. What to plant

  • Attracting Bees -

    Bees are pollination workhorses, increasing garden production. Many plants will not produce fruit unless flowers are pollinated. Colorful annuals, such as Cosmos, edible African Blue Basil, and Salvias attract bees. You can also allow herbs and other plants to flower to create bee-friendly landscapes.

    The University of California at Davis has a garden dedicated to bees. They're Honey Bee Haven website has more resources, including a list of plants they grow.

    - March, April, May, June, September, October
  • Bare-Root Fruit and Nut Trees, Berries and Grapes -

    March or April is an excellent time to add bare root fruit and nut trees, grape vines, and bramble fruits to the landscape. These perennial edibles can provide decades of food production with a minimal investment of time and money. For more detailed information on specific varieties, take a look at the UC Backyard Orchard website.

    - March, April
  • Flowers To Attract Beneficial Insects -

    Certain flowers help attract natural enemies of pest insects in the garden. Tiny wasps that parasitize certain insect pests or their eggs need pollen and nectar to survive. Predatory insects (syrphid fly larvae, lady beetles, lace wings, and many others) and mites survive on pollen and nectar from flowers when pest populations are low, and some feed on pollen in order to reproduce.

    Most of these beneficial insects are small, and so the best flowering plants to include in the garden are those that have small flowers that have pollen and nectar easily accessible and that bloom throughout the season. Avoid flowers that are difficult to weed out when they reseed.

    Many flowers that attract beneficial insects are easy to start from seed and this month is a good time to start them – some indoors any time or outdoors later in the month after frost danger has passed. Examples include sunflowers (try dwarf varieties like ‘Sunspot’ for smaller spaces), calendula, cosmos and many herbs like dill, basil and borage.  

    Other flowers and herbs that attract beneficial insects are easier to buy as plants. A few examples that can be planted this month are coreopsis, asters, and thyme.

    Reference info:
    UC Pest Note on Biological Control and Natural Enemies of Invertebrates
    UCCE notes on Attracting Beneficial Insects to Your Garden.

    - March
  • Ornamental Shrubs and Trees -

    March is a good time to plant many trees, shrubs, and perennials. They'll have a chance to develop root systems before the heat of summer, and should be well-established before the next cold season. One example is bare-root roses.

    - March
  • Plant Asparagus Crowns -

    Asparagus crowns can be planted now. Dig a trench eight to twelve inches deep, mix in fertilizer at the bottom and cover with two inches of soil. Set the roots in the trench about 18 inches apart, and cover with two inches of soil. Gradually fill in the trench as the plants start to grow. Asparagus is a perennial vegetable that will produce for several years. It's best to wait until the second year to harvest to let a strong root system develop for long term production. For more information, read UC Davis' Growing Asparagus in the Garden.

    - January, February, March
  • Plant Summer Blooming Bulbs -

    Dahlias, cannas, and gladiolus can be planted now for summer bloom. Choose large, firm bulbs. They can be planted in containers or in the ground where there's good drainage. As a general rule, plant bulbs so that the soil above the top of the bulb is about twice the diameter of the bulb.

    - March
  • Plants to Attract Butterflies -

    Butterfly populations fluctuate in response to climate and habitat conditions. Many have specific host plants on which they feed and breed. Some common plants for attracting butterflies are milkweed, lantana, buddleia, and zinnias. For an extensive list of relationships between specific butterflies and host plants, see Art Shapiro's Butterfly Site at UC Davis.

    - March, April, May, June
  • Vegetable Planting Chart -

    Wondering what vegetables can be planted now? To get the best success—whether planting from seed or transplants—refer to our Santa Clara County Vegetable Planting Chart. It's based on our own garden experiences.

    - February, March, May, June, July, August, November
  • Vegetables From Seed -

    Starting your own seedlings is fun, easy and can please your taste buds, too. You can select vegetables that are grown for a particular flavor such as heirloom varieties, many of which are not offered in garden centers. This month may be the last month that you can successfully start some vegetables (tomatoes, peppers, eggplants) from seed for transplanting this summer season. If seed starting isn’t for you, consider buying transplants from our Spring Garden Market in April.

    There are two ways to start your seeds: direct sow straight into your garden or indoor sow. Direct sowing is easy for some plants such as peas and beets—see our Vegetable Planting Chart for more vegetables suitable for direct sowing this month. Tomatoes, eggplants and peppers are best started indoors and then planted in the ground after they are developed and sturdy. Three factors influence germination: water, temperature, and light. Information found on the seed packages will show which conditions are best for germination. Peppers in particular germinate best with high soil temperature (Reference: Arizona Master Gardener soil temperature table). Using a heating pad is one way that this can be attained indoors.

    When reusing pots for seed starting, prevent the spread of plant diseases by making sure they are clean. Remove any remaining soil and cobwebs; then clean the surfaces with a 10% bleach solution: 1 part bleach to 9 parts water.

    If you started seeds earlier in the year, March may be a good time to move them into larger pots if they are outgrowing their pots. The soil temperatures outside are still too cold in March for planting summer vegetables in the ground.

    - March

3. Pests and Diseases

  • Brown Rot on Apricot and Peaches -

    Brown rot apricot fruit mummy. Photo by WW. Coates, UC Cooperative Extension.If your apricots or peaches had brown flesh last year, especially in the part surrounding the pit, they were probably infected with brown rot. It's a common fungal disease of stone fruit. You can spray with a copper spray at pink bud stage. A more important means of control is to remove affected fruit as soon as you notice it. The UC Pest Note on Brown Rot has more information.

    - March
  • Camellia Petal Blight -

    Blossom damaged by camellia petal blightCamellias provide beautiful blooms in the spring. If any blossoms turn brown and mushy and fall to the ground, remove them immediately to halt the spread of a disease called petal blight. Don't put camellia leaves or petals in home compost if you plan to use that compost around your camellia plants. See UC Pest Note on Camellia Petal and Flower Blight for further information.

    - March
  • Codling Moth -

    "Worms" in your apples are actually the larval form of the codling moth. Codling moth larvae can cause a great deal of damage to apples, pears, plums and walnuts by penetrating the fruit and boring into the core.

    Trees should be monitored every week for signs of infestation. Infested fruit should be removed and discarded, to break the coddling moth life cycle. Sanitation is an important non-chemical step in controlling this pest. Make sure to pick up fallen fruit promptly, and pick apples with holes that are still on the tree. This will keep future populations down.

    Pheromone traps can be hung in isolated trees. But if you have just one apple tree don't bother. You will just attract codling moths to your tree.

    Fruit can be bagged for protection, but this is a very labor intensive method. Heavy infestations may require the use of pesticides on the moths, before fruit is affected. For more information, refer to the UC Pest Note on Codling Moths.

    - March, April, May, June, August, September, October, November
  • Integrated Pest Management and Beneficial Insects -

    UC IPM LogoOur gardens contain far more beneficial insects than pests. Any time pesticides are used, both good and bad insects die. This upsets garden ecosystems. Use of pesticides can also pollute waterways and may put our children and pets at risk, along with other environmental consequences. We can dramatically reduce pest problems by practicing  Integrated Pest Management, which includes planting native species, following good cultural practices, and encouraging beneficial insects, such as lady beetles, lacewings and soldier beetles

    - March, April, May, June, July, August, September, October
  • Rats -

    Have you found snail empty shells stashed in out of the way places, hollowed out Navel oranges, Meyer lemons with no skins, tomatoes with bite marks, fruit with holes gnawed in them or grape skins or cherry tomato skins scattered around? This could indicate the presence of rats. The UC IPM Pest Note on Rats provides a wealth of scientific information.

    Rats show up when your citrus, tomato or fruit first start to ripen. Rats are agile climbers and usually live and nest in shrubs, trees, and dense ground cover like ivy. Good sanitation is required. Garbage and garden debris should be eliminated. Use tight fitting lids on garbage cans. Thin out dense vegetation to make the habitat less desirable. Mow ivy once a year to the ground. Climbing ivies on fences or buildings should be removed.

    Trapping is the safest and easiest method for controlling rats. The simple snap trap is effective. The most important thing about trapping rats is to have lots of patience and keep trying. Wet some oatmeal enough for it to hold together, add dog or cat kibble or bits of lightly cooked bacon mixed in. Tie a walnut to the trigger and add a dab of peanut butter.

    Other baits to try are peanut butter and fresh fruit, but try to have something tied to the trigger. Set traps where rats are likely to travel or where you see droppings along fence lines or buildings. Bait the trap but do not set it for several days. Try different baits in multiple traps until you find one the rats like. Put two traps facing each other. After the rats are accustomed to being fed, then set the traps. If the rat springs the trap but doesn't get caught, move the traps to a different place and change to different baits. Rats prefer secluded spots and will be less wary there. Be sure to secure the trap with a wire or nails. Above all be patient and use multiple traps.

    - March, April, July, August, September
  • Snails and Slugs -

    Snails and slugs are patrolling your garden right now looking for new growth. Our preferred non-toxic method for dealing with them is to handpick early in the morning, or at night by flashlight. They can be saved for your friends with chickens, or crushed in place. If you do use snail bait, those made with iron phosphate are not toxic to pets and wildlife and they work well enough. For a full run-down of which management methods work, see the UC Pest Note on Snails and Slugs.

    - February, March, April, June, October
  • Weed Management -

    Whichever variation of “One year’s seeds makes seven years’ weeds” you prefer, the truth remains: a key part of weed control is not letting them go to seed. For best results, work on removing weeds before they go to seed, and when the ground is moist. Hand pulling and hoeing are effective methods for killing many common weeds. Knowing what kind of weeds you have can be helpful in choosing the best management method - to learn more, see UC's Weed Gallery for help identifying weeds and the UC Pest Note on Weed Management in Landscapes for information about control.

    - February, March, April, May, June, July

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