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. Also, refer to our list of tips useful for any month.

All data grouped by category by Months applicable : March

1. To-do

  • 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
  • Irrigation and Graywater -

    As temperatures rise, irrigation becomes more important. Container plants will begin to dry out and need to be checked every few days. Inspect irrigation systems for leaks, clogged drip emitters, misaligned sprinkler heads, and other problems which could waste water. Make sure the water is going to the root zones of the plants.

    Things to consider:

    Use a smart irrigation controller. These help adjust watering based on local conditions. Learn more about smart controllers.

    Collect water from the shower as it heats up and use it to water any plants.

    Use graywater from garage sinks and washing machines to water ornamentals and lawns. UC has a publication titled Use of Graywater in Urban Landscapes in California.

    - March, April, May, June, July, August
  • 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
  • Wet Soil -

    The clay soils which dominate our area are particularly susceptible to compaction, especially when they have received a lot of rain. These soils are characterized by small mineral particles. Hence squeezing out the air spaces makes it more difficult for plant roots and soil organisms to get the oxygen they need to flourish. Try to avoid walking on or using heavy equipment on soil that is wet. Digging in wet soil can also destroy the structure, breaking up useful soil aggregates and earthworm tunnels. Try to wait until the soil is moist, not wet or dry, for easiest tillage. If you must walk or stand on the soil, use a board to distribute your weight over a broader area. Mulch can also create a bit of a cushion and help minimize compaction.

    - February, 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
  • 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
  • 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, Any month
  • 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. 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
  • 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 Roses to Minimize Disease -

    Midas Touch rose blossomA chemical-free way to keep roses healthy and minimize disease associated with foggy summer mornings is to prune to improve air circulation. Think of your rose bushes as large vases, with open centers. Good air circulation allows the morning dew to dry, and helps prevent rust and powdery mildew. UCCE's Center for Landscape and Urban Horticulture has more info about the Fundamentals of Pruning Roses. The UC Pest Note on Roses has more about general cultural practices and weed control.

    - January, February, March, April, December
  • 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
  • Frost Dates -

    The first and last frost dates for Santa Clara County are November 15 and March 15. These 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).

     

     Also see: Frost—Avoidance and Dealing with Damage

    - January, February, March, November, December

2. What to plant

  • 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
  • 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. The Honey Bee Haven website has more resources, including a list of plants they grow.

    - March, April, May, June, September, October
  • When to Plant Cool-season Vegetables -

    In Santa Clara County, cool-season vegetables such as beets, Cool season leafy vegetablesradishes, peas, arugula, bok choy, chard, collard, lettuce, mustard greens, broccoli, cabbage, and spinach, can be planted in very early spring for early summer and harvested before they bolt (go to seed), or in late summer for harvest in winter. Use our Vegetable Planting Chart as a planting guideline.

    Cool-season vegetables grow well in temperatures ranging from 55°F to 75°F. Take a good look at your garden to determine the best areas for planting, remembering that cool-season vegetables need 6-8 hours daily of sun. 

     

    - February, March, April, September, October
  • 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
  • Starting Warm-Season Vegetables -

    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. You can successfully start some vegetables (tomatoes, peppers, eggplants) from seed for transplanting this summer season. If seed starting isn’t for you or it is too late for you to start with seeds, 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 now. Tomatoes, eggplants, and peppers are best started indoors and then planted in the ground after they are developed and sturdy. New plants and seedlings started indoors need to be hardened off. See Hardening off Seedlings before you plant them in the ground.

    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. Using a heating pad is one way that this can be done 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 with a 10% bleach solution: 1 part bleach to 9 parts water.

    If you started seeds earlier in the year and they're outgrowing their pots, March may be a good time to move them into larger pots. Don’t try to plant them outdoors until after the soil reaches 65°F for healthy growth (and nighttime temperatures over 55°F). The soil temperatures outside are still too cold in March for planting summer vegetables in the ground.

    When transplanting, be sure to read packet directions for planting depth, spacing, and sun requirements for the best results.

    - February, March, April
  • 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, October, Any month
  • 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
  • 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
  • Asian Vegetables -
    You can easily grow some vegetables used in different types of Asian cuisine and found in Asian markets. They are not necessarily native to Asia but have found their way into various cuisines. One way to decide which food to grow yourself is to choose varieties that aren't readily available or are more expensive in your local markets. It’s also fun to impress your family, friends, and neighbors with something they may not have seen growing before. Possibilities include sesame seeds, bitter melon, daikon radishes, gai choy, and opo. You can start cruciferous vegetables such as bok choy and Napa cabbage from seed now.
     
    More Information: Asian Vegetable Varieties
    - February, 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

3. Pests and Diseases

  • 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, Any month
  • 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
  • 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
  • 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
  • Weed Management -
    While some weeds are edible (purslane, nettles, dandelions), many are a nuisance and compete with your chosen plants for water and nutrients.

    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 are able to propagate. Hand pulling and hoeing are effective methods for killing many common weeds.

    It’s less important to know the names of the weeds than to know how they spread. If they propagate by seed, pull or hoe them before they flower and go to seed. If they re-grow from roots, pull up as much of the root as possible. Only non-propagating parts are advisable to throw in the compost bin.

    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, August, Any month

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