- Author: Help Desk Team
We often get questions at the help desk from local gardeners who have lost many or sometimes even all their newly planted vegetable seedlings to one malady or another. Whether you have grown them from seed and tended your precious seedlings for many weeks, or have purchased them as young plants, this can be a heart-breaking occurrence. Here are seven steps you can take to give your young plants the best chance to survive and thrive.
Be patient and wait until the soil is the optimum temperature.
This applies for both purchased plants and for home-started seedlings. Your plants may have grown large enough to go into the ground, but if the outdoor temperatures are not yet at the optimal range, don't be tempted to plant them yet! When planted in soil that is too cold, many summer vegetable plants will just not grow. They are also more susceptible to being damaged or killed by fungal diseases. How does one know if the soil is the right temperature? The best way is to use a soil thermometer. A good kitchen thermometer will also work, although you may want to have one that is designated for use only in the garden. If you don't have a thermometer, watch for daytime high temperatures to remain consistently above 60 degrees and nighttime temperatures above 50 degrees. For more information on this, you may want to review our previous blog posting published on February 20th entitled: “Indoor Seed Starting."
Cool-season vegetables such as peas, cabbage, lettuce, carrots, cauliflower, broccoli, beets, and Swiss chard will do best when average temperatures range from 55 - 75ºF. Warm-season vegetables prefer temperatures that range from 65 - 95ºF. Examples of these are eggplants, tomatoes, beans, squash, melons, and peppers. Best planting times will differ for many vegetable varieties. Check seed packets or the planting guide listed below for information on the best dates for planting in your area.
CCC Vegetable Planting Guide-Interior Regions
CCC Vegetable Planting Guide-Coastal Regions
Avoid letting plants become pot bound.
Move your plants into containers that give them more room for healthy root growth. Transplanting into 4-inch, quart, and even gallon sizes is often necessary. Use a good quality soilless potting mix and avoid planting mixes and garden soil. To check if your plant needs a larger pot, gently tap the sides of the container it is in and carefully slide it out (soil, roots, and all) to look at the root growth. Transplant into larger containers before the roots begin to circle the edge of the soil, create a mat of roots at the bottom of the container, or grow out of the drain holes. Pot bound, stressed plants will often have early flower and fruit development. This can stunt their growth and impact the plant's health as well as reducing future harvests.
Harden off young plants to prepare them for their life outdoors.
Sunscald is a common problem in young plants and seedlings that have suddenly received more sunlight than they were previously accustomed to getting. Sunscald causes areas on the leaf to dry out and die, turning thin and papery and a white or light tan color. Most seedlings will bounce back from a moderate amount of sunscald damage and continue to grow new, healthy leaves. When the damage is so extensive that all or nearly all the leaf surfaces or areas of the stem are affected, the plant may not be able to survive.
To avoid this problem, plants must be hardened off. This is a process used to acclimate young plants and seedlings to the conditions outdoors. For seedlings that have been grown in a greenhouse, indoors under lights, or other protected environment, this is a crucial step. The hardening off process will take about 10 days to two weeks. Here is an excellent article from Penn State Extension with step-by-step instructions on how to harden off plants.
Keep your plants safe from hungry pests- snails, slugs, earwigs, and birds.
Even the most experienced gardeners will lose some of their young vegetable plants to one or more hungry garden pests. My first suggestion is to always have a few extra plants to replace those that may get eaten. My second is if you have had problems in the past with one or more pests consuming your vegetable seedlings, start taking steps to control them before you plant. Don't wait until the damage is already done. The methods of controlling many of the pests are similar and include keeping your garden free of plant debris and favored hiding places, trapping, barriers, and baits. Baits that are safe for children, pets, and wildlife are available to the homeowner, and are very effective. Because they can take several days to take effect, it is best to use them in conjunction with the other suggested control methods. The best time to start using these control methods is several days to one week before planting.
Birds can also be a serious pest in the vegetable garden- especially early in the season as many vegetable starts are a favorite food. While there are many products advertised to scare birds away and keep them from eating your plants, bird netting is the solution that I find to be most effective. Make sure that the netting is raised above the plants to keep birds from reaching through to eat, and securely staked to the ground so that they cannot get underneath. Check your netting regularly, keep netting stretched snugly over supports, and avoid any loose ends that can trap and kill birds, lizards, and other wildlife. As plants mature, they are less attractive to the birds, and netting can often be removed. See one of our earlier blogs for more information on protecting your plants from a variety of pests: https://ucanr.edu/blogs/CCMGBlog/index.cfm?tagname=birds
Space requirements for healthy vegetable plants
Before planting it is important to consider the mature size of the plants, and the space necessary for them to grow and flourish. Vegetable plants do not do well in overcrowded situations where they need to compete for nutrients, water, and sunlight. They will tend to be stunted and much less productive than those that have plenty of room. For information on space requirements for a variety of vegetable plants, click here: https://ucanr.edu/sites/MarinMG/files/343708.pdf.
Transplanting tips, suggestions
If transplanting from flats with several plants growing in them, be sure to take up some soil with each plant as you carefully remove each one from the flat. If transplanting single plants from individual containers, try to remove them from the container with the soil as intact as possible to avoid root damage. This will be much easier to do if the plants have been watered recently and the soil in the container is well moistened. Choose a cool, cloudy day to transplant or wait until late in the day when the sun is low in the sky. Don't forget to thoroughly water your plants immediately after planting. If you have questions about the best way to handle and transplant seedlings, see this video from the Master Gardener Program of San Luis Obispo County:
Give your plants some shade after planting in the garden.
It is difficult to completely avoid damaging a plant's root hairs when transplanting. Root hairs are necessary to take up water and nutrients. Giving your plants some shade in the hottest part of the day for the first 5–7 days after transplanting will help keep them cooler while they regrow their root hairs. Garden shade structures do not have to be complicated and can either be purchased or made at home with items you may already have. Shade cloth, or even the plant flats used for carrying pots can be used. They are easy to set up and can be used year after year. Learn more about shading your plants in this link to a previous blog post:
Be sure to look at our Master Gardener Program website to find a wide variety of useful information. Our previous blogs can also be found here: https://ccmg.ucanr.edu/
Help Desk of the UC Master Gardeners of Contra Costa County (SMH)
- Author: Help Desk Team
It is not unusual to find tomato seedlings for sale in local nurseries and big box stores as early as February or March. Don't make the mistake of rushing to plant them in your garden. In our County it is much too early to put tomato seedlings in the garden, but it is the perfect time to make plans for a bumper summer crop of garden-ripened tomatoes.
When should you plan to plant tomato seedlings in the garden? The easiest way to determine when it is time to plant is to check the soil temperature. The soil should be no less than 60º Fahrenheit when you transplant tomato seedlings. When soils will reach that temperature will depend not only on the climate of the garden location but also on soil type. Sandy soils will warm sooner than clay soils, and soil or potting mixes in containers and raised beds will warm more quickly than soils of in-ground garden beds.
To check, use a thermometer—a soil or kitchen type both work--and measure the temperature at a depth of four inches below the soil surface. Check early morning when the soils are at their lowest temperature. The soil temperature will reach and maintain at least 60º F only after daytime highs are reliably in the 60's and overnight temperatures don't fall below 50º. In Contra Costa County those temperatures generally are achieved late April or early May. If you transplant seedlings by the end of May, the plants still have time to produce well.
So, you still have at least two months to get ready to plant tomato seedlings in your garden. Use that time to decide which tomato varieties you'll grow to get the best results. Two important topics to consider are identifying varieties that will grow well in your local climate and choosing varieties with resistance to diseases that may have been a problem in prior years.
If you live in a cool, foggy or windy climate, choose varieties with shorter “days to maturity”. “Days to maturity” is the estimated time the tomato variety will take to start producing harvestable tomatoes after seedling transplant to the garden. Tomatoes requiring 75 or fewer days are more likely to produce crops in cool climates than those with longer maturity. Most cherry tomato varieties need less than 75 days to start producing, and you can also find some “slicer”,” paste” and “beefsteak” tomato varieties that reach maturity in 75 or fewer days.
If you live in the hot, dry climate found in interior areas of our County, look for varieties with good heat tolerance. They may include both varieties with short days to maturity and those with longer maturities. An internet search for “tomatoes for hot, dry climates” will identify sites with lists of tomatoes well adapted to grow and produce in such conditions.
If you have had disease problems when growing tomatoes in your garden in prior years, try to determine which disease was present. These links provide information that you can use to diagnose and manage common tomato diseases and other problems: https://ipm.ucanr.edu/home-and-landscape/tomato/index.html (Managing Pest in Garden) and https://ucanr.edu/sites/ccmg/files/140320.pdf (Tomato Growing Tips).
Often disease pathogens remain in the soil long after diseased plants are removed. If you've had disease problems, grow your tomatoes in a garden bed where you haven't previously grown tomatoes or other members of the Solanaceae (nightshade) plant family such as peppers, eggplants and potatoes. If your garden area is small and you don't have a disease-free planting area, grow your tomatoes in large containers or plan to plant hybrid varieties instead of heirloom varieties.
Heirloom tomatoes are “open pollinated” varieties that are grown from seeds passed down for more than fifty years. Seeds from open pollinated varieties grow plants that are a genetic match to those of the parent plant. A shortcoming of heirloom tomatoes is that they rarely possess resistance to common tomato diseases.
Hybrid tomatoes are varieties that are created by intentionally cross-pollinating two or more tomato varieties to achieve desired characteristics which may include disease resistance. Seeds from hybrids won't produce matching tomato varieties, so don't bother to save their seeds. If you have identified a disease that has caused problems in your garden, choose tomato varieties with resistance to the disease. Seed packages and descriptions of tomatoes in seed catalogs typically include letter codes to indicate any disease and pest resistance. Common codes include:
- V: Verticillium wilt
- F: Fusarium wilt; a code such as FF or FFF indicates resistance to multiple strains
- T: Tobacco mosaic virus
- A: Alternaria
- EB: Early Blight
- LB: Late Blight
- N: Nematodes (not a disease but microscopic worms that feed on plant roots
If you don't know the disease resistance of a tomato variety you want to grow, you can likely find it on this Cornell University website:
https://www.vegetables.cornell.edu/pest-management/disease-factsheets/disease-resistant-vegetable-varieties/disease-resistant-tomato-varieties/ You may not find tomato varieties with disease resistance to all tomato diseases. For those diseases, be sure to check the UC websites referenced above for tips on managing the disease.
Once you have identified tomato varieties you would like to grow, check with your local nursery to see if it plans to carry them. If you plan to shop the Great Tomato Plant Sale (GTPS) sponsored by UC Master Gardeners of Contra Costa County, you will find a list of tomato varieties that will be available at https://ccmg.ucanr.edu/EdibleGardening/GreatTomatoPlantSale/ If you aren't sure your targeted varieties will be available locally, it's not too late to order seeds and start your own plants. It will only take about six weeks from the time you plant seeds to have seedlings ready to transplant to the garden. Stay tuned for our next blog post to get tips for caring for seedlings and transplanting them to the garden. And mark your calendars for the GTPS which will be held “in person” at the Walnut Creek Our Garden location on April 1, 2, and 3 and at the Richmond Library on April 29.
photo credit: Terry Lippert
Help Desk of the UC Master Gardeners of Contra Costa County (TKL)
- Author: Help Desk Team
A great way to get a head start on your spring and summer vegetable garden!
The seeds of many vegetable plants can be planted indoors several weeks before the usual outdoor planting date. In addition to the bonus of earlier harvest times, your young plants are protected at their most vulnerable stage from inclement weather and the hungry pests that love to feast on small, tender vegetable plants. Planting from seed also gives you access to a much wider variety of vegetables than you would get when purchasing seedlings from local nurseries or big box stores.
Most of us are not lucky enough to have a heated greenhouse or cold fame. Despite that, you can have success starting seeds indoors as long as you provide the conditions they need to germinate and grow. Here are some tips for successful indoor seed starting:
· Purchase your seeds from a trusted source. Fresher, higher quality seeds will have a higher germination rate (meaning more will sprout). Know your local climate zone and last frost dates and choose varieties that are appropriate for your area.
· Some vegetables do best when their seeds are planted directly into the garden. Peas, beans, and most root crops such as carrots, beets, and radishes are some of them. Check the information on the backs of seed packets and consult the CCC Vegetable Planting Guide below to find out which of the plants you wish to grow can be started early, and those that should be directly seeded in the garden.
· Time your seed planting. Not all vegetable plants grow at the same rate. From seeding to planting in the garden, tomato plants can take 5–8 weeks, while cucumbers or melons take 3–4 weeks. Plan your seed planting so that your plants are ready to go outside when the soil and air temperatures are sufficiently warmed up. A good rule of thumb is to wait to transplant outdoors when nighttime temperatures are consistently above 50°F. For more information on the timing of planting, check the backs of seed packets and the CCC vegetable planting guides provided below.
· Use a seed-starting mix. These mixes don't contain any actual soil, but they provide ideal conditions for sprouting seeds. Most importantly, they provide a good balance of drainage and water-holding capacity. Soilless mixes commonly contain some combination of these materials: peat moss, sphagnum moss, perlite, and vermiculite. Don't use garden soil as it doesn't drain well and may harbor plant diseases.
· Container choices. A wide variety of containers can be used- just make sure they are at least 2 inches deep. Recycled containers such as empty plastic yogurt or takeout containers work well. Make sure to poke holes in the bottom that will allow excess water to drain out. Used plastic plant pots, six-packs and flats are good choices and can be reused for many years but should be sanitized before reuse.
· Sanitizing previously planted containers. Remove all soil and debris by scraping, brushing, and rinsing. Use a solution of 9 parts water and 1 part bleach to kill any possible plant pathogens. Soak plastic and other non-porous containers in a bucket of this solution for 10 minutes. Porous containers such as terra cotta should be soaked for 3 hours to overnight. Rinse thoroughly and allow to dry before using.
· Plant seeds at the proper depth. Check the seed packet for planting depth recommendations. You don't need to be too precise, just be sure not to plant any deeper than the directions suggest. The general rule is to plant the seed two to three times as deep as the seed is wide. For example, large seeds like beans should be sown about an inch deep, and very tiny seeds should be barely covered by the soil mix. Tamp down the soil very gently after planting and water right away to thoroughly moisten the soil (until excess water runs out of the drain holes). You will not always get 100% germination, so plant a few extra seeds.
· Don't forget to label all your containers. Do this before or while you are planting your seeds. Use materials that will stand up to wet conditions. Pencil on plastic or wooden stakes will work well.
· After sowing, set the containers in a warm location. Most vegetables germinate best at temperatures between 65° and 75°F. A warm location in your home is one option. Another is to invest in an electric heat mat. They are made specifically for starting seeds and growing indoors, are an excellent way to provide consistent warmth, and will last for many seasons. Find heat mats online or at local garden shops and nurseries.
· Keep the seed-starting mix moist, but not soggy. Plant roots need both air and water. Saturated soil can cause seeds to rot and seedlings to die. Also do not allow soil to dry out. Check daily and water as needed. Clear plastic dome covers or plastic bags (be sure to keep them from touching the soil surface) can be used to help keep the soil evenly moist. Remove the covers after germination to allow for air circulation and to help avoid fungal diseases.
· As soon as seedlings emerge, make sure they get bright light. Placing them next to a sunny window is an option, but containers will need to be turned occasionally to keep the plants growing straight. Better results can be obtained by providing additional light from 40-watt cool white fluorescent tubes. Suspend the lights about 4¬–6 inches over the tops of the plants and keep them on for 14–16 hours each day. Be sure to move the lights higher as the plants grow taller.
· When the seedlings have one or two sets of true leaves, it's time to thin and transplant. If planted in individual pots, you will want to remove all but one seedling per pot. Cut or pinch extra seedlings off at the soil line. If several seeds are planted in flats or small cell packs this is the time to transplant them into larger individual pots. Four inch or quart size containers will give seedlings enough room to grow until it is time to plant in the garden.
· Begin to fertilize weekly. Plants that remain in the seed starting mix will now need added nutrients. When your seedlings have one set of true leaves (see illustration below), use a half-strength fertilizer (liquid fertilizers are easier to use and apply). Organic mixed fertilizers are a good choice. Many of them will provide a range of nutrients that include micronutrients. You may decide to transplant your seedlings into a potting mix that already contains added nutrients, in this case adding fertilizers may not be necessary.
· Be sure to see our upcoming blog posts- on March 6th the blog will provide tips for preparing to grow healthy tomatoes at home, and the March 20th post will be on transplanting your vegetable seedlings into the garden.
Illustration and photos courtesy of S. Hoyer
Vegetable planting guides:
Contra Costa County Vegetable Planting Guide-Interior Regions
Contra Costa County Vegetable Planting Guide-Coastal Regions
Climate zones and last frost dates:
Local Frost Dates for Garden Planning
More information on vegetable gardening can be found in the links below:
Vegetable Gardening Handbook for Beginners
Help Desk of the UC Master Gardeners of Contra Costa County (SMH)
- Author: Help Desk Team
If you've been frustrated when growing onions because the plants produce flower stalks instead of bulbs, it is time to try again. In our Contra Costa County climate, when onions are started in the fall, it is not unusual for them to flower the following spring. After flowering, the onion plants cannot produce a good bulb for harvest. To avoid this result, plant your onions in February.
Onions are biennial plants meaning that they should grow for two years before flowers develop to produce seeds. To understand why premature flowering occurs for onions planted in the fall in our climate, it is helpful to understand two aspects of onion growth—the requirement for long periods of daylight for bulb production and vernalization which is exposure to cold temperatures that triggers flower production.
Depending on the variety, onions need between twelve and sixteen hours of daylight to produce bulbs. Contra Costa County has twelve hours of daylight by early April and about fourteen hours and forty-five minutes of daylight by late June. Consequently, depending on the onion variety, bulbs will not start to develop until late spring or early summer.
Vernalization is a botanical process that induces a plant's flowering production to occur following exposure to cold temperatures. When onions are planted in the garden in the fall in our climate, they can mature quickly. If onion stalks have grown to at least the size of a pencil while fall temperatures remain warm and are then exposed to cold nighttime temperatures in December or January, vernalization occurs. When temperatures begin to warm in early spring, flower production is triggered. Since daylight hours are still too short to produce bulbs before flowers form, the result is an onion plant that grows flowers but will never produce a bulb.
Try planting your onions in February to avoid vernalization. In our climate, if seedlings are planted in February, they are unlikely to encounter nighttime temperatures cold enough to induce vernalization. Without vernalization, flowers will not develop prematurely and good size bulbs can develop as soon as there are sufficient daylight hours.
When starting onions in February, it is best to transplant seedlings into the garden bed rather than placing seeds directly into bed. Using seedlings makes it more likely that the plants will mature sufficiently to allow bulbs to form as soon as daylight hours are sufficiently long.
If you want to plant your own seeds, start them indoors in December so that the seedlings are ready for transplant by February. Keep in mind that onion seeds only remain fully viable for one or two years so always use fresh seeds. If you haven't yet started your own onion seedlings, look for them in local nurseries.
Avoid using onion sets if you want onion bulbs. Onion sets are small onion bulbs that grew the prior season and were harvested and allowed to dry. When you plant them, the plant that grows will be in its second year of growth and will be ready to produce flowers even without vernalization from cold temperatures.
This video produced by the UC Master Gardeners Program in Santa Clara County shows how to transplant onion seedlings into the garden and explains how to harvest the mature onion bulbs: https://www.youtube.com/watch?v=Gb1WhqtsdMI.
For additional cultural tips for onion production, see this UC website: https://ipm.ucanr.edu/home-and-landscape/onions-and-garlic/cultural-tips/index.html?src=307-pageViewHLS
This UC website will help you manage onion pests and diseases: https://ipm.ucanr.edu/home-and-landscape/onions-and-garlic/index.html
Help Desk of the UC Master Gardeners of Contra Costa County (TKL)
- Author: Help Desk Team
Are you noticing that the leaves on your citrus trees are looking yellow, and wondering if now is the time to fertilize? We have some answers for you.
Should You Fertilize Now?
First of all, don't be too worried about the yellow leaves. The yellowing, especially the yellowing of the leaf veins, is related to a lack of nitrogen. Citrus leaves are frequently yellow in the winter due to the trees' inability to take up nitrogen in cold weather. But now, as the days get longer and the soil begins to warm, the trees are getting ready to pick up nitrogen from the soil which means we are getting closer to the start of the citrus tree fertilization process.
Citrus trees are typically fertilized at three points in the year. The first is in January or February just before the trees begin to bloom. Exactly when will depend on your microclimate and the trees' readiness. Given the climate differences In Contra Costa County, in west county, you may need to apply the first fertilizer in late January, while the trees in central and east county may not be ready until mid- to late-February.
The next application time is in May, with a third application in June if necessary. And that is it for the season. Avoid fertilizing any later in the year, since late-season fertilization can have adverse effects on the fruits, including reduced fruit quality, delayed fruit coloring, and rough rinds. Late-season fertilization can also cause off-season growth making the trees more susceptible to diseases, disorders, and pests. Frost damage and leaf miner infestations are two common problems with late-season fertilization.
What Kind of Fertilizer Should You Apply?
Nitrogen is the main nutrient that you need to provide. Contra Costa soils are typically deficient in nitrogen and citrus trees are heavy nitrogen users. There are many sources of nitrogen. An easy choice for the home gardener is an organic citrus fertilizer. Fertilizers are labeled with three numbers on the front of the package, indicating percentages of N (nitrogen), P (phosphorous) and K (potassium). Look for a fertilizer where the first number (nitrogen) is the highest of the three, e.g., 7-3-3.
Citrus can also suffer from micronutrient deficiencies including zinc or iron. Most organic fertilizers contain these micronutrients, but if the leaves on your citrus have yellow patches between green veins you may need to correct these deficiencies by applying a foliar application of a liquid chelated micronutrient solution as the new growth emerges in the spring.
You can check here on the signs of different nutrient deficiencies to get an idea of what you are dealing with: https://ipm.ucanr.edu/PMG/C107/m107bpleaftwigdis.html
No matter which product you are applying, make sure that you carefully follow all label directions on the amounts and timing of the fertilizer application. Avoid over fertilizing which can cause excessive new growth, making the trees susceptible to other disorders such as bacterial blast.
Micronutrient deficiencies can also occur if the soil is too acidic or too alkaline. Citrus trees can tolerate a pH in the range of 6.0-7.5, with 6.5 being optimum. Contra Costa soils tend to be on the higher, alkaline side. If you have taken the actions above and are still not seeing the results you want, a soil pH test may be your next step. You can use an off-the-shelf home soil test kit or send a soil sample to a commercial soil test company.
How Should You Apply the Fertilizer?
The fertilizer should be scattered evenly on the soil under the tree's canopy. Make sure that you distribute the fertilizer at least as far out as the drip line. Avoid the area near the trunk. Lightly scratch the fertilizer into the surface of the soil and then irrigate.
For more information on citrus fertilization, including guidelines on the amount of nitrogen needed based on the age of the tree, see: https://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/citfertilization.html
For a full set of tips on growing citrus, see: http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/citrus.html
We wish you the best with your citrus trees. Proper fertilization and care should provide you with healthy trees and tasty fruit.
Help Desk of the UC Master Gardener Program of Contra Costa County (ECS)