- Author: Judy Quan
Container gardening is enticing. We love the option to grow plants where space and sunlight might otherwise limit our choices. Most perennials, shrubs and trees are better off planted in the ground, but, with care, we can maintain our larger woody plants in containers.
Container plants need more monitoring
We must carefully monitor and nurture our container plants since nutrients and water are confined to what is available in the container. Woody plants such as trees and shrubs need larger containers and more care over the years since they have larger root systems than most annuals and perennials.
The importance of repotting
The periodic repotting of container plants is an important aspect of care that is often neglected. Over time, as plants mature, plants naturally produce more leaves above ground and more roots below ground. Most container plants tend to become root-bound, meaning the roots outgrow the container, and the roots overlap each other, often circling the bottom of the container and growing back up its sides. Being root-bound results in stunted growth and poor plant health. The organic portion of the potting soil slowly decomposes over time and compacts, losing pore space, air space and drainage space.
When to repot
Generally, containers should be repotted every two to three years.
Signs that indicate the need for repotting:
- Surface/drainage hole roots
- Sunken soil level
- Plant seems too big for pot
- Discolored or yellowing leaves
- Frequent wilting
Container selection and preparation
It is important to have the right size container. You need enough space for roots, and enough room for soil for hydration, thermal insulation and fertility.
Managing large containers
Selection of container, usually you need half wine barrel size to accommodate a larger plant like a tree or a shrub. TIP: Having a plant caddy with quality wheels that turn easily can make the job of moving the barrel and the plant ball much easier. There are plant caddies that are built to deal with the weight of a fully loaded half barrel filled with potting soil and a tree or shrub. Plant caddies are also helpful to monitor drainage.
Adequate drainage
Make sure that there are adequate drainage holes in the bottom of the container. No need to add rocks or gravel as they can interfere with proper drainage and take valuable depth from soil. To stop soil from leaking out, a mesh screen works well. Avoid sealing the hole.
Plan to elevate the wine barrel to provide air space so that wood will have a chance to dry out underneath.
Potting soil (not garden soil) and potting soil mix recipes
Plants in containers do not do well using ordinary garden soil, especially clay soil; they need a more porous soil mixture to thrive.
If you are buying potting soil, remember you get what you pay for. Consider getting potting soil from your local nursery. Another way to get quality potting is to mix your own. Here are links to some recipes: Soil Mixes for Container Gardening by UC Master Gardeners of Napa County
It is good practice to refresh containers with additional new potting soil or to replace all the potting soil with new potting soil. Prepare the potting soil that you are planning to use. If you are using old and new potting soil, mix the two. If you add compost, mix well with the potting soil. Never exceed 1/3 of the mix when adding compost.
Fertilizer
Mix in some slow-release 16-16-16 fertilizer. The slow release is recommended since plants in containers need to be watered more frequently than those in the ground, and nutrients are lost as the water drains out of the container.
During the growing season, apply a water-soluble fertilizer every 2 to 3 weeks, supplementing the slow-release fertilizer.
Whatever fertilizer you use, be sure to follow the directions on the label.
Getting the plant out of the container easily and safely
Break down sides of a worn-out wooden barrel by tapping on metal rings and they should just drop down allowing you to take out the wooden slats, exposing the root ball.
Readying plant for transplanting
Camellia's extremely matted roots being loosened with garden tool - photo courtesy of Judy Quan 2024
![Camellia being taken out of container and its extremely matted roots being loosened with a gardening tool. Camellia being taken out of container and its extremely matted roots being loosened with a gardening tool.](http://ucanr.edu/blogs/mgalameda/blogfiles/103795.jpg)
Inspect and trim root mats, circling roots, tangled roots
Remove any diseased or damaged roots. When the plant is out of the container, gently separate the roots.
If the plant is root-bound, slice off outer 1/2 inch of roots including soil and root mats. Trim circling roots and any roots growing upward. Make sure not to remove more than 1/3 of the roots.
Transplant plant to new container
Fill by mounding potting soil for ease in root placement
Begin filling the container with potting soil. Build a mound in the center. Roots should be placed around the outer edge in a lateral, radial, slightly downward manner.
Place the plant on top of the soil mound, arranging roots away from the stem. Try to help roots avoid circling and being tangled with one another. Spread the roots apart as much as you can.
Position root crown in new container
Identify the plant's root crown. The crown is located where the first lateral roots start to appear. Estimate the location of the crown when it is planted in the container so it is at or slightly above the soil level. Positioning the root crown is especially important for trees since below soil level placement may lead to crown rot diseases. Crown Rot in the Garden - UCANR Pest Note
Be sure to keep track of the crown and keep it above the soil level as you are adding potting soil. Avoid packing the soil down. You can gently pat the soil just enough to remove big air pockets
Next, after transplanting into container
Gently water your plant.
Check by feeling the soil to make sure that the root ball is moist. When the root ball has dried out, it may be difficult to re-wet the root ball. A very thorough soaking may be necessary more than once. When you are finished, you can add some mulch.
Re-Check Soil Moisture and Soil Level Over the Next Few Days.
Check the top 2-3 inches of potting mix in the container for moisture over the next few days since it may be drier than you anticipate. You may need to add some additional potting soil once the soil has settled more.
Schedule frequent ongoing soil moisture checks
When it is dry, the plant needs water. Plants need more frequent watering when in smaller containers, higher temperatures, higher wind, and direct sun. Mature plants are more likely to need frequent, perhaps daily, watering in warm or hot weather., especially if located near heat-retaining hardscapes such as concrete, rocks, bricks, pavers, or stone.
When repotting is NOT enough, transplant to in-ground
Sometimes we realize that our plants are not thriving in their containers, no matter what we have done, and we need to plant them in the ground. Follow the same steps of separating the roots, and cutting and removing the roots mats that are at the bottom of the container. The holes should be wider than the root ball so that the roots can radiate out. Large rooted plants should be arranged so the roots are not tangled or only on one side. Remember, however the roots are placed, that is how they stay and grow. Repotting or transplanting plants in-ground often results in happier, healthier plants.
Resources:
Container Planting by Oregon State Master Gardeners Clackamas County (PDF)
Outdoor Container Flower Gardening by UC Master Gardeners of San Joaquin
Planting Landscape Trees - UCANR (PDF)
Repot Your Plants by UC Master Gardeners of Napa County (potting soil mix recipes included)
Repotting and Fertilizing Houseplants by University of Arkansas Cooperative Extension
Repotting Basics - Tips to Ensure Vitality in Woody Contain Plants, University of Georgia
Healthy Garden Tips -- Soil Mixes for Container Gardening by UC Master Gardeners of Napa County
Tips For Beginners: How to Transplant a Container-Grown Plant, Virginia Tech
Alameda County Master Gardeners Help Desk:
This blog post is brought to you by the Help Desk of the UC Master Gardeners of Alameda County.
Have a gardening question? We'll help. You can reach us by:
- Emailing acmg@ucanr.edu. Please include a photo of the problem, if you can, plus your name, phone number, city and a description of the problem.
- Using our online form.
- By phone, during our office hours, 10 am to noon Wednesday and 11 am to 1 pm Thursday: 510-670-5645. At other times, please leave a message and we'll return your call during our office hours.
- In person at our Hayward office, during our office hours, only by appointment.
- Author: Anne E Schellman
Rho Yare will teach you everything you need to know about growing spring vegetables in containers.
How can I watch the presentation live?
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- Author: Anne E Schellman
If you've always wanted to grow vegetables, but don't have the space, this class will help you get started. You'll learn which vegetable plants grow best in containers, which size container to choose, and how to plant, care for, and harvest warm season vegetable crops. This is a great class for beginning gardeners. Attendees will receive free seeds.
To sign up for the class, please see information below. Do not post to this blog. These classes are taught by our Master Gardener Program volunteers.
Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Thank you for contacting the Help Desk of the UC Master Gardener Program of Contra Costa County. Your recent email had three related questions:
1. Growing watermelons and tomatoes in large containers…what is the best soil composition for successful growth?
2. What type of soil is best for your tomatoes that will be grown in wine barrels in 8 hours of hot sun?
3. Your compost material has lots of worms in it. The compost will be mixed into a wine barrel in the hot sun. How can you keep the worms alive and well in wine barrels planters in full sun?
Here are some additional thoughts about each approach as well as some notes on the benefits and disadvantages of each approach.
Soil, sand, compost and coconut coir. If you use this approach, it would be best to use a loamy garden soil. Silty loam would be the best. Sandy loam could be used, but in that case you should use less sand in the mixture. Clay soils are generally avoided for watermelon culture because they drain poorly, but they can be productive if irrigated with care to prevent prolonged saturation of the root zone (a condition that favors the development of root rot pathogens) and to allow good drainage between irrigations. Adding plenty of organic matter (e.g., compost or coconut coir) would make both the clay and sandy soils more productive.
If you use garden soil, keep in mind that it can contain insects, weed seeds and disease organisms. For this reason, it would be best to heat the soil in an oven for 1 hour at 210°F to kill any bacteria, fungi, insects, or weed seeds before the soil is combined with the compost and sand.
This soil mixture will be heavier than the commercial potting mixture. Added weight is sometimes a disadvantage for containers. However, since the containers may become a bit top heavy if you have a good crop of large watermelons or tomatoes growing upward on a support structure, the added weight could be an advantage. If you want the planter to be lighter, you could replace the sand in the mixture with either perlite or vermiculite. Those amendments will aid in drainage just as the sand does but would produce a mixture that weighs less than one that includes sand.
Commercial Soil Mixture Combined With Compost And Coconut Coir. Usually a commercial soil mixture does not include any actual soil, but they can still provide a very good growing medium. If you use an available commercial soiless mixture, it would probably not be necessary to add either compost or coconut coir. This commercial mixture's ingredients already include compost, and the peat moss would function in much the same way as coconut coir to improve water retention. Adding compost and coconut coir wouldn't detract but would add to the cost.
One disadvantage of the mixture is that it uses peat moss which is less sustainable than the coconut coir alternative. Peat comes from very slow-growing, slow rotting plants and it typically takes 1,000 years for a bog to add 1 yard to its depth. Coconut coir is a byproduct of the coconut industry and is more easily renewed than peat.
If you want to make your own potting mixture that does not include garden soil or peat moss, you can use a combination of one-third each of compost, vermiculite or perlite and coconut coir. Measure the volume of the coconut coir only after it has been soaked in water since its volume will increase significantly once it absorbs the water. I've have been regularly growing vegetables in containers for many years and always use this potting mixture. It would work well for both the tomatoes and the watermelons.
For additional information on growing watermelons, I suggest you look over the information found at:http://anrcatalog.ucanr.edu/pdf/7213.pdf . For information about growing tomatoes in containers, see http://ccmg.ucanr.edu/files/229047.pdf.
Compost Worms In Containers. In our research, there are varying opinions about the viability of worms in containers. Considering that you mentioned having worms in your containers that will be in the hot sun for 8 hours per day, the worms would not survive in this environment. They prefer moist, cool soil which might be hard to manage in your situation. However, experimentation is always a great learning experience (although maybe not for the worms). For example, you could consider using some shade protection on very hot days. Possibly you could set it up in a way that shades the container but not the plants. Also, be sure that the soil mixture has plenty of peat and/or coconut coir to help retain water.
Thank you for contacting the Help Desk. Feel free to check back with us if you have additional questions.
Help Desk of the UC Master Gardeners Program of Contra Costa County (tkl)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/CCMGBlog/).
- Author: Carolyn Neumann
In spring, a cheerful pot of blooming tulips by the front door can snap dreary winter to a close. The bright colors and jaunty stance of springtime’s most famous flowers signal milder days ahead.
Fall is when spring blooms are planted. But why settle for just tulips, when you can also enjoy daffodils, crocus, and grape hyacinths planted in the same pot to produce three waves of bloom, brightening your spring scene for weeks and weeks on end?
The Technique
The technique is called layering or planting lasagna-style. It involves planting layers of different types of bulbs in the same pot, with the various types blooming in secession. By overlapping their bloom times you can create pots of seemingly “perpetual color” featuring double-decker and two-tone color effects.
To enjoy the dramatic display, put layered pots where you’ll see them daily: by doorways, next to the garage or driveway, by the mailbox or lamp post, along walkways or right outside your kitchen window. Spectacular!
The instructions feature crocus, daffodils, grape hyacinths and tulips as the early, mid and late blooming bulbs, but any early-mid-late combo that pleases you will work.
Color & Texture
When selecting bulbs, consider their flower color, as your Lasagna simmers from one planting to the next, having different flower colors adds a sense of “newness” as the waves of color progress. Likewise, there is delightful textural value to each plant, including flowers and leaves. As the bloom progresses, you will be left with leaves from the previous bloom. They may be fine and short like grass or long and strappy, thick and leathery. Having a variety of textures will leave your container with more interest, but also urges you to think, how could I have done this and not hidden my beautiful crocus with leathery leaves.
Planting Bulbs in Layers, Lasagna-style
For three waves of bloom, you’ll need bulbs that bloom in early-spring, mid-spring, and late-spring. Different types of flower bulbs bloom at different times. Bulb packages list this information on the labels. When making bulb selections, consider choosing bulbs with overlapping bloom times so that the planting remains colorful all season. Include grape hyacinths in the mix, for instance as they bloom for weeks on end, providing a colorful cobalt blue under-planting to mid-season daffodils, and continue to bloom in support of the late-season tulips, as well.
Minimize Cold, Wind Exposure
In choosing a pot, the larger the better so as to provide added insulation to the roots. In colder climates, freezing can be an issue so you may need to place your pot(s)in protected areas away from extreme cold and wind (against a house foundation, on a porch, or deck where they receive “radiant heat”, for instance).
Choose Early, Mid, Late Blooming Varieties
Excellent bulb choices for layering would be crocus (early-season), daffodils and grape hyacinths (mid-season), with the same grape hyacinths still there in bloom with the tulips (late season). The cobalt blue grape hyacinths (aka muscari) are the “glue” that hold this particular scheme together, by virtue of their extremely long bloom season.
Positioning the Bulbs
- Pretend you are making lasagna! You’ll plant the largest bulbs approximately 8-inches deep, smaller bulbs 5-inches deep. Potting soil provides the layer (the sauce) under and over your bulbs.
- The Sauce (potting soil) is now added, about 2”-3” deep, so when you measure from the top rim of your pot down, the potting soil level should be about 11 inches below the rim. Sprinkle on a fistful of bonemeal.
- The 1st layer will be a bulb such as a large size (king Alfred) daffodil, allium, or tulip. Place your bulbs in tight so you’ll have quite a color show. Or you can mix them up or in a pattern.
- The Sauce - Add 3” inches of soil above the first layer. Sprinkle on a fistful of bone meal.
- The 2nd Layer will be a bulb that is planted about 6” below the surface such as Dutch Hyacinth or a jonquil narcissus. Leave about ¼” between them.
- Don’t overcrowd, remember these bulbs are fairly well dehydrated and will swell once watering begins!
- The Sauce – Cover with about 1” inch of soil above the previous bulbs. Sprinkle on a fistful of bone meal.
- The 3nd Layer will finish your container off with bulbs like grape hyacinth (muscari) and/or crocus. Remember to leave a little space in between bulbs.
- The Sauce – Top off with five inches of potting soil, add some pansies or other colorful cool weather annuals.
- The Cheese- (mulch) Top dress your creation with mulch, water regularly and wait for the show.
Let the Show Begin
As spring arrives, sit back and watch the show as the waves of colorful flowers come up, bloom and move on.
As each wave blooms, then fades and dies back, that wave’s leaves will remain. Crocus leaves are attractive, slim and grass-like, just let them be. Daffodil /Jonquil leaves are also nice but you may want to snip off the faded flowers and stems to the leaves. Tulips can be the grand finale if you late blooming variety, which is a good thing as fading tulip leaves are unattractive.
Once the last ones fade, it is time to dig up the whole lot and replant everything in the yard or garden in a less-than-primetime location or just put the whole container somewhere out of sight but still being watered until foliage turns brown. Bulbs use their leaves to absorb nutrients which are stored in the bulb itself. If you cut the leaves off too soon, they will not have the energy stores to flower again next year. After all foliage is brown, it’s time for hair cut and decisions for your bulbs future. Daffodils, crocuses and grape hyacinths are bulbs that naturalize well and can be easily planted in the yard where they do not get much water. If you choose a well-drained, sunny spot to replant these bulbs, there’s a good chance they’ll come back in future years to bloom again and even multiply.
Don’t be tempted to leave the bulbs in the same big pot if summer flowers will be planted in it next. Routine watering and fertilizing for summer flowers will damage/rot bulbs. Bulbs originate from areas that have harsh winters and hot waterless summers. Better to plant them into the ground, along a path or in a bed just for bulbs, this way come fall, you can gear up, fertilize them and get them back on the road to bloom again
Fertilization
Both spring and summer bulbs need phosphorous to encourage root development. Keep in mind that phosphorous moves very little once applied to the soil. Some bulbs are planted 6 to 8 inches deep. The phosphorus needs to be mixed in the soil below where the bulbs will be located so it can be utilized by the bulb roots. Mix bone meal with the soil in the lower part of the planting bed as it is being prepared.
If bulbs are going to be maintained in a planting bed more than one year, it is important to supply additional fertilizer bone meal each autumn. Spring flowering bulbs should have mixed into the soil in the fall five tablespoons of 10-10-10 soluble fertilizer (or equivalent bulb fertilizer) plus two cups of bone meal per ten square foot area. With the arrival of new shoots in the spring, repeat the above soluble fertilizer application. Do not fertilize spring flowering bulbs after they have started flowering. This tends to encourage the development of bulb rot and sometimes shortens the life of the flowers.
Summer and fall flowering bulbs should be fertilized monthly from shoot emergence until the plants reach full flower. Apply seven tablespoons of 10-10-10 soluble fertilizer (or equivalent bulb fertilizer) split over two or three applications over a ten square foot area.
For good bud development, work bone meal into the soil at planting and check your soil ph twice a year and adjust as necessary.