- 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
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: Janet Hartin
European Flower Boxes Provide Beauty and a Welcoming Ambiance. Many European countries pride themselves on colorful displays of geraniums, ivy, and other flowers adorning window planters of hotels, restaurants, and even train stations. I had always marveled at their use, particularly by Austrians and Germans whose love of these colorful planters seems equal to their affinity for weiner schnitzel. What a surprise to find them plentiful in Ireland, as well! As I walked through Dublin (Read More) the last few days I noted the great care that both shopkeepers and plant care companies exercise in tending these lovely and delicate works of art. I walked by the same restaurant one morning and again in the late afternoon to find the same two horticulturists tediously fussing over a dozen or so planters sporting bright hues of blues, yellows, and reds with over twelve varieties of annuals. With plentiful natural rainfall, most are not on irrigation systems which reduces maintenance costs and time. I asked ‘Carol' (one of the crew) what she liked most about her job and she quickly answered “seeing smiles on so many faces from just seeing the flowers”. Well said! I hope these photos help brighten your day as well.
- Select a location where you can truly enjoy the fruits of your labor.
- Select a box that has drainage holes and line wooden boxes with plastic (punch holes to match drainage holes) to prevent chemical leakage from certain types of wood.
- Draw a rough sketch of what you hope your final box will resemble once mature.
- Select annuals that won't outgrow the space and that tolerate the sunny or shady microclimate and that require similar amounts of water (eases hand-watering).
- Select plants with a wide array of colors and forms. Adding trailing varieties with upright plants enhances the beauty and adds interest.
- Fill the planter box half-way with loose garden soil or compost. An alternative is to use potting soil. Avoid heavy soils with poor drainage. Moisten the soil until it resembles a well rung-out sponge.
- Take one last look before you plant by carefully setting your plants on top of the soil. Consider the final size of the mature plants to avoid overplanting.
- Once you're satisfied with your design, plant your selections at the same depth they were in their pots, gently tamping the soil around them for support.
- Thoroughly water the plants, making sure water drains through the holes.
- Water as often as needed the first few weeks after planting since container boxes dry out faster than garden plants. The frequency of irrigation can decrease as plants mature.
- Hand-weed and apply fertilizer as needed.
By T. Eric Nightingale, U.C. Master Gardener of Napa County
Gardening and a love for nature is on the rise these days. Many people I know would like to garden more but believe they can't because they live in an apartment or have only a small yard. That's not so. While they may not be able to have massive oaks or cultivate long rows of tomatoes, there are still many ways to grow plants.
The first task in any small space, be it a balcony or yard, is to understand the microclimate. Small yards are often protected from the elements by overhanging roofs and fences, while balconies may be more exposed to wind and rain. Study where sunlight hits your growing space. Spend a day at home watching the patterns of sun and shade as the day progresses.
Even if you have only a small yard, you can increase your growing capacity by using containers. Because they're mobile, you can “go vertical” and put them on shelving or place them in spots that would normally be impractical as a growing space. Think creatively
about where your containers can go.
Most plants, properly cared for, will do well in a container for a while at least, but they may require extra attention to keep them healthy. From personal experience, I recommend firm resolve and objectivity during the plant-selection phase. It can be easy to talk yourself into attempting to grow a cactus on a shady patio or a fern on a baking-hot balcony. In the end, both you and the plant will be unhappy with the situation.
When planting in containers, choose an appropriate potting mix. Soil pulled from your yard or garden will likely be too dense. Commercial potting mixes contain perlite and other porous ingredients that enhance aeration and drainage. If you fill a container with garden soil, the soil will settle over time and become compacted, eliminating pore space.
I have seen container gardens that incorporate old charcoal grills, rubber boots, teapots, pasta colanders and paint buckets. If it can hold soil and you can make a hole in the bottom, it can be a planter. For food production, look for food-safe containers. Certain plastics, metals and even woods may leach small amounts of chemicals. This may not be a problem with an ornamental plant, but it is undesirable for edibles. Otherwise, you are limited only by your imagination. Of course, no one will criticize you for just using terra cotta pots.
Compared to in-ground gardening, container gardening presents a few unique challenges, Plants in containers tend to need more frequent watering. Extreme weather conditions also take more of a toll. Plants in containers are more exposed and can't rely on the warmth and water reserves that soil-grown plants can access. In winter I move most of my potted plants against the house to a provide a little more shelter and warmth. Keeping them well watered and covered with frost cloth is also important during harsh winter nights.
One aspect of container planting that caught me by surprise is the issue of water quality. Over time, minerals in the water build up in the soil, sometimes to excess. This buildup is more likely when a plant is not getting thorough watering. To prevent the buildup, deep-water container plants occasionally, watching for water to flow from the bottom of the pot. This tactic will help flush out excess salts and minerals.
If you have a garden hose fed by an in-home filtration system, you may not experience mineral buildup. But if you are using softened water, you may have more problems than expected. Water softeners add salts, which quickly affect plants. One sign of excess salts and minerals in a container is a whitish crust on the soil surface.
I see this buildup in my houseplants, which are lightly watered and never exposed to rain. Poor plant health also signals soil problems. Excess salts can cause a pH imbalance, which can keep the plant from absorbing nutrients. Adding fertilizers, which contain salts, may only make the problem worse. In fact, fertilizer can also build up in containers and should be occasionally flushed as well.
Container gardening offers flexibility and the potential for creativity. It's a hobby anyone can enjoy.
Workshop: Napa County Master Gardeners will hold a workshop on “Culinary Herbs and Cocktail Garnishes” on Saturday, June 23, from 9:30 a.m. to 11:30 a.m., at Central Valley Hardware, 1100 Vintage Avenue, St. Helena. The workshop will be repeated on Sunday, June 24, from 1 p.m. to 3 p.m., at Yountville Community Center, 6516 Washington Street, Yountville. Plant a plethora of herbs to add color and delight to your plate and to your beverages. Cilantro, basils, thymes, mints and their flowers, nasturtiums, roses, pansies, borage and calendula are only the beginning. Learn to grow these useful plants. Demonstrations and hands-on activities add to the fun. Online registration (credit card only); Mail-in/Walk-in registration (check only or drop off cash payment). To register for the Yountville workshop, call the Parks & Recreation Department at 707-944-8712 or register online.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
No, wait, I didn't mean it like that. Well, yes it's true that I'm not a big fan of complaining. But I'm all about being resourceful. So your patio isn't big enough. Or maybe you just overplanted your spacious veggie beds. And just before snap pea season! Either way, there's still hope. Beyond saving space, growing veggies vertically has many advantages. In addition to using less square footage, plants grown vertically benefit from much better air circulation which can result in fewer pests and less disease.
I saw you look over at your big blank fence. Nothing going on there. You're thinking about it, aren't you? With sturdy 8- or 10-gauge wire and some eye hooks, you can get anything from grapes to blackberries to transform that otherwise strictly utilitarian space. Pick a wire size that is strong but flexible enough for your own hand strength. Feeling like putting down roots? That big strong arbor over your back deck looks pretty bare.
If wrangling with rolls of wire is not your thing, you can try hog panels. Also known as cattle panels or feedlot panels. No matter what you call them, don't let the uninspiring terms dissuade you. Attach a few of these 5' x 7' wire sections to your fence and watch the (insert skyward climbing plant here) take off! If properly secured, these panels will provide plenty of support for just about any plant. Or perhaps you're not looking for a permanent installation. In that case, a roll of garden twine will come in handy. Lightly tap in a few nails at the top and bottom of the fence, spaced six to twelve inches apart, then run regular old garden twine up and down between the two rows of nails. Beans, peas and cucumbers will grow skyward for easy harvesting.
If you garden in containers, there is no shortage of compact trellis options that will fit perfectly inside a pot. From fancy wrought iron to practical, inexpensive wooden lattice, your local nursery will have something for all your vertically-growing veggies. Or you can go minimalist with a few bamboo stakes and some twine.
From lightweight beans and peas to the heavyweight class (sorry, the Olympics are on after all) --wisteria, grapes, kiwi and climbing roses—growing plants vertically is a sure way to add height, color and even privacy to your garden.
So no more whining about your lack of space. Grow up already!
by UC Master Gardener Cayce Hill
This article first appeared in the August 16 issue of the Morgan Hill Times.
Food Day is a nationwide celebration and a movement for healthy, affordable and sustainable food. This year the focus of Food Day in Napa County is food education, and the U.C. Master Gardeners of Napa County will once again participate.
On Saturday, October 25, from 8:00 a.m. until 12:30 p.m., we will be joining many other nonprofit organizations at the Napa Farmers' Market for a health and wellness fair. Exhibitors will showcase the importance of fresh, local and sustainable food production and consumption; offer local resources related to health and wellness; and provide information on sustainable farming.
Napa County residents are probably most familiar with Master Gardeners through our help desks, workshops, tomato sales and garden tours, but we also offer many programs that support the objectives of Food Day. Several of our workshops focus on growing your own food, from citrus to berries to vegetables. Last year, we started a School Garden Task Force to assist schools in developing and maintaining gardens that will provide healthy learning environments.
This year at Food Day the Master Gardeners will focus on edible gardening. Most people have some idea about how to grow food in the ground, but did you know you can grow many edibles in a container or a bale of straw? If you have a spot that receives at least six hours of direct sunlight each day, you can grow food in a container.
The container doesn't have to be anything special. It just needs to be large enough to accommodate the roots of whatever you want to grow. It also needs to have adequate drainage so that water does not accumulate at the bottom.
Many people in Napa Valley use old wine barrels cut in half to create a container garden. I have used old recycling bins. They make great container gardens as they are the right size and already have drainage holes. If you have an old wheel barrow you are no longer using, consider turning it into a container garden. After you drill a few holes for drainage, it will be ready to plant. The big advantage of a wheel barrow is that it can be moved to follow the sun.
Another option for people with limited space is straw bale gardening. All you need is a bale of straw, which costs less than $10. In summer, a bale will accommodate two or three tomato plants or the same number of zucchini. You can also grow beans, cucumbers and eggplant in straw bales. In the cooler months, you can grow lettuce, kale, chard or whatever leafy greens appeal to you.
Keep in mind that straw bales require three to four weeks of conditioning before planting. To condition them, keep the bales moist, add fertilizer and wait for decomposition to commence.
If I have piqued your curiosity, then come see the Master Gardeners at the Napa Farmers' Market on Saturday, October 25. We'll show you how you can grow food for your table in less space than you ever imagined. We'll also supply you with a complimentary package of carrot seeds so that you can get your edible garden off to a healthy start.
Workshop: Napa County Master Gardeners will lead a workshop titled “Be Successful with Citrus” on Saturday, October 18, from 9:30 a.m. to 11:30 a.m., at the Calistoga Community Center, 1307 Washington Street, Calistoga. This workshop will give you all the tools to be successful with your new or mature citrus trees. Learn about choosing varieties, planting, fertilization, and seasonal care including frost protection. Online registration (credit card only); Mail-in registration (cash or check only).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners (http://ucanr.org/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.