By Deborah Pilkington, NC State Extension Master GardenerSM volunteer of Durham County
Container gardeners, me included, give a lot of thought to choosing which plants will go into the containers. But not a lot of thought is given to the containers themselves. Yet, to have a successful container garden in full sun, shade, or anywhere in between, the choice of pot is as important as the choice of plant. So, for the next few minutes, we’re going to look at factors that should be considered for container choices, especially in our newly-designated hardiness zone 8.
Porosity
Examples of porous pots. (Image credit: Deborah Pilkington)
Some containers, such as the familiar terra cotta (“baked earth” in Italian) are very porous, meaning the pot draws water from the potting media through its walls. Other porous materials include hypertufa, unglazed ceramic, and clay. Because of this, these porous pots may require more frequent watering, something to think about if they are going to be in full sun. Less porous choices would be wood or concrete, and the least porous pots are made of metal, fiberglass, plastic, or glazed ceramic. That means they are going to help the potting mix conserve water.
Size
The smaller the pot size, the more frequently it will need to be watered, sometimes more than once a day. A larger container is going to be heavier and less likely to tip over. Larger containers will require less frequent watering but can be a bear to move from location to location…unless you own one of these (see the photo below). And the cost of filling the container with potting mix is also a consideration.
The difficulty of moving very large pots! (Image credit: Deborah Pilkington)
Fragility
If a container is fragile and susceptible to cracking in cold temperatures, it will need to be moved to a sheltered area for winter. Terra cotta, clay, unglazed ceramic, and hypertufa are all fragile materials. The sturdiest are metal, plastic, concrete and wood.
Heat Holders
Metal containers, and dark-colored containers are heat holders in full sun. They can even be hot to the touch! Potting mix in these containers can rise to well over 100°F. Keeping roots well-watered, unless you are growing cactus, is a must.
Shape
If you are going to grow a shrub or tree in a container, at some point the plant will need to be lifted from the container to be root pruned—an onerous but necessary task. So, for shrubs or trees you want to choose a container that is wider at the top (below on the right) rather than narrower (below on the left) to make lifting easier.
(Left) This container is more narrow at the top and would make it difficult to remove a shrub that had grown in the pot. (Right) In contrast, this pot is wider at the top than the bottom and it would be easier to remove a shrub that had been grown in the pot. (Image credit: Deborah Pilkington)
Drainage
Good drainage is a must in container gardening. If the container doesn’t have drainage holes, you can add them using a drill and the appropriate drill bit. And to ensure correct drainage, don’t put anything in the bottom of your container but soil mix. Adding gravel or covering the hole with broken terra cotta not only defeats the purpose of ensuring drainage, but it also raises the level of the perched water table, moving the level of saturated soil even higher in the container and closer to the roots.
Drilling holes in metal containers at Cocoa Cinnamon Demo Garden on Geer Street. (Image credit: Deborah Pilkington)
For gardeners with limited space, especially the newcomers to Durham’s condominiums and apartments with balconies, container gardening can bring some beauty and food to your home. For urban container gardening inspiration, visit the International Award-Winning Master GardenerSM Container Demonstration Garden at Cocoa Cinnamon at Foster and Geer streets in Durham.
Get more ideas on container gardening by visiting the Cocoa Cinnamon Demonstration Garden at 420 West Geer Street in Durham, NC. (Image credit: Deborah Pilkington)
Resources and Additional Information
Check out the links below to learn more about plant hardiness zones including the history and factors used to determine the hardiness zone of an area. What does this really mean for North Carolina gardeners?
By Gary Crispell, NC State Extension Master GardenerSM volunteer of Durham County
OMG! Was February wild or what? It was consistent in its inconsistency and that’s about all there is to that. Don’t look now, but it is March. Not the parade kind of march with bands and floats and stuff. March as in “Look at all the green things coming up in the garden!” That March. The garden wakes up in March and stretches like a dog after a nap.
Pansies provide a reliable punch of late-winter and early-spring color in your containers and landscapes. (Image credit: Gary Crispell)
The Accidental Cottage Garden (ACG) is still hibernating for the most part. There are some grape hyacinths (Muscari armeniacum) in bloom, and the saucer magnolia (M. soulangeana) is opening just in time to get frosted. We’ve been here six years now, and we got to enjoy that tree in full flower once. It would really prefer to be in Wilmington, but the bus ticket is too expensive. We must depend on the pansies (Viola x wittrockiana) on the deck for floral color outside right now. But not for long. There are truck loads of perennial rosettes out there. It will be a grand adventure seeing who has returned and who was just resting preparing to show off.
(Left to right) Although the ACG is still sleeping, the saucer magnolia (M. soulangeana) and grape hyacinths (Muscari armeniacum) are erupting with color, and tiny green basal rosettes are peeking out from the soil and promising more spring flowers to come. (Image credit: Gary Crispell)
We have attained meteorological spring, so get out those garden gloves and hat. Locate the sunscreen just in case, and don’t forget the liniment and heating pad and ice packs. Just being real here. Let’s go work in the garden before the insects wake up.
Lawn Care
It is time to fertilize cool season grasses (tall fescue, bluegrass, perennial rye). A slow-release high nitrogen (the “N” /first number on the bag) fertilizer will give you the greenest lawn into the summer. These grasses typically want to go dormant in the heat of summer (July and August), so unless you want to water them a lot during that time, this will be the last time to fertilize them until late August/early September.
(Left to right) Images of large crabgrass (Digitaria sanguinalis) and smooth crabgrass, (Digitaria ischmaemum) which typically germinate March through May in North Carolina once soil temperatures rise to 53-58 degrees. (Image credit: NC State University Turf Files)
Preemergent crabgrass control should be applied between the time the forsythia (Forsythia intermedia) bloom and the time the native dogwoods (Cornus florida) bloom. Later than that and the soil temperature will be warm enough that the crabgrass will have already germinated. Mowing can commence whenever it seems appropriate. You know, like when the lawn looks raggedy and the soil is dry enough that the mower won’t leave ruts. Mow to a height of 3” to 4.” That height allows the grass blades to shade the soil (read root zone) and protect it from the heat of summer. It also helps weed control by preventing enough sunlight for weed germination and growth. Win, win. Let the clippings return to the ground unless they are too long (Waited a bit between mowings, did we?) or wet and clumping (and we are mowing the grass when it’s wet, why?). Clippings do not belong in the landfill. If leaving them on the ground isn’t an option use them in the compost pile or as mulch.
Fertilization
(Other than the lawn): Green things that can be fertilized this month include shade trees, shrubs, and spring-flowering bulbs. Green things that should not be fertilized this month include St. Patrick’s Day revelers and leprechauns. Moderation is the key here. (Take note revelers.) Asparagus beds should be fertilized early in March before the new spears appear. Work some fertilizer into the veggie garden bed(s). Lime may also be worked in now if your Soil Test so indicated. It will take 3 to 6 months for the calcium to become available to the plants, but that should be just in time for the June tomatoes and great timing for the fall garden. Besides, if you don’t do it now, when will you do it? (Note: While there is no time like the present to remind you of the importance of testing your soil, please note that soil testing at no charge begins April 1 and runs through the end of November.)
Planting
All the things you didn’t get around to planting in the fall (Life got in the way, right?) can be planted now, and sooner than later. Just be cognizant of the fact that they will probably have greater water needs through the summer than anything planted in the fall. Fall planted material has all winter to establish a root system strong enough to carry it through less than severe droughts. (I know. There are exceptions, but there are always exceptions. Take the aforementioned revelers and leprechauns, for example.)
Other things to be planted this month include perennials, for example coreopsis (C. bipinnata, C. lanceolata), foxglove (Digitalis purpurea), purple coneflower (Echinacea purpurea), balloon flower (Platycodon grandiflorus), etc., and roses (Rosa sps.) While you have the trowel in hand, might as well hit the vegetable garden. The same things that could be planted in late February can still be planted now. We’re talking root veggies (beets, carrots, potatoes, turnips, etc.) and salad greens (leaf lettuces, cabbages, kale, etc.). There is still time to start annuals and warm season vegetables inside for transplanting in April or May.
Pruning
(Left to right) When new buds begin to swell in the early spring on roses, it’s time to prune certain types. As a general rule, prune canes on rose bushes toward an outward facing bud and to a 5-leaflet leaf. (Image credit: Illinois Extension)
Be advised, finish any fruit tree pruning ASAP. Prune some types of roses mid to late March.1 (As an aside, now that we have been bumped up a USDA zone to 8, that timeline may need revising to an earlier date. I’ll research that for next year, so stay tuned.) Prune roses to a 5-leaflet leaf if those are visible. Otherwise prune the cane to an outward facing bud. Prune spring-flowering shrubs soon after the blooms fade.2 Dead head (pick off spent blossoms) on pansies (Viola x wittrockiana) to prolong bloom time.
Spraying
Break out the sprayers! However, before using said sprayers check the plants for pests. With few exceptions (There they are again and we’ll get to them yet again in a minute), prophylactic pesticide application is unwarranted. Always know what it is you are trying to control so that you can use the appropriate product. ALWAYS read the label and ALWAYS follow the instructions thereon. Applying a horticultural dormant oil to fruit trees, particularly those that have recently been pruned, will help control several insect problems. (I told you we’d see exceptions again.)
More Things to do when the Weather is Highly Unpredictable
Get all the soon-to-be-needed gardening equipment ready for use. If it is supposed to be sharp, sharpen it. If it needs calibrating (sprayers and spreaders), calibrate it. If it has moving parts, lubricate them. If it has a four stroke motor, change the oil and filter.
Plant a tree for Arbor Day. Here in North Carolina that is March 22nd this year. It is always the first Friday after the 15th. There will be several city, county, and state-sponsored events that will be posted on the various websites after March 1.
In all things gardening, have fun. If it isn’t fun, hire it out or plant something that doesn’t require the burdensome task you deplore. Gardening should be fun, relaxing, therapeutic even.
1–Make sure you take note of the type of rose you are pruning. Certain types of roses that bloom only once in the spring such as “old-fashioned” roses and climbing varieties (like ‘Yellow Lady Banks’) should only be pruned immediately after flowering as they flower on last season’s woody growth. Prune before spring flowering and you will prune away all the flowers for the season. Some roses take a few seasons before they need a good pruning, and some varieties tolerate more severe pruning than others. If unsure what type of roses you have, research before you prune! See the factsheet on roses below for guidance.
2–If you need additional information on appropriate pruning times, NC Cooperative Extension’s pruning calendar offers some helpful tips. https://polk.ces.ncsu.edu/pruningcalendar/.
Resources and Additional Information
Clemson Cooperative Extension’s Home and Garden Information Center factsheet on pansies, violas, and panolas is a helpful guide for planting and care of these cold-hardy annuals.
Take a deeper dive into the art and science of pruning woody plants on University of Georgia and Clemson Cooperative Extension’ s Home and Information Garden Center’s extension websites.
To understand soil and plant nutrients and the role of fertilization when needed, the online NC State Extension Gardener Handbook dedicates and entire chapter to the subject.
The timing of hydrangea pruning can be tricky, as it depends on what type of hydrangea(s) you have in your landscape. Visit one of our previous blog posts for more information on when to prune.
