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Environmental Factors and Plant Placement

Earth, air, fire, and water.  These four classical elements correspond to the four most important environmental factors we thoughtfully consider and manage in every successful landscape: soil, temperature, sun, and water. Understanding the balance of these four elements in your outdoor space will help you choose the right plants that will flourish and thrive without the need of additional water or insecticides, which is the first step in growing a sustainable garden.

Soil

Most plants do best in well-drained, evenly moist soil that is slightly acidic. Our notoriously clay-filled soil in Northern Virginia certainly meets the general need for acidity. However, in the construction of our neighborhoods, we bring the hardest clay to the top layers of the soil. As a result, to create ideal growing conditions, we amend our clay soil with organic matter. This increases drainage and moisture retention so that plants can establish roots quicker, equipping them to withstand temperature extremes as the seasons change.

You can read more about preparing soil for low maintenance gardens in my friend and colleague Nikki Norton’s post on this topic.

Temperature

Soil type is fairly uniform throughout the northern Virginia region, but air temperatures range widely. Travelling east from the Blue Ridge, through the Piedmont into the area around Falls Church, the elevation drops as the mountains give way to the coastal plain. As a result, gardeners in our region may be in one of several hardiness zones –  regions assigned by the USDA according to the average minimum temperature expected in the winter. These zones are widely used in horticulture as a guideline for choosing plants that can survive in the landscape. Higher numbered zones have warmer climates, and lower numbers have cooler climates. People living out west might be in zone 6, while people closer to Washington, DC will be closer to zone 7.

Visit the US Department of Agriculture to learn more about your neighborhood’s hardiness zone.

While our regional hardiness zones serve as a general guideline, remember that environmental factors can create warmer and cooler spaces in our gardens that enable plants to grow outside of their usual hardiness zones. For example, camellias and gardenias are rated for zones 7 and above; but anyone in the cooler end of zone 7 or zone 6 may still be able to have these beautiful plants! Plant them close to your house to protect them from winter winds. The warmer temperatures of a sheltered space next to a home is just one example of a microclimate.

Limelight Hydrangea, Shrub

Sun

Sun exposure can be the most confusing environmental aspect to understand.The light requirements found on plant labels generally fall within a recommended range that can seem vague or confusing to beginner gardeners.

To demystify these labels, here is some more information on the most common sun requirements:

  • Full sun means that an area receives 6 hours or more of direct sunlight.
  • Part sun means an area receives 2-6 hours of direct sunlight.
  • Part shade receives 2-3 hours of sun per day or less, but indicates that the sun should be dappled, or filtered through the canopy of a tree.
  • Shade is anything less than 2 hours of direct sun.

While these labels address duration of sunlight, they do not address intensity. The eastern sky provides the ideal sunlight. The less intense morning sun brings cooler temperatures, while the southern and western skies give the hottest, most intense sun of the afternoon. Delicate plants will prefer the cooler morning sun, while heat tolerant plants will do fine in hotter temperatures of southern and western exposure.

If you are not sure how much sun the area you will be planting in receives or when it will receive it, try staking a white paper plate into the ground and checking it periodically throughout the day to get an idea of how much direct sunlight is shining on the plate.

Water

Water is life, but the most important part of watering is to remember to never water a plant unless it needs it.

You can see our proper watering guidelines for more information.

Soil drainage and the amount of sun a location receives both affect the amount of water needed in an area and the types of plants that will thrive in it. Some plants are unable to tolerate poorly draining soil—which is why gardeners talk about plants not liking “wet feet.” While it is certainly possible to amend your soil to improve drainage, it may be easier to select plants which can handle that soil type. Sweetbay Magnolia or Inkberry holly are great choices.

If you have questions, come see us!

Understanding the basic conditions that affect plant health is the first step toward growing a sustainable, low-maintenance garden. A happy plant is a healthy plant, so it is important to know the balance of these elements in your own garden so your plants will thrive. As always, our experts at Merrifield Garden Center are always here to help you make the wisest plant selections for your garden.

Back to Basics: Houseplants

Paul Knight, Merrifield Plant Specialist

Growing houseplants is a fun and rewarding hobby that can truly enhance your interior spaces. Houseplants naturally soften the straight lines and hard edges of furniture, cabinetry and other architectural elements, and make your home healthier by absorbing carbon dioxide and providing clean oxygen in exchange.

For many, the idea of growing plants inside the home may seem like an intimidating endeavor. But once you understand a plant’s ideal growing conditions, you will be able to easily enjoy plants that otherwise wouldn’t be able to survive in our area.

There are two important factors to consider when selecting a tropical houseplant: light requirements and moisture preferences. Understanding the light requirements will ensure you choose a plant that will thrive in your location. Understanding the moisture preferences will help you select a plant you can monitor and water regularly.

Light

Just like outdoor plants, light is the most important factor to consider when choosing where indoor plants can grow. Different areas of your home will have different levels of light intensity, depending on the number of windows and the directional exposure of those windows (north, south, east or west). Indoor plants typically require one of the following light levels.

Direct Light: Two to five hours of direct sun, daily

You can find direct light in sunny areas of your home within one to two feet of an unobstructed south or west facing window. In these spaces, the sun should directly touch the plant. Indoor plants that thrive in direct light locations include:

  • Cacti
  • Ficus
  • Gardenia
  • Jasmine
  • Bougainvillea
  • Citrus
  • Hibiscus
  • Succulents

Bright, Indirect Light: Three to four hours of early morning or late afternoon sun

Bright, indirect light is an all-purpose light level in which foliage plants thrive and flowering plants are maintained. You can find bright, indirect light in an unobstructed east facing window or a few feet back from a south or west facing window. In these areas, you will be able to cast a shadow in the room. Indoor plants that enjoy bright, indirect light include:

  • African violets
  • Anthurium
  • Cyclamen
  • Violets
  • Orchids
  • Bromeliads
  • Palms (Areca, Bamboo, Majesty)
  • Aralias

Moderate to Low Light: Two to three hours of indirect sun to light that is not bright enough to cast a shadow

You can find moderate light several feet back from a west or south facing window, or right next to an obstructed north facing window. In moderate light areas, there is enough light to read in the room. You can find low light areas a foot or more away from a north facing window or back from an east or west facing window that receives moderate light. Indoor plants that enjoy bright, indirect light include:

  • Peace lily
  • Chinese evergreen
  • Dracaena
  • Sanseveria
  • Cast iron plant
  • Pothos
  • Snake plant
  • Philodendron

Water

All plants require water to survive. While some houseplants prefer to remain moderately moist, others prefer to be on the dry side. For example, ferns, carnivorous plants, spathiphyllum and citrus (when they’re in bloom) all prefer to be on the moist end. Dracaena, cast iron plant, sanseverias and succulents all prefer to be on the slightly dry side.

There are two basic rules to follow to ensure proper watering:

  1. Before you water your plant, always check the soil first to see if it needs water.
  2. When your plant does need water, always water thoroughly.

You can use a moisture meter, the sharp end of a pencil, a popsicle stick or your finger to check if your plant needs water. Insert your tool of choice into the soil at least 1/3rd deep into the soil. Some plants that prefer to be on the drier side will require that you check the soil at a deeper level. Our greenhouse team will be able to tell you the specific depth at which you should check for any plant you select.

When you insert the tool into the soil, turn it in place and then lift it out of the pot. If the plant is sufficiently moist, you will see light moisture marks and specs of soil. If the plant is dry and in need of water, the pencil will have very little, if any, moisture marks or soil specs on it.

How to Water

When it’s time to water your houseplants, you can either take it to the sink or water it in place with a saucer underneath. If you water in the sink, run lukewarm water over the soil until water runs all the way through and out of the holes at the bottom of the pot. If you plant is on the smaller side or covers most of the pot, try filling up a small watering can or cup with a spot and pour water into the pot to reduce mess.Turn the water off and let the plant sit for a few minutes. Then repeat this method one or two more times. Be sure to allow all of the water to drain out of the bottom of the pot before putting it back in place.

If you water in place, pour lukewarm water over the soil until the water runs all the way through and out of the bottom of the pot into the saucer. Let the plant sit for five to ten minutes. If there is no water in the saucer, pour water over the plant again until it runs out into the saucer at the bottom and let it sit. Repeat this process until the water level in the saucer stops dropping. When done, empty the saucer or wick away any excess moisture.

We invite you to come explore the many different houseplans at our three greenhouse locations. Our greenhouse plant specialists look forward to helping you select a plant that will fit your personality and thrive in your light conditions!

Watering

Don’t let your plants go into winter thirsty!

With the extremely dry fall we’ve had this year, we’re enjoying the rain that is coming our way this week and next. But even with the rainfall, our plants will still be dry and thirsty as we’re down roughly six inches of rain since September.

We recommend supplementing the rainfall by thoroughly soaking your plants as if we had an entire day’s worth of rain.

Don’t worry, you can’t overwater your plants during a single watering session as the excess water that is not absorbed by the plant will simply run off the soil. No plant wants to go into winter dry! If our plants go dormant for the winter while dry, it’s less likely that they’ll thrive in the spring or even survive.

With new plantings, it’s important to follow our planting and watering instructions throughout the fall season and continue to check the plants for water every three to five days, and water as needed. With established plants, check them weekly through the rest of the calendar year and thoroughly soak them when needed.  Broadleaf evergreens such as hollies, rhododendrons and laurels tend to need water the most at this time of year. This is especially true if we have less than the normal amount of rainfall, like we’re experiencing in our area right now.

Remember that it’s not too late to plant your trees and shrubs. You can continue planting throughout the rest of the year and into winter. The only time to avoid planting is when the ground is deeply frozen, which may occur in our area only for only a few weeks in January or February.

As we enter the winter months, we also recommend turning off the water to the outside of your house to prevent hose bibs and pipes from freezing. If we have a warmer day in January or February, remember to turn the water back on and thoroughly soak all of your plants in the landscape, especially new plantings and broad-leaf evergreens. A pocket hose can be a great tool for this type of watering as they roll up and store easily. When you’re done watering, turn the water to the outside of your house back off to prevent the pipes from freezing in the future.

If you have any questions about specific plants and their water requirements, please visit our Plant Clinics at any of our three stores, or call in and speak with one of our plant specialists. We will also update you on our Facebook page with our latest recommendations throughout the rest of the season.

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