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Great Gardening by Sally Cunningham: A perennial primer

Winter is a great time to learn, plan and review, so I am presenting some basic gardening principles and practices this month. Most recently – if you missed a Friday – I covered groundcovers and vegetable gardening, especially the timing for spring planting and what to grow from seeds or seedlings.

This week the topic is basic perennials: what everyone should know to get the most satisfaction from growing this essential type of plants. No landscape should be without some perennials, and frankly way too many are still designed without them.

Perennial principles
1. Definition: First, new gardeners learn that a perennial is a plant that “comes back every year.” Or, rather, it never leaves but just goes to sleep underground in the winter in cold climates. In warmer climates the plant grows above ground but goes through a seasonal cycle (actively growing, flowering, producing seed, then resting a bit). Perennials do not complete their life cycles in one season, as do annuals.

The names sometimes confuse people, because we use “annual” in everyday language that suggests every year: We refer to the “annual picnic” or “annual plant sale.” True annual plants live their lives during one season only. (They may reseed – but those are new plants.) To keep it straight this hint helps beginners: “P” is for “Perennial” as well as “Permanent.”

2. Permanent is variable: The second concept is the sometimes disappointing truth that perennials do not always “come back every year.” They are species that can continue to perform year after year in our yards, but only if we put them in suitable sites and meet their needs. A delphinium, for instance, is a favorite perennial for its beautiful blue colors, but it has a taproot that grows best in deep topsoil with perfect drainage. Since few Western New York gardens provide that, a perennial may be considered a “short-lived perennial” here.

A gorgeous delphinium from Proven Winners. (via Proven Winners)

3. Confusing the categories: Adding to the confusion for some shoppers, most garden centers have Annual Departments and Perennial Departments, and sometimes you’ll see a plant with a tag that says “Perennial plant” in the Annual Department.

What gives? Is it a mistake? Well – now I think you know – the plant itself is perennial in its own climate (perhaps where it was grown), but in a cold region it will not survive winter. It’s perennial in North Carolina but a “Tender Perennial” (or a dead one) in Syracuse. The plant is still a perennial in its life cycle. Watch for USDA hardiness Zone 5 or 4 or lower, to be sure a perennial is winter-hardy in our climate.

Also, some hardy perennials (lavenders, coral bells) may be found in both commercial departments. That is because they are great garden perennials, but are also wonderful in container combinations.

Shoppers who are filling their summer planters may not ever wander through the perennial department to discover them, so the smart garden center manager puts some of them among the true annual plants.

4. Right site required: The fundamental principle of all horticulture is that all plants have a set of site requirements. Those include the light and water available, the soil (pH, nutrients, texture), and other elements such as wind, salt, pollution and animal predation. You should analyze the site for a garden as well as for a tree – and that should guide your crop or plant choices.

Unfortunately, most plant shoppers (even the best gardeners and collectors) fall in love with a plant because of its looks (or it’s a new discovery for them) and then take it home and try to find a place to put it.

Horticulture professors teach that at least 95 percent of plant failures – death or poor performance – are for cultural reasons: wrong site, unexpected weather extremes, or poor/wrong care. It’s not the plant’s fault.

Coral bells (in container with dark foliage) also work well in gardens. Photo from Proven Winners.

Choose the right perennials
Once you know your site, plant selection should be easy, right? This is only true if you understand the clues on plant labels or if you have expert help or do good research. Three areas cause big problems if the plant shopper doesn’t understand this information:

• Ultimate size: All plants grow, some fast and some slower. All have a “mature size” – a height and width they reach and tend to remain. Read the plant label (or look it up, including the plant’s full name) for clues like “Mature height, grows 20 feet in 10 years, 3 feet high and 4 feet wide.” Then believe it. Put a perennial (or shrub etc.) where it won’t get too tall or wide for the location in three years or more.

• Habit or behavior: Like adopting a dog with the right temperament and energy for your lifestyle, it’s important to consider a plant’s behavior. How quickly does it spread? Does it droop and lean, or stand upright or become vase-shaped? Watch for words like “spreads quickly” to know what’s coming. Most perennials are valuable somewhere. Just know their ways.

• Maintenance needs: I will spend many more words and much time on correct watering, pruning, planting, and dividing in articles to come. For now what’s important is that you know its needs before you choose a plant.

Does it need frequent watering or is it drought tolerant (once established)? Does it tend to flop – and you don’t want that look – so it will need propping or tying up? Is it a “heavy feeder” so it needs lots of fertilizing or does it thrive in poor soil so you can leave it alone. Does it have predictable disease, insect or predator problems, so you will have to prevent, prepare or treat those? In short, know what maintenance you’re buying into, and then choose.

Perennial gardening offers infinite joy, challenges and interest. Just start with the right principles and the rest will follow – delightfully.

Sally Cunningham is a garden writer, lecturer and consultant.


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