Monday, June 19, 2017

Proper Pruning Protocol

Deadheading Dwarf Korean Lilac

The daily June $64,000 question for garden center horticulturists is: Why didn't my ___________________ (forsythia, lilac, hydrangea, spirea, weigela) bloom this spring? If you dropped more than one species on that blank line, read on to get a handle on what's amiss in your shrub border, and get a leg up on flowers for next year.

Certainly there are a lot of possible answers to the why-didn't-it-bloom question:
  • Too much shade (for a sun-loving shrub)
  • Plant too immature to flower
  • Previous year the plant was heat or drought-stressed
  • Inadvertent exposure to high nitrogen lawn fertilizer formulations flung into beds with rotary spreaders. Lots of yummy nitrogen will often create a let's-grow-leaves-and-forget-the-flowers state.
  • Plant is in a "happy hole". For the uninitiated (and that's everyone since I just made that up), a happy hole is a site where everything is so-o-o perfect the plant is locked into a leaf-growing hormonal state, rather than a reproductive (flowering) one.

Another possibility mustn't be overlooked. How about - The shrub was simply pruned too late the previous year. This is so logical you're likely to take your open palm and slam it against your forehead as a cartoon cloud light bulb appears in your mind.  

Here's the golden rule for pruning flowering deciduous shrubs. If it has a conspicuous flower (to me that means large enough that it's considered a seasonal attribute), and it flowers before July 1, it's a spring bloomer. Spring bloomers flower on stem growth made last summer. So, it makes sense the plant should be pruned within four to six weeks after it blooms. Four being better than six, if you're asking. That gives the plant all summer to produce the stems that will flower the following spring. If you (or your gardener) prune these spring flowering shrubs too late, say July or later, your'e cutting off next year's potential flowers. Didn't I tell you it's so explicable. A sampler of spring bloomers that would fall in the above category: deutzia, forsythia, lilac, mockorange, weigela, to name a few.

Pruning Lilac after bloom

Conversely, those shrubs that bloom their hearts out for you after July 1 are flowering on the growth they made in spring- April, May, June. So, you can prune and shape them EARLY as they're coming out of dormancy, just showing leaf buds. Don't wait to trim them later in the spring, say May or early June, as you'd be eliminating or pushing back potential flowering branches. Some favorites that fall in the summer bloom category are: hydrangea, potentilla, rose of Sharon.

April-pruned Hydrangea = July flower buds

There are a couple of ringers in the viburnum and spirea clans. Because they are such broad genera they have "family" members that bloom in spring, some in summer. Therefore, each species or variety should be researched and pruned on a case-by-case scenario.

Proper pruning protocol, like so many things in life, is all in the timing.

Same species: Properly pruned vs. not

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Sunday, June 4, 2017

Potting Techniques - 200 Level Course

As I was making containers yesterday I realized I'd never written a post about just that. What are some of the tips I've appropriated from others over the years, not only to make the potting process easy and fun, but to ensure the plants grow successfully?

1. If you need height for your focal point plant (say that five times fast) mound the potting soil in the center. It can even be higher than the edge of the pot as long as you taper the soil dramatically so it's well below the rim ate the edges. As you might expect this keeps the soil in the container, not on your patio, after the first watering. I've seen only one person do this over the years and it gave her pots dimension and drama from Day 1.

2. Drop-potting is my favorite trick. Fill your decorative container with soil to the depth of the deepest plant pot. Place that empty pot in place, proceed to fill around it until the soil level is at the depth of the bottom of the rest of the of the pots. Fill in and around these empty pots with potting soil. Use your fingers to       tamp in and around the pots. Pull one empty pot out at a time and simply plug the desired plant in its new home! Once the plants are in place it's a simple matter to gently firm the root ball into even better contact with the surrounding soil. This makes potting so much easier. This is especially true for plants that have leaves and stems close to the ground that are easily broken with traditional "backfilling" of soil. Hopefully, the picture will solidify the concept.

3. If you have vining/cascading plants, and who doesn't, angle those empty pots with the tip at the edge of  the container. Planting at this angle will expedite the vine's bungee drop over the side. Notice how the pot at 6:00 in the pic is tilted at the edge, rather than flat like its neighbor. Cunning, huh?

4. If you have heavily knotted root systems don't be afraid to tease apart those sections with the heaviest tangling. Don't be shy, you won't hurt the plant unless you tear all the soil from the root system.

5. Occasionally we use tropicals as focal points in mixed containers. Know that certain tropicals bloom best   when pot-bound, and are therefore "stressed". Examples would be: Agapanthus, Bougainvillea and Hibiscus. So, taking them from their grower's smaller pot and placing in a much larger soil mass may give them too much freedom. Your reward for this generosity is a plant that changes its goals to growing roots at the expense of flowers. What you might do is faux pot by simply placing the plant, still in its plastic grower's pot, into your container with the lip even with the finished soil surface. Attention please, this will mean you will water that plant-in-pot-bondage more, but the increased bloom will be worth it, I promise.

6. No matter what your potting soil bag says about "fertilizer added" it ain't enough. Standard potting mixes are overwhelmingly peat or bark-based so there's virtually no innate nutrient value. Every time you water nutrients are leaving exiting the pot via the drainage hole. For that reason it's important to fertilize consistently - less for plants in shade than sun, though. If you're that busy person that isn't going to use a water soluble fertilizer every two weeks, then at the very least add a time-release fertilizer (like Osmocote that feeds for 4 full months) at planting. The takeaway is feed your plants regularly throughout the growing season.

One last tip, consider shoving the plant tags down in the middle of the container. That way when the compliments pour in from envious family and friends, and you draw a blank on what Angelonia variety you used, simply pull out the tag and share. Now who's the cunning one?