1: Feed Them
Plants require food if they are to grow and bloom. The difficulty with the perennial garden is that overfeeding the garden creates a lush look that is prone to weather damage and insect infestation. If delphiniums, for example, are overfed, they invariably stretch upwards and are knocked down by the first wind or rain storm that passes by.
Gardeners solve this problem by staking the delphiniums. Now we have ugly stakes in the garden, holding up stretched plants. Similarly, if Artemesia plants are fed, they invariably turn into floppy masses of gray leaves by the middle of summer and a ridiculous amount of short staking would be required to contain this plant. There is also a growing body of research suggesting that plants with lush growth caused by excessive amounts of nitrogen are more prone to insect attacks than plants fed a little less.
These two problems are economically avoided by not using commercial granulated fertilizers on the perennial beds.
Instead, lay a thick layer of fallen leaves over each perennial bed every fall and allow the leaves to remain over the winter to decompose in the following summer months. Within a few years, the rapidly expanding population of earthworms will have most of the mulch consumed by July and their activity and the decomposition of the leaves will enrich the garden soil. The leaves provide all the food the garden and its plants require.
Heavy Layer of Mulch Feeds Plants When it Decomposes
If you heavily mulch your gardens with bark chips as I do to reduce weeding, a thin layer of compost (1/4” to 1/2″) applied in the fall or very early spring will adequately feed the perennial garden. The worms do work at the smaller chunks of decomposing bark and the small amount of compost completes the plants needs.
The only caveat to applying thick mulches on herbaceous borders is that many plants may resent the increased moisture created by the mulch. This resentment translates into rotting and death; pull the mulch away from plant stems and crowns to reduce overwintering problems.
Feeding the garden in this manner does reduce the size of some spiked blooms but it also encourages the bloom to be more weather-resistant, thus lasting longer in the garden.
To Stake or Not to Stake
Proper feeding reduces the need for staking. I rarely stake my perennial gardens. I try very hard to put plants that tend to be floppy next to more sturdy plants that will help support them. My delphiniums were planted amidst some bush roses and did quite nicely there when I had them in the main perennial garden.
When I do stake, it is most often for peonies or other perennials I’m experimenting with. For the peonies, I use a straightened-out coat hanger, with a small loop at each end. When the plant starts sending up buds, I wrap the coat hanger around the plant about two thirds of the way up the plant, locking the looped ends together to hold the wire in a circle. The circle of wire holds the plant upright and is invisible against the foliage.
I find that holding the foliage upright will also hold the blossoms upright in all but the most extreme winds and weather. True, heavy blossoms do tend to bend the stalks of some varieties but this is a fault of the variety, not the technique. These are the same varieties that bend with more traditional stick and string staking. The older and thicker the clump of peony, the better this looped wire technique works.
For perennials that might need some staking, I use old Christmas tree branches. When the needles fall off the Christmas tree, there is a perfect lattice work arrangement of branches that are well suited to supporting wayward perennials. The branches are cut to 24-30 inches in length and then stuck into the ground quite early in the spring next to the plants that will require staking. The plants grow up to cover the branches and the branches, with their fine fingers of support, cushion the perennials from wind damage. I particularly like stakes of this kind because they are easily cleaned up in the fall, can be composted, and do not leave lost chunks of string, old posts or metal pieces around to foul up garden machinery, tools, or knees.
2: Prune Them
Deadheading, or the removal of fading flowers, is a critical technique for keeping many plants blooming. Coreopsis lanceolata and C. grandiflora (Tickseed) or Leucanthemum x superbum (Shasta Daisy) varieties are the best example of this. If the gardener keeps these plants well deadheaded before seed has a chance to set, the plant will throw new blossoms in an attempt to set seed.
As in many gardening techniques, this is a contest between the plant and the gardener. If the gardener is vigilant and wins, the plant sets more flowers. If the gardener misses the timing or work, the plant wins, sets seed and stops producing flowers.
Shearing the plant is another of the pruning techniques that will often bring a healthy spring- or early-summer flowering perennial plant back into bloom. Geraniums are the best example of this. If these plant are sheared – taking 1/4 to 1/2 of the top growth off the plant immediately after blooming – they will re-bloom again in early fall.
Re-blooming is hard on a plant and I recommend spreading a few shovels of compost over or around plants that are being asked to regrow and re-bloom. I often will feed these repeat bloomers with a fish emulsion or other liquid organic plant food.
Failure to provide for this extra nutrition can lead to plant decline, particularly in colder climates where the plant may not have enough time to recover after the second blooming season.
3: Water Them
Perennial flowers, those lush ephemeral creatures of our dreams, are largely composed of water. Maintaining an even supply of moisture in the perennial garden by watering thoroughly and deeply twice a week will provide all the water these flowers require to bloom constantly. In our summer heat, I try to provide 1 1/2 inches of water a week to the garden by applying it in two equal sessions of 3/4 of an inch.
Our sprinkler system is more uniform than my hand watering and I place a small container under the sprinkler pattern to tell me how long it takes to apply 3/4 of an inch of water. I get uniform watering and my plants bloom better for it. I used to apply an inch of water a week but I have recently moved to this slightly higher amount due to increases in both summer heat and the subsequent evaporation.
The mulch in the gardens does help considerably to control evaporation and maintain even soil moisture conditions and I would not be without it during extreme periods of heat. While I use 1 1/2 inches of water a week to maintain even moisture conditions, the soil types in your garden may demand slightly more or less.