Spring is the busiest season of the year for the gardener.
Pruning
Which perennials to cut back, and how? There are basically four types of perennial growth patterns to be aware of when it comes to cutting things back in spring:
Evergreen perennials, including many alpines, will require no cutting back or only a minimal amount of tidying up. If the plant looks green and healthy, then leave it alone. Spring-flowering alpines such as Wall Cress (Arabis), Rock Cress (Aubrieta), Basket-of-Gold (Aurinia), Pinks (Dianthus), Candytuft (Iberis), Moss Phlox (Phlox subulata), may suffer a few brown tips over the winter, but no major pruning should be done until after they finish blooming. At that time plants may be trimmed back to half their height to encourage a dense and bushy habit.
Semi-evergreen perennials sometimes stay completely green in mild winter regions but for many of us they may look so beat up by spring that some of the more tattered leaves need to be removed. Among these are: Bergenia, Coral Bells (Heuchera), Foam Flower (Tiarella), and Japanese Sedge (Carex).
The upright flower stems of Shasta Daisies, Coreopsis and Rudbeckia die back in late fall, but these plants keep low ground-hugging rosettes of evergreen leaves that become obvious in early spring. Remove the dead upright tops.
Woody perennials are better left alone until well into mid-spring before pruning. Generally about 6 inches of woody stem is left at the base where the new buds will appear. Accidentally cutting them right back to the ground will sometimes cause these plants to die. Some examples of woody perennials are Artemisia, Butterfly Bush (Buddleia), Blue-beard (Caryopteris), Fuchsia, St. John's-Wort (Hypericum), Lavender (Lavandula), Tree Mallow (Lavatera), Russian Sage (Perovskia), Cape Fuchsia (Phygelius), Lavender Cotton (Santolina).
True Herbaceous perennials are those that die back completely in winter. Fortunately, this includes the vast majority of common garden perennials. With these, it's an easy decision — cut everything right back to ground level and rake off any dead leaves that could be harboring pests or diseases. A few examples are Peonies, Daylilies (Hemerocallis), Summer Phlox, Solomon's Seal, Hosta.
Fertilizing
Some gardeners fertilize every spring, others not quite so often. Newly planted borders are usually good for a couple of years if the soil was prepared well initialy. Older gardens often are re-invigorated by a spring feeding and if you use a mulch of wood chips or bark it is a wise idea to fertilize your perennials every spring. When mulch begins to rot the bacteria will rob the soil of available nitrogen.
Whatever product you choose, follow the manufacturer's instructions carefully. Sprinkle fertilizer AROUND your perennials, not directly on top of the clumps. This will help to avoid burning the foliage. Bone and blood meal for can be used as a fertilizer for perennials rather than chemical fertilizers.
To Mulch, or not to mulch...
The benefits of organic mulch are many. Mulches add humus-forming organic matter to the soil, improving its structure and eventually supplying food to your perennials. They cover the soil and smother many unwanted seeds, reducing the amount of weeding required. The biggest benefit with mulching is that it helps to keep the soil cool and moist during the summer months, thereby reducing watering needs and avoiding drought stress. Mulch should be no thicker than 2—3 inches and should taper off to nothing as it approaches your perennial clumps. Don't heap mulch all over and smother your plants to death.
If you have had problems with slugs, consider removing all of your old mulch in the spring, leaving the soil exposed to the sun for a few weeks, then replacing with fresh mulch. This will help to eliminate over wintered slugs, snails and their eggs.
Moving or dividing perennials in the spring
Spring is an ideal time to move or divide most perennials. Even the early spring-bloomers can be moved, so long as it gets done before they flower. You can nearly always divide/transplant in the spring, but the rule-of-thumb for when to move or divide perennials is:
If the plant blooms between early spring and late June, then early fall division/moving is ideal. If the plant blooms after late June, then early spring division is ideal.
Exceptions to the rule are: Peonies (move/divide in fall), Oriental Poppies (move/divide in August), Bearded Iris (move/divide in July through September ideally, or spring as a second choice) and true Lilies (move/divide in mid to late fall).
If you move or divide a perennial later in the season when it's big and bushy, always cut back the foliage by at least half. This helps to keep the leaf mass in proportion to the reduced number of roots.
Transplanting
One week before indoor grown seedlings are planted outdoors, start to harden them off by moving the trays/flats of plants outside into a sheltered/shady area such as a porch or under a tree. If it gets really cold at night, move them back inside. Gradually increase their exposure to the sun to a full day. Make sure the plants are well watered during this period.
Before moving your plants into the garden, water both the ground outside and the transplants. It’s preferable to do your transp2lanting on a cloudy day or late in the afternoon so the heat of the sun won’t cause excess wilt.
Dig a hole twice the size of the root ball. Set the transplant into the holes so the root ball will be covered by ¼ inch of soil, and press soil firmly around the roots. Water well after transplanting and again every day for about a week until the plants are established.
