Putting the garden to bed
what to do now to get your plants ready for winter
Late October/early November is the time to start preparing your plantings for the cold, wet weather to come. lt’s also a great time to plant new additions to your garden, move things around, and divide perennials.
WHAT TO CUT BACK
Herbaceous perennials and grasses (i.e. those that die down to the ground) need to be cut back to ground level sometime after the top growth starts to turn brown and before new growth begins in spring.
Cutting back makes the garden look tidy, removes dead foliage that can shelter baby slugs and harbor fungal spores, makes it easier to mulch between the crowns, and allows the new growth to develop unhindered in spring. Exactly when to cut specific plants down depends on time available and personal preference—some people love the look of tan grasses and black iris seed pods, other people want to get rid of stems as soon as the leaves go brown around the edges.
WHAT NOT TO CUT BACK
Evergreen perennials (Epimedium, Euphorbia, Hellebore, Heuchera, Pacific Coast lris, Primula) and evergreen grasses should not be cut back now. Most of these can just be tidied up in spring. Leaves should be removed from Epimedium and Hellebore in early spring to reveal the flowers.
Semi-evergreen perennials (Penstemon and Phygelius) survive our winters better if they are not cut back in fall. They should be cut to just above the new growth in spring.
Evergreen ferns (Sword Fern, Deer Fern) should not be cut back until late spring as the old fronds protect the new fiddleheads.
Sub-shrubs (Lavender, Santolina) can be tidied up and old flowers removed, but more severe pruning should be left until growth resumes in spring.
Shrubs and trees generally should not be pruned now. If pruning is needed to correct shape, it is better to wait until late winter so that new growth is not stimulated.
Hydrangeas should have their old flower heads left on until after frost as these protect the new buds from freezing.
Roses should not be pruned until late February, but long canes can be cut back so they don’t whip around in the wind.
MULCHING AND PROTECTING PLANTS
After perennials have been cut back and fallen leaves removed from the ground, it is a good idea to add a layer of mulch to reduce temperature fluctuations in the soil. This is particularly important for marginally hardy perennials like Dahlias, Chocolate Cosmos and Agapanthus. Two or three inches of mulch is usually enough. Many different materials can be used as mulch, including compost, manure-based products, shredded leaves, and straw.
During hard freezes (25° F or lower) tender perennials and shrubs (Phormium and some Hebe) may benefit from being wrapped in fabric such as Harvest Guard™.
Plants in pots are particularly sensitive to cold as the roots are so close to the air. Pots should be moved into a protected area during cold spells or the plant and pot can be wrapped as above, or the pot wrapped in insulating material like bubble-wrap.
Many perennials can be divided in fall. Dividing perennials is an easy way to propagate them, to get more clumps for your garden or to give to friends. Dividing rapidly growing perennials (Shasta Daisy, Daylilies) keeps them in proportion to the rest of your plantings. Some plants (Aster) die out in the center after a few years, so should be divided then, and the center portion discarded. Others
(Primula, Bearded lris) become congested and do not flower well if they are not divided every few years. Some plants are very easy to divide - you can simply pull apart the individual growth points for Hostas, Primulas and many other plants. Others form thick root masses and require more drastic measures.
WHAT NOT TO DIVIDE
Perennials and sub-shrubs with a single stem that becomes woody (Artemisia, Lavender Rosemary and Santolina) are very hard to divide, so other methods of propagation should be used. Large old plants, woody at the base may need to be discarded,
Plants that are marginally winter hardy (Dierama, Dahlia) or are intolerant of wet soil ( Penstemon, Salvia, Agastache) should be divided in spring after danger of frost.
Herbaceous grasses (Calamagrostis, Miscanthus, Panicum, Pennisetum) seem to do better if divided just after new growth starts in spring.