September is definitely a time of transition in the garden. While there are many signs that summer is holding on, there are at least as many telling us that its time to change things up. And while the spring and summer gardening season are flush with "how to" resources, there seems to be less consistency and generally fewer words said about the fall garden. Here are some common questions that we get asked frequently in September, and our best advice to answer each:
Should I cut back my perennials in the fall, or leave this for the spring?
This is a great question, as we often see both of these approaches promoted as the best! However, I feel there is a pretty strong case for the leave things standing camp, particularly for us zone 3 gardeners. The main reason for this is the need for perennials to enter into proper dormancy ahead of the really cold weather setting in, a process that can be significantly disrupted by pruning plants down; trimming often stimulates new growth during bursts of warm fall weather, and these fresh shoots are very susceptible to frost damage. The second advantage of leaving plants standing is simply to encourage snow cover, which offers winter protection. And lastly, one less chore... you've been working hard on your gardens all summer!
Should I till under my annual garden?
Once again, gardeners are polarized on this question. For sure it looks beautiful to have annual and veggie beds cleared out and pristine so they are ready for spring planting, but this may come at a cost. Tilling the soil often brings up weed seeds, and a growing consensus suggest that the less soil is worked that better its over all health. A strategy for the annual veggie garden might be to pull all the plants (once they are done, of course), and compost these (if not diseased), then spread compost and mulched leaf litter over the bed, without doing any tilling.
If amending my beds, do I spread the compost on top or do I have to work it in?
Just as with the situation in the veggie garden, perennial beds benefit from no till soil amendment. It is a great idea to add high quality compost around perennials in fall, and a remarkable free soil building resource is mulched leaves; these can be spread right over the bed and around perennials, and certainly do not need to be worked into the soil.
When should I bring patio plants indoors, if wintering them?
It is a great idea to bring higher zone perennial plants indoors for winter - many make for gorgeous houseplants, and others are worth keeping and growing back to glory in spring. Examples include everything from geraniums to tropicals such as hibiscus (or cool herbs like allspice!). The trick is to move these indoors with the least amount of shock, so the earlier in fall they move the better. The basic science around this is that as nights, and then days, get cooler plants get a strong signal to slow down metabolically; if plants experience cooler outdoor temperatures, then move indoors where it is warmer and drier, they often exhibit signs of stress like leaf drop or at the extreme they just die! All of this can be hard to judge, as many plants will look just fine outdoors as weather cools off, but internally lots of change is going on. Long story short: realistically Labour Day weekend is an ideal time to move plants indoors; the further we get from this date, the greater the challenges.
There are two exceptions to the above guideline: plants that need to be wintered in dormancy, and plants that like cooler temperatures indoors over winter. Container plants like figs or lemon verbena require a period of cool and calm, and ideally should behave like a deciduous plant and lose all of their leaves for winter. This is best achieved by exposing them to fall chill, and even a light frost or two! By purposely letting them experience a change of seasons outdoors before bringing them into the warm house, you can count on them being in their required state of dormancy. Plants that prefer to be cool over winter, but that do not normally lose all of their leaves, can also benefit from exposure to colder weather outdoors. Two examples are mint and parsley; leave these outdoors well into fall, them trim them right back and watch them explode with new growth when brought inside (and try to locate lower zone perennials in a cooler spot indoors.
Are there things to plant in the fall?
Yes! A lot of planting can happen in the fall. First off, it is an ideal time to establish just about anything that is zone hardy. The ground is warm and the air is going to start to cool off, which is the perfect combo for a low stress planting season for trees, shrubs and perennials. Do be sure to water these well, even as it gets colder, so that they establish roots and go into winter hydrated. Fall landscaping is often easier to visualize compared to spring, as you have a current sense of what everything that is already established looks like (size, colour, vigour etc), and therefore you can make additions or make adjustments that are better informed.
Secondly, many cool season veggies LOVE fall conditions and there are so many advantages to this second season (far fewer pests, the joy of eating fresh from the garden more months of the year These can be direct seeded to larger pots, raised beds or the garden, and many will flourish into late October. However, you can't wait too long to seed these, as they do need a little warmth to get established if they are to yield - in fact a good goal would be seed by Labour Day. That said, at Sage Garden we planted a nice little greens-garden the second week of September this year, and things are up and looking good... so it is not too late to give this a try!
Third, fall is for planting bulbs (including garlic). These are always the latest outdoor planting project, as they require air temperatures that are cool enough to prevent the bulbs from sprouting above ground. We have planted as late as November, literally using a drill to make holes in ground that was starting to freeze! The ideal would be to plant into warm soil that is still workable, but once air temperatures regularly include overnight frost. Fall garlic should be mulched with loose leaves or straw to further ensure it does not sprout above ground before winter.
Have more questions? Drop by the garden centre to let us know how we can help!