Fall Weather Plays Tricks on Plants
When I was moving some potted plants the other day, I realized that they were bone dry, even though the surface of the soil looked moist (valuable tip: simply picking up a pot, to judge its weight, can tell you if it needs water).
This phenomenon happens every fall, but every year I forget about this subtle change. In summer, it is obvious which containers need watering but in the fall, when the sun gets lower on the horizon, the soil surface often looks dark and appears damp but the roots have used up all the moisture in the potting soil; the plant is actually dry.
If I lose any plants from lack of water, it is usually in the fall, when my guard is down. I think summer is over so I don’t have to water as often, but the weather is drier than ever.
Something similar happens to plants growing in the ground, but the containers especially need careful watching.
I must pay particular attention to seedlings that I am growing for the winter garden. Once they dry out, they never seem to be the same and are stunted for life.
Sometimes Santa Ana conditions bring this on. The plant’s roots need to replenish the moisture lost to the wind through its leaves.
This is one of several little changes that come over the garden in autumn. More obvious, especially after daylight saving time ends, is how short the days become.
A couple of neighbors and I were lamenting the other day that although reverting to standard time may help the dairy farmers, it does little for the average working person who now gets home when it is too dark to do anything in the garden.
Less noticeable is where the sun is in the sky, even though the low sun seems to be in your eyes all day long.
On the plus side, the autumn light is very dramatic, with a distinctly orange hue. In many ways, it is the prettiest light of the year.
But with the sun lower on the horizon, plants that were safe in some shady place are suddenly exposed to the sun, and if we get a hot spell in fall or winter, they are likely to burn.
Sketch a Sun Map
Camellias that were safe under a tree limb are now bathed in sunlight, and leaves may burn. Potted plants that had been growing in a shady spot suddenly burn because they are now out in full sun on one of our hot fall days.
You can move the potted plants, but you’ll just have to put up with the burned leaves on the camellias.
To avoid the problem in future plantings, you might want to make a map of the garden that shows where it’s sunny and where’s it’s shady at this time of the year. Just sketch in the plantings and mark the areas where it is shady from about 10 a.m. to 3 p.m., the times when sunlight could do the most harm to shade-loving plants.
While you’re at it, you may find some places that are sunny enough in winter to grow a few short-lived, cool-season annual flowers or vegetables. A favorite place to plant tulips, for instance, is where they will grow in winter sun but get some midday shade in spring, which will prolong their blooming.
Besides setting the clock back, other fall adjustments are in order. The weeds sprouting now in the garden are mostly annuals, unlike spring’s perennials, and they can be easily hoed out. But you must be careful not to leave them lying about or they will re-root into the soil.
I’ve hoed weeds at this time of year only to have them right themselves and start growing again several days later. Now I rake them up and put them in the compost, though sometimes they even root into the pile. Such a will to live.
Perennial garden plants are nearly as tough at this time of year, which is why late fall is the perfect time to dig and divide those that need it. Included in this group are plants as common as agapanthus and Japanese anemones and the less common alstromerias and asters.
You need only do this every few years, and not everything should, or can, be divided. But plants that grow as a spreading clump of stems or little plantlets eventually must be dug out of the ground, split into smaller sections with a spade or serrated knife and then be replanted in improved soil.
If you do not dig up and divide these, the spreading clump will exhaust the soil, and the center will stop flowering and eventually die.
Like the weeds, these perennials will quickly re-root at this time of the year, and I’ve even left them sitting out of the ground for a night or two before replanting, when the workday has simply run out of light.
For similar reasons, November and December are good times to move plants that are in the wrong place. Many plants, including camellias, azaleas and roses, can be moved easily at this time, if they are only a few years old.
If the plants are much older than a couple of years, moving is a possibility but more difficult and problematic because their roots are so spread out. After digging, I have even left roses and camellias out of the ground for a day or two while I try to decide where to replant them, and I always try to temporarily cover the roots.
Even fertilizing changes a little in the fall. Plants in the ground or in pots respond best to fertilizers that have much of their nitrogen in the nitrate or nitric form, usually found in some kind of water-soluble fertilizer. Look on the label for this information.
Reverse the Formula
If you are still planting bulbs in the garden or are growing them in pots, note that they prefer potassium over nitrogen.
Bulb expert Charles Hardman suggested in a recent talk that gardeners reverse the importance of the typical N-P-K mix, so that potassium has the highest percentage, followed by phosphorous and then nitrogen. Think of bulb fertilizer as having a K-P-N ratio. If you can, put this fertilizer into the planting hole so it is down by the roots, but cover it with a thin layer of sand so it is not in direct contact.
And until it rains, remember to water. In our garden, we are even watering our drought-resistant plantings this month, because the last soaking rain was so long ago.
