Jeff Lowenfels: Advice for indoor growing

Jeff Lowenfels

I think I have covered the care of poinsettia over the years, but I keep getting questions. Here is the summary: No drafts. Do not let them dry out, which means they should be watered when they are dry to the touch on the surface. Temperatures of 65 degrees are ideal and nothing higher than 70 degrees is important. Drainage, as with any plant, should be good, which means when you water, it should flow out the bottom.

Oddly enough, there are also questions about spring flowering holiday cacti. Of course, these are epiphyliums. They require the same care as do the other holiday cacti. In other words, they should have natural light and "natural" temperatures. In the case of the fall and winter plants, this means that the temperatures should be cool. In the case of spring plants, a warming temperature, along with the increasing day length, is required.

Next, many Alaska gardeners have taken to heart the new way of growing sweet peas, that is to start them way earlier and to pinch back new growth and a few leaves every couple of weeks. The question is, can one start them too early? The answer is "yes," as they will start blooming too early. My advice is not to start them until the end of January and to only do so if you can pay the added attention that starting a plant this early requires.

Next, how often does one need to change grow lights, if at all, to ensure that they are effective? That is an easy question for fluorescent lights, be they the regular tubes, incandescent replacements or T5 bulbs. Generally, they last one to two years. Look for blackening at the "ends" of the bulbs. Once they start to show this, they need to be replaced as their efficiency is way down. You can use them for other purposes, but not for growing plants efficiently.

It is a bit different when you are dealing with ballast bulbs, mercury vapor and the like. These all have set hours listed either on the packaging or on the manufacturers website. Follow those recommendations. The take away here is that no bulb lasts forever and every gardener needs to pay attention to the ones they use.

Next, when is the proper time to take cuttings for plants? This is a question to which an entire column or three could be devoted. In general, as long as the gardener has lights, she can take cuttings. This is particularly so when the plant displays symmetrical characteristics, that is the leaves are on opposite sides of the stem as opposed to alternating.

By the same token, are rooting hormones useful when taking cuttings? In the past, I had not been very impressed with these solutions. The gardener would take a cutting and then dip it in the substance before planting. These days, the hormones and other substances used are really much improved. In short, they work well. A novice may find them very useful. Those that have started lots of plants from cuttings may not find the expense necessary.

Related to this question are a couple on pelargoniums, aka "geraniums." Now is the time that those growing indoors should be flowering. Even if they are not, it is a good time to start taking cuttings. This is one instance where the cuttings should be allowed to "air out" for a couple of days before putting them into a rooting medium. For that, incidentally, I like a mixture of 1/4 soil and 3/4 sand, perlite or vermiculite. Once plants are rooted, keep an eye on them and pinch them back a few times between now and early March. Thereafter, leave them be as it takes about six weeks before they will flower and you want them in bloom, either when you put them out or immediately thereafter.

That covers the mail for this month. Obviously, if you have questions, you can send them to me via or simply ask when you see me around town. One of the best benefits of writing this column is getting to speak to readers and gardeners.

Jeff Lowenfels is America's longest running gardening columnist. You can reach him at

Garden calendar

Worm composting: Saturday, Dec. 8 at the Alaska Botanical Garden (there is a building now!) Abg's Lacey Ott will guide you through the process. Registration is required; go to

Holiday gifts: the best way to find out what the gardener(s) on your list wants, is to either ask or start laying hints now. Don't wait until the week before you are planning on giving your gifts.

Watering: make sure yours are not drying out. Stick your fingers an inch or so into the soil.

Master gardener's 25th anniversary party: 1 to 4 p.m. On Dec. 15 at cooperative extension service building at 1675 C St. Patrick Ryan will be playing some music and the group will make a video with those there by 2 p.m. The event is for all Alaska Master Gardeners that have been through the program the past 25 years. Kudos to Julie Riley.

Jeff Lowenfels