How to fertilize iris |Daphne Richards |Central Texas Gardener


Hi I’m Daphne Richards. Our question this week is, when should I fertilize my irises? Well since spring will be upon us very
quickly, it’s definitely the right time to start thinking about what to do when
our plants wake up. And iris blooms are not only gorgeous
but also short lived, so if you’ve ever had a year or two with no blooms,
and most of us have, you want to do whatever you can to
ensure a good spring show. And fertilization definitely plays a key role
in blooming. With irises, over fertilization can cause
just as easily problems as not fertilizing at all. As with most plants, too much nitrogen
leads irises is to concentrate more on green growth at the expense of flowering and sometimes
to not even bloom at all. So if you have irises it might help to use a bloom boosting fertilizer, one with the high middle number in the
three-number ratio on the package. That means it has a high relative amount
of phosphorus to nitrogen potassium. But even more important than a high
middle number for many flowering plants would be a very low first number, which means a low amount of nitrogen.
Reducing nitrogen for flowering plants is just stress inducing enough to switch
their focus from green growth by themselves to blooming which will lead to the next
generation. So back to when. Here in Central Texas our winters are
most often non-existent or gone in the blink of an eye, but we
usually have a roller coaster of warm days and at least one late spring frost. So fertilizing too early can be damaging,
but not for irises. They start leafing out before winter is
over anyway and are usually not damaged by late spring frost. So boosting their growth early is just
fine. Mid-february to early March is a good time to apply
fertilizer. Most of the iris specific fertilizers you’ll see will have a 6 10 10 ratio, which would work
very well to boost the blooms and lead to an overall healthy plant. You might also
fertilize again lightly just after blooming. to assist in the plant’s recovery after it
flowers. Since we had such a great question on fertilizing them, irises are also our pick of the week.
This super tough drought tolerant genus of plants is full of species that do fabulously well in Central Texas gardens. And they’re
virtually indestructible, making them the perfect plant for both
beginning gardeners, who need some successes to boost their confidence, and more seasoned folks, who need at least
one or two garden beds to be easy-care. Irises are available in almost
every color in the rainbow, from glaring vibrant purples and yellows
to the most muted lavenders, creams and blues. With so many different sizes, colors, and
types to choose from, it’ll be very difficult not to end up
planting more irises than you planned on. Bearded irises are perhaps the most
familiar to most people but there are also German, Siberian,
Japanese and Louisiana irises. Some grow best in full sun, while others need a
bit of shade. And some, such a Siberian and Louisiana,
prefer soggy soil. So if you have heavy clay, those would be great
for you. Although the blooms don’t last long, the foliage is beautiful, providing a
nice sculptural element to the landscape. Like roses, irises are old-fashioned and tough. Growing from a large underground stem, irises are very easy to divide and pass along.
The non-boggy species require very little water to survive and thrive, so
don’t over water them. Be also careful to clean
up around them in winter since they can get infected with insects
and other diseases. To do in your garden this week, look
around and see if any of your roses need pruning. We’d love to hear from you so please
visit KLRU.org/CTG to send us your
questions and plants from your garden.

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