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Question of the Week © 2017 Mike McGrath
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How far South Can You Grow Raspberries?
Q. Can raspberries be grown successfully in central Florida? If so, when should they be planted? Do they like shade, full sun, or mixed? We have had nights drop into the mid to high twenties, usually warming into the thirties during those days. Cold snaps go in cycles of two to four days, and occasional frost is seen—mostly from January thru mid-March. I'm interested in trying raspberries partially because Pillsbury used to make great raspberry strudel toaster pastries, but I have not seen them in stores for months and thought maybe I could grow the berries and make my own.
(P.S.: Blueberries do really well here.)
---Marion in the Ocala area, about 40 miles south of Gainesville
A. Listeners in colder parts of the country may be shocked to hear about frost and freezing cold in central Florida, but that's the surprising reality. When one of my favorites bosses (WTOP's Jim Farley) retired from radio and decided to move to Florida, he made it a point to only look at places "below the frost line" so that he could grow exotics and tomatoes year-round without having to worry about protecting the plants.
So he can't grow raspberries; because they require a certain number of 'chilling hours' (nights in the mid to low 40s or colder) to bear fruit. 'The book' says that the most basic type—red raspberries—can only be grown as far South as USDA Zone 6. But I personally know of patches that thrive in zones 7 and 8. The trick a little further South in central Florida will be to plant a 'low chill' variety in a spot that gets morning sun and afternoon shade.
I know; I know. It seems like I say "morning sun and afternoon shade" about every plant, but the further South you grow the more universal that advice becomes. (Except for heat-sensitive-anywhere plants like dogwoods, where it always applies.)
Anyway: In the Northeast, mid-Atlantic, Midwest and other cold winter regions, raspberries should get full sun. So should popular summer plants like tomatoes and peppers. But when you get to areas where winter is mostly mild and summers are intensely hot, those same plants need a break later in the day.
I like to say that for most plants "full sun" means full sun in the North, a little shade in USDA Zone 7, and serious afternoon shade in the higher Zones. It's easy to forget that catalog and online descriptions have to try and cover the entire country while, in reality, plants are going to have very different needs in, say, Minnesota than San Diego (where raspberries are difficult to impossible to grow.)
But we have two strong clues that our listener might do better than if she were in Southern California or Phoenix. One is that it seems like she gets a decent number of chilling hours. The other is her notation that blueberries do well in her area. I presume these are types of blueberries bred to do better down South, like rabbiteyes—but all blueberries still need a winter chill; and if they produce in her area, so should raspberries.
Planting time? In the Spring. You buy dormant canes mail-order or from a local nursery and plant them in the ground about the same time as tomatoes. If you know someone who's already growing raspberries nearby, see if you can bum a few plants from them in the spring, when lots of new shoots pop up in established patches; those canes should already be adapted to the local climate. At the very least, see if they know the variety name and seek to purchase the same plants.
Now, time for a little primer on my all-time favorite fruit!
There are two basic 'types' of red raspberries. The most common type is known as 'fall-bearing', which is half-right; or 'ever-bearing' which is a complete lie. These are the kind of raspberries I grow, and they actually fruit twice a year—but in a way that confuses the heck out of people when they first hear the sequence: New canes sprout up from the soil in the Spring, grow all season long and then produce a nice crop of berries at the very tips of the canes in the Fall. Then the canes go dormant and may look dead, but don't dare prune them—because the following year they'll sprout new green growth and produce a big flush of berries all up and down those canes just as Summer arrives.
I never have any raspberries to share in the Fall, but I give away pints when that 'second year' late Spring harvest comes in; it's a ratio of almost 10 to 1. That so-called 'second crop' is enormous.
The other basic type of raspberry is truly 'everbearing'; sometimes called 'summer bearers', they pretty much fruit all season long. Consult your local county extension service when choosing varieties; they're the real experts on what varieties do best in your area.
And now it's time for me to get in trouble: Unfortunately, some extension services are not the best when it comes to what we call 'cultural care', as many continue to recommend high potency chemical salts as fertilizers, which is K-RAY-ZE in any situation, but especially so with raspberries, which do best in poor soil with little to no added nutrition; maybe a couple shovelfuls of compost every once in a while. If you foolishly use chemical fertilizers on these plants, you'll get insects, disease and inferior fruit.
What raspberries need most is room to spread; they are not well-behaved plants, and the best patches are planted with room to roam. They also need superior drainage, especially in warm climes, where they'll need extra water on really hot days.