In New Hampshire, covering is 

 done between the 1st and 3rd week 

 of November, depending on the 

 year and the grower. Uncovering is 

 usually between the 1st and 3rd 

 week of March. A rule of thumb 

 that I follow is: in the fall when in 

 doubt, cover early, and in the 

 spring when in doubt, uncover 

 early. Something that always wor- 

 ries me is quick drops in tempera- 

 ture in the fall— say, into the mid- 

 teens. At what temperature do you 

 risk root damage? This fall we kept 

 a soil thermometer in some pots, 

 with the sensor 1 inch below the 

 soil line. When night temperatures 

 dropped to 12 degrees in Novem- 

 ber for two nights, the soil tem- 

 perature only went down to 29 de- 

 grees. Since this I've become much 

 less concerned about sudden 

 dips in temperature. 



4) The wetness of the soil at the 

 time of covering is important. Water 

 is the main insulator around the 

 roots. It is important that the soil 

 be wet when the plants are cov- 

 ered. It is often suggested that the 

 plants be irrigated the day before 

 covering. Each time I try this, I 

 end up with a bunch of frozen 

 sprinklers. Lately I have depended 

 on fall rain to wet the plants. I try 

 to time the covering within 2 or 3 

 days of a good rain. 



5) Disease can be a big 

 overwintering. Under the blankets 

 there is plenty of moisture and no 

 air circulation. This is one of the 

 big advantages to overwintering in 

 unheated poly houses with blan- 

 kets. Since the blankets are out of 

 the wind, they don't have to be 

 weighted down, so the edges can 

 be left open to allow air circulation. 



The first step to disease preven- 

 tion is to remove as much of the 

 foliage as is possible. We use a 

 string trimmer and cut all the de- 

 ciduous plants back. Be sure that 

 the person running the string trim- 

 mer is familiar with the plants: you 

 don't want them cutting back your 

 evergreens or the above-ground 

 eyes on plants like Heuchera. After 

 cutting back, we rake all the beds. 

 Some nurseries use backpack blow- 

 ers for this. 



The other thing we try to do is 

 to keep the blankets off the ever- 

 greens. We do this by either laying 

 the plants on their sides if they are 

 tall or rigid (Iberis), or by putting 

 inverted plant trays over the foli- 

 age. I choose trays with a mesh 

 bottom to allow more light to get 

 through. We do this on Vinca, 

 Phlox stolonifera, and other low- 

 lying evergreen plants. 



Fungicides are also widely used. 

 However we have found no appre- 

 ciable benefit from using them. I 

 would like to experiment with using 



anti-desicants on the evergreens. 

 This is being used successfully by 

 some nurseries. 



6) Mice can cause devastation to 

 overwintering plants. Our first line 

 of defense is to keep mouse traps 

 set in the nursery for a month be- 

 fore the cover-up. We feel that this 

 greatly reduces the populations. We 

 put a trap every 15 or 20 feet. Just 

 before covering, mouse bait should 

 be spread. Either poisoned grain or 

 paraffin blocks of rodenticide can 

 be used. 



In summary, the most important 

 thing seems to be getting familiar 

 with the different plants. I think in 

 the future we will overwinter some 

 difficult plants in poly houses with 

 foam blankets. Also getting familiar 

 with the sensitive evergreens and 

 learning which form of overwinter- 

 ing works, or how to best keep the 

 blankets off the foliage, will be 

 valuable to us. Advice from other 

 growers and professional journals 

 has helped us a lot. But trial and 

 error has been our best teacher, 

 and each year we learn a few more 

 tricks, t^ 



Peter and Leslie van Berkum own 

 and operate van Berkum Nursery, 

 4 James Road, Deerfield, NH 03037. 

 For further information, call them 

 at (603) 463-7663. 



CANTERBURY, NEW HAMPSHIRE 03224 



EXIT 18, 1-93, 1/2 MILE 



TELEPHONE 1 -800-287-471 6 



SOD FARMS & WHOLESALE NURSERY, INC. ,0 



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