While the Vermont landscape has changed quite a bit over the past decade, and the winters seem to be getting milder, we at Horsford’s still expect frost well into May. We advise people to plant frost-sensitive plants on Memorial Day weekend. Some annuals can be planted earlier if they have been hardened off.* These include: pansy, alyssum, sweet pea, snapdragon, bacopa, osteospermum, brachycome, lettuce, parsley, spinach, broccoli, scaevola, cabbage, cauliflower and edible peas. If you have these planted and the weatherman predicts frost, we suggest that you cover them.

Some plants will never tolerate cold. Tomato seeds, for example, need warmth — 75–80 degrees — to germinate. Tomato plants need night temperatures that are consistently in the 50- degree range. Pepper plants exposed to temperatures below 50 degrees do not produce fruit. Varieties that we know from experience will die if frosted are: tomatoes, basil, marigolds, petunias, some salvias, impatiens, pentas, begonias, and geraniums.

*“Harden off ” your plants over a 4–6 day period to slowly get them used to outdoor conditions. Hardening off forces the exterior stem cells to harden. The hardened stem is able to sustain colder temperatures. The best technique is to put plants out in a protected shady spot for a half day, and then for a full day. Bring them in at night. Gradually move them into a full day of sun, still bringing them in at night. Once you’ve done this for four days you can plant them.